CA1297558C - Process control sytem with action logging - Google Patents

Abstract

PROCESS CONTROL SYSTEM WITH ACTION LOGGING

ABSTRACT
An integrated system for process control in which a process supervisor procedure defines parameters for one or more controller systems (or control procedures). The supervisor procedure changes control parameters only in discrete changes, and the decision to act is sufficient-ly constrained that every change must be a significant change. Every change is logged (or otherwise reported out to human experts). Since every change is sig-nificant, the history of changes will provide a meaning-ful record which can be reviewed by human experts.

Description

~ Q~_5h~ Invention The present invention relates to expert systems (also known as knowledge-based systems~, to process control systems, and to hybrids thereof.
eiasYa~15~s~_RelatPd Art Various known teaching~ which are believed to be related to various ones of the innovations disclosed in the present application will now be discussed. However, applicant specifically notes that nst every idea discussed in this section is necessarily prior art. For example, the characterizalions of the particular patents and publications discussed may relate them to inventive concepts in a way which is itself based on knowledge of some of the inventive concepts. Moreover, the following discussion attempts to fairly present various suggested technical alternatives (to the best of applicant's knowledge), even though the teachings of some of those technical alternatives may not be "prior art" under the patent laws of the United States or of other countries.
Similarly, the Su~mary of the Invention section of the present application may contain some discussion of prior art teachings, interspersed with discussion of generally applicable innovative teachings and/or specific discussion of the best mode as presently contemplated, and applicant specifically notes that statements made in the Summary section do not necessarily delimit the various inventions claimed in the present application or in related applications.

Process CQntrol Generallv To compete in global markets, manufacturers must csntinually improve the quality and cost of manufacture of their products~ They must do this in the face of changing market needs, changing raw materials costs, and 7~5~3 reduced staffing. Automatic computer control of the manufacturing process can play an important part in this, especially in the chemical process industry~ Most process plants already have the basic automatic regula~inq controls (low level controls) needed to control the plant at a given operating point. These provide the foundation for higher level supervisory controls (referred to here as supervisor procedures or supervisors) that seek to improve quality, reduce cost, and increase plant uptime by moving the plant to a different operating point. These changes can be made directly via the lower level controls, or indirectly via the plant operator.
Although supervisory controls have been in use for years, they have lacked a number of desirable features.
To best improve quality and cost, a supervisor procedure should:
- help control the quality of the end product;
- reduce the cost of operating the plant;
- help avoid unnecessary upsets or shutdowns;
- work effectively with plant operators;
- act in concert with standard operating procedures; and - be s~lpportable by plant operating and support people.
To measure quality, a supervisor procedure should ideally have access to measurements of the basic properties of the product which affect its value and usefulness to the customer. Since most product properties measurements are sampled (and are measured in a laboratory), the supervisor should have access to a historical process database which can store these measurements as well the basic process data from the lower level control systems. Since sampled measurements and the process itself normally include some components ~.7~i~8 of random variation, the supervisor should include statistical tests which can de~ermine if a sequence of ~ampled measurements is varying normally around its aim value (~ is "on aim"), or has shifted significantly from aim (is "off aim"~.
To control quality, a supervisor procedure should have the capability to chang~ the operating poin of the process (via the lower level controls) when a measured property goes off aim. It should have the ability to act in response to new data or statistical tests, or to act at regular time intervals. It should also be able to preemptively change the operating point when basic conditions (such as plant production rate) change. It should allow a number of independent control objectives, and new ones should be easy to add. Sinc~ the process - may use any number of different low level controllers, the supervisor should be able to communicate with all of them.
To work effectively with plant operators, a supervisor procedure should be understandable. It should carry out its control actions in a way that is natural and understa~dable to operators. It should provide enough information about its current state and its past actions for the operator to judge its performance. It should inform the operator when it acts (or chooses not to act), explaining how much action was taken, where it was taken, why it was done, and what effect it might have. Since the effect of actions taken to control quality and reduce cost can last longer than a single shift, it should provide a record of all its actions.
To act appropriately under all circumstances, to reduce operating c05ts in a way consistent with quality, to help avoid unnecessary upsets and shutdowns, and to take operating procedures into account, a supervisor A~8 should ideally include the logical decision making capabilities of expert syste~s. Because decisions will normally focus on a specific task or area, many independent expert systems should be allowed. The expert systems should have access to the many sources of process measurements, laboratory measurements, and control system parameters. They should be able to reason symbolically using that information, and to make their decisions take effect through communication and control actions. To work effectively, the supervisor should be able to control its expert system functions in concert with its cther functions.
To be supported by plant personnel, the supervisor should be easy to use. It should allow common control actions to be set up easily, with a means of customizing less common functions. It should allow control actions to be changed ~asily. It should have a simple means of specifying the informative messages to be generated about it actions. Its expert systems should allow process knowledge to be entered, stored, and updated in a way that plant support people understand. It should provide a simple, appropriate knowledge representation which naturally includes data retrieval, symbolic reasoning, and effective means of implementing decisions in the plant. The knowledge structure should allow any authorized plant expert to enter knowledge, without restricting access to those who know computer languages or have memorized special rule structures.
The present invention addresses many of these concerns.
Normally supervisory control has been thought of separately from another higher level of control called optimizing control, which seeks to minimize operating cost. In some cases, the requirement to minimize variation in product properties (i.e. to improve produc~
s 1~. 7S~8 quality) is absolutely primary, so that Gost optimization only be performed as an objective secondary to quality objectives. In this environment, use of classical optimization techniques to achieve ~ost optimization may n~t be possible. In other cases, it has been possible to integrate a balance of supervisory and optimizing control into the sup~rvisor.
~odularitv Supervisory control systems using a modular structure are well Xnown. For example, the Process Monitoring and Control-1000 (PMC-1000) control package marketed by Hewlett Packard is a modular control package which c~n function as a supervisory control system. PMC
modules, called blocks, perform alarming and limiting, proportional/integral/derivative control, trending, driving an electrical output, running programs, and other functions. Each block writes one or more output values into memory. To build PMC control structures, the user creates as many blocks as needed and links them to other block output values. A new runnable system must then be generated. Once the system is running, parameters such as gain constants can be changed, but the linking of blocks is fixed. PMC runs on a base time cycle, and blocks can only be scheduled to execute at multiples of the base cycle time. Although PMC
maintains a historical database, it cannot be used for control, and does not effectively store intermittently sampled data. It is believed that there is no maxi~um number of blocks.
It is bel~eved that zome earlier discussion of the significance of modul~rity in process contxol ~oftware i~ found in Watson, WProcess Control Using Modular Package So~tware,~ IEE Conerence Publications number 102 (1973) ~"~375S!3 Historical Process Database A database of historical process data i~ gen~rally described in Hale and Sellars, "Historical ~ata Recording for Process computers~" 77 Chem. Enq'a P~oqress 38 (1981), Continuous Control Actions In classical feedback and feedforward control, the prior art teaches that the best control results are achieved by making continuous changes to the process.
In computer control, where cyclic operation forces changes to be made in discrete steps, many small, frequent steps are conventionally preferred. While in principle this gives the best possible control lS performance, such control ac~ions are very difficult to visualize. In fact, it may be impossible to determine what actions have been taken by what control strategies, and how long the control strategies have been making changes. This makes it very difficult to judge whether control strategies are working properly, or even if they are working at all. This method of control also runs counter to the methods used by opexators, who generally ~ake a few significant changes and wait to see the effects.
In feedback control, the use of a deadband is a well known way of ~voiding small actions caused by a noisy measurement. (That ~s, if the control variable ~alls with~ n a spec~fied deadband of values surrounding the goal v~lue, the control value will not be nanipulated. ) This deadband, as is well known, ~elps to ~void ~nst~lbility in control systems. Statistical process co~trol ~lso tends to reduce the number of feedback control actions. However, neither technique is sufficient to make all control actions understandable, since some action~ will not b~e c~nsidered noisy.

The use of a feedforward relation among control variables is also well known among those skilled in the art of process control. That is, in some cases, whenever one variable changes (e.g. if a particular control variable i5 manipulated lor any reason), another variable will also be m~nipulated according to a predetermi~ed relationship. For example, in a distillation process, it may be-desirable to immediately decrease the heat input whenever the rate of feed of the crude feed stock is decreased. In feedforward control, a deadband is normally not used.

Control of Multi~le ManiDulated Variables In many process control applications, several manipulated variables must be jointly controlled in a single control loop (e.q. in some relation to a single measured variable). A special (and very common) case of this is seen in many situations where a single manipulated variable can normally be used, but alternate manipulated variables should be used instead if the first-choice manipulated variable becomes constrained.
When human operators optimally handle problems of this kind, their choice of which output to change will often be made heuristically, based on cost, quality, response dynamics, and process stability.
"Decoupling" is a conventional way of reducing multi-input multi-output problems to sets of single-input single~output problems. In decoupling, it is usually assumed that all of the manipulated variables should be changed.
A different but related problem arises when a number of manipulated variab~es ("knobs") can be changed to resp~nd to ~ ~ingle ~e~6ur~d v~riable. Oper~tDr~
often u~e ~ h~uristlc Approach in choosing wh~ch knob (or ~nobs) to manipulate, and ~omet~es choose not to ~ct. ~he heurist~c approach may consider cost, quality, response dynamics, nnd process stability. I~ may include ~ltern~te knob~ to be used when ~11 of the preferred knobs ~re constrained. Classic control methods ~re not well suited to this approach.

~xpert Svstems Gene~llv The term ~expert sy~tem" is used ln the present application (in accord~nce with what is believed to be the general usage at present) to refer to a syst~m which includes non-tri~i~l zmounts of knowledge about an underlying problem. Almost any control system which has 15 been customized for ~ particular ~pplication might be argued to embody small ~mounts of relevant knowledge in its very structure, bu~ the term expert 6ystem is gener~lly used only for systems which contain enough accessible information that they can usefully supple~ent the knowledge of ~t least ~ome (but normally not all) human users who must deal with problems of the type addressed. Expert systems ~t their best may serve to codify the expert knowledge of one person (2 "domain expertn), ~o that th~t person's expertise can be distributed ~nd n~de ~cressible to many less expert users who mus~ address problems of ~ certain type. Some well-known 6uccessful examples include ~ ~edical diagnostic progr~ (HYCIN) and -~ dingnostic program wh~ch ~s8i6ts ~ech~nics working on diesel engines.
As these ex~ple~ show, one very com~on ~rea of applicat~on for expert ~y~tems has been ~ault diagnosis.
~any other are~ o~ ~ppl~cat$on have been recognized;
gener~lly ~ ~5L~Y~ (ed. R. Forsythe 1984) 7~5~
P. }larmon and D King, Expert Svstems (1985); and Donald ~aterman, A auide to Expert Systems (1984).

S Xnowledqe In~ut and Updatinq One of the very general problems in the area of expert systems is how knowledge is to be gotten into an expert system in the first place. That is, specialists in arti~icial intell~gence often assume that a "know-ledge engineern (that is, a person who is experienced and competent in ~e specialized computer languages and - software commonly used for artificial intelligence applications) will interview a "domain expert" (that is, a person who actually has expert knowledge of the type of problems which the expert system is desired to be able to address) to extract his expertise and program an expert system accordingly. However, there are some very important drawbacks to this paradigm. First, competent "knowl~dge engineers" are not readily available. In particular, the requirements of maintaining 2 real-world application ~suc~ as an expert system ~or chemical process control, as in the preferred embodiments disclosed below) are such that it is dangerous to rely on a ~ufficient supply of "knowledge engineers" to go through the itera~ions necessary to not only input the knowledge base reliably, but also maintain the software base once it is created.
The rapidly developing art of software engineering h~s shown thnt one o~ the key requirements or a large ~oftware system is ~hat it be maintainable. Thus, for example, the so~tware system must be set up so that, after the te~hnoloqi~t who f~rst puts together ~n expert system is gone, lt can be maintained, modified, and updated as necessary by his successors.

~7S5~3 Thus, onQ key problem in the area of expert systems is the problem of maintenance and updating. Especially in more complex real-world applications, it is necessary that a large software structure, such as that required for a sophisticated expert system, be maintainable. For example, in an expert contr~l system, control strategies may be modified, new con~rol strategies may be intro-duced, sensor and/or actuator types and/or locations may be changed, and the economic fact~rs relevant to cost versus throughput versus purity tradeoffs may change.
Normally, exper~ systems ~t~empt to maintain some degree of maintainability by keeping the inference rules which the processor executes separate from the software structure for the processor itself. However, this ncrmally tends to lead to a larger software structure - which operates more slowly.
Specialists in expert systems also commonly assume that expert systems must be built in a symbolic processing environment, e.q. in environments using LISP
or PROLOG. Even for complex processes, a single large knowledge base is usually assumed. The program which processes t~e knowledge therefore requires complex procedures for processing the knowledge base, and these are typically coded separately from the knowledge. This leads to large software structures which execute slowly on conventional computers. Specialized "LISP machines"
~re commonly recommended to speed up the inference process.

ExPert SYstem Knowledae Structures Published ~teri~l regarding knowledge based ~y6tems (expert systems) has proposed several clas-¢ifications ~or the types of rules which are to be used.
For example, U.S. Patent No. 4,658,370 to Erman et al., describe "a ~ 7 3.~

t~ol.. for building and interpreting a knowledge base having separate portions ~ncoding control knowledge, factual knowledge, and judg~ental rules." (Abstract).
The method described in this pa~ent still appears to rely on the availability of a "knowledge engineer." This patent appears to focus on the applica~ion of an expert system as a consultation driver for extracting the relevant items of knowledge from a human observer.
Rnowledge i5 separated into factual knowledge such as classes, attributes, allowed values, etc., which describe th~ objects in the domain; judgmental knowledge, which describes the domain (and its objects3 in the form of rules; and control knowledge describing the problem solving process to be used by the inference procedure in processing the knowledge. (The control - knowledge has nothing to do with control of an external process.) This knowledge structure is designed to make the task of knowledge engineering easier, and to make the knowledge system and its reasoning during a consultation easier to understand. The knowledge base is written in a specialized progra~ing language. This is a very powerful structure, which requires a very high skill level.
Expert system development tools which are designed to make the input of knowledge easier have been developed. U.S. Patent 4,648,044 to Hardy, et al., describes "a tool for building a knowledge system ~which] includes a knowledge base in an easily understood English-like language expressing facts, rules, and meta-facts for specifying how the rules are to be applied to solve a specific problem". lAbstract).
Although this tool is not as complex as some current expert systems tools, the knowledge must be entered in a rigidly structured format. The user must learn a specialized language before he can program the knowledge 5~
base. Despite SGme simplification in the development process, a fairly high skill level is still required.

Expert SYstems_for Process Control Chemical processing plants are so complex that few people develop expertise except in limited areas of the process. Plants run around 1:he clock, production rates on a single line are very high, and startup is usually long and costly, so improp~er operation can be very costly. It has also been found that, in a complex chemical processing plant, some operators can achieve substantially higher effici~ncies than others, and it would be advantageous if the skill level of the best operators could be made generally available. Expert systems promise significant benefits in real-time analysis and control by making scarce expertise more widely available. However, application of expert systems in this area has not progressed as far as it has in interactive, consultative uses.
Integration of ~xpert system software with process control software poses special problems:
First, there is the problem of how the software structure for an expert system is to be combined with the software for a process control system.
Several expert systems which have been suggested for process control have used an expert system as the top-level supervisor procedure for the control system.
Second, as discussed above, many process control strategies have difficulty with situations where there are multiple control parameters tinputs to the process) which could be manipulated. That is, for processes which have only one primary control parameter (as many do), the problem of what value to set for that control parameter is in significant ways a much simpler problem than the question of which one or ones of 5~
multiple control parameters should be addressed, and in which direction.
It should also be noted that the u~e of an expert system to design a new process (or to debug a newly introduced processl has signifiçantly different features from the problem of optimally controlling an existing process. Similarly, while expert systems have also been applied to the automatic distribution of jobs to multiple workstations through an automated materials handling system (an example of this is the DISPATCHER
Factory Control System developed by Carnegie Group Inc.), the queuing problems presented by the allocation of different types of materials in batches to many paxallel assembly workstations making different products are quite different from the problems in continuously operating single line processes, particularly chemical processes.

"RE:SCU"
The system known as "RESCU-I resulted from a collaborative demonstration project between British government and industry. See, e.q., Shaw, "RESCU online real-time arti~icial intelligence," 4 ComPu~er-Aided En~lneerinq J. 29 (1987): and the Digest of the IEE
Colloquium on 'Real-Time Expert Systems in Process Control', held 29 November 1985 at Salford, U.K.... From available information, it appears that this is a real-time expert system which was developed to provide advice on quality control in an detergent plant. The system searches for a hypothesis about the plant which is supported by process data, and uses it as the basis for advice. This system also uses a single knowledge base of the entire plant and thus requires complex inference control ~ethods.

.7~S~
"Falcon" i5 a fault diagnosis system for ~ chemical reactor, which monitors up to ~l0 process measurements and seeks to identify a set of up to 25 failures in the process. This was developed as ~ demonstration project betw~en DuPont, the Foxboro Company, and the University of Delaware, and is described, for example, in D. Rowan, "Using an Expert System for Fault Diagnosis,N in the February 1987 issue of Contrl Enqin Q ~ing See also "Trou~leshootlng Comes On Line in the CPI" in the October 13, 1986 issue of ~he~iç~l_Engineerina at page 14. This system required several man years of development, and because it is programmed in LISP, it has proven difficult to maintain the knowledge base through process changes.

~O~SPEC SuPerintendent"
The "ONSPEC Superintendent" (TM~, marketed by Heuristics Inc., is a real-time expert systems package wh~ch monitors data from the ONSPEC (TM) control system.
See Manoff, rOn-Line Process Simulation Techniques in - Industrial Control including Parameter Identification ~nd Estimation Techniques," in Proceedinqs of the ~leven~h ~ çed Control con~ence (1985);
and Manoff, "Control Software Comes to Personal Computers." at page 66 of the March 1984 issue of Control Enqinee~inq. The "Superintendent" monitors for conformance with safety and control procedures and documents exceptions. It can also notify operators, generated reports, and cause control outputs.

1~'.1:3755~

HpICON"
The PICON (TM) system, which was marketed by Lisp ~achines, Inc. (LMI), was apparently primarily intended for real-time analysis of upset or emergency conditions in chemical processes. It can monitor up to 20,000 input process measurements or alarms from a distributed control system. It uses a single knowledge base (e.g.
containing thou~ands of rules) for an entire process.
To handle such a large nllmher of rules, it runs on a LISP computer and includes complex inference control methods. PICON mu~t be customized by a LISP programmer before the knowledge base can be e~tered. The domain expert then enters knowledge ~hrough a co~bination of graphics icons and Lisp-like rule constructions. See, 15 for example, L. Hawkinson et al., "A Real-Time Expert System for Process Control," in Artificial Intelliaence ADP1 cations in Chemist~ (American Chemical Society 1986), and the R. Moore et al, article in the May 1985 issue of InTech at page 55.

Self-tuninq Controllers Another development which should be distinguished is work rel~ted to so-called ~self-tuning controllers. n Self-tuning single- and multiple-loop controllers contain real-time expert systems which analyze the performance of the controller (See "Process Controllers Don Expert Guises~, in Chemlcal Eng'g, June 24, 1985).
$hese expert syste~s adjust the tuning parameters of the controller. They ~fect only low-level parts of the systeM, ~nd use a flxed rule base e~bedded in a ~icroprocessor.

7~

SUMMARY OF THE INVENTION
In this 6ection various ones of the innovative teachings presented in the present application will now be discussed, and some of their respective advantages described. Of course, not ~11 of the discussions in this section define necessary features of the invention (or inventions), for at least the following reasons: 1) various parts of the following discussion will relate to some (but not all) classes of novel embodiments disclosed; 2) various parts of the following discus~ion will relate to innovative teachings disclosed but not claimed in this specific application as filed; 3) various parts of the following discussion will relate specifically to the "best mode contemplated by the inventor of carrying out his invention" (as expressly required by the patent laws of the United States), and will therefore discuss features which are particularly related to this subclass of embodiments~ and are not necessary parts of the claimed inYention; and 4) the following discussion is generally quite heuristic, and therefore focusses on particular points without explicitly distinguishing between the features and advantages of particular suhclasses of embodiments and those inherent in the invention generally.
Various novel embodiments described in the present application provide significant and independent innovations in several areas, including:
- systems and methods for translating a domain expert's knowledge into an expert system without using a knowledge engineer;
software structures and methods for operating a sophisticated control system while also exploiting expert system capabilities;
generally applicabl~ methods for controlling a continuous process; and 3~

innovations7 applicable to expert systems generally, which help provide highly maintainable ~nd user-friendly experts.
Various classes of embodiments described herein provide a process rontrol system, wherein a process which operates substantially continuously is controlled by a system which includes (in addition to a process control ~yste~ which is closely coupled to the underlying process and which operates fairly close to real time, i.e. which has a maximum response time less than the minimum response time which would normally be necessary to stably control the underlying process) at least so~e of the following features:
1) A supervisor procedure, which has a modular structure, and retrieves process measurements from the - process control system (or other process data collection systems), passes control parameters to the process control system, and communicates with people.
Preferably, the supervisor includes the capability for statistical process control. The supervisor preferably runs on a computer system separate from the process control system.
23 The supervisor procedure can preferably call on one or more expert ~ysteu proceduros as sub-routines. This is particularly us~ful in control applications where there are multiple possible manipulated variables, since the expert system(s) can specify which manipulated variable (or variables) is to be adjusted to achieve the end result change desired, and the supervisor system can then address simpler one-dimensional control problems.
3) Preferably, at least some users can call on a build-supervisor procedure which permits them to define or redefine modules of the supervisor procedure by editiny highly constrained templates. The templates ;?5~8 use a standardized data interface (as seen by the user), which facilitates the use in control actions of data from a wide variety of systems. The templates in the available template set preferably contains highly constrained portions (which are optimized for the most common functions), and pointers to functions whic:h can be customized by the user.
4 ) Preferably, the build-supervisor user can also call on a build-user program procedure, which allows fully customized control functions to be programmed by sophisticated users. The build-user program procedure can also be used to create customized message generation functions. These can be used to generate messages describing the actions of the supervisor, and also to call other sub-procedures, such as the expert procedures.
5 ) Preferably at least some users are also permitted to call on a build-expert procedure which can be used to construct an expert system. Knowledge is specified by user input to a set of highly constrained, substantially natural language templates. The templates use a standardized data interface (as seen by the user), which facilitates the use in the expert system of data from a wide variety of systems. The completed templates can then be compiled to produce a runnable expert system. Preferably, the user can also retrieve, examine, and modify the input from previously specified templates. Thus, an expert system can be modified by recalling the templates which specified the current expert system, modifying them, and recompiling to generate a new runnable expert.
6 ) A historical process database advantageously standardizes the access to current and historical process data by the supervisor and expert procedures. This is particularly useful for collecting 1~7~S?-~8 the results of laboratory characterizations over time of the underlying process.

CGntrol of Continuous Processes The goals in management of a substantially continuous process include the following:
1) Maximizin~ quality: In the chemical process industry, it is important to reduce variation in measured properties of the product, and to control the average measured properties at specified aim values.

2) Minimization of cost of manufacture: The process must be operated in a way that efficiently uses energy and feedstocks without compromising quality objectives. Upsets and inadvertent process shutdowns, which adversely affect quality and production rate, and reduce the total utility (fractional uptime) of the plant, are all ccstly and must be avoided.

Control of Multiple ManiDulated Variables As noted above, in many process control applications, several manipulated variables must be jointly controlled in a single control loop (e.q. in some relation to a single measured variable). A special (and very common) case of this is seen in many situations where a single manipulated variable can normally be used, but alternate manipulated variables should be used instead if the first-choice manipulated variable becomes constrained. When human operators optimally handle problems of this kind, their choice of which output to change will often be made heuristically, ba~ed on cost, guality, response dynamics, and process stability.
one novel approach to this problem (which is used in several of the preferred embodiments below) is to decompose the multiple-variable problem into a set of single-variable problems. ~l expert procedure is used to decide which control parameter(s) to adjust, and one or more from a set of single-input single-ou~put procedures are used to make the adjustment(s). Not onl-y 5 does this facilitate quality, cost, and plant operability objectives, but it results in control strategies which art properly over a much wider range of conditions. Correct actions are taken, where con~entional control methods would make no action or wrong actions. This improves the usefulness of the control strategy to the operator, and leads to higher use of the controls.
The various novel ideas described below are particularly advantageous in such multiple control parameter problems. In the presently preferrPd embodiment discussed below, a dimethyl terephthalate process ~DMT) process is presented as an actual example to show the advantages achieved by ~he various novel ideas disclosed in this context.

Discrete Control Actions As mentioned above, control systems that continuously change manipulated parameters are very difficult to monitor. Since operators depend on the supervisor procedure to maintain important product properties and process operating conditions, it is important that they be able to understand and judge supervisor performance. By restricting supervisor changes to a reasonably small number of significant discrete actions, supervisor performance becomes much more understandahle.
One novel teaching stated in the present application is an integrated system for process control in which a process supervisor procedure (which is preferably the top level procedure) defines parameters ;75X8 for one or more control syste~s (or control procedures).
The supervisor procedure changes control parameters only in discrete actions, and the thresholds for the decision to a~t are preferably made large enough (for each control parameter) that every action must be a significant change.
A related novel teaching herein is that every control action taken by the supPrvisor should be reported out to plant personnel in a substantially natural language message. Preferably, instances where action would be desirable but i5 not possible (because of constraints or other unusual circumstances) should also be reported. Preferably, a cumulative record of the messages is kept, and is available for review by operators and plant support people. Preferably, the message should report the time, amount, location, and reason for each action. Other relevant information, such as the time stamp of relevant sampled data, and the nature of statistical deviations from aim should preferably be included as well. Sinre every action is significant, and the number of actions is reduced, the cumulative record provides a meaningful record of supervisor performance.
This is particularly advantageous for systems where some of the relevant time constants are so slow that dyna~ic process responses last several hours (or longer). A new operator coming on duty at a shift change can use the cumulative record to judge what effects to expect from supervisor actions on the previous shift.
The use of a deadband in feedforward action is one novel means that is advantageously used to discretize ~upervisor actions. Feedforward action is taken only when the measured value changes by more than the deadband from its value at the last action. This generates a series of discrete changes in the manipulated variable, which 5an be effectively logged and evaluated by operators.
Statistical filtering of discretely measured values S also serves to reduce control actions to a f w significant changes. Statistical tests, as is well known, distinguish normal variation around the average from significant deviations from the average. In most ca~es, a number of measurements will be needed to indicate a deviation. By only acting on statistical deviations, relatively few, but significant, actions will result.

ExPert Svstems for Process Control A general problem with expert systems is how the 15 - expert system software is to be integrated with process control software. Several expert systems which have been suggested for process control have used an expert system as the top-level supervisor procedure for the control system. However, several of the novel embodiments disclosed herein achieve substantial advantages by departing from this conventional structure. For one thing, if the expert system is the top level procedure, then it becomes more difficult to accommodate more than one expert in the system (or, to put this another way, the potential modularity of the expert system cannot be fully exploited). Thus, one significant advantage of several of the novel embodiments disclosed here is that use of more than one expert system within a single integrated system becomes much more advantageous.

~vDes of Process Control Svstems ~ '3~
It ~hould also be noted that the use of an expert system to design a new process (or to debug a newly introduced process~ has significantly different features from the problem of optimal:Ly controlling an existing process. While various ones of the novel ideas disclosed herein may have significant applications to such problems as well, the presently preferred embodiment is especially directed to the problem of optimally controlling an existing operating process, and the various novel ideas disclosed herein have particular advantages in this context.
A significant realization underlying several of the innovations disclosed in the present application is that the structure of expert systems for process control applications can advantageously be significantly - different from that of other expert system problems (such as consultative expert systems prsblems, in which a human is queried for infonmation). The Hardy et al.
and Erman et al. patents illustrate this difference.
Consultative exper~ systems seek to substantiate on~ of a number of possible causes by interactively guerying the user about the symptoms. Such systems must use complex knowledge representations and inference methods to minimize the number of user queries by carefully selecting the information they solicit. Moreover, since the user is not an expert, the system should be able to explain why it is requesting information.
In contrast, the real-time process problem is much simpler. The information needed by the expert is typically in the form of process measurements, which can be rapidly retrieved from process control and data systems without human intervention. There is much less need to minimize the requests ~or information. In fact, it may be f~ster to retrieve all the data that could be relevant to the problem than to determine what data is 75~1 relevant. Moreover, since the e~perts will run automatically, there is no need to explain the reasoning during the inference process. As long as the rulebase is not too large, the process control expert can operate effectively using a simple "forward chainingJ' (or data driven) infere~ce method. There is no need for the complex "backward chaining" procedures used in the consultative systems. Moreover, if a number of modular expert subprocedures are used wi~hin a single process, each expert tends to be smaller, and is more likely to work effectively in forward chaining mode. The presently preferred embodiment is especially directed to process control and monitoring, and the novel ideas disclosed herein have particular advantages in this context. However, various ones of the novel ideas may have significant applications to other problems as well.
It is believed to be a significant innovation to use expert system techniques to point to the direction of action in a multi-parameter control problem, as discussed above. One advantage is that the use of the expert permits more cases to be handled; for example, when one control parameter is up against its limits, the expert system can specify another parameter to be changed. The expert can also be especially advantageous in preventing a wrong action from being taken: in some types of processes it is conceivable that erroneous control strategies could potentially cause property damage or injuries, and the natural language inference rules of the expert (possibly combined with a more quantitative optimization scheme) can usefully ensure that this cannot happen. Thus, one advantage of various of the process control expert system embodiments disclosed in the present application i~ that they facilitatP reliable implementation of a control strategy which (primarily) prevents a clearly wrong action from ?5 J~S~;~
being taken, and (secondarilyj permits minimizing costs.
In particular, it i6 especially advantageous to use a knowledge based (functional) structure where the rules are constralned to be of the three types described ln the context of ~ process control application. Th~ retrieval rules permit the predominantly quantitative sensor data (and other input data) to be trzlnslated into a format which is suitable for expert system application, and the control rules provide a translation back from expert system reas~ning into an output which m~tches the constraints of the control problem.
The present invention is particularly advantageous in controlling processes which are substantially continuous, as distinguished from job shop processes.
That is, while some computer-integrated manufacturing systems focus primarily on iss~les of queuing, t~roughput, statistical sampling of workpieces for inspection, etc., su~stantially continuous processes (such as bulk chemical synthesis and/or refining processes) typically demand more attention to issues of controlling continuous flows.

~pert ~YStems Generallv The present application contains many teachings which solve specific problems and offer corresponding advantages in the sub-class of expert systems used for process control, or even the sub-sub-class of expert systems used for control of substantially continuous processes. However, the present application also discloses many novel features which could be adopted into many o~her types of expert systems, and/or into ~ny other types o control applications, while still retAining many (if not ~11) of the advantages obtained ln the context of the presently contempl~ted best mode~

Similarly, while the present application describes numerous novel features whish are particularly applicable to rule-based forward-chaining expert systems, some of the innovations described herein are believed to be very broadly novel, and could be adapted for use with other types of expert systems too.

Natural-Languaae Rule Statements One of the innovative teachings in the present application provides an expert system tool in which knowledge is entered into the knowledge base through a limited set of pre-deflned, highly constrained, natural-language knowledge structures which are presented as templates. In typical previous expert systems, knowledge is coded in the strict syntactical format of a rule or computer language, which allows great flexibility in knowledge representa~ion. The person entering the knowledge (hereafter referred to as the developer) must learn the syntax, must choose an appropriate knowledge representations, and must formulate syntactically correct input.
In contrast, by restricting the developer to constrained, pre-defined structures, the need to learn rule or language syntax and structure is eliminated.
Moreover, if the number of such pre-defined knowledge structures is small enough, the total knowledge representation in the expert system can be easily understood. Thus, a knowledge engineer is not needed.
The domain expert can enter the knowledge to build an expert system directly. The developer's input can then be translated automatically into an operational expert system. The developer need not be conc~rned with or aware of the specific language or system used to implement the expert.

1~7~

Another innovative teaching is that the knowledge entered into the pre-defined n~tural-language structures is stored in substa~tially natural-language ~orm. This permits the knowledge to be revised at any tine in the form in which it was originally entered: the developer simply recalls th~ stored template information, modifies it, and stores the modified knowledge. This is also simple enough to be done by the domain expert. The modified knowledge can then be automatically translated into a modified operational expert.
Another significant advantage of several of the disclosed novel embodiments for creating an expert system is that the expert can be significantly more compact and f~st2r in execution. This is achieved by integrating the expert system's rules with the code which performs the inference function. This allows many independent runnable expert systems to be crea~ed.
Moreover, the ease and simplicity of knowledge updating can still be preserved by maintaining the natural language form of the knowledge. The knowledge base can easily be reviewed and modified without hindrance from the specific inference method used in the runnable system.
Another novel feature of several of the disclosed embodiments is the use of a standardized data interface (as seen by the user) in the knowledge ~emplates, which facilitates the use in the knowledge base of data from a wide variety of systems. Expert systems are allowed to reguire data from process or laboratory measurements (both current and historical), or data collected from other sources ~such as on-line analyzers), or data and parameters from the process control systems. A standard interface to all such data sources facilitates use of the data in expert systems, since domain experts usually ~8 lack the programming expertise that would otherwise be needed to access these data ~ources~

~xDert Svstem Rule 'rv~eS
As mentioned above, previous expert systems tools normally use a rule or computer language which allows great flexibility in knowled~e xepresentation. One innovative teaching in the present application is the restriction of the knowledge structure within an expert system to rules of three highly constrained types. The three rule types are: 1) retrieval rules, which ea~h assign one o~ several descriptors to a name in accordance with the values of numeric inputs; 2) analysis rules, which each can assign a descriptor to a name in accordance with the descriptor/name assignments made by other rules; and 3) action rules, which either execute or don't execute a command in accordance with the descriptor/name assignments made ~y other rules.
Preferably only the retrieval rules include numeric operations. Preferably only the action rules can enabie execution of an external co~mand (~ of a command which does not merely affect the operation o~ the expert procedure~, Preferably each of the action rules requires only a logical test for the assiynment of a ~ descriptor to a name. Preferably none of the action rules can assign a descriptor to a name.
While ~his organization of an expert system's structure is especially advantageous in the context of a process control expert system, it can also be applied to other types of expert systems. In a process con~rol system, the relevant inputs will nor,~ally be process data, laboratory data, or control system parameters.
The relevant outputs will normally be executable procedures which affect the operation of control or supervisor systems, or co~munioate with operators or 7~5~8 domain experts, This teaching could also be applied to expert systems generally, in which o~h~r input and output functions are more important.
For example, in consultative use, retrie~al rules need not be confined to numeric inputs, but could accept the natural language ~escrip~or/name assignments 2S
input from the user. To better control the requests for input, such consultative retrieval rules could advantageously execute cont;ingent upon a test fsr the previous assignment of a descriptor to a name.
In general, this structuring of the inference rules provides for a more understandablP expert. The retrieval rules provide access to process and control system data, and translate from quantitative input data into a natural language form. The emulation of natural-language reasoning is concentrated as much as possible in the analysis rules, which capture Xnowledge in a form which might be used to communicate between domain experts. The action rules translate from the natural language inference process back to output procedures which are meaningful in the computer and control system being used.

Modular O~anization The organization preferably used for process control has substantial advantages. The top level procedure is a modular process supervisory controller.
The supervisor modules allow flexible specification of timing and coordination with other modules. Modules carry out commonly used control functions, using data specified throuqh a standard data interface, as well as calling user ustomized functions. User customized functions might generate messages, perform unusual control actions, or call expert system procedures.
Using the build-supervisor procedure, users can define 7.S~i~
or redefine msdules by editing highly cons~xained templates which include a ~andard data interface specification. The standardized data interface (as seen by the user) facilitates communications with an extremely wide variety of systems. Dynamic revision is achieved by storing the user input to the constrained templates as data in a storage area accessible to both the supervisor and build-supervisor procedures. The running supervisor examines the stored data to determine which functions have been specified for that module, and what data sources have been specified through the standard data interface. The supervisor then calls an approp iate modular function and passes the user-specified data.
This organization is especially advantageous in providing parallelism and branching in control strategies. That is, the modular organization of the presently preferred embodiment permits at least the following capabilities:
a) control strategies for more than one independent control application can be defined and updated;
b) control strategies for more than one lower level process control system can be defined and updated;
c) alternative control strategies can be defined and stored, so that an expert system (or other software or user command) can switch or select between control strategies merely by selecting or "de-selecting"
modules;
d) timing and coordination of module functions is facilitated;
e) multiple- independent expert system procedures can be utilized within a single supervisor;
f) more than one user can define control 7~58 strategies by açcess;ing different modules, 6imultaneously if d~si~ed.
Another innovatiYe teaching herein is that each supervisor module (or, less preferably, less than all of the module types) should preferably contain a pointer to optional user-customized functions. These funrtions can be used to generate informative messages about module actions, or a sophisticated user can implement unusual or non-standard control functions, or other customi2ation utilities (such as the build-expert procedure in the presently preferred embodiment) can be used to generate functions accessed in this manner.
This structure is "modular" in the sense that users can call up and modify the various blocks separately;
but, as will be discussed below, the command procedures which perform the standardized block functions are not necessarily separate within the source code. That is, modularity is advantageously achieved by storing the template-constrained user inputs to each block as data;
when the user wishes to modify the block, the data is translated back into corresponding fields in the template.
Preferably, one of the modular functions in the supervisor is statistical filtering. This is particularly useful in that statistical filtering can be introduced wherever it is advantageous, without requiring extensive custom programming by the users. As described above, statistical filtering is advantageous both for avoiding overreaction to insignificant changes, and also for aiding the understanding by plant operators by reducing the number of actions.
One of the novel teachings contained in the present application is that the use of statistical filtering helps to minimize the number of control parameter adjustments performed by the expert system, which in 5~

turn is very advantageous (as discuss~d below) in pr~viding an understandable log of control actions taken, Seuuencinq Modular Blocks One innovative teaching her~in is a system for process control having a modular supervisor procedure which includes novel module timing and sequencing methods. Users can preferably specify modules by editing highly constrained templates, which include several specifiers for methods to be used in controlling and coQrdinating module execution. Preferably the module timing options include: 1) execute module function at fixed time intervals; 2) execute module function when new data becomes available for a specified data source; 3) execute module function whenever another module executes; 4) execute module function only on programmatic request; and combinations of these.
Preferably a standardized data interface is used to specify the data source for the second of these options.

Inteqration of ~XDert Procedures The integration of expert systems into process control has been a challenging problem. Most previous attempts to use expert systems in process control have used LISP based expert systems running on a dedicated machine, often a symbolic processing machine. Usually only one expert system with a single large knowledge base is created for a process. since the knowledge base could contain many rules, a complex knowledge representation and inference process are needed to make inferences fast enough for real-time use. The expert system typically runs independently, scheduling its own activities, and thus is effectively the "top level"
procedure. Using a top level exper~ makes it more ~r~ ~J ~

difficult to accomm4date ~ore than one expert system.
(Another way to regard this area sf advantage is to note that, without the inventions contained in the present application, the potential modularity of the expert system cannot be fully exploited.) Several of the novel embodiments descri~ed herein achieve substantial advantages by using more than one expert system subprocedure within a single integrated system. Since expert decisions will normally focus on a specific task or area, the modularity of the problems can be exploited in the structure of the expert system.
Also, if the experts run under control of the supervisor, it is much easier to coordinate the decisions of the expert systems with the control actions of the supervisor. Since many important uses of expert systems will affect control actions, this is an important factor.
Another advantage of a modular structure, where expert systems are included as independent procedures called by the supervisor, is that the overall process control system i5 more reliable. A badly or incompletely functioning expert system within an overall supervisor system will affect only the functions it specifically interacts with. However, the failure of a top level expert system, which controls timing and execution of control functions, could disable all supervisor functions. The modular structure also has significant advantages in maintenance and debugging.
Thus, the organization preferably used for process control has substantial advantages. The ~op level procedure is a cycling procedure which functions as a process control supervisor. The supervisor process can call on one or more expert system procedures, and the user can call on a build-expert procedure which can reconfi~ure one of the expert systems already present, 7 ~ ~ 8 or create a new expert sys~em. The supervisor procedure can prefer bly also call on a historical data base.
The modular organizati~n described is especially advantageous, as discuss~ed above, in providing parallelism and branching in control strategies. This is especially advantageous in process control situations, since the appropriate strategies for different circumstances can be fully pre-defined by the user, and he can rapidly switch between pre-defined strategies s the need arises.

Historical Process Database The use of a historical database of process data n combination with a process supervisor pr~cedure and/or expert system procedure is particularly advantageous.
In the presently preferred embodiment, a historical database is used which can provide a time-stamp with each piece of output data, to clearly indicate provenance, and can retrieve the stored data (for a given parameter) which bears th~ time-stamp closest to a given time. The historical database can preferably maintain a record of continuously measured process data (such as temperature, pressure, flow rate), as well as discretely sampled, time-delayed measurements, such as laboratory measurements. The database greatly facilitates the use of laboratory (or other sampled type) measurements. Because of the time delay in making laboratory measurements, the value of the measurement when it becomes available in the database will correspond to the continuously measured data for the instant at which the measurement sample was actually taken, which might be several hours in the past. The historical database allows time delayed measurements and their corresponding continuous ~easurements to be used together. This is advantageous for balancing component 1~7r~

material flows in the process. In the presently preferred embodiment, the historical process database may be thought of as providing a way to l'buffer" tim~-stamped data and provide a standardized data interface, but it also permits other functions to be served.
The historical database also advantageously provides a basis for statlstical tests. Some statistical tests will require a number of past measurements, which can be retrieved from the database.
The database also advantageously allows the calculation of time average values of measurements. This can be useful in dampening noisy signals for use in a control action. In general, the database advantageously serves to buffer data input from a number of sources, standardizing access from the supervisor and expert procedures.
One of the innovative teachings in the present application is an integrated system for process control in which a process supervisor procedure (which is preferably the top-level procedure) is configured as a modular software structure, with modules which can be revised by a user at any time, without significantly interrupting the operation of the process supervisor.
The supervisor can define control parameters for many process control procedures, and can retrieve data from - many sources (preferably including a historical database of process data, which can provide time-stamped data).
The supervisor can also call on various expert subprocedures. Preferably the expert subprocedures can also be modified by an authorized user at any time, by calling up and editing a set of natural-language rule templates which correspond to the rules being executed by the expert subprocedure.
One of the innovative teachings in the present ; 35 application is an integrated system for process control :~L,~>'r~!7rj,' i !3 in which the user can customize the process gupervisor procedure with reference to a standardized data interface. The data values to be used by the supervisor are specified in the standard interface by two identifiers. The first identifies which (software) system and type of value is desired. The value of a setpoint in a particular distributed control system, the value of a sensor measurement in a particular process monitoring systPm, the value of a constraint from a process control or supervisor system, and time averages of sensor measurements from a particular historical database are examples of this. The second identifier specifies which one of that type of value is desired, for example the loop number in the distributed control system.
Data values specified through the standard interface may be used as measured values, manipulated values, or as switch status values indicating an on/off status. Preferably the interface allows the user to specify data in any of the relevant process control and data collection systems used for the process, or for related processes. Preferably, the interface also allows specification of data (both current and historical) in a historical process database. Since multiple control systems (or even multiple historical databases) may be relevant to the process, the standard interface greatly facilitates the use of relevant data from a wide variety of sources.

RIEF ~SCRIPTION OF TH~ PRAWING
The present invention will be descri~ed with reference to the accompanying drawings, wherein:
~igure 1 schematically shows the structure of hardware and procedures preferably used to embody the novel process control system with expert system capabil-ities provided by various of the innovative features contained in the present application.
Figure 2 is a schematic representation of the flow of information in the expert system structure preferably used.
Figure 3 shows the template used for a retrieval rule in the presently referred embodiment, together with a sample of a retrieval rule which has been entered into the template.
Figure 4 shows an example of a different kind of retrieval rule, known as a calculation rule.
Figure 5 shows ~n example of an analysis rule.
Figure S shows the presently prefesred embodiment of the template for action rules, and an example of one action rule which has been stated in this format.
Figure 7 ~hows an example of a chemical synthesis processing layout in which the method taught by the present invention has been successfully demonstrated.
2S Figure 8 schematically shows the structure preferably used for a supervisor procedure and a build-supervisor procedure.
Figure 9 shows a menu which, in the presently preferred e~bodi~ent, is presented to the user by the build-supervisor procedure to select a template to pro~ide user inputs to define or ~odify ~ block within the superYisor procedure.
Figures 10-13 show specific templates which, in the presently preferred e~bodiment, are presented to the user by the build-supervisor procedure to provide input to define or modify a feedbclck, feedforward, statistical filtering, or program block, respectively.
Figure 14 shows a block-editing utility menu presented to the user, ln the presently pref~rred embodiment, by the build-supervisor procedure~
Figure 15 shows a flow chart for the base cycle procedure used in the supervisor procedure in the presently preferred embodiment.
Figure 16 shows a menu which, in the presently preferred embodiment, is the top-level menu presented to the u er by the build-supervisor procedure, and Figure 17 shows a menu which is the top-level menu within the build-expert procedure.
Figure 18 is another schematic representation of the interrelations among the various procedures which permit user customization of functionality.

l.Xr~ 75S~
D~SCRIPTION OF THE P~FERRED EMBODIMENTS

~eneral Oraanl zation of Ha~dware and_Procedures Figure 1 schematically shows the structure sf hardware and procedures pre~erably used to embody the novel process contr31 system (with expert system capabilities) provided by various of the innovative features contained in the present application. An underlying process (for example a chemical process) is very schematically represented as a single pipe 160, on which sensors 156 and one actuator 158 are explicitly shown. Of course, real world examples are substantially more complex; Figure 7 shows the chemical process flow of a sample system in which the presPntly preferred embodiment has been successfully demonstrated. The lS various actuators 158 are controlled, in accordance with feedback signals rPceived from various sensors 156, by one or more controllers 154.
In the presently preferred embodiment, the controller 15~ is configured as a pneumatic proportional, integral, derivative (PID) controll~r.
However, a wide variety of other controller technologies and configurations could be used. Pneumatic controllers are used in this example because they are common in the chemical process industry, and match well with the feedback requirements of chemical process control.
Alternatively, an all-electronic distributed control sy~tem could be used instead. Moreover, the controller functionality could be different, e.a. a proportional/integral controller or a proportional controller could be used instead. In the presently preferred embodiment, the PID controller 154 is directly controlled by a computer control system 152. (This system 152 is referred to, in the various examples of user menus shown, as "PCS" (process control sys~em.3 The ~_r~ 75~3~3 computer controller system :L52 and the PID controller 154 may be regarded together as a single first level controller 150, and could easily be configured in that fashion (as with a distributed digital control system) to implement the present invention.
The control system 150 receives at least some of its parameters 132 ~e.a. setpoints or feedforward ratios) from a supervisor procedure 130, which is preferably a higher level of control software. (In many of the sample u~er menus and forms shown, the supervisor procedure 130 is referred to briefly as "ACS.") The supervisor not only receives inputs 157 indirectly (or directly~ from various sensors 156, it also receiYes lab measurement data 162, and also can issue calls to and receive inputs from the expert system 120, as will be described below.
In the presently preferred embodiment, the supervisor and build-supervisor procedures run on a minicomputer (e.a. a VAX 11/785), while the computer control system 152 is a PDP-ll.
The supervisor 130 is preferably also connected to a historical process data base 140, which directly or indirectly receives the inputs from the sensors 157 and the off-line lab measurements 162. Thus, when the 2S supervisor needs to access a value 157 or 162, it is not necessary for it to call on a physical device or read a real-time signal. It can simply call a stored value (together with a time stamp) from the database 140.
However, many of the advantages of the present invention could also be obtained without using the historical process data base 140.
In addition, the supervisor 130 preferably also embodies a statistical control system. Statistical control systems, as are well known in the art of chemical processes, are advantageous when the process characteristics and measurement characterlstics are subject to significant random variation, as they normally are in the chemical process industry.
Statistical filtering tests are preferably performed to filter out statistically normal variation, and ascertain whether a process has significantly deviated from its current goal or average. (Alternatively, the statistical filtering functions could be performed elsewhere in software, e. a . in the database software.) The supervisor procedure 130 is preferably run as a cycling process, and can call multiple expert systems 120 when indicated. (In many of the sample user menus and forms shown, the expert and build-expert procedures are referred to briefly as "PACE.") A sample realistic process context (in which numerous innovative features have been successfully demonstrated) will first be described. The operation of the historical process database will next be described, since that provides a standardized data interface to which many of the other functions connect. Next, the functioning of the build-supervisor procedure will be described in detail, since that provides many details of how the supervisor is configured in the presently preferred embodiment, and after that the organization of the supervisor procedure itself will be discussed in greater detail. In later sections, the structure of the expert systems preferably used will be described in detail, and the operation of the build-expert procedure which constructs the expert systems will also be described in detail.
Sam~le Process Context Figure 7 schematically shows a sample embodiment of a chemical process incorporating several novel features described in the present application. ~he system shown is one in which various novel aspects set ~orth in the . 4~

~,~,~!75'~8 present applicatio~ have b~en advantageously demonstrated.
It should be understoocl that the present invention provides a tool of very broad applicability, which can be used in many processes very different from that of Figure 7. Thus, for example, various of the claimc herein may refer to sensors which sense "conditions" in a process, or to actuators which change "conditions" in a process, without referenoe ts whether one sensor or many sensors is used, whether one or several parameters is ~ensed by respective ones of the sensors, whether the actuators ar~ valves, motors, or other kinds of devices, etc.
Figure 7 shows par~ of the distillation train of a process in which paraxylene is air oxidized to make terephthallic acid, which is then esterified with methanol and refined to dimethyl terephthallate (DMT).
DMT is sold as a bulk product, and commonly used as a polyester precursor. The esterification process will produce a significant fraction of the impurity methyl formyl benzoate (MFB). One of the key objectives in a DMT synthesis process is controlling the compositional fraction of MFB, since it affects the properties of products made from DMT. The refining train shown in Figure 7 will reduce the average MFB fraction to a fairly constant level~which is (in this example) about 22 ppm (by weight).
. The crude feed 707 will typically have a composition which is (by weight) about 74% DMT, about 20% orthoxylene (and related components which tend to recycle with the orthoxylene), about 5% methyl hydrogen terephthallate (MHT), and about 0.2% of methyl formyl benzoate (MFB). The MFB-depleted product 740 is preferably further refined to reduce the MHT fraction.

~ .~B

The crude feed 702 is fed into approximately the middle of a fir~t distillation column 710. The column 710 is heated at its base by a steam reboiler 712. The steam flow i5 contrslled by a flow controller 714 (which is connected to an actuator 716 and a sensor 718.) Similarly, the feed flow controller 704 is connected to an actuator 706, and a sensor 708. ~he column 710, as operated in the presently preferred embodiment, has internal pressures and temperatures which range from about 230 Torr at about 230- C at its bottom to about 55 Torr at about 70 C at its top. The vapor stream 720 is passed through a condenser 722, and some of the resulting condensate i fed back into the column as reflux 724. The product stream 726 has a mass flow rate of about 20~ of the crude feed 702, and is recycled. A
bottom product 728 is fed to the top of a second distillation column 730. The second distillation column has a steam reboiler 732 near its bottom (controlled by a steam flow controller 734, actuator 736, and sensor 738). The pressures and temperatures in the second column 730 (which in the user screens of the presently preferred embodiment is frequently referred to as the "MFB column") range from about 240- C at about 235 Torr at the bottom of the column to about 70 Torr and about 190- C at the top of the column. The bottom product 740 of the column 730 (which ~s a ~ass flow of about 0.8 of the crude ~eed 702) is the MF~-purified product. (In this product the fraction of MFB will on ~verage have been reduced to about 22 ppm, for the conditions given.) The top product 742 of the column 730 is passed through a condenser 744 and reintroduced into column 710 as a bottom feed. (Column 710 is referred to, in the specific example given below, as the "xylene column".) The mass flow in the loop 728/742 is quite large:

5~8 typically the mass flow of Elow 728 will be about three times the mass flow of the crude feed 702.
In addition, a third distillation column, in the presently preferred embodiment, is operated in parallel with a niddle section of column 710. This third column 750 is fed a side draw stream 752 from the first column 710. The vapor stream 75~ of column 750 is passed through a condenser, and part of the condensate is reintroduced to column 750 as a r~flux 758. Most of the remaining cond~nsate i5 reintroduced to first column 710 as an upper middle feed. Similarly, the liquid stream ?62 of third column 750 is partly reintroduced as a bottom feed after being vaporized in the reboiler 764, but is also partly fed back into column 710 as a lower middle feed 766. The additional separation provided by - the third column 750 enhances the net compositional segregation of MFB. The middle product 768 of the third column 7S0 is a low-flow-rate product flow (typically 0.003 timPs the mass flow of the'crude feed 7023, and this product flow removes most of the undesired MFB
impurity from the system. The temperatures and pressures in the third column 750 range from (in this example) about 230- C at about 260 Torr at the bottom of the column to about 60 Torr at about 125- C at the top of the column. Stream 761 is a small purge stream removing intermediate materials.
In the sample embodiment, the three primary control points for control of MFB composition are the steam feed to the MFB column reboiler 730, which is controlled by flow controller 734; the steam feed to the xylene column reboiler 710, which is controlled by flow controller 714; ~nd the feed of crude feed stock to the xylene column 710, which is controlled by flow controller 704.
Numerous other controllers, pumps, and other process equipment maintain the temperatures, pressures, and flow 7~8 rates at other points in the process. In accordance with principles well known in the art of chemical engineering, this serYes to maintain mass and energy balances and compositional trends consistent with the ultimate control objec~ive, which is to maintain a high and constant purity in the product stream 740.

Hist~rical Process Database In the presently preferred e~bodiment (as shown in Figure 1), the supervisor 130 receives data primarily through a historical process data base 140, which directly or indirectly receives the inputs from sensors 157 and off-line laboratory measurements 162. Thus, when the supervisor needs to access a value 157 or 162, it is not necessary for it to call on a physical device or 15 . read a real-time signal, since it can simply call a stored value (together with a time stamp) from the database 140.
In the preferred embodiment, every data value provided by the historical database has a timestamp attached. Data are received in at least two ways: first, some parameters are recPived as nearly continuous data flows (more precisely, as high-sampling-rate time series). For example, the data 157 from sensors 156 (e.q. temperature sensors) will be received as a series of digital values from analog-to-digital converters 155.
In the presently preferred embodiment, compression algorithms are used to reduce the storage requirements of this data, and permit a usefully long period of time to be represented without requirin~ impractical amounts of storage space. However, this operation (which includes both compression and decompression algorithms) is essentially invisible to the supervisor procedure 130.

75~
Secondly, lab analysis data 162 can also be stored in the historical database 140. For example, compositional measurements must normally be done off-line. A physical sample will be pulled from the physical process flow and sent to th~ laboratory for analysis.
The resulting lab analysis value is entered into the historical database, timest~mped with the time the sample was taken.
A third source of data is simulations: running ~
processes can be simulated, using any of a variety of currently available simulation methods, and predicted conditions oan be stored in the historical database (together with the proper timestamp). Thus, for example, control strategies can access data generated by complex real-time simulations.
Thus, many of the advantages of the database 140 derive from the fact that it can provide a timestamp to accompany every piece of data it provides. In addition, in the presently preferred embodiment, the database also stores the name and units for each parameter. As presently practiced, the database is also able to perform a variety of other functions, including monitoring, activating al~rms if certain sensed measurements reach certain critical levels, output processing ~i.e. loading data out to physical devices), generating plots of selected parameters over time, as well as other common database functions (e., generating reports) .
T~is structure is quite flexible: for example, in alternative embodiments, one supervisor procedure could interf~ce to multiple databases 140, and/or one database 140 could receive calls from more than one ~upervisor procedure 130 (which optionally could be running on different ~y5tem5 ~ .

1i~^~3 7S~8 , ~ lperv sor Procedures The present application describes ~ome very advantageous features of novelty in the supervisor procedure 130 and build-superYisor procedure 810, which could optionally and less preferably be incorporated in embodiments which did- not include at least some of the inno~ative features described in the context of th~
expert and build-expert systems 1~0 and 120.
The supervisor procedure 130 preferably used contains a modular software structure which greatly facilitates initial setup and also modlfication~
Preferably the super~isor procedure 130 is a cyclin~
procedure constructed as a set of blocks. That is, each block defines a core procedure which (as seen by the user, both initially and whenever called up for modification) is substantially self-contained, and which (in the presently preferred embodiment) is of one of four types. Preferably each block is either a feedforward block, a feedback block, a statistical filter block, or a program block. (That is, preferably each block is configured by user inputs to a template for one of these block types.) Preferably each kind of block also has the capability to call a user subroutine, and in fact the "program blocks" used in the presently preferred embodiment perform no other function.
The functional templates and data interface definitions for the most commonly used functions are pre-defined, but the user can also add code of his own if he wishes to do so. Providing standardized templates for the most commonly used functions expedites initial functional definition, and also facilitates maintenance, but sophisticated users are not prevented from writing their own customized functions (such as messaging).
Feedback blocks are used when a manipulated parameter must be adjusted to keep a measured parameter &
near a d~sired goal. Feedforward blocks are used when two parameters (which are not necessarily in a causal relation) are linked, i e. when a manipulated parameter must be adjusted tG keep it in some ratio (or other relation) to a meRsured para~eter. Statistical filterin~
blocks are used, in the presently preferred embodiment, to provide the advantages of statistical process control, and to facilitate minimizing the number of control parameter adjustment actions.
Preferably a maximum number of blocks is pre-defined. (In the presently preferred embodiment, 20a blocks is the preset maximum, and this number is large enough to se~ve the control needs of several different systems simultaneously.) The imposition of a maximum helps to maintain the software, by limiting the number of functions which can be crowded into any one software structure, and hy motivating users to delete obsolete block definitions.
Thus, a software structure like that described can be used to control several systems and/or used by several users. The provision of "ownership"
identification for each block, which may optionally be combined with access privilege restrictions, advantageously helps to preserve maintainability in multi-user environments.
Figure 8 shows the preferred organization of the supervisor procedure 130. The top level loop (shown as a base cycle controller procedure 802), which calls the various blocks 851, a52, 853, ..., sequentially, is preferably a cycling procedure. For example, the dormant time waiting bl~ck 891 might be set, in the dimethyl terephthalate synthesis application described, so that the base cycle procedure 802 is executed e~ery 15 minutes (and therefore the entire sequence of blocks 851 etc. is called for possible execution every 15 minutes~.

~.t'~ 58 The base cycle procedure al50 preferably performs some overhead functions. For example, the base cycle procedure 802 optionally contains the appropriate commands for branchlng on interrupts 804, and for initializatisn after a start command 806. Secondly, ~he base cycle procedure 802, upon calling each block, will preferably look at the header of the block (which is stored as data in shared memory, as discussed below), and usually also at some external information, such as the system clock value or the time stamp of a variable, to see if that block is due to execute. In the presently preferred embodiment, each block will also have status flags which indicate whether it may be executed, and will also have timing options which can be used by the user to specify, for example, that a particular block i5 to be executed only every 175 minutes.
The base cycle procedure 802 is not the only procedure which is relatively "high-level" with respect to the blocks 851, 852, etc. The build-supervisor procedure 810 is able to present the user with templates 812, and to (effectively) change the operation of the blocks 851, 852, etc., by changing shared memory values in accordance with the user's inputs to the templates 812.
That is, the real time control actions of the supervisor procedure blocks are supervised by the base cycle procedure 802. The base cycle procedure is responsible for determining when blocks are on/off, when blocks should be initialized, and when blocks should be executed. It also controls the timing of the base scan through all blocks.
In the presently preferred embodiment, each time the base cycle procedure executes a block, it checks the block type label (in shared memory) and calls the appropriate subroutine. That is, a single block of 7,~
~xecutable code is used for all of the feedback blocks, and similarly another block of c~de is used for all the feedforward blocks, etc~, so that all 200 blocks require only four subroutines for their standard functions. Each time the base cycl~ routine executes a feedback block, it calls up the user-defin~d parameter set for that particular ~lock, and passes those para~eters to the subroutine which performs feedback fun~tions in accordance with thos~ parameters.

Base Cycle Procedure Figure 15 shows a flow chart of the logic preferably used in the base cycle procedure 802. The sequence of actions used in the main control program, when it is first started (e.q. by submitting it to a job 15 . queue) is:
- Check to see if more than 30 minutes has passed since the last control cycle in the supervisor procedure. If so, initialize all blocks whose status is "On", "Active", or "Just turned on". ~Initialization sequence is given below).

Start the control cycle loop: (This loop is shown as 1510 ~n the flow chart of Figure 15.) - S e t t h e s y s t e m s t a t u s t o "Running-Computingn.
- Compute the next cycle ti~e by adding the base scan interval to the current time.
Start a loop through all blocks, ~tarting with block number 1 and counting up to the maximum number of blocks (This loop $s shown as 1520 in the ~low chart of Figure 15):
- Check block status:
* Get the switch status o~ the block. If the block is switching with an external switch 7~8 parameter, get its status. (The switch statu~ will be "On" if the external switch is on, or "Off" if the external switch is off.) If the loop i5 switched manually, the s~itch status is the same as the block's current status.
* If the switch status is "On", "Active", "Toggled On", or "Just turned on", the block is on.
* If the block is on, and the current block status is not "On" or "Just turned on", then th~
block is just being turned on. Set the Block Status ~o "Just turned on".
* If the block is on, and the current block status is "On" or "Just turned on", then the block is continuing to be on. Set the Block Status to "On".
* If the block is not on, it is off. Se' the block status to "Off".
- If the block status is lOff--, "Inactive", or "Failed", loop back up and start the next block.
- If the block status is "Just turned on", INITIALIZE the block (These steps are shown as 1524 in the flow chart of Figure 15):
* If the block has a measured variable, set the "Last measured time" equal to the current time of the measured variable.
, * If the block has a Key block, set the "Key block time" egual to the "Last execution time" of the key block.
* Set the "Last execution time" of the block to the current time.
* If the block is a feedforward block, set the "Old measured value" equal to the current value of the measured variable.
- If the block has a measured variable, get its current time.

~X~ a~

- If the block has ~ key block, get its last execution time.
- If the block timing option includes fixed interval, and if the elapsed time since the "last executiGn time" of the bloclc is greater than or equal to the execution time interval, set the execute flag for the block.
- If the block timing option includes keying off the measured variable, and if the curren time of the measured variable is more recent than the "last measured time" of the block, set the "last measured time" for the block equal to the current time of the measured variable, and set the execute flag for the block.
- If the block timing option includes keying off another block, and if the last exec~tion time of the key block is more recent than the "key block time", set the l'key block time" equal to the last execution time of the key block, and set the execute flag for the block.
- If the execute flag for the block is set, set the last execution time for the block equal to the current time, and execute the block. Only execute the block once, even if more than one timing option was satisfied. (The block execution procedures are discussed in greater detail below, and are shown generally as 1530 in the flow chart of Figure 15.) - If more blocks need to be processed, loop back to the next block.
This is the end of the loop 1520 through all the blocks.
- Set the system status to "Running-Sleeping".
- Set a wake up timer for the next cycle time computed above, and go to sleep until the timer expires, or until awakened by a request to terminate the program.

7~5~

- Wake up. Check to see if interrupted to terminate. If so, set the system status to 'tTerminated normally", and top comple ely.
- If not terminated, branch back to the start of the control cycle loop 1510.

SamDle Source Code The source code for the procedure which actually performs this function, in the presently preferred embodiment, is as follows. Due to the formattin~
requirements of patent applications, some portions o this and other portions of source code providçd herein contain statements which are wrapped across more thar.
one line ~and hence would need to be restored to single-line format, or appropriate leaders inserted, before being loaded for execution); but those skilled in the art will readily recognize these instances, and can readily correct them to produce formally perfect code.
Table 1 C************~**************~******
C

C Control.for C Main control program for the Advanced Control C System, C a high level optimization and control system C running on the Vax, using Vantage facilities.

C********~****~*********************
C Program Control Include 'ACSSincludes:Block parameters.inc/nolist' Include 'ACSSincludes:Van functions.inc/nolist' Include 'ACS$inc~udes:Sys functions.inc/nolist' Include 'ACSSincludes:Manlp Params.inc' Include 'ACS$includes:Meas params.inc' Include 'ACS$includes:Filter Params.in Include 'ACS~includes:ACSserv.inc' Include 'ACSSincludes:ACSstatus.inc' Integer*4 Block - -Integer*4 Intçger_Now Character*20 Character_now ~ 5~J~

Integer*4 Timbuf(2) Integer*4 Measured time stamp Integer*4 Key block exec time Logical*2 Execute block Logical Suceess Logical First Character*18 Debug time Logical Force initialization Parameter (Force initialization = .True.) Logical Dont force initialization Parameter (Dont force_initialization = .False. , Integer*2 Meas type Integer*2 Meas_var Integer*2 Filt type Integer*2 Filt var Integer~4 Event_flag state Integer*4 Timer flag Integer*4 Interrupt flag Character*9 Cluster name Parameter ( Cluster name = 'ACS_FLAGS' ) Integer*4 ~lag mask Logical Interrupt flag_set Interrupt flag set() = Btest(Event flag state,l) Timer flag = 64 Interrupt flag = 65 First = .True.
Flag mask = O
Flag mask = Ibset ( Flag mask , O ) Flag mask = Ibset ( Flag mask , l ) C...Record control program startup in the log file Van status = Vss5 from ascii time ( ' ' , Integer now ) Van status = Vss$ to ascii time ( Integer now , 1 Character now ) Write (6,~) ' Started the ACS control program at ', 1 Character now C

C...Create the event flag cluster , clear interrupt flag C

Sys status = SysSascefc ( %Val(Timer flag ) , 1 %descr(Cluster name) , O , ) Sys status = sys$clref ( %val(Interrupt flag )) C

C...Check to see if ~CS control has been down for more than C 30 minutes. If so, lnitialize all active blocks.
Van status = Vss5 from ascii time ( ' ' , Integer_noW !

~l r~ ~7 ~

If ( Integ r now - Intege!r next cycle .gt. 30*60 ) Then Do 10 Block = l,Max b].ocks If ( ( Block_status(Block)(1:2) .eq. 'On' ) .or.
1 ( Block_status(Block)(1:6) .eq. 'Active' ) .or.
1 ( Block status(Block)(1:14) .eq. 'Just turned on' j ) 1 Call Inltialize_block ( Block ) Csntinue End I~
C

C....The main block control loop 1 Continue C

C....Set system status ts Running C

System_status = 'Running-Computing C

C...Set Wake up time to ACS_base_scan minutes from now C

Van_status = Vss~_from ascii_time ( ' ' , Integer_now ) Van_status = Vss$_to_ascii_time ( Integer now , 1 Character_now ) Integer next_cycle = Integer now + ACS_base_scan*60 Call Vss5_get_systime ( Integer_next_cycle , Timbuf ) C
C....Loop through all the blocks C

Do 100 Block = l,Max_blocks C

C....Vpdate the block Status from the info coming from PCS
C

Call Check block status ( Block ) C
C...Check the block status, if inactive or off, skip it C

If ( ( Block status(Block)(1:8) .eq. 'Inactive' ) .or.
1 ( Block status(Block)(1:6) .eq. 'Failed' ) .or.
1 ( Block status-(Bleck)(1:10) .eq. 'On-holding') .or.
1 ( Block status(Block)(1:3) .eq. 'Off' ) ) The Go To 100 End if d If ( First ) d 1 writet6,*) ' ~lock: ',block,' 5tatus = ' 1 block_status(block) C... If the block has just been turned on, initialize it If ~Block status(Block)(1:14) .eq. 'Just turned on' ) Then Call Inltialize block( Block ) End if C

C....Check to see if it is time to execute the block c C...... Use appropriate calls for the block type C

If ( 1 ( Block_type ( Block )(1:8 ) .eq. 'Feedback' ) .sr.
1 ( Block type ( Block )(1.11) .eq. 'Feedforward' ) .or.
1 ( Block type ( Block )(1:7 ) .eq. 'Program' ) 1 ) Then ACS_status ~ ACS get meas var type ( Block , Meas_type ) If ( Meas_type .eq. Cur val van var ) Then ACS_status - ACS_get meas var num ( Blosk , Meas_var ) Van_status = Vss$g curtime ( ~eas_var , 1 Measured time_stamp ) Else Measured_time_stamp = o End If C

Else If ( 1 ( Block type ( Block )(1:8 ) .eq. 'Shewhart' ) 1 ) Then ACS status = ACS_get_filtered var type ( Block , Filt_type If ( Filt type .eq. Van var filter ) Then ACS status = ACS get filtered var_num ( Block , Filt_var Van status = Vss~g curtime ( Filt var , 1 Measured time_stamp ) Else Measured time stamp = 0 End If End If C

C...Get exec time of key block, if defined C

Rey block = Var num2(Block) If ( Key block .ne. Empty ) Then Key block exec time = Last_execution time ( Key block ) Else Key block exec time = 0 End If C

Execute block = .False.
d If ( First .eq. .True. ) Then d Van STATUS = vss$ to ascii time ( integer now , Debug_time ) d write(6,*) ' Block - ',block d write(6,*) 'Integer now = ',Debug time d Van STATUS = vssS to ascii time ( last execution time(block) d 1 , Debug time-~
d write(6,*) 'last execution time = ',debug time d Van STATUS = vss$ to ascii time ((~ Frequency(block)*60 d 1 , Debug time ) d write(6,*) 'Frequency(block) = ',Debug time d Van STATUS = vss$_to ascii time ( last_measured time(block) d 1 , Debug time ) ~"'~J~ t~i~8 d write(6,~) 'last measured time - ',Debug_time d Van STATUS = vssS to_ascii_time ( m~asured_time stamp d 1 , Debug_time ) d write(6,*) 'measured time s~amp = ',Debug tim~
d write(6,*) 'timing option = ', Var_num3(BLock) d End If C

I timing sption = Var_num3(alock) If ( ( I timing option .eq. Interval ) .and.
1 ( Integer now - Last execution _time(Block) .ge.
1 Frequency(Block)*60) ) Then 1 Last execution_time(Block) = Integer now Last measured time(Block) = Measured_time_stamp Execute_block = .True.
C

Else If ( I timing_option .eq.
1 Key_off_measured_variable ~Tnen If ( Measured_time stamp .gt.
1 Last measured_time(Block) ) Then Last_execution time~Block) = Integer now Last measured time(Block) = Measured_time_stamp Execute block = .True.
End If C
Else If ( I timing option .eq.
1 Rey off ACS block ) Then If ( Rey block exec time .gt.
1 Fix time(310ck) ) Then Last execution time(Block) = Integer now Last measured time(Block) = Measured time stamp Fix_time(block) - Key block exec time Execute block = .True.
End If C

Else If ( I timing option .eq.
1 Intrvl and key_off ACS block) Then If ( 1 ( Key_block exec time .gt.
1 Fix time(Block) ) .or.
1 ( Integer now - Last execution time(Block) .ge.
1 Frequency(Block)~60) 1 ) Then Last execution time(Block) = Integer now Last measured time(Block) = Measured time stamp Fix time(block) s Key block exec time Execute block z .True.
End I f C

Else If ( I timing option .eq.
1 Intrvl and key off meas var) Then X~ ( 1 ( ~easured time stamp .gt.

~ S5~

1 Last_measured time(Block) ) .or.
1 ~ Integer now - ~Ist_execution time(Block) .ge.
1 Erequency(Block~*60) 1 ) Then Last execution time(Block) = Integer now Last_measured time(Block) = Measured time stamp Fix time~block) = ~ey block exec time Execute_block G . Tnle .
End If C

Else If ( I_timing option .eq.
1 Xey off meas var and block) rhen If ( 1 ( Rey_block exec time .gt.
1 Fix time(Block~ ) .or.
1 ( Measured_time stamp .gt.
1 Last measured time(Block~ ) 1 ) Then Last execution_time(Block) = Integer now Last_measured time(Block) = Measured_time stamp Fix time(block) = Xey block exec time Execute block = .True.
End If C

Else If ( I timing_option .eq.
1 Intrvl and Key meas and block)Then If ( 1 ( Key block exec time .gt.
1 Fix time(Block) ) .or.
1 ( Measured time stamp .gt.
1 Last measured time(Block) ) .or.
1 ( Integer now - Last executisn timelBlock) .ge.
1 Frequency(Block)*60) 1 ) Then Last execution time(Block) = Integer now Last measured_time(Block) = Measured_time_stamp Fix time(block) = Key block exec time Execute block = .True.
End If End if C...If Time to execute, call the Subroutine for the appropriate block C ..
If ( Execute block .eq. .True. ) Then If ( Block type(Block)(l:ll) .eq. 'Feedforward' ) then Call Feedforward block(Block) Else If ( Block type(Block)(1:8 ) .eq. 'Feedback' ) then Call Feedback block(Block) Else if ( Block type(Block)(1:7 ) .eg. 'Program' ) then Call Program block ( Block) Else if ( Block type(Block)(1:8 ) .eq. '~hewhart' ) then Call Shewhart block( Block) *,5~>J~ 'iiX~3 End if End if C

C100 Continue C...All Blocks checked and executed if needed; go to sleep until ne~de C 102 ContinUe Sys status = Sys$setimr ( %val(Timer_flag) , %ref (Timbuf),, If (Sys status .eq. %loc(Ss$ normal) ) Then d Write(6,~) ~ Successfully set timer.' Else ~rite(6,*) ' Error return from setimr in Control at ', 1 Character now End If System_status = 'Running-Sleeping Sys status c Sys~wflor ( %val(Timer flag) , %val(Flag mask) If ( .not. Sys status ) Call LibSsignal~%val(Sys status)~
Sys status = sysSreadef ~ %val(Timer_flag ) , 1 Sref(Event flag state) c If ( .nnt. Sys status ) Call Lib$signal(Sval(Sys status)~
If ( ( Sys status .ne. %loc(Ss5 wasclr) ) .an~.
1 ( Sys status .ne. ~loc~Ss$ wasset) 3 ) Then Write(6,*) ' Problem reading event flag status' End If C.. Test the interrupt bit- if set, process the request If ( Interrupt flag set() ) Then d Write(6,*) 'got an interrupt' Call Shutdown ( Event flag state ) Else d WRite(6~*) 'Ti~er expired.' End If C
First ~ .False.
Go To 1 C

End Copyright (c) 1987 E.I. DuPont de Nemours & Co ., all rights reserved Build-SuDervisor Procedur~
The build-supervisor procedure 810 presents templates 812 to the user and stores the user responses to these templates in a "global section" portion of memory (1 e. a shared or commonly accessible portion of memory). That i5, the user inputs to thP templates for the various blocks 851, 852, etc., are stor~d where the base cycle procedure 802 can access them and the build-supervisor procedure 810 can also access them. Thus, an authorized user can ~t any time interactively call up data from shared memory space 814, see these parameters in the context of the templates 812, and modify the functions of the various blocks 852, 853, etc. and/or define new blocks (and/or delete existing blocks), while the base cycle procedure 802 continues to call the various blocks on the appropriate schedule. That is~ the base cycle procedure 802 is preferably a cycling procedure which satisfies the real-time process control demands of the underlying process, while the build-supervisor procedure 810 retains the capability for reconfiguring the operation of the various blocks in the supervisor, according to user input.
It should be noted that the structural features and advantages of the build-supervisor procedure are not entirely separate from those of the supervisor procedure. The two procedures are preferably operated separately, but they provide an advantageous combination. The features of the supervisor procedure are partly designed to advantageously facilitate use of the build-supervisor procedure, and the features of the build-supervisor procedure are partly designed to advantageously facilitate use of the supervisor procedure.
In the presently preferred embodiment, the nexus between the build-supervisor procedure and the ~297~;~;8 supervisor procedure is somewhat different from the nexus between the build-expert procedure and the operating expert procedures. The user entries made into the more constrained parts of the templates can be transferred fairly dire~tly to the operating supervisor procedure: the build-supervisor procedure stores values (corresponding to the data input by the user in the accessible fields of the templates~ in a shared section of memory, which is immediately accessible by the supervisor procedure as soon as the stored status value for the block is changed to "Active". 8y contrast, if the customized user routines (including the expert routines generated by the build-expert software) are modified, they must be compiled and linked with the supervisor procedure.
The build-supervisor procedure 810 prefera~ly also has the capability to stop or restart the base cycle procedure 802, independently of whether the build-supervisor procedure 810 has updated the shared memory 814 in accordance with user inputs to templates 812.

ToD-~evel Menu The user who begins an interaction with the build-supervisor procedure is first presented with a menu which (in the presently preferred embodimPnt) resembles that shown as Figure 16. This menu provides options which permit the user to setup (or modify) blocks, to monitor blocks, to call block-management utilities, to exit, or to go into a structured environment for writing user programs.
If the user chooses block setup, he next sees a menu like that shown in Figure 9. ~his menu is presented to the user by the build-supervisor procedure 810 to select a specific existing template 812' (i.e. a template with the previously defined data values of a particular bloc~ are hown in the appropriate fields of the template) or a blank template 812 of a given type to provide user inputs to define or modify a block ~51, 8 2, etc.
This form allows the user to choose which block to enter setup parameters for, and, if the block is a new one, allows a choice of which type block it will be. To go back to the previous form (in thi~ case the top-level menu), he can press the "-" key on the keypad.
To set up a new block, the user can either enter a block number which he knows is not in usP, or the build-supervisor procedure will provide him with the lowest number block which is not ln use. To enter a block number, the user can simply type the number in the block number field and press the return key. To get the build-supervisor procedure to find the lowest number unused block, the user can press keypad 8. The cursor will move to the block type field and the build-supervisor procedure will request that the user enter the number from the list for the type of block desirad. The build-supervisor procedure will then present the user with a block setup form for that block type. If the user mistakenly enters a block number which is already in use, the build-supervisor procedure will go directly to the setup form for that block, but the user can simply press keypad minus on the setup form to go back to the block setup selection form and try ayain. To enter or modify setup parameters for an existing block, the user can simply enter the block number and press the return key, and the build-supervisor procedure will present the block setup form for that block.
In the best ~ode as presently practiced, all four block setup forms have some common features. Keypad 9 will move the cursor from anywhere on the form up to the block number field. Keypad 8 will find the lowest number 12~5S~
available block and ~et it up as the same block type as the form howing on the screen. Keypad 7 tests all the parameters on the block and changes the blsck status to switch it on or off, or requests new data if the user has not yet supplied it~ (In addition, many of the parameters are checked for gross error as the user enters them.) The various block ~etup forms shown as Figures 10 through 13 will be individ~ally described below; but first, some features common to some or all of the block setup forms, and some features characteristic of the operation of the blocks thus defined, will be described.
When a block is turned on, the block status will not go directly to "On." (The full system of block status options (in this embodiment) is described below.) Depending on how the block is set up to be switched on and off, the status will change to "Toggled on" or "Active". The base cycle procedure will update the status as the block is executed, changing to "Just turned on" and then to "On". When turning a block off, the status will change to "Off" or "Inactive", again depending on how the block is set up to switch. These status sequencing rules facilitate use of initialization and/or shutdown steps in controlling block functionality.
Any time a parameter is entered or changed on a setup form, the block status will be set to "Inactive."
This means that the block parameters have not been checked to assure that everything needed has been entered and is consistent. If a parameter is changed on a block which is currently on, the block must be toggled from "Inactive" to "Active" or "Toggled On" using Reypad 7.

~129755~

~ata Sou~Q~_QzQQification The templates presented to the user for block customization include a standardized data interface. The data values to be used by ~he supervisor are specified in the standard interface by two identifiers. The first identifies which (software) system and type of value is desired. The value of a setpoint in a particular distributed control system, the value of a sensor measurement in a particular process monitoring system, the value of a constraint from a process control or supervisor system, and time averages of sensor measur~ments from a particular historical database are examples of this. The second id~ntifier specifies which one of that type of value is desired, for example the loop number in the distributed control syskem.
For example, in Figure 10 the user has entered "4"
in the highlighted area 1002 after the phrase "Measured Variable Type:". This particular identifier (i e. the value entered in this field by the user) indicates that the variable type here is a current value of a variable from the historical database, and the build-supervisor procedure adds an abbreviated indication of this ("Current Val Hist Dbase Var #") onto the user's screen as soon as the user has entered this value in the field 1002. (If the user entered a different code in the field, a different short legend might be shown. For example, as seen in Figure 10, the user has indicated a variable type of "2' after the phrase "Manipulated Var Type", indicating that the manipulated variable is to be a loop goal of the DMT control system.) As the second identifier, the user has indicated a value of "2990" in field 1004, to indicate (in this example) ~~
particular Database variable's current value is to be used. For this identi~ier too, the build-supervisor procedure adds an abbreviated indication of its ;58 interpretation of this identifier ("DM~ PRD MFB 5~WRT
DEYIAT") onto the user's screen as soon as the user has entered this value in the field 1004.
Data values specified through the standard interface may be used as meas~lred values, manipulated values, or as switch status values indicating an on/off status. Preferably the interface allows the user to specify data in any of the relevant process control and data collection systems used for the process, or for related processes. Preferably, the interface also allows specification of data (both current and historical) in a historical process database. Since multiple control systems (or even multipl~ historical databases) may be relevant to the process, the standard interface greatly facilitates the use of relevant data from a wide variety of sources.

Block Timinq Information In the presently preferred embodiment, all blocks except the Shewhart block provide the same block timing options. Block timing determines when a block will perform its control actions. The build-supervisor procedur provides three fundamental block timing options, which can be used in any combination, providing a total of 7 block timing options. The three fundamental options are:
Fixed Time Interval: the block will execute at a fixed time interval. The user specifies the time interval, e.~. in minutes. (Note that a combination of this option and the following has been speeified in the example of Figure 13, by the user's entry of ~" into field 1306.) Xey Off ~easured Variable: the block will execute every time a new value is entered into the process database for the measured variable. The measure~

i2~ B

variable must be a ~sampled~' type variable. (Note that this option has been specified in the example of Figure 10, by the user's entry of "2" into field 1006.) Key Off Another ACS Block: the block will execute every time a (specified) lower numbered block executes. The user specifies which block will be the key blocX. Any combination of one, two or three timing options can be used. Blocks using a combination timing option execute whenever any of the speci'ied timing options are satisfied. (Note that this option has been specified in the example of Figure 11, by the user's entry of "3" into field 1006.) Block timing options are represented on the setup forms by a number code. The user enters the number code corresponding to the desired timing option. If the timing option includes fixed interval timing, an execution time interval must also be specified. If the block is to key off another block, the key block number must be specified.
In future alternative embodiments, the block timing options set forth here may be especially advantageous in multi-processor embodiments: the separation of the control action specifications in multiple blocks shows the inherent parallelism of the problem, while the keying options in which one block keys off another show the block sequencing constraints which delimit the parallelism. The standardized data interface used in the presently preferred embodiment may also be advantageous in this context, by allowing block execution to be keyed off events external to the supervisorO

,Primarv_Block Switchin~
The supervisor procedure provides several ways to switch block actions on and off. If the block needs to be turned on and off by an operator, t~e build-supervisor procedure allows the user to specify an external switch system and a switchable entity within that system which the block on/off status is ~o follow.
For example, the user may specify a specific control system and a loop number within that system. The block will turn on when ~ha~ loop is on, and off when that loop is off. The standardized data interface allows any accessible control system to act as the switch system.
As a further alternative, the blocks can be set to switch on and off only under the control of the developer (i.e. under the control of the build-supervisor user~. In this case, the block can snly be switched using the toggle on/off function on the block setup form.
The external switch system is represented on the - block setup forms by a number. The user enters the number corresponding to the external switch system he wants to use. The entity within the switch system (e.q.
the loop number) is entered in the next field. (In the example of Figure 10, the user entries in fields 1008 and 1010 have specified an external switching variable.) If the block is to be turned on and off only from the build-supervisor procedure setup form, a zero is entered for the switch system number, and the word "Manual" will show in the field for the switch entity number. (This option has been selected in the example of Figure 13.) Secondary Block Switchin~
The supervisor also provides secondary means of controlling block execution. Blocks which have been turned "on" by their primary switch controls may be "~el~cted", "de-selected", or "held" by programmatic requests. ~he ~tatus of selected blocks changes to "On-selected". Selected blocks continue to function as if they were "On". The s'atus of blocks which are 12~t~558 deselected by programmatic request changes ~o "On-deselected". De-selected blocks take no control action. However, they differ from blocks which are "off" because they continue to maintain all their internal information so that they are always ready to execute if "selected". The status of blocks which are held by progra~matic request changes to "on- holding".
The programmatic request includes the length of time the block is stay on hold. Blocks which are holding act as if they were off. When the holding time expires, the status of holding blocks changes to "Just turned on, ~7 and they initialize.
One advantage of thPse block switching options is that they provide a way to embed alternative control strategies in the supervisor procedure. That is, control strategies can be readily changed merely by selecting some blocks in the supervisor procedure and/or deselecting other blocks. This is advantageous in terms of software documentation, since it means that alternative control strategies can be documented and maintained within the same software structure. It is also advantageous in interfacin~ to other procedur~s:
for example, the expert systems called by the presently preferred embodiment will frequently take action by selecting and/or deselecting blocks of the supervisor procedure.
These block control options facilitate the use of one supervisor procedure to interface to multiple controllers, and the use sf one supervisor procedure by different users to control different processes. The block status system permits one or more blocks to be updated without interfering with the running supervisor process; in fact, in optional environments, multiple users could be permitted to update different blocks at the same time.

~29~558 D~s~
All blooks allow the user to enter three descriptive ~ields. These fields are for user reference and can be searched when printing lists of block parameters. They have no effect on block actions~ The "control application name" field allows the user to group blocks that are part of the same control application by giving them all the same application name. (In the example of Figure 10, the user entry in field 1014 has pecified "MFB Control". Note that the examples of Figures ll, 12, and 13 show corresponding entries in this field.) The bloc~ description ~ield allows the user to describe the block' specific action or purpose. (In the example of Figure 13, the user entry in ~ield 1316 has explained that this is a "Block to run expert deciding where ~o take MFB feedback action" . ~ l~he ownership ~ield specifies which user has control of the block. (In the example of Figure 10, the user en~ry in field lOl~ has specified "Skeirik". Note that the examples of Figures 11, 1~, and 13 show corresponding entries in this field.) This field facilitates use of the organization described in environments where multiple users are defining bloc~s which run within the same supervisor procedure.
Of course, in multi-user environments it may be desirable to allow some users a greater degree of access than others. Thus, for example, some users may be authorized to edit a block, while others may be authorized to toggle the block on or of~ but not to edit it, and others may be authorized to monitor block operation but not authorized to change it. Similarly, access to expert systems may be constrained by giving greater au~horization to some users than to others; some users may be permitted to make calls to the expert ,, ~X9715S8 system but not to edit the ~lebase, and other users may not be permitted to do either. In the presently preferred embodiment, all Qf these choices can readily be implemented by using the file ownership and access control list options available in the VMS operatiny systems, but of course this functionality could be implemented in many other ways instead.

Action Loaaina The supervisor procedure provides a means of reporting control actions and/or logging them in a file for recall. Control action messages are written by a user routine. Cantrol blocks call user routines after their control actions are complete, and pass data regarding their actions. The action log file field allows the user to enter the name of the file to which logging messages will be written. The same log file can be used for more than one block (e.a. if the two blocks' actions are part of the same control application). (For example, note that field 1018 in the example of Figure 10 and field 1118 in the example of Figure 11 both specify "MFBCONTROL" as the action logging file.) The log file name is limited to letter and number characters, and no spaces are allowed (except after the end of the name ) .
Block Status Note that, in the example of Figure 10, a block status of "On-selected" is displayed in area 1020. This is not a field into which the user can directly enter data, bu~ it will change in response to user actions (e.a. the user can toggle the block on or off by hitting keypad 7). The block status codes used in the presently preferred embodiment reflect several aspects of block ~etup and execution, including:
Proper configuration of block parameters;

On/of f status of block;
Failure of block actions, and Failure of user routines.
Some common block status values are:
S "Inactive:" this indicates that the block has not been properly configured and toggled on, or that a parameter was changed. This is also the normal "off"
status of a block which has been configured to switch on and off with a switch system variable, if the user toggles it off from the setup form.
"On:" this is the normal status for blocks which are performing their control actions.
"Off:" this is the normal status, for a block which has been configured to switch on and off with a switch system variable, when that variable is in its off state. This is also the normal status for blocks which are configured to switch on and off through the setup form only and have been toggled off from the setup form.
"Active:" this is the status to which a block is toggled on if it is configured to switch on and off with a switch system variable. This status will change on the next cycle of the control program, to "On" or to another value, depending on the state of the switch system variable.
"Toggled on:" this is the status to which a block is toggled on if it is configured to switch on and off through the setup form only. This status will change on the next cycle of the control program.
NJust turned on:" this is a normal transition state for blocks going from an "off" status (eg: off, inactive) to "On" status. Blocks whose status is "Just turned on" will be initialized by the base cycle procedure, which resets the last execution time and the measured variable and key block times used for block ~2~7~i5~

timing. Feedforward blosks initialize ~he "old"
measured variable value to the current value.
"On-selected": indicates that a block which i5 on has been selected by a programmatic request. The S block continues to function as if it were On.
"On-deselected": indicates that a bloc~ which is on has been de-selected by a programmatic request.
The block takes no control actions, but continues to maintain its internal parameters as if it were On. This keeps the block ready to act if selected.
"On-holding": indicates that a block has been put on hold for a specified length of time by a programmatic request. The block takes no control action. A block that has been holding will re-initialize and go back to "On" status when the holding period expires.
"On-Failed usr routin:" this status indicates that a user routine called by this block had a fatal error which was bypassed by the supervisor procedure on the most recent execution of the block. Fatal errors in user routines are reported in the control program log file (not the same as action log files), and can be reviewed using the "List log file" option on the System Functions screen, described in the section on block monitoring.
"On-Recovrd usr Error:" this indicates that a fatal error was bypassed in the user routine, but that the user routine ran successfully on a later execution.
Again, the log file will give more details about what happened.
"On-Err ...... :" many abnormal status values can indicate that problems were encountered in block execution, e.a~ problems in the input or output of data to control systems. The latter part of the status field ~2:~8 gives some indication of the problem. Most such errors are als~ recorded in he control program log file.
Various other block status values can readily be inserted, along the ]ines demonstrated by these examples.

Feedback Blocks Figure 10 shows a sa~ple of a template 812 presen-ted to the user to define a feedback block. In the specific example shown, the block being worked on is block number three of the 200 available blocks 851, 352, etc., and the various data values shown in this Figure reflect the entries which have ~een made at some time to define this particular block.
The feedback block provides proportional feedback action. In feedback action, the user specifies a measured value (called the 'Imeasured variable") and a goal value (setpoint) t which he wants to maintain it.
Feedback action calculates the "error" in the measured variable (measured variable value - goal), and computes its action by multiplying the error times the "proportional gain". The current value of the "manipulated variable" is changed by the amount of the calculated action.
The basic fe~dback action can be altered by several additional parameters. A deadband around the goal can be specified. I~ the measured value falls within plus or minus the deadband of goal, no action is taken. The amount of action taken can be limited to a fixed amount.
The range over which the value of the manipulated variable can be changed can be limited to keep it within operable limits. Screening limits can be specified on the ~easured variable value, in which case measured values outside the screening limits will be ignored.

~75~;8 Block timin~ and switching and the block description fields follow the general outlines given above.
Specifying a feedback block on the block s~tup selection form (Figure 9) brings up a feedback block setup form, as shown in Figure 10.

Parameters The parameters which the user is asked to specify include:
Measured variable type: a number code lQ representing the software system and the type of entity which the block should use for the measured variable.
(A sample response might be a number code indicating a Historical database variable.) Measured variable number: the number of the entity within the specified system which the block will use for the measured variable. For example, if the measured variable type is a historical database variable, the measured variable number is the number of the variable in the historical database. After the measured variable type is entered, the label next to this field will show what type of data is needed. When the measured variable number is entered, other fields will also be filled in: the name and units for the measured variable, deadband and goal; units and default values for the max and min measured values. If block timing is to key off entry of new data into the measured variable, only discretely sampled variable types can be used.
Goal: the value at which the measured variable is to be "held". The value is entered in entered in the units of the measured variable.
Manipulated variable type: a number code representing the "target system" - the software package and the type of entity which the block should 1~9 manipulate. Ex~mples are: control system loop goal, historical da~abase variable, a setp~int in a distributed control system, or a setpoint for a programmable loop controller.
S Manipulated variable number: the number of the entity within the target system which the block will manipulate~ For example, if the manipulated variable type is a control system loop goal, the manipulated variable numb~r would be the number of the loop whose goal i5 to be changed. The label next to this field will show what type o~ information is needed; in this case the label would show "Cont Sys loop #".
Proportional gain: the constant relating the change in the manipulated variable to the error. The units of the gain ~re shown to the right of the field after the measured and manipulated variable have been specified. Control action is calculated:

Error - tHeasured variable value - goal value3 Manipulated delta = Error ~ ~Proportional gain]

The manipulated delta is added (subject to limits) to the current v~lue of the manipulated variable.
Deadband: A range around the goal value. If the value of the measured va~able 4all~ within a range defined by the goal plus or minus the deadband, no action is taken Timing option, execution time interval, and Key bloc~ number: these parameters are those dascribed above.
External ~witch system and switch number:
thQse para~eter~ are described above.
Maximum wan~p delta: the maximum change that 1~:9'7~

can be made in the manipula~ed variable's ~alue in sne control action.
Minimum and maximum valu~ of the manipulated variable: limit values outside which control action will S not move the value of t~e manipulated variable. If a computer control action would put the manipulated value outside the limits, the value i5 set equal to the limit.
If the manipulated value is moved outside the limits (by operator action, for example) the next control action will return the value to within the limits.
Minimum and maximum value of measured variable: 5creening limits for reasonable values of the measured variable. Any time the measured variable value falls outside these limits, the value will be ignored and no action is taken.
Action log file: this specifies the name of the log file for action logging.

Feedback Block ODeration The sequence of actions performed by each feedback block, when exe~-uted by the base cycle routine, is:
- If block status is "On-deselected", do no further actions;
- Get the current value of the measured variable (If not accessible, set status to "On-err...."
and do no further actions);
- Get the current time stamp of the measured variable;
- Test the value of the measured variable. If it is outside the minimum and maximum allowed values, set status to "On-msrd out of lims" and do no further actions.
- Get the current value of the manipulated variable. If no~ accessible, set status to "On-err ..... " and do no further actions.

- Compute the error (= Measured value - Goal).
If absolute value is less than the deadband, do no further actions.
- compute the c:hange in the manipulated variable:

Delta manip - Error * proportional Gain If the absolute delta is greater that the maximum allowed delta, set it equal to the maximum (maintaining proper sign).
- Compute the new value of the manipulated variable:

New manip value = Current manip value ~ delta manip If the value is outside the max/min limits, set it equal to the nearest limit. If limited, recompute the delta using the limit.
- Change the manipulated variable value to the new value computed. If not accessi~le, change status to "On-err ..." and do no further actions.
- Load user array values for use by the user routine.
- If delta manip is not zero, update the past action values and times.
- Call the user routine.

Data ~assed to the user routine In the presently preferred embodiment, each feedback block is able to pass information about its actions to the user routine, by using a commonly accessible memory block named "User vars~" (The use of this data by the user routines is described in more detail below.) The data passed by the feedback block may include:
"User integer(l)" - the time stamp of the measured variabl~ (from the datab2lsP);
"User integer(2)" - the time the action ~as taken;
"User real(l)" - the c!hange in the value of the manipulated variable;
"User real(2)" - the co~puted error; and "User character(l)" - a string (alphanumeric) sequence which describes the block type; for ~ee~back blocks this is set to be = 'Feedback'.

SamDle Source Code The source code for the procedure which actually performs this function, in the presently preferred embodiment, is as follows.
Table 2 C****~*******************~********
C

C Feedback block.for C ACS subroutine to do feedback action on the Vax, communicating C directly with the target system.
C

C****~*******************************
Subroutine Feedback block ( Block ) Include 'ACS$includes:Block parameters.inc/nolist' Include 'ACSSincludes:Van functions.inc/nolist' Include 'ACSSincludes:User vars.inc/nolist' Include 'ACSSincludes:ACSstatus.inc/nolist' Include 'ACSSincludes:ACSserv.inc' Include 'AcsSincludes:TIserv.inc' Include 'AcsSincludes:TIstatus.inc' Include 'ACSSincludes:Manip params.inc' Include 'AC5$includes:Meas arams.inc ~t7~;8 Integer*2 Meas var syst~m Integer*2 Meas _var_number Integer*2 Manip var system Integer~2 Manip_v~r_number Integer*4 Block Integer*4 Measured_time stamp Integer*4 Integer Now Character~20 now time Real*4 Measured_value Real*4 Current manipulated value Real*4 New_manipulated_value C...Special handling for 'On-deselected' status - do nothing C

If ( Bloc~ status(Block)(1:13) .eq. 'On-deselected') Then Return End If C

ACS_status - ACS_get meas_var_type ( Block , MEAS VAR_system ) Manip_var_system = Manipulated_variable(Block) Manip var number - New manipulated variable(Block) D Write(6,*) ' Calling new feedback - block = ',block C

C...Get the measured value C

Van_status = Vss$ from ascii time ( ' ' , Integer_now ) van status = VssS to ascii t1me( Integer now , now time ) C

C... Measured Value is TPA PCS loop goal If ( Meas_var_system .eq. PCS TPA_Loop_goal ) Then ACS_status = ACS get Pcs-goal( 'TPA
1 Measured_variable(Block) , Measured_value ) If ( ACS Status .ne. Sloc(ACS success) ) Then C... ..........If PCS goal value not available, don't execute Block status(Block) a I On-Err-PCS goal getl Write( 6, *) 'Feedback exit due to measured var not availa write(6,*)' ACS Block: ',block,' at: ',now time Return End If C

C............... Measured Value is DMT PCS loop goal Else If ( MEAS var system .eq. PCS DMT_loop goal ) Then ACS status = ACS get_pcs goal( 'DMT ' , 1 Measured variable(Block) , Measured_value ) If ( ACS Status .ne. %loc(ACS success) ) Then C......... If PCS goal value not available, don't execute Block ~tatus(Block) - 'On-Err-PCS goal get' Write( 6, *~ 'Feedback exit due to measur~d var not availa write~6,*)' ACS Block. ',block,' at: ',now time Return End If C

C...Measured Value is ACS block goal C

Else If ( MEAS var system .eq. ACS block goal ) Then ACS status = ACS get_goal 1 1 Measured variable(Block) , Measured_value ) If ( ACS Status .ne. ~loc(ACS succ~ss) ) Then C... ..........If ACS goal Value not available, don't execute Block status(Block) Y 'On-Err-ACS goal get' Write( 6, *) 'Feedback exit due to measured var ~.~i v~ila write(5,*3' ACS Block: ',block,' at: ',now time Return End If C... Measured Value is Vantage variable C

Else If ( Meas var system .eq. cur val Van var ) Then Van Status = VssSg current( Measured_variable(Block) , 1 Measured_value ) If ( Van Status .ne. ~loc(vss normal) ) Then C....... ....If Varlable Value not available, don't execute Block status(Block) = 'On-Failed Msrd var ' Write( 6, *) 'Feedback exit due to measured var not availa write(6,*)' ACS Block: ',block,' at: ',now time Return End If end if Van status = Vss$g curtime ( Measured variable(Block) , 1 Measured time stamp ) C

C....Check the Measured variable to see if it is within limits C

If ( (Measured value .lt. Measured min(block) ) .or.
1 (Measured value .gt. Measured max(block) ) ) Then C....... ....Reject the data point Write( 6, *) 'Feedback exit due to out of limts measured' write(6,~)' ACS Block: ',block,' at: ',now time Block status(Block) = 'On-Msrd out of lims ' Return End if C
C

C..;Get the current manipulated value C

C..... Target is TPA PCS loop goal If ( Manip _var system .eq PCS_TPA Loop ) Then ACS status - ACS get_pcs goal( 'TPA
1 Manlp Yar number , Current m~nipulated value , If ( ACS_Status .ne. %loc(ACS_success) ) Then C.. ~.. ..........If PCS goal value not available, don'~ execut2 Block status(Blsck) = 'On-Err-PCS goal get' Return End If C

C...Target is DMT PCS loop goal C

Else If ( Manip var system .eq. PCS_DMT_loop ) Then ACS status = ACS get pcs goal( 'DMT ' , 1 Manip var number , Current manipulated value If ( ACS Status .ne. ~loc(ACS_success) ) Then C....... ......If PCS goal value not available, don't execute Block_status(Block) = 'On-Err-PCS goal get' Return End If C

C... Target is ACS block goal -C
Else If ( Manip var system .eq. ACS block ) Then ACS status = ACS get goal ( Manip var number , 1 Current manipulated value ) If ( ACS Status .ne. %loc(ACS success) ) Then C... ..........If ACS goal Value not available, don't execute 31Ock status(Block) = 'On-Err-ACS goal get' Return End If C

C...Target is Vantage variable C

Else If ( Manip var system .eq.
1 Vantage variable ) Then Van Status = Geteuval ( Manip var number , 1 Current manipulated value ) If ( Van Status .ne. %loc(vss success) ) Then C....... ......If Variable Value not available, don't execute Block status(Block) = 'On-Err-Vant var get ' Return End I f C

C...Target is Texas Instruments PM550 controller setpoint in CRD
C

Else If ( ( Manip var system .ge. Low PM550 ) .and.
1 ( Manip var system .le. Hi PM550 ) ) Then If ( Manip var_system .eq. CRD_ESCHS PM550_01 ) Then ACS status - TI get loop setpoint ( 'TI_PM550 01 PORT' ~7~i8 1 Manip var number , Current:_manipulated value ) Else If ( Manip var_system .eq. CRD_ESCHS_PMS50 02 ) Then ACS status = TI_get loop cietpoint ( 'TI PM550 02 PORT' , 1 Manip var_number , Current manipulated value ) Else If ( Manip var system .eq. CRD ESC~S_PM550 03 ) Then ACS status - TI get loop setpoint ( 'TI PM550 03 PORT' , 1 Manip var_number , Current_manipulated_value ) El~e I~ ( Manip var system .eq. CRD_ESC~S PM550 04 ) Then ACS status = TI get loop setpoint ( 'TI PM550 04 PORT' , 1 Manip var number , Current_manipulated_value ) Else ~f ( Manip_var system .eq. CRD_ESCHS PM550 05 ) Then ACS_stat~s - TI_get_loop_setpoint ( 'TI PM550 05_PORT' , 1 Manip_var_number , Current_manipulated_value ~
Else If ( Manip_ Yar - system .eq. CRD_ESCHS_PM550_06) Then ACS_status = TI get_loop setpoint ~ 'TI_PM550_06_PORT' 1 Manip_var_number , Current manipulated_value ~
Else If ( Manip var_system .eq. CRD_ESC~S_PM550 07) Then ACS status = TI get loop_setpoint ( 'TI_PM550_07_PORT' 1 Manlp_var_number , Current_manipulated_value ) End If If ( ACS_Status .ne. %loc(TI_success) ) Then C....... ......If PM550 setpoint value not available, don't execute Block status(Block) = 'On-Err-TI setpnt get' Write( 6, *) 1 ' Feedback exit - TI PM550 Manlp var not gettable.' Write (6, *) ' ACS Block: ',block,' at: ',now_time Return End If Else ! Other Manip device type End If C

C...Value is within limits - Test to see if the error is less th deadband C

Error = Measured value - Goal(Block) If ( Abs(Error) .lt. Absolute_deadband(Block) ) Then d Write( 6, *) 'Feedback error less than dead~and' Return End If C

C..... Compute proportional Feedback Response-Test Delta to see if too C

Delta - Error * Proportional_gain(Block) If ( Abs(Delta) .gt. Max_manip_delta(Block) ) Then Delta = Sign(Max manip_delta(Block),Delta) End If C

C...Calculate new manipulated value, check to see it within limits C

New manipulated_value = Current_manipulated_value ~ Delta If ( New manipulated_~alue .gt. Manipulated max(Bloc]~

s~

New manipulated value - Manipulated max(BlocX) Else If ( New_manipulated value .lt. Manipulated min(Block) ) New manipulated value - Manipulated_min(Block) ~nd If Delta = New manipulated value - Current manipulated value C... Transmit the new Manipulated Yalue to the manip variable C

C...Target is TPA PCS loop goal C

If ( Manip var system .eq. PCS_T~A_Loop ) Then ACS status - ACS put pC5_ goal( 'TPA ' , 1 Manip var_number , New_manipulated_value j If ( ACS Status .ne. %loc(ACS_success) ) Then C... ..........If PCS goal value not available, don't execute Block status(Block) z 'On-Err-PCS goal put' Write( 6, i) 'Feedback exit due to failed manip var put.
Write(6,*)' ACS Block: ',block,' at: ',now_time Return End If 'C
C... Target is DMT PCS loop goal Else If ( Manip var system .eq. PCS_DMT loop ) Then ACS status = ACS put pcs goal( 'DMT ' , 1 Manip_var_number , New_manipulated value ) If ( ACS Status .ne. %loc(ACS_success) ) Then C... ..........If PCS goal value not available, don't execute Block_status(Block) = 'On-Err-PCS goal put' Write( 6, *) 'Feedback exit due to failed manip var put.
Write(6,*)' ACS Block: ',block,' at: ',now time Return End If C

C...Target is ACS block goal C

Else If ( Manip_var system .eq. ACS block ) Then ACS_status = ~CS put_goal ( Manip var number , 1 New manipulated value ) If ( ACS Status .ne. Sloc(ACS success) ) Then C....... ......If ACS goal Value not available, don't execute ~lock status(Block) = 'On-Err-ACS goal put' Write( 6, *) 'FeedbacX exit due to failed manip var put.
Write(6,*)' ACS Block: ',block,' at: ',now time Return End If C

C...Tarqet is Vantage variable C

~;29~

Else If ( Manip_var_system .ec~.
1 Vantage variable ) Then Van status = Puteugen ( Manip var number , 1 New manipulated value 3 If ( Van Status .ne. ~loc( ss success) j Then C....... ......If Variable Yalue not available, don't execute Block status(Block) = ~)n-Err-Vant var put ' Write( 6, ~) 'Feedback eXit due to failed manip var put.
Write(6,*)' ACS Bloc~: ',block,' at: ',now time Return nd If C

C...Target is Texas Instruments PM550 controller setpoint in C~D
C

Else If ( ( Manip var system .ge. Low PM550 ) .and.
1 ( Manip var system .le. Hi PM550 ) ) Then C

If ( Manip var system .eq. CRD ESCHS PM550_01 ) Then ACS status - TI ~ut loop setpoint ( 'TI PM550_01_PORT' , 1 Manip var_number , New manipulated value ~
Else If ( Manip var system .eq. CRD ESCHS PM550 02 ) Then ACS_status = TI put loop setpoint ( ITI PM5~0 02 PORT' , 1 Manip var number , New manipulated_value ) Else If ( Manip var system .eq. CRD ESC~S PM550 03 ) Then ACS status = TI put loop setpoint ( 'TI PM550 03 PO~T' , ~anip var number , New manipulat d value ) Else If ( Manip var system .eq. CRD ESCHS PM550 04 ) Then ACS status - TI put loop setpoint ( 'TI PM550 04 PORT' , 1 Man1p var number , New manipulated value ) Else If ( Manip var system .eq. CRD ESC~S PM550 05 ) Then ACS status = TI put loop setpoint ( 'TI PM550 05 PORT' , 1 Manip var number , New manipulated value ) Else If ( Manip var system .eq. CRD ESCHS PM550 06) Then ACS status = TI put loop setpoint ( 'TI PM550 06_PORT' , 1 Manip var number , New manipulated value ) Else If ( Manip var system .eq. CRD ESCHS PM550 07) Then ACS status - TI_put loop setpoint ( 'TI PM550 07 PORT' , 1 Manip var number , New manipulated value ) End If If ( ( ACS Status .ne. %loc(TI success) .and.
1 ( ACS status .ne. Sloc(TI clamped) ) Then C........... ....If PM550 setpoint value not accessible, dont execute Block status(Block) = 'On-Err-TI setpnt put' Write( 6, *) ' Feedback exit - TI PM550 Manip v puttable.' Write (6, *) ' ACS Block: ',block,' at: ',now time Return End If Else ! Other manip device types End If C
C.~..Load special arrays for user programs to log messages.

User integer(1) = Measured time_stamp User integer(2) z Integer now User real(l) = Delta User real(2) ~ Error User character(l) ~ 'Feeclback C

C...If Delta is non-zero, update past actions C

If ( Delta .ne. O ~ ~hen Do 90 J - 5,2,-1 Past action value(Block,J) = Past_action value(Block,J-l) Past_action time (Block,J) = Past_action_time (Block,J-1) Past action value(Block,l) = Delta Past action time (Block,l) = Integer now ~nd If C

C....Call ~ser subprograms for this block Call User Programs(Block) C...All done C

Return End Copyright (c) 1987 E.I.DuPont de Nemours & Co., all rights reserved 5~
Feedforward Block Figure 11 shows a sample of a template 812 presen-ted to the user ~y ~he build-supervisor procedure to.
deine a feedforward bl~ck. In the sp~cific exampl~ shown, the block being work~d on is block number six of the 200 available blocks ~51, ~52, etc., and the various data values shown in this Figure re~Elect ~he entries which have been made at some time to def ine this particular block.
lo The feedforward block provides proportional feedforward action. In fePdforward action, the user speci~ies a measured value (called the "measured variable") and a manipulated variable whose value is to be changed in proportion to (or, more generally, in accordance with) the change in value of the measured variable. Feedforward action begins when the "old measured value" is set equal to a current value (usually when the block is first turned on). The measured variable is then ~onitored for changes in value and the manipulated variable value is chanqed in proportion. The "old measured value" is then updated to the value at the time of ~is action. (The use of the "old measured v~lue~ in feedforward rules is one reason why an initialization ~tage is needed: if a feedforwar~ block were switched from inactive status directly to on status, it might indicate a very large change to the manipulated variable i~ the delta were calculated fro~
an out-of-date ~old measured value.n) In the pr~sently pre~erred embodiment, the ~asic feedforw~rd action can be altered by ~everal additional parameters. A deadband can be specified, so that, if the me~sured value changes by less than the deadband, no ~ction i~ taken. ~he ~mount.of action taken can be l~mited to a fixed amount. The range over which the 3~ value of khe ~anipul~ted variable can be changed can be s~
limited to keep i within operable limits. Screening limits can be specified on the measured variable value, so that measured values outside the screening limits are ignored. Block timing and switching options and the block description fields follow the general outlines given above.
In the presently preferred embodiment, specifying a feedforward block on the block setup selection form tFigure 9) brings up a feedforward block setup form like that shown in Figure 11.

Parameters The parameters are:
Measured variable type: a number code representing the software system and the type of entity which the block should use for the measured variableO
Measured variable number: the number of the entity within the specified system which the block will use for the measured variable. For example, if the measured variable type is a historical database variable, the measured variable number is the number of the variable in the historical database. After the measured variable type is entered, the label next to this field will show what type of data is needed. When the measured variable number is entered, other fields will also be filled in: the name and units for the measured variable, deadband; units and default values for the max and min measured values. If block timing to key off entry of new data into the measured variable, only discretely sampled variable types can be used.
Goal: the goal field cannot be used for feedforward blocks.
Manipulated variable type: a number code representing the software package and the type of entity 755~

which ~he block should manipulate. Examples are: control system loop goal, historical database variable.
Manipulated variable number: the number of the entity within the specified system which the block will manipulate. For example, if the manipulated variable type is a control syst~m loop goal, the manipulated variable numher would be the number of the loop whose goal is to be changed. The label next to this field will show what type of information is needed; in this case the label would show "Cont Sys loop ~".
Proportional gain: the constant relating the change in the manipulated variable's value to the change in the measured variable's value. The units of the gain are shown to the right of the field after the measured and manipulated variable have been specified. Control action is calculated as:

Measured delta s [Measured variable value - Old value]

Manipulated delta = Measured delta ~ [Proportional gain]

The manipulated delta is added (subject to limits) to the current value of the manipulated variable.
Deadband: A range around the "
old measured value" (i.e. the measured value at the time of the last block action). If the value of the measured variable is within plus or minus the deadband of the old measured value, no action -is taken and the old measured value is not changed.
Tining option, execution time interval, and Xey block number: these parameters are described above.
Switch system and switch number: these are described above.

;8 Maximum output delta: the maximum change that can be made in the manipulated variable's value in one control action.
Minimum and maximum value of the manipulated variable: limit values outside which control action will not move the value of the manipulated variable. If ~
computer control action would put the manipulated value outside the limits, thP value is set equal to the limit.
If the manipulated value is moved outside the li~its (by operator action, for example) the next control action will return the value to within the limits.
Minimum and maximum value of measurea variable: These define screening limits for rPasonable values of the measured variable. Whenever the measured variable value falls outside these limits, the value will be ignored and no action is taken.
Action log file: this field is described above.
The use of a deadband in feedforward blocks is one of the features which tend to force process control into discrete steps, rather than continuous small changes.
One advantage of this novel teaching is that full logging can be used: every single change made by the supervisor procedure can be logged, without generating an excessive number of messages. This in turn means that monitoring, diagnosis, and analysis of processes (and of process control systems) becomes much easier.

Block Operation The sequence of actions performed by a feedforward block is:
- Get the current value of the measured variable (If not accessible, set status to "On-err..."
¦ and do no further actions~;

ss~

- Test the value of the measured variable. If it falls outside the ~llowed range of values, set status to "On-msrd out of lims" and do no further actions.
- Compute the change in the value of the measured variable:
D~lta measured = Measured value -- Old measured value.
If the absolute value of the change is less than the deadband, d~ no further actions.
- Compute the change in the manipulated variable:
Delta_manip = Delta measured * Proportional gain.
- Set "old measured value" equal to the current value of the measured variable.
- If block status is "On-deselected", do no further actions;
- Check the magnitude of the manipulated value delta. If greater than the maximum allowed delta, set magnitude equal to the maximum.
- Get the current value of the manipulated variable. If not accessible, set status to "On-err ..... " and do no further actions.
- Compute the new value of the manipulated variable:
New ~anip value = Current manip value + delta manip.
If the value is outside the max/min limits, set it equal to the nearest limit. If limited, recompute the delta using the limit.
- Change the manipulated variable value to the new value computed. If not accessible, change status to "On-err .. ." and do no further actions.
- Load user array values for use by the user routine.
- If delta manip is not zero, update the past action values and times.
- Call the user routine.

~'975~ii8 E~ta passed to th~_ user routine The feedforward block passe~s information about i~s actions to ~he user rou~ine through the User vars common block. The use of this data is described in more detail in the chapter covering User routines. In the presently preferred embodiment, the data passed by the feedforward block includes:
User integer(1) - the time stamp of the measured vari~ble;
User integer(2) - the time the action was taken;
User_real(l) - the change in the value of .he manip variable;
User real(2) - the change in the value of the measured variable from the last time the "old measured value" was updated;
User character(l) - = 'Feedforward'.

Sam~le Source Code The source code for the procedure which actually performs this function, in the presently preferred embodiment, is as follows.
Table 3 C*************~*~********************
C

C FEEDFORWARD block.FOR
C
C Subroutine to do feedforward calculations on the Vax, C communicating directly with the target system.
C
C**~***~*********************.********
Subroutine Feedforward block ( Block ) Include 'ACS$includes:310ck ~arameters.inc/nolist' ~7SS~3 Include 'ACSSincludes:Van functions.inc/nolist' lnclude 'ACS~includes:User vars.inc/nolist' Include 'ACSSincludes:ACSstatu-;.inc/nolist' Include 'ACS~includes:ACSserv.inc' Include 'AcsSincludes:TIserv.inc' Include 'Acs$includes:TIstatus~inc' Include 'ACS~includes:Manip Darams.inc' Include 'ACS$includes:Meas params.inc' C

Integer~2 Manip var type Integer~2 Manip var num Integer*2 Meas_ var type - Integer~2 Meas var num Integer*4 Block Real*4 Measured value ~2al*4 Current manipulated value Real*4 New manipulated value Integer~4 Integer Now Character*20 Character now Integer*4 Measured time stamp Van status = Vss~ from ascii_time ( ' ' , Integer now ) Van status = Vss$_to ascii_time( Integer now , Character now ) C
C...Get the measured value ACS status = ACS get meas var type ( Block , Meas var type ) ACS status = ACS get meas var num ( BlocX , ~eas var num Measured time stamp = O
C

C...Measured Value is TPA PCS loop goal C

If ( Meas var type .eq. PCS TPA Loop goal ) Then ACS status - ACS get ~cs goal( 'TPA
1 Meas var num , Measured value ) If ( ACS Status .ne. %loc(ACS success) ) Then C....... ......If PCS g~al value not available, don't execute Block status(Block) = 'On-Err-PCS goal get' Write( 6, *) 'Feedback exit due to measured var not availa write(6,*)' ACS Block: ',block,' at: ',Character_now Return End If C

C...Measured Value is DMT PCS loop goal C

Else If ( Meas var_type .eq. PCS DMT loop goal ) Then ACS_status = ACS get pcs goal( 'DMT ' , 1 Meas var num , Measured value ) If ( ACS Status .ne. %loc(ACS success) ) Then C..... ~.. ......If PCS goal value not available, don't execute 310ck status(~locX) = 'On-Err-PCS goal get' ~rite( 6, *) 'Feedback exit due to measured var (lOt ava~le lX~75S~

write(6,~)' ACS 810ck: ',block,' ~t: ',Character_now Return End If C

C...Measured Value is ACS block goal C

Elæe If ( Meas vax_type .eq. ACS block yoal ) Then ACS_status = ACS get goal ( 1 Meas var num , Measured value ~
If ( ACS Status .ne. %loc(AOS success) ) Then C....... ......If ACS goal Value not available, don't execu~e Block_status(Block) = 'On-~rr-ACS goal get' Write( 6, *) 'Feedbaok exit due to measured var not avai wrlte(6,*)' ACS Block: ',bloc~,' at: ',Character now Return End I f C

C...Measured Value is Vantage variable C

Else If ( Meas var type .eq. cur val Van var ) Then Van_Status ~ VssSg current( Meas var num , 1 Measured value ) If ( Van Status ne. %loc(vss normal) ) Then C....... ....If Variable Vaiue not available, don't execute Block status(Block) = 'On-Failed Msrd var ' Write( 6, *) 'Feedback exit due to measured var not availa write(6,*~' ACS Block: ',block,' at: ',Character now Return End If Yan status 5 Vss$g_curtime ( Meas var num , 1 Measured time_stamp ) End If C....Check the Measured variable to see if it is within limits C

If ( (Measured value .lt. Measured_min(block) ) .or.
1 (Measured value .gt. Measured_max(block) ) ) Then C..... Reject the data point Return End if C

C...Test to see if the change in the measured value is less th deadband C
D~lta_meas - Measured value - Old measured value(Block) If ( Abs( Delta meas ) .lt.
1 Absolute deadband(810ck) ~ Then Return End If C

~9i7S58 C...Special action for 'On-deselectecl' ctatus ~ update old meas valu exit.
C

Old measured_value(Block) = Measured value If ( Block_status(Block)(1:13) .eq. 'On-deselected' ~ Then Return End If C

C...Value is within limits - Compute Eeedforward Response C

Delta manip - Delta_meas * Proportional gain(Block) C

C...Test Delta manip to see if too sreat C

If ( Abs(Delta_manip) .gt. Max manip delta(Block) ) ~hen Delta manip = Sign(Max manlp delta(Block),Delta_manip) End If C

C...Get the current manipulated value C

ACS status = ACS_get_manip_var_sys ( Block , Manip_var_type ) ACS_status = ACS get_manip_var_num ( Block , ~anip_var num C

C...Target is TPA PCS loop goal C

I f ( Manip var type .eq. PCS TPA Loop ) Then ACS status = ACS get pcs goal( 'TPA
l Manip var num , Current manipulated_value , ) If ( ACS_Status .ne. Sloc(ACS success) ) Then C....... ......If PCS goal value not available, don't execute Block status(Block) = 'On-Err-PCS goal get' Return End If C

C...Target i5 DMT PCS loop goal C

Else If ( Manip var type .eq. PCS DMT_loop ) Then ACS status = ACS get pcs goal( 'DMT ' , 1 Manip var_num , Current_manipulated_value ) If ( ACS Status .ne. %loc(ACS_success) ) Then C....... ....~.If PCS goal value not available, don't execute Block status(Block) = 'On-Err-PCS goal get' Return End I f C

C................... Target is ACS block goal Else If ( Manip_var_type .eq. ACS_block ) Then ACS status = ACS_get_goal ( Manip_var_num , 1 Current manipulated_value ) If ( ACS Status .ne. %loc(ACS_success) ) Then C........ If ACS goal Value not available, don't execute ~X97~58 Block status(Block) 3 'On-Err-ACS goal get' Return End If C

C...Target is Vantage variable C

Else I~ ( Manip_var type .eq.
1 Vantage variable ) rhen Van Status = Geteuval ( Manip var_num , 1 Current manipulated value ) If ( Van Status .ne. %loc(vss SUCC2SS) ) Then C... ..........If Variable Value not a~ailable, don't execute Block status~Block) = 'On-Err-Vant var get ' Return End If C... Target is Texas Instruments PM550 controller setpoint in ~P~D
C

Else If ( ( Manip var type .ge. Low PM550 ) .and.
1 ( Manip_var_type .le. Hi PM550 ) ) Then If ( Manip_var_type .eq. CRD ESCHS PM550 01 ) Then ACS status - TI_get_loop setpoint ( 'TI_PM550_0I_POR~' , 1 Manip var num , Current manipulated_value ) Else If ~ Manip var type .eq. CRD ESCHS PM550 02 ) Then ACS status = TI get_loop_setpoint ( 'TI_P~550_02_PORT' , 1 Manip var num , Current manipulated value ~
Else If ( Manip var type .eg. QD ESC~S PM550_03 ) Then ACS status = TI_get loop setpoint ( 'TI PM550_03_PORT' , 1 Manip var num , Current manipulated_value ) Else I~ ( Manip var type .eq. CRD ESC~S PM550 04 ) Then ACS status = TI get loop setpoint ( 'TI PM5S0_04 PORT' , 1 Manlp_var num , Current manipulated value ) Else If ( Manip var_type .eq. CRD ESC~S PM550 05 ) Then ACS status = TI get loop setpoint ( 'TI PM550 05 PORT' , 1 Manip var num , Current manipulated value ) Else If ( Manip var type .eq. CRD ESCHS PMS50 06) Then ACS status = TI get loop setpolnt ~ 'TI PM550 06_PORT' , 1 Manlp var_num , Current manipulated_value ) Else If ( Manip var type .eq. CRD ESCHS PM550 07) Then ACS status -- TI get loop setpolnt ( 'TI PM550_07 PORT' , 1 Manlp_var num , Current manipulated_value ) End If If ( ACS_Status .ne. ~loc(TI success) ) Then C......... ....If PM550 setpoint value not available, don't execute Block status(Block) = 'On-Err-TI setpnt get' Write( 6, *) 1 ' Feedforward exit - TI PM550 Manip var not accessible Write (6, *) ' ACS Block: ',block,' at: ',now time Return End If Else ! Other Manip device type ~7~5~

End If C

C...Calculate new manipula~ed value, check to see it within limits C

New manipulated value = Current Manipulated value + Delta_mani C

If ( New manipulated_value .gt:. Manipulated_max(BlocX) ) Then New manipulated value = Manipulated max(Block) Else If ( New_manipulated_value .lt. Manipulated min(Block) New manipulated_value = Marsipulated_min(Block) End If Delta manip = New manipulat2d_value - Current Manipulated valu C... Transmit the New Manipulated Value to the manipulated variable C

C...Target is TPA PCS loop goal C

If ( Manip var type .eq. PCS TPA_Loop ) Then ACS status = ACS_put DCS goal( 'TPA ' , 1 Manip var num , New_manipulated_value ) If ( ACS Status .ne. %loc(ACS success) ) Then C....... ......If PCS goal value not available, don't execute Block_status(Block) = 'On-Err-PCS goal put' Write( 6, *) 'Feedback exit due to failed manip var put.
~rite(6,*)' ACS Block: ',block,' at: ',now_time Return End If C .. , C...Targe. is DMT PCS loop goal C

Else If ( Manip var_type .eq. PCS_DMT_loop ) Then ACS_status -- ACS put pcs goal( 'DMT ' , Manip var num , New manipulated value ) If ( ACS Status .ne. %loc(ACS_success) ) Then C.~........... If PCS goal value not available, don't execute Block status(Block) = 'On-Err-PCS goal put' Write( 6, *) 'Feedback exit due to failed manip var put.
Write(6,*)' ACS Block: ',block,' at: ',now_time Return End If C

C...Target is ACS block goal C

Else If ( Manip_var_type .eq. ACS_block ~ Then ACS status = ACS put goal ( Manip var_num , 1 New manipulated_value ~
If ( ACS_Status .ne. %loc(ACS_success) ) Then C....... ......If ACS goal Value not available, don't execute 810ck_status(Block) = 'On-Err-ACS goal put' Write( 6, *) 'Feedback exit due to failed manip var put.

755~

Write(6,*)' ACS Block: ',block,' at: ',now ~ime Return End If C

C...Target is Vantaye variable C

Else If ( Manip var type .eq.
1 Vantage variable ) Then Van_status = Puteugen ( Manip var num , 1 New_manipulated_value ) If ( Van Status .ne. %loc(vss_success) ) Then C....... ......If' Variable Value not available, don't execute BlocX_status(Block) = 'On-Err-Vant var put ' Wxite( 6, *) 'Feedback exit due to failed manip va- ?ut.
Write(6,*)' ACS Block: ',block,' at: ',now time Return End I f C

C...Target is Texas Instruments PM550 controller setpoint in C~3 C

Else If ( ( Manip var type .ge. Low_PM550 ) .and.
1 ( Manip var_type .le. Hi PM550 ) ) Then If ( Manip var type .eq. CRD ESCHS_PM550 01 ) Then ACS status = TI put_loop_setpoint ( 'TI PM550 01_PORT' , 1 Manip_var num , New manipulated value ) Else I~ ( Manip var type .eq. CRD ESCHS PM550 02 ) Then ACS_status = TI Put-loop setpoint ( 'TI_PM550 02 PORT' , 1 Manip var_num , New_manipulated_value ) Else If ( Manip_var_type .eq. CRD_ESCHS PM550 03 ) Then ACS status = TI put loop_setpoint ( 'TI_PM550 03_PORT' , 1 Manip var_num , New_manipulated value ) Else If ( Manip_var_type .eq. CRD ESC~S_PM550_04 ) Then ACS_status = TI put_loop_setpolnt ( ITI_PM550_04_PORT' , 1 Manip var num , New manipulated value ) Else If ~ Manip_var type .eq. CRD ESCHS PM550 05 ) Then ACS_status = TI PUt loop setpoint ( ITI PM550 05 PORT' , 1 Manip var_num , New manipulated value ) Else 1~ anip var type .e~. CRD ESC~S PM550 06) Then ACS_status = TI put loop setpoint ( 'TI PMS50_06 PORT' , 1 Manip_var num , New manipulated value ) Else If ( Manip_var_type .eq. CRD_ESCHS_PM550 07~ Then ACS status = TI put loop setpoint ( 'TI PM550_07_PORT' , 1 Manip var num , New manipulated_value ) End If If ( ACS Status .ne. ~loc(TI_success) ) Then C......... ....If PM550 setpoint value not available, donlt execute Block status(Block) = IOn-Err-TI setpnt put Wri~e~ 6, *~
1 ' Feedforward exit - TI PM550 Manip var not pu~table.' Write (6, ~) ' ACS Block: I,block,' at: I,now time Return lX~5~3 End If Else I Other Manip device type End If C....Load special ~rrays for user programs to log messages.
User ~nteger(1) = Measured time stamp User integer(2) = Integer_now User real(l) - Delta manip User real(~) = Delta meas User_charac~er51) = '~eedforward C

C...If Delta is non-zero, update past actions C

If ( Delta manip .ne. O ) Then Do 90 J ~ 5,2,-1 Past aCtion value(Block,J) = Past action value(Block,J-l) Past action time (Block,J) = Past_action_time ~Block,J-l~
Past action value(Block,1) = Delta manip Past action time (Block,ll = Integer now End If C

.C....Call User subprograms for this block C

Call User Programs(Block) Return End Copyright (c) 1987 E.I. DuPont de Nemours & Co.
all rights reserved lX97~

Figure 12 sh~ws a sample of a template 812 presen-ted to the user by the build-super~isor procedure to define a statistical filteriny block. In the specific example shown, the block being worked on is block number one of the 200 available blocks ~51, 8S2, etc~, and the various data values sho~n in this Figure reflect the entries which have been made at some time to define this particular block.
The Shewhart ~lock provides statistical filtering of a sampled me~surement using Shewhart tests. ~he user specifies an aim value (field 1222 in Figure 12) and a standard deviation (sigma) (field 1224 in Figure 12) which characterizes the normal variability in the measuxement. The Shewhart tests a series of rules to determine whether the sequence of measurements are statistically the same as ("on aimn) or different from ("off aimn) the normal variability with the a~erage at the aim. After each test, the Shewhart block stores in the process database an estimate of the deviation from aim and a value indicating what rule was ~roken.
In the presently preferred embodiment, Shewhart blocks do not ~llow timing options to be specified. They perform their tests only when a new measure~ent is entered into th~ database for the filtered variable. In the presently preferred embodiment, the conditions tested for by the Shewhart block ~re:
Was the last point more than 3 sigma different from aim?
Were two of the last three points more than 2 sigma different from a~m in the same direction?
Were four of the last five points more than 1 ~igma d~fferent from aim in the same direct~on?
- Wer~ the last ~even points ~11 o~f ~i~ on the same side of ~im~

~97558 The rules are tested in the order shown. For the second and third rules, the test i5 ~irst applied to the last two (sr four~ points in a row, then to the last thres (or five) points. I any rule is violated, the process S is off aim, and a deviation from aim is calculated by averaging the points which broke the rule. For example, if the last four points were outside the 1 sigma limit, the average of the four is taken as the deviation. If four of the last five points were outside the 1 sigma limits, the average of the last five points is taken.
The basic Shewhart action can be altered hy several additional parameters. A fix time interval can be specified (in field 1226), so that, if one of the Shewhart tests shows a rule violation, Shewhart tests will be suspended for this interval after the time of the sample that violated the rule. This is useful in process control to allow control action in response to a rule violation to have time to move the process back to a statistically "on aim" position before taking any further actions. The range of calculated deviations can be limited, as specified by the data entered into fields 1228 and 1230. Screening limits can be applied to the filtered variable, so that measurements falling outside the range defined in fields 1232 and 1234 are ignored.
The Shewhart block differs from the feedback ~nd feedforward blocks in that it requires resources outside of the supervisor procedure. It uses two process database variables to store its computed deviation from aim and its rule value. To configure a Shewhart block, in this sample em~bodiment, the user must get database variables allocated and properly configured. Since this is usually a database system manger's function, the details are not covered here.
Specifying a "Shewhart" (i.e. statistical filtering) block on the block setup selection form ~5~

(Figure 9) brings up the Shewhart bloc~ setup form shown in Figure 12.

Parameters The parameters shown on this form include:
Filtered variable l:ype: a number code representing the software system and the type of entity which the block should use for the filtered variable.
Filtered variable numb~r: the nu~ber of the entity within the specified system which the block will use ~or the filtered variable. For example, if the filtered variable type is a historical database variable, the filtered variable number is the number of the variable in the historical database. ~fter the filtered variable type is entered, the label next to this field will show what type of data is needed. ~en the filtexed variable number is entered, other fields will also be filled in: the name and units for the filtered variable, aim, and sigma: units and default values for the max and min filtered values. Since Shewhart block timing always Xeys off entry of new data into the filtered variable, only discretely sampled variable types can be used.
Deviation variable type: a number code representing the software system and the type of entity into which the block should store the computed value of deviation from aim.
Deviation variable number: the number of the entity within the specified system into the block will store the computed deviation from aim. For example, if the deviation variable type is a historical database variable, the deviation variable number is the number of the variable in the historical database. After the deviation variable type is entered, the label next to this field will show what type of data is needed. ~hen 1~7~i58 the deviation variable number is entered, other information will be automatically filled in by the build-supervisor procedure; in the example of Figure 12, region 1236 indicates the pre-stored designation of historical database variable 2084. Such automatically complet0d in~ormation will preferably include the name and units for the deviation variable; units and default values for the max and min deviation values. since Shewhart blocks execute on entry of new data into the filtered variable, only discretely stored deYiation variable types can be used.
Rule variable type: a number code representing the software system and the type of entity into which the block should store a number code indicating which rule was broken.
- Rule variable number: the number of the entity within the specified system into the block will store a number code indicating which rule was broker.. For example, if the rule variable type is a historical database variable, the rule variable number is the number of the variable in the historical database.
After the rule variable type is entered, the label next to this field will show what type of data is needed.
When the rule variable number is entered, the name and Z5 units for the rule variable will also be filled in.
Since Shewhart blocks execute on entry of new data into the filtered variable, only discretely stored rule variable types can be used.
Aim: the "on aimU value of the filtered variable.
Sigma: the standard deviation of the value of the filtered variable when the measurement is "on aim".
Fix time: A time interval after rule violations during which no rule tests are done. ~ew measurements entered during the fix time interval are 5~

ignored. The fix time is ent:ered as a delta time character string: "ddd hh~D:ss" where "ddd" is the number of days, "hh" is the number of hours, "~m" is the number of minutes, and "ss" is the number cf 6econds.
~he fix time is taken from the timestamp of the filtered variable value which caused the deviation to be identified. The timestamp of later samples is compared against this, and if the difference is less than the fix time interval th~ sample is ignored.
Switch system and switch number: these are described above.
Minimum and maximum value of the calculated deviation: limits on the allowed value of the calculated deviation from aim. Deviations outside this range are set equal to the closest limit.
Minimum and maximum value of filtered variable: Screening limits for reasonable values of the filtered variable. Any time the filtered variable value falls outside these limits, the value will be ignored and no action is taken.
Action log file: this field is described above.

810ck O~eration In the presently preferred embodiment, the sequence of actions performed by the Shewhart block is:
- If the block status is "On-deselected", do no further calculations.
- Retrieve the last 7 values of the filtered variable. If not available, do no further calculations.
- Check the last value of the filtered variable. If it is outside the allowed limits, do no further calculations.
- Search backward through the stored values of the deviation variable for the most r~cent non-ze~o ~7~97'5~8 value. If a non~zero value is found within one fix time interval before the present instant, do no ~urther calculations.
- Compute the cutof time = time of last non zero deviation plus the ~ix time.
- Initialize the deviation and rule values (to zero).
- Begin testing Shewhart rules:
* If the l ast point is ol der than 'che cutoff time, do no furthar caloulations.
* I~ the last point is outside the 3 sigma limits ( i.e. Abs(point-aim) is greater than 3 sigma3, then:
Deviation = ~ast point - aim Rule = 1 - SXip remaining rules.
* If the second newest point is older than the cutoff time, Skip remaining rules.
~ If the last 2 points are both either greater than aim + 2 sigma or less than aim - 2 sigma, then:
Deviation = Sum~last 2 points )/2 - Aim Rule = 3 Skip remaining rules.
* If 2 out of the last 3 points are both either greater than aim + 2 sigma or less than aim - 2 sigma, then:
Deviation = Sum(last 3 points)/3 - Aim Rule = 3 Skip remaining rules.
* If the last 4 points are all either greater than aim + sigma or less than aim - sigma, then:
Deviation Sum(last 4 points)/4 - Aim Rule = 5 S~ip remaining rules.

lX~75~i~
* If 4 of the last 5 points are all either greater than aim ~ sigma or less ~han aim -sigma, then:
Deviation = Sum(last 5 points)J5 - Aim Rule = 5 Skip remaining rules.
* If all of the last 7 points are greater than aim or all less than aim, then:
Deviation = Sum(last 7 point)/7 - Aim Rule = 7 S~ip remaining rules.
- Check and s ore result:
* If the deviation is outside the allowable limits, set equal to the closest limit.
* Store the deviation value and rule value in the respectiv~ variables. These values are time stamped the same as the last filtered value.
- If the deviation is non-zero, update past actions.
- Call the user routine.
Of course, other statistical filtering methods could be used instead. It is generally realized that statistical filterins is highly advantageous, and that numerous algorithms can be used to accomplish statisti-cal filtering.The Shewhart algorithm used in the presently preferred embodiment could be replaced by any of a wide variety of other known algorithms.

SamDle Source Code The source code for the procedure which actually performs this function, in the presently preferred embodiment, is as follows.

55~3 ~;L~
C~*****~**********~**~******~***
c C Shewhart block.for C
C********************************
C

Subroutine Shewhart block ( Block) C

Include 'ACSSincludes:Block ~arameters.inc/nolist' Include 'acs$includes:ACSserv.inc/nolist' Includ~ 'acs~includes:ACSstatus.inc/nolist' Include 'Acssincludes:van functions.inc/nolist' Include 'ACSSincludes:Filter ~arams.inc/nolist' Include 'ACSSincludes:dev_params.inc/nolist' Include 'ACS$includes:rule params.inc/nolist' Include 'ACS$includes:User vars.inc' Integer*4 Block Integer Error lun Parameter ( Error lun ~ 6 ) Character*20 Store time Character*20 now_time C

Integer~2 Filtered variable Integer*~ Deviation variable Integer~2 Rule variable Integer*2 Filtered variable type Integer*2 Deviation variable type Integer*2 Rule variable type Integer*4 I4 deviation variable Integer*4 I4 rule variable Real*4 Aim Real*4 Sigma Integer*4 Integer fix time Integer*4 Cutoff time Integer*4 Safe tlme Real*4 Deviation Real*4 Rule Real*4 Last filtered_value Logical All same sign Logical Need_violation Integer*4 Num points Parameter (Num Points = 7) Real*4 Point(Num Points) Integer~4 Times(Num_points) Character*18 Char times(Num Points) Integer*4 Num pointsl Parameter (Num Pointsl = 8) ~X3755~

Real*4 Pointl(Num_pointsl) Integer*4 Timesl(Num Dointsl) Character*18 Char timesl(Mum_pointsl) Real*4 Violation_value(1) Integer~4 Violation_time(1) Integer*4 Newest_time Integer~4 Oldest_time Integer*4 ~uffer_size Logical*1 First_re~uest Integer*4 Block_location Integer~4 ~ntry_count Integer*4 Begin_span status Byte Interp_flags Integer~4 Begin span_time Integer*4 End_span time Integer*4 Num ~oints_rtrieved Integer*4 Integer_Now Integer*2 Start_point C

C....Special case for 'On-deselected' status C

If ( Block status(31Ock)(1:13) .eq. 'On-deselected' ) Then Return End If C

C..Set the value of the local variables C

ACS_status = ACS_get_filtered_var_type(Block,filtered_variable Filtered_variable = Measured_variable(Block) ACS status = ACS_get_dev_var_type ( Block , deviation variabl ) Deviation variable = Manipulated_variable(~lock) ACS status = ACS_get_rule_var_type ( Block , rule_variable_typ Rule_variable = New_manipulated_variable(Block~
Aim - Goal(Block) Sigma = Absolute_deadband(Block) Integer_fix_time = Fix_time(~lock) C

Van_status = VssS from_ascii_time ( ' ' , Integer_now ) Van status = VssS to_ascii_time ( Integer_now , now_time ) d Van_status = VssS_to_ascii_time ( Integer_now , Store_time ) d write(6,202) ' Calling Shewhart on var ',filtered variable,' a d 1 Store_time d 202 format(//,a,' ',i5,' ',a,' ',a) C

C...Retrieve enough points tv test all th~ rules C

If ( Filtered_variable_type .eq. Van_var_filter ) Then C

Newest_time = Integer_now Oldest_time = Newest_time - 365*24*60~60 7S5~

Buffer_size s Num_points First reguest - .True.
Num points retrieved = O
Start ~olnt ~ 1 C

Do 777 j = l,Num points Times~j) = 0 777 Point(j) - 0.0 C

Van status = %loc(vs-~_systemdown) Do While ( (Van status .eq. %loc(vss_systemdown)) .or.
1 (Van_status .eq. ~loc(vss_unavaildata)) ) c Yan status = Vss~_Retrieve ( Filtered_variable , Newest ti~
1 -Oldest time , Buffer size , Times(start Point) , 1 Point(Start_point) , 1 First_request , Block_location , Entry cou~t , 1 Begin span status , Interp flags , Begin_span_time , 1 End_span time ) Num_points_retrieved = Num_points retrieved + Entry_count If ( Num_points retrieved .lt. Num_points ) then Buffer size = Buffer_size - Num points retrieved Start_point = Start point + Entry count End If d write(6,*) 'Fi~ished data retr.' c End Do d do 11 J =l,Num_points d 11 Van status = VssS_to_ascii_time ~ Times(j) , Char_times(j)) d write(6,1~) (Char_times(j),Point(j),j=l,num Points) d 12 Format( /,' Here are the times and points:',//
d 1 (' ',al8,' ',fl2.4 , / ) d write(6,~) ' Got ',Num Points-retrieved~l points.' If ( Num points retrieved .lt. Num points ) then Write(~rror_lun,*) 1 'Shewhart Failed to get enough data on Variable ', 1 Filtered variable write(error lun,*)'from ACS block:',block,' at:',now_time Write(Error_lun,*) 'Wanted ',Num Points,'; Got ', 1 Num points_retrieved Return End If d write(6,*) 'Got enough points.' C
C

C....Check the Measured variable to see if it is within limits C

Last filtered value = Point(l) If ( (Last filtered value .lt. Measured min(block) ) .or.
1 (Last filtered value .gt. Measured_~ax(block) ) ) T
C..... Reject the data point 7~58 Write( 6, *) 'Shewhart exit due to out of limts filtered.' write(6,~)' ACS Block: ',block,' at: ',now time Return End if Else if ( Filtered variable_typ~e .eq. Van run 2 filter ) Then Newest_time = Integer now Oldest time = Newest_time - 365*24*60*60 Buffer size D Num Polnt First request = .True.
Num points retrieved = 0 Start_point = 1 Do 1777 j - l,Num pointsl Timesl(j) = 0 1777 Pointl(j) = 0.0 C

Van status = %loc(vss systemdown) Do While ( (Van_status .eq. %loc(vss_systemdown)) .or.
l (Van_status .eq. %loc(vss_unavaildata)j ) Van status = VssS Retrieve ( Filtered variable , Newest_tim l Oldest time , Buffer size , Timesl(start point) , l Pointl(Start_point) , 1 First request , 81Ock location , Entry count , 1 ~egin span status , Interp flags , Begin span time , 1 End span time ) Num ~oints retrieved = Num points retrieved + Entry count If ( Num points retrieved .lt. Num_pointsl ) then Buffer size = Buffer_size - Num Points retrieved Start Point = Start_point + Entry count End If d write(6,*) 'Finished data retr.' End Do c d do lll J =l,Num Pointsl d 111 Van status = VssS to ascii time ( Timesl(j) , Char_timesl(j)) d write(6,112) (Char timesl(~),Pointl(j),j=l,num pointsl) d 112 Format( /,' Here are the times and points:',//
d 1 (' ',al8,' ',fl2.4 , / ) d write(6,*) ' Got ',Num Points_retrieved,' points.' If ( Num Points retrieved .lt. Num_pointsl ) then Write(Error lun,*) 1 'Shewhart Failed to get enough data on Variable ', l Filter~d variable write(error lun,*)'from ACS block:',block,' at:',now_time Write(Error lun,*) 'Wanted ',Num pointsl,'; Got ', 1 Nu~ points retrieved Return End If d write(6,*~ 'Got enough points.' lX~755~3 C
c C....Check the Measured variable to see if it is within limits C

Last ~iltered value = (Pointl(l)+Pointl(2))/2.
If ( (Last filtered_value .11:. Measured min(block) ) .or.
1 (Last filtered value .gt. Measured max(block) ) ) T
C..... Reject the data point Write( 6, *) 'Shewhart ex:it due to out of limts filtered.' write(6,*)' ACS Block: ',block,' a~: ',now time Return End if C

Do j = 1,num_points ! running avera~e point(j) = (pointl(j)+pointl(j~l))/2 times(j) = timesl(j) end do Else ! Improper filtered type Write( 6, *) 'Shewhart exit due to invalid filtered var -ype.' write(6,*)' ACS Block: ',block,' at: ',now_time Return End If ! Filtered types C
C....Check to see if the last violation was within the Fix time -C I~ so, do no calculations.

C

C...Retrieve the last stored nonzero deviation from aim If ( Deviation variable type .eq. Van var dev ) Then Newest ti~e = Integer_now Oldest time = Newest_time - 365*24*60*60 Buffer size = l First request = .True.
Need violation = .True.
Do ~hile ( Need violation ) Van_status - VssS Retrieve ( Deviation variable , Newest_ti l Oldest time , Buffer size , Violation time , l Violation value , l First request , Block location , Entry_count , l Begin span status , Interp flags , Begin span time , l End_span time ) If ( ( Yan status .ne. %loc(vss systemdown) ) .and.
l ( Van_status .ne. ~loc~vss unavaildata)) .and.
l ( Van status .ne. ~loc(vss notallfound)) ) Then c Write(6,~3~ Shewhart Violation retr - status vss_badva write(6,*)' ACS Block: ',block,' at: ',now time ~2~'7558 Else If ( Van status . eq. %loc (Vss badtime) ) then Write(6,*) ' Shewhart Violation retr - status vss badti write(6,*) ' ACS Block: ',block, ' at: ',now time c Else If ( Van status ~eq. 96].0c(Vss badtirQespan) ) then Write ( 6, *) ' Shewhart Violation retr - s vss badtimespan' write(6, *) ' ACS Block: ' ,block, ' at: ' ,now time Else If ( Van status . eq. Sloc (Vs5 badbufsize) ~ then Write(6,*) ' Shewhart Violation retr - status vss_badbu write(6,*~ ' ACS ~locX: ',block, ' at: ',now_time Else If ~ Van s~atus .eq. %loc(Vss normal) ) then Wrlte(6,*) ' Shewhzrt Violation retr - status vss _ norina write(6, *j ' ACS Bloc3c: ' ,block, ' at: ' ,now time c Else If ( Van_status . eq. %loc (Vss_nonefound) ) then Write(6,*) ' Shewhart Violation retr - status vss _ nonef write(6,*) ' ACS Block: ',block,' at: ',now time c - Else If ( Van_status .eq. %loc(Vss _ nomoreonline) ) then Write(6,*) ' Shewhart Violation retr - s vss_nomoreonline ' write(6,*) ' ACS Block: ',block,' at: ' ,now_time c End I f WRite ( 6, ~ 3 ' Van status = ', Van_status Van status = Vss$ to ascii time ( Violation time(1), Stor Write (Error lun, * ) 'Shewhart-couldn' 't get a non zero deviation - exiting' write~6, ~) ' ACS Block: ',block,' at: ' ,now time Write (Error_lun, * ) ' Oldest violation got: ' ,Violation value(1), ' at ' ,Store_ Return End I f If ( ( Abs(Violation value(l) ) .gt. 1.0 E-10 ) .or.
( Violation time(l) .lt.
(Times(7) - Abs( Integer_fix_time ) ) ) ) Then Need violation = . False .
End I f c End Do Else ! Improper deviation var type Write( 6, ~) 'Shewhart exit due to invalid deviation var type write(6,*)' ACS Block: ',block,' at: ',now time Return End If ! Get last deviation for allowed deviation types c ~97S58 c d Van status = Vss$ to ascii tim~ ( Violation time(l) , Store ti d write(6,~) ' Got a vlolation of ',Yiolation value(~ at ', d 1 Store time C

C....Go through the shewhart Rules - any point older than the last vio C time + the fix time is not acceptable.
Cutoff time = Violation time(1) + Abs(Integer fix time) d Van_status = VssS to ascii time ( Cutoff time , Store time ) d wxite(6,*) ' Cutoff time is ', Store time c Deviation = 0.0 Rule = 0.0 C

If ( Times(l) .lt. Cutoff time ) Return d write(error lun,*) '~esting 1 out of 1 rule.' If ( Abs(Point(1)-Aim) .gt. 3*Sigma ) Then Deviation = Point(l) - Aim Rule = 1.0 Go To 1000 End if ' C
C.... Test 2 in a row outside 2 sigma C

If ( Times(2) .lt. Cutoff time ) Go To 1000 d write(error lun,*) 'Testing 2 out of 2 rule.' Sum ~oints = 0.0 Num out high = O
Num out low = O
~o 2 J = 1,2 Sum Points = Sum Points + Point(J) If ( (Point(J)-Aim) .gt. 2*Sigma ) Then Num out high = Num out high +l Else If ( (Point(J)-Aim) .lt. -2*Sigma ) Then Num out low = Num_out low + 1 End If 2 Continue If ( ( Num out high .eq. 2 ) .or.
1 ( Num out low .eq. 2 ) ) Then Deviation = Sum_points/2 - Aim Rule = 3.0 Go To 1000 End If C

C... Test 2 out of 3 outside of 2 sigma C
I~ ( Times(3) .lt. Cutoff time ) Go To 1000 d write(error lun,*) 'Testing 2 out of 3 rule.' Sum Points = Sum Points + Point(3) If ( (Point(3)-Aim) .gt. 2*Sigma ) Then ;S~
Num out high = Num out high +l Else If ( (Point(3)-Aim) .lt. -2*Sigma ) Then Num out low - Num out 1 9w + 1 End If If ~ ( Num out high .eq~ 2 ) .or.
1 ( Num out low .eq. 2 ) ) Then Deviation = Sum~points/3 - Aim Rule - 3.0 Go To 1000 End If C

C...Test 4 in a row outside 1 sigma C

If ( Times(4) .lt. Cutoff time ) Go To 1000 d write(error_lun,*) 'Testing 4 out of 4 rule.:
Sum points = 0.0 Num out_high = O
Num out low = O
Do 3 J - 1,4 Sum Points = Sum Points + Point(J) If ( (Point(J)-Aim) .gt. l*Sigma ) Then Num out high = Num out high +l Else If ( (Point(J)-Aim) .lt. -l*Sigma ) Then Num out low = Num_out low + 1 End If 3 Continue If ( ( Num out high .eq. 4 ) .or.
1 ( Num out low .eq. 4 ) ) Then Deviation = Sum Points/4 - Aim Rule - 5.0 Go To 1000 End If C
C... ...... Test 4 out of 5 outside 1 sigma C
If ( Times(5) .lt. Cutoff time ) Go To 1000 d write(error lun,*) 'Testing 4 out of 5 rule.' Sum Points - Sum Points + Point(5) If ( (Point(5)-Aim) .gt. l*Sigma ) Then Num out high z Num out high +1 Else If ( (Point(5)-Aim) .lt. -l*Sigma ) Then Num out low = Num out low + 1 End If If t ( Num out high .eq. 4 ) .or.
1 ( Num out low .eq. 4 ) ) Then Deviation = Sum Points/5 - Aim Rule = 5.0 Go To 1000 End If C... Test 7 in a row - same side of aim ! C

~9755~3 If ( Times(7~ .lt. Cutoff_tiDIe ) Go To 1000 d write(error lun,*) '~esting 7 in a row rule.' Sum Doints S o. o Sign_deviation = Sign( l.O,(Aim-Point(1)) ) If ( ~Aim-Point(1)) .ne. 0) Then All same sign = .True.
else All same_sign = .False.
End if Do 4 J = 1,7 If ( (Aim-Point(J)) .eq. O) Then All same sign = .False.
Else If ( Sign( 1.0,(Aim-Point(J)) ) .ne~ Sign_deviation ) All same sign = .False.
End if 4 Sum ~oints = Sum ~oints ~ Point(J) If ( All same_sign ) then Deviation = Sum_points/7 - Aim Rule = 7.0 Go To 1000 End If C

- lOOO Continue d write(6,*) 'Got deviation, rule of ',deviation,rule C
C...Clamp the deviation at allowed limits C

If ( Deviation .gt. Manipulated_max(Block) ) Then Deviation = ~anipulated max(Block) Else If ( Deviation .lt. Manipulated min(Block) ) Then De~iation - ~anipulated min(Block) End If C...Store the Computed Deviation and Rule number with Timestamp C

d Van status = VssS to ascii time ( Times(l) , Store_time ) d write(6,*) 'putting var ',i4_deviation_variable,' at ',store_t d 1' with value ',deviation c If ~ Deviation variab}e type .eq. Van var dev ) Then I4 deviation variable = Deviation variable Dmt status = Dmt$ Dutlab ( I4_deviation varia~le , Times(l) , 1 Deviation , 2 , .False. ) Else ! Other deviation types End If ! Deviation types d write(6,*) ' Did putlabs -first status = ',dmt status d write(6,*) 'putting var ',i4 rule variable,' at ',store time, d 1' with value ',rule If ( Rule_varia~le_type .eq. Van var rule ) Then ~31 X37Sss~;B
I4 rule variable - rule_vari~ble ~mt status c ~mt$~putlab ( I4 rule variable , Times(1~ , 1 Rule , 2 , .False. ) Else ! Other rule types End If ! Rule types c c 5tatu5 = vss$ mehclose() !close file just in ca c d write~6,*) ' Did putla~s -second status = ',dmt status d write(6,*) ' Did putla~s -exi.ting' C If ~eviation is non~zero, update past actions I f ( Deviation .ne~ o ) Then Do 90 J = 5,2,-1 Past action value(Block,J) = Past action value(~lock,J-l) Past action time (Block,J) = Past action_time (810ck,J-l) Past action_vAlue(Block,1) = Deviation Past_action time (Block,l) = Times(l) End If C

C...Load user arrays for user programs User integer(l) = Integer now ! Time of Tests User integerl2) = Rule User real(1) = Deviation Do J - 1 , Max ( Num Points , 18 ) User_integer(2+J) = Times(J) ! Time of samples used in test User_real (2+3) = Point(J) ! Value of samples used in tes End Do If ( Rule .eq. 0.0 ) Then User character(l) ~ 'On aim, No rules broken ' User character(2~ ~ 'On aim, No rules broken.' Else If ( Rule .eq. 1.0 ) Then User character(l) ~ 'Shewhart 1 out of 1 rule' User character(2) ~ 'Shoe heart 1 out of 1 rule' Else If ( ~ule .eq. 3.0 ) Then User_character~ 'Shewhart 2 out of 3 rule' User character(2) ~ 'Shoe hear~ 2 out of 3 rule' Else I~ ( Rule Oeq. 5.0 ) Then User_char~cter(l) c 'Shewhart 4 out of 5 rule' User character(2) ~ 'Shoe heart 4 out of 5 rule' Else If ( Rule .eq. 7.0 ) Then User character(l) = 'Shewhart 7 in a row rule' User character(2) - 'Shoe heart 7 in a row N le' End If C
- C...C~ll User routine C
Call User ~rograms ( Block ) Return End Copyright (c) 1987 E.I. DuPont de Nemours & co.
all rights reserved 9~55~3 User-De~ined Proqram_~lock Figure 13 shows the form which (in the presently preferred embodiment~ is presented to a user who has chosen the "User program" optisn from the menu shown in Fiqure 9.
The user program block provides a means of controlling the execution of a user written FORTRAN
subroutine. The blocX itself performs no control actions, but allows the user to specify a timing option and switch parameters for executing the block's user routine. A user routine exists for every block in the supervisor procedure. (In the example shawn in Figure 13, where the block shown is block number 2, the block will (selectively) make calls to BLOCK2 USER_ROUTINE. ) Initially these routines (BLOCXl USER_ROUTINE, - BLOCX2_USER ROUTIN~:, BLOCX3_USER ROUTINE, etc. ) do nothing (i.e., their default content is merely the FORTRAN statements Return and End), but they can be modified by the user. The user program block only sets up parameters for controlling execution of the user program.
¦ The user program timing options include Xeying off a measured variable. In this case the variable is not used for anything but timing. This option can be altered by specifying screening limits on the measured variable value (using fields 1332 and 1334), so that mea~ured values outside the screening limits are ignored. Block timing and switching and the block description fields follow the general outlines given above.

paramete~s The parameters arP
Measured variable type: a number code representing the software system and the type of entity which the block should use for the measured variable.

~ s~

Measured variable number: the number of the entity within the specified syst~em which the block will use ~or the measured variable. For example, if the measured variable type is a historical database Svariable, the measured variable nu~ber is the nu~er of the variable in the historical database. After the measured variable type is entered, the label next to this field will show what type of data is needed. When the measured variable number is entered, other fields 10will also be filled in: the name and units for the measured variable; units and default values for the max and min measured values.
Timinq option, execution time interval, and Rey block number: these parameters are described above.
15Switch system and switch number: these are described above.
Minimum and maximum value of measured variable: ~hese define screening limits for reasonable values of the measured variable. Whenever the measured 20variable value falls outside these limits, the value will be ignored and no action is taken.
Action log file: this field is described above.

Proaram Block ODeration 25The sequence of actions performed by a User program block is:
- If block status is "On-deselected", do not execute the user routine.
- If a measured variable is specified:
30* Get the current value of the measured variable (If not accessible, set status to "On-err..."
and do not execute the user routine).
* Test the value or the measured variable. If it outside the range of allowed values, se 7~S8 status to "On-msrd out of lims" and do not execute the user routine.
Execute the user routine. The routine name iq derived from the block number. Block 1 calls Bl o c kl use r routine, bl ock 199 calls Blockl99_user routine, etc.
- If a fatal error occurs in the user routine, bypass the rest of the routine, and set the block status to "On-Failed usr routin".
- If the block failed on the last execution, but did not ~ail on this execution, set the block status to "On".
- Clear all the values in the user vars common block.

Build-User-Pr_qram Procedure The build-supervisor procedure (in the presently preferred embodiment) also provides a structured environment for creating user programs. As will be described below, the build-expert procedure will create the source cod for one or more customized expert systems; but the user must still insert a call to this expert code into one of the blocks in the supervisor procedure. The build-user-program procedure facilitates this, and also provides convenient support for sophisticated users who are able to write their own utilities.
In the presently prefer-ed embodiment, this is a structured environment in which users can write FORTRAN
subroutines and incorporate them into control blocks.
User programs can be run as the only block function by defining a User Program block (as dèscribed above), or they can be used to take additional actions (such as message logging) in combination with feedback or feedforward control blocks.

1~97~58 At a minimum, a user with no programming knowledge can insert a one-line call int~ a user program block, to make use of an expert subprocedure ~reated using the build-expert procedure. However, to take full advantage of the capability for user programming, the user should (in the presently preferred embodiment) already be comfortable programming in FORTRAN and using FORTRAN
functions and subroutines, and in using the Vax EDT
editor. The build-user-program environment 1810 in this embodiment is menu driven rather than forms driven, and therefore provides less online help than some of the other functions described.
Writing a basic user program involves 5 steps:
- Selecting which block number's user program to edit:
- Editing the file which contains the user program code for that block. The EDT editor 1812 is used to write and modify the FORTRAN language code;
- Checking the code for errors in FORTR~N
syntax;
- Updating the supervisor procedure by incorporating the latest version of the user program into the base cycle procedure and running the new base cycle procedure; and - Monitoring user program execution to assure that the program is executing properly.
In the example shown in Figure 16, the top level build-supervisor menu permits the user to enter the build-user-program environment by pressing keypad 5.
While in the build-user-program environment, the user can edit the block user routine; check the block user routine for errors in FORTRAN syntax; and update the supervisor procedure by incorporating the new version of the blocX user routine. The first prompt from the user program menu asks what block number's routine the user 1~9~5~
wants to work on. En~ering ~he block number and pressing return brings up another program menu, with options which will now be described.
Editing the user routine begins by selecting menu option 1 ("Edit user routine"). This will start the EDT
editor. User routines of some sort already exist for all the blocks. ~loc~s which have never had any ~pecial programming have a user routine which does nothing - it consists simply of a RETURN statement followed by an END
statement, and, if the block's user routine has never been worked on, this default routine will be brought up by the editor. To make a functioning routine, the user must add FORTRAN code before the RETURN statement to perform the desired function. (In the presently preferred embodiment, the user can simply edit the file like any other FORTRAN source code file on the VAX.) For example, code for logging messages or calling an expert subroutine can be inserted at this point.
Once the user has edited the user routine and returned to the menu, he can select option 5 to check for FORTRAN syntax errors. If the new routine has no FORTRAN syntax errors, the screen will show "The user's routine compiled with no errors in syntax." If the new coding has syntax errors, the user will see them reported on the terminal screen. The user can then correct the errors using Option 1 (edit), and repeat until all errors have been removed.
Once the user has a routine that compiles with no errors, he can include it in the running version of the supervisor procedure by using menu option 8 ("Update").
This will compile the user's routine, relink the base cycle procedure using the user's newly compiled routine, stop the procedure which is currently running, and restart the base cycle procedure using the newly linked version containing the user's new routine.

1297~

After compiling the user's routine, the build-supervisor procedure will ask if there axe any other subroutines in separate files that need to be compiled.
Some application may require ~ore than one subroutine, and, if desired, they can be split up in separate files.
To make a routine in a separate file, the user can select option 2 ("Edit a separate FORTRAN subroutine") to create and modify the file, and then select option 6 ("Check a separate subroutine for FORT~AN errors") to check for FORT~AN errors. ~o include the separate file into the super~isor procedure, the user can use the update option, then answer "Y:" when asked if any separate routines need to be compiled and included. The base cycle procedure can then be linked, and then restarted.
After the user's routine has been incorporated into the base cycle procedure, the user can monitor it to make sure it executes properly. There are two key indicators of a problem with the user's user routine:
the block status and the control program log fileO If the user's routine has an error which would normally cause a stand-alone FORTRAN program to terminate, the base cycle procedure will bypass the error and the remainder of the user's routine, and change the block status to "On-Failed usr routin". This can be seen using the block monitoring screen. If the user's routine fails once but runs successfully on a subsequent execution, the block status will be changed to "On-Recovrd Usr Error", and a message will be posted in the control program log file indicating which user routine had the error, when it occurred, and what the error was. The log file can be viewed using the "List lo~ file" option on the System functions screen.
The user can print a listing of a user routine by using option 3 (or option 4 for a separate routine).

~97S58 If the user ' s user xoutine fails and the user needs to r~treat to the last version ~:hat was running, he can use the restore option (keypad 9). This will promp~ the user for any separate routines that need to be restored, and retrieve the old versions saved by the build-supervisor procedure.
In the presently preferred embodiment, there are several include files which can he used in user routines: "User vars. inc" contains a cornmon block which is used to pass information about control block actions to user routines. The common block contains a Real array, an integer array, and a character~80 array.
Control blocks load values into these arrays for the amount of change made in the manipulated variable, the error in a feedback block, the time the action was taken, etc. The user program block zeros out these values after the user routine executes a REIrURN
statement. "ACSserv. inc" declares all the ACS service routines (which are integer*4 functions) .
"ACSstatus. inc" declares all the legal ACS status return values. These values must be declared external before they can be used. "Van functions. inc" declares some of the retrieval and time functions from the historical process database, and declares some of the status return 2 5 values .
Of course, many different computer languages and architectures could be used in practising the presen, invention: the sample FORTRAN routines specified (as well as other features which, for example, relate specifically to the use of a VMS opera~ing system) simply sets forth the best mode as presently practiced, but a tremendous variety of other languages, operating environments, and/or hardware could be used instead.

755~1 ~,~!5 Figure 14 shows a menu which is preferably presented to a user who has elected to use the utilities provided in the build-supervisor procedure (e.~. by hitting keypad 9 when faced with the menu shown in Figure 16). While these utilities are not necessary parts of every implementation of the innovative concepts described in the present application, they do help users to taXe advantage of the full power available.
In the presently preferred embodiment, the supervisor procedure includes the capabilities for copying and deleting blocXs, and for printing listings of block setup parameters. Deleting a block (Xeypad 7~
removes all the block type and setup parameter data for the block, leaving it available for another use. Copying a block (Keypad 8) reproduces the block type and setup parameters of one ~lock into another. Printing blocks (Keypad 9) allow the user to select blocks to be printed either by number range or by searching ~or string matches in the application name or block description fields, and makes full or abbreviated listings of block parameter data on the printer of the user's choice.
If the user elects to copy a block, the build-supervisor procedure prompts the user to enter in the "Source block" field 1402 the number of the block to copy. ~he build-supervisor procedure then fills in the information fields appropriately for that block, allowing the user to confirm that he has entered the right block number, and prompts the user again for the target block into which the block should be copied (field 1404). After this is entered the build-supervisor procedure fills in the information fields for the target block, and prompts the user again. When the user cohfirms that the block is to be copied, the block type and parameters are overwritten in the shared memory 814.

~7~i~5~

After the block i5 copied, the build-supervisor procedure prompts the user again, asking whether the source block should be deleted or left unchanged. The build-supervisox procedure confirms that the source block was ei~her deleted or not deleted.
Block information can only be copied into target blocks whose s~atus i5 "Off" or "Inactive". To copy information into a block with an active status, the user must go to the block setup form for that block, and toggle the block off. This safeguard provides greater system integrity.
In the presently preferred embodiment, keypad 9 will initiate printing a listing of selected block parameters. The build-supervisor procedure will prompt the user to enter in field 1410 for the starting range of block numbers to print, or to hit return if he wishes to select blocks by string searches. To print a range of block numbers, the user can enter the lowest number block in the range, press return, then enter the higher number block (in field 1412) and press return. To select the blocks to be printed by search for string matches, the user can press return without entering a number for the starting block. To search the block description fields, the user can enter the desired string in the description search string field 1406. To search the block application name field, the user can press return without entering anything in the description field, and enter the desired string when prompted in the application name field 1408. In either case, the user can use capital and lower case letters interchangeably, since case is not checked in the string searches. The user need not fill in the whole search string field. A
block will be selected to print if the string the user ent:ers appears anywhere in the searched field.

~X97558 The build-sup~rvisor procedure will now prompt the user for a short or long list. A short list shows only the block number, type, description, and application name. A long list shows the entire setup form for that block. The build-supervisor procedure will clear the screen and promp~ the user for the printer he wishes to use. The user can type the number of the printer if he knows it, or enter L to get a list of printers to choose from. The user' 5 terminal screen and its attached printer can be selected, as well as Vax system printers.
When the prlnt job is completed, the build-supervisor procedure will report the number of blocks that were printed.

Monitorina In addition, the supervisor procedure provides several functions for following the performance of control strategies as they operate. The block monitoring screen allows the actions of individual blocks to followed. The sy~tem functions screen shows the status of the supervisor procedure. The control system runs as a batch-type process on the Vax, and so it has a log file which contains all the error messages generated by the system.
A user who requests block-monitoring is presented with a block description form which includes a block number field in which he can insert the number of the block to be monitored. The remaining fields on the form then are filled in appropriately by the build-supervisor procedure, and are subsequently updated every S seconds.
~he information shown includes:
- the current time;
- the time at which the supervisor base cycle procedure will make its next scan through the blocks (and blocks which are due to execute will b~ executed);

~2975~8 - the block type (whic:h was speci~ied during block setup, ~.q. feedforward, feedback, etc.);
- the block description (which was entered during setup);
- the type, number, name and units of the measured variable which was specified in block setup ~if none was specified (e.~. in a program block), this field will be blank);
- the current value ~nd time sta~p of the lo measured variable (the time stamp fcr compressed variables is the time the last new value was received, for manual entry variables it is the time stamp of the last entered value; and if no measured variable was specified, this field is blank);
- the goal value for feedback blocks (~or other block types, this field is empty);
- the number, name, units and type of manipulated variable;
- the ~urrent value of the manipulated variable (with time stamp if one has been defined);
- the timing option entered during block setup;
- the execution time interval specified during block setup. If the block timing does not include any fixed frequency, this field is blank.
- the time the block last did its scheduled actions (this is normally the last time the block was scheduled to execute according to its timing option parameters, regardless of whether the block acted to change the manipulated variable);
- the current status of the block; and - the last five control actions made by the block (or, for Shewhart blocks, the last five deviation values) and the times at which they occurred.

97~-5~3 In the pr~sently preferred embodiments, a similar overhead function permits the user to take a look at the current status of key system parameters, including:
- Base scan in~erval: the time interval at Swhich the base cycle procedure scans through all the properly configured blocks, checking for changes in the on/off status, testing each according to its timing option and status to determine whether it should execute, and executing those that are due to execute.
10- Next base cycle time: the time at which ~he supervisor procedure will actually do the next scan.
This time should always be in the future, and should never be more than the base scan interval away.
- Current system status: provides information 15about what the supervisor procedure system is currently doing. Since the supervisor procedure only does its actions once every base scan interval, the system spends most of its time sleeping - i.e. waiting for the next cycle time to come. The normal system status values are:
20* Running-Sleeping : the normal status value. All control actions on the last scan have completed and the system is waiting for the next scan.
* Running-Computing : the system is currently performing block checks and executing bloc~s.
25Since calculations in the supervisor procedure finish rather quickly, this status will rarely be seen.
* Terminated normally: This status indicates that the supervisor procedure system has been stopped in an orderly way. Normally this status value 30will only be seen if ~he system manager has stopped the system, or briefly when a user performs the Update function on the user program menu.
An authorized user can change the bass scan interval, stop the supervisor process (together with any 35auxiliary processes used for communication with PCS or other control systems), restart the supervisor process ~and any auxiliary processes), s~r view the log file to which the base cycle procedure writes error reports and messages.

~lockl nitialiæation Blocks are initialized whell they are first turned on, or when the supervisor procedure is restarted after an outage of 30 ~inutes or more and the block h~d already been on. Block initialization sets the "last execution time" of the block to the current time. The "last execution time" value is used in fixed interval timing and also as a block monitoring parameter. If the block has a measured variable, the "last measured time"
is set equal to the current time of the ~easured variable. This parameter is used when block timing is keyed off the measured variable. If the block timing is set to key off another block, the key block ti~e is set equal to the last execution time of the key block. For feedforward blocks, the "old measured value" is set equal to the curren~ value of the measured variable.

~97558 ~L~: ~~cedures ~he procedures for constructing an expert system from a domain expert's knowledc~e will now be described, toyether with the procedures by which the expert system is called up by the operating software (preferably the process control supervisor procedure, as described above).
It should be noted that the structures and advantages of the build-expert procedure are not entirely separate from those of the expert procedure (or prooedures) generated thereby. The two procedures are preferably operated separately, but they are designed for advantageous combination. The features of the expert procedure are partly designed to advantageously facilitate use of the build-expert procedure, and the features of the build-expert procedure are partly designed to advantageously facilitate use of the expert procedure.
The build-expert procedure works especially advantageously as an integral part of the supervisor procedure, which ~in the presently preferred embodiment) is a VAX-based layered control system. The build-expert procedure produces complete FORTRAN subroutines that execute the expert ~ctions. The supervisor procedure (e.q~ via a user program block) provides the functions ~or running an expert subroutine at specified times, and Also provides c~llable routines that can be used by these subroutines to ~ke and modify SUperViSGr actions.
The build-expert procedure c3n be used without the preferred supervisor proced~re, but the user must provide a host p~ogram running at ~ppropriate times to call the ~ubroutines.

~X9755~3 In the presently preferred embodiment, the build-expert procedure is ~ccessed by selecting the "User program" option on the top-level menu in the build-supervisor procedure (see Figure 16), entering the desired block number, and then selecting the Expert system development option on the user program menu. This will take the user to the build-expert procedure, which (in the presently preferred embodiment) presents a menu as shown in Figure 17.
From this menu the user can access setup templates for the 3 rule types. The user also has access to functions for printing the rulebase, and for building a new expert subroutine.
The rule templates used in the build-expert procedure allow the user to enter and ~odify the specification information for rules. The build-expert procedure is different from the build-supervisor procedure in the way it handles data. When a rule name is entered in the build-expert procedure and the RETURN
or TAB key pressed, the letters are capitalized and the embedded spaces are transformed to underscores. This is how the build-expert procedure stores all character data. The other fields on rule templates are not transformed like this until the rule is stored. When the rule is recalled onto the template, the other fields will be capitalized with embedded blanks changed to underscores. In the presently preferred embodiment, the rule name, data type, and data number fields are the only fields on the rule templates for which the user's entry i5 checked immediately (others may be modified in the future to do this). The remaining fields can be filled in with any data that the template allows (some fields accept only integers, some only alphabetics, etc). The data on the remaining fields is tested only s~a when the user presses the keypad "-" to store the rule~
The build-expert procedure then examines the data for errors, ~nd requests corrections if needed. The build-expert procedure always checks rule names (and condition names) to be sure the~ are valid and ~eaningful where entered. In the presently preferred embodiment, the build-expert procedure chec~s other data for most errors, but it does not check for all concPivabls errors. Data entered on a rule template is NOT stored until the keypad "-" key is pressed to store the rule.
~ata on a te~plate will not be stored if the rule name field is blank. Data on a template can be lost if the user enters the data, then modifies the rule name field before pressing keypad "-". All the rule templates have a "delete rule" (keypad "-") and "top of form" (keypad 9) softkey. The delete rule key will ask the user to confirm the deletion by pressing the key again, and then deletes the rule from the rulebase. The top of form key simply takes the user to the top of the template.
After all the rules have been entered, the FORTRAN
expert subroutine must be generated using keypad 9, "Generate Expert". Changes made in the rule~ will not become effective until the expert is rebuilt. ~hen the build-expert procedure is used within the build-user-program environment (as discussed above), the FORT~AN
subroutine is generated in the same directory with the user program and is named Blockn expert system.for, with the subroutine name Blockn expert system (n is the number of the block `oeing worked onA) To use the expert from within the supervisor procedure, a one line user program must be written to call the expert. The one executable line is:
Call Blockn expert system .

~t~ndardi~ed Data Interface The ~uild-expert procedure use~ ~ ~tandard data interface~ In the presently preferred em~odiment, data ~ources are speci~ied by 4 p~.ir of integer parameter5.
One, the ~data type", is a coded value which identifies the type of data desired and the data collectio~ system fro~ which the data ~s to come. The 6econd , the "data number", identifies the specific data entity of that type within that sy~tem. Some data types (e.q. time averages) require z t~ird parameter specifying the time over which to.~verage.
This system has ~everal advantages. First, it provides a s~mple method of data identification in a many-system envîronment. Secondly, it allows the rules to easily reference data of many types fro~ ~any diverse - (and possibly remote) ~ources without requiring the user to write ~ny ~ustom program code ~or data retrieval.
Some u~eful d~ta ~ources might include: ~ny lower level process control ~yste~; any supervisor process (whether running on the ~a~e hardware ~ystem or another); any process dat~ase (whether running on the s~e hardware ~ystem or another); of any ~omputer which collects or generateæ data (ncomputer" being defined very broadly to include, e.qL,, any syste~ which ~ncludes a ~icroprocessor, such ~s ~ microprocessor based single loop controller).
In the presently preferred embodi~ent, the data types ~llowed by the build eXpert procedure ~re: 1) the l~te~t ~alu~ o~ a dat~ba~e var~blo; 2~ a ti~e we~ghted average over a given ti~e interval of the value of a dat2b~s~ variable; 3) n ~i~ple average over a given t~me lnterval o~ the d~crete d~ta values of ~ databa~e ~ariable s ~ ) the ~eedba~k error ~f a ~eedback block in th~ cuperYi~or proce~; 5~ ~he change in ~he value of the ~e~sured vari~ble o~ a super~isor feed~orw~rd block '7~5~

since the last time the block acted; 6),7) the goal values of sontrol loops in two particular lower level control systems; 8) th~ second ~ost recent value of a discretely sample process database variable; 9),10) the maximum and minimum limits for the manipulated variable ~alue in a supervisor control block. Other sources could be used, for example any kind of parameter from any of the systems named in the previous paragraph, or system lexical functions (such as the system clock). As a further alternative, it might also be advantageous in some embodiments to make one of the options here a one~line blank, in which the user could enter a pointer to a callable procedure to fetch a variable value.
In the presently preferred embodim~nt, the user must specify the data type before the data nu~ber. When - the data type is entered, a prompt line pops up on the template indicating the specific data type, which aids the user in entering the proper value for the data number. When the data number is entered, it is tested to be sure it is a meaningful entry for the data type specified. Some additional information is then displayed (such as a variable name and its units) to aid the user in confirming his input. These fields also serve to aid understanding of rule function and meaning when recalled for review or modification.

Constructinq the Expert System An expert system goes through four steps in using knowledge: 1) The expert gets information from the outside world; 2) analyzes that information using its rules; 3) deduces the correct conclusion from its analysis; 4) communicates its decision to the outside world.
Rules state that WHILE one thing is true THEN
something else must be true. For example, WHILE the s~

composition of water in the Feed mix drum is greater than 12%, we say "FEED MIX WATER COMPOSITION" is "HIGH".
Or, ~HILE "FEED MIX WATER COMPOSITION" is "HIGH", AND
"DEHY COLUMN BOTTOMS WATER" is "HIGH", we say "TOTAL
SYSTEM WATER" is "TOO HIGH". WHILE "TOTAL SYSTEM WATER"
is "TOO HIGH", we "Give a high water warning message."
This simple example shows the three basic types of rules which are used in the build-expert procedure: the sample retrieval rule described tests the VALUE (12~) of a process measurement (FEED MIX WATER), and assigns a value (HIGH, LOW, etc.) describing the condition of the measurement. The sample analysis rule given tests for combinations of values defined by other rules. If it finds the combination, the analysis rule creates a new condition (TOTAL SYSTEM WATER) and assigns a value (TOO
HIGH) describing that condition. The sample action rule described tests for one specific condition (TOTAL SYSTEM
WAT~R) has one specific value (TOO HIGH), and takes a specified action (Give a high water warning message).

Sample ExDert System An example of construction of an expert system using novel methods and system as set forth in the present application will now be described in detail.
~he sample system here chooses an optimum control action from among three possibilities. A key element of the problem here is to control the composition of by-product MFB in the product stream of a refining train like that shown in Figure 7. MFB is separated in two columns in series. Essentially equivalent response in MFB
composition can be achieved by changing the steam flow to either column. Both columns use high value steam in their reboilers. The first, the Xylene column, dumps the steam energy to cooling water. The second column, the MFB column, recovers most of the energy by generating ~'~9~;58 steam overhead. Equipment limitations constrain both steam flows to within high and low limits.
As column feed rate Yaries, steam loading can change from minim~m Steam on both cslumns to maximum steam on both columns. The optimum operation maximizes steam on the low cost column (MFB) and minimizes steam on the high C05t column (XYL).
In this example, control of the MFB composition is done statistically. The laboratory measurements of MFB
are statistically tested using Shewhart tests. The Shewhart tests determine the on aim status of MFB: Off aim high, Off aim low, or on aim. When MFB is off aim, the Shewhart test generates an estimate of how far off aim MFB i5. This estimate can be used to compute the feedback action needed to bring MFB back to aim: off aim high requires an increase in steam to the two columns, off aim low requires a decrease.
The expert system which is sought to be developed should instruct the supervisor procedure to make the least cost control action. Plant startup, problems, or poor manual operation may distribute steam in a non-op~imal way, and this cannot be known beforehand.
The objective will be to move toward the optimum steam distribution through control action response to off aim conditions. Steam will not be shifted for cost savings only, since this complicates control and may negatively affect quality.
Although this may seem like a trivial decision, it actually involves considering 3 variables in the correct sequence. This is where the "expertise" gets into the "expert" system. Developing the logic is the task of the human expert ! and the system disclosed herein merely expedites the transfer of that logic into the expert system. The process control decision tree which will be 5~

implemented, in the sample e~oodiment described, is as follows: First, decide whether to add or cut steam:
(l~ If adding steam:
(1.1) First check the MFB column. If MFB
S column stean below maximum, add steam here.
(1.2~ If the MFB c:olumn steam is maximum, then (1.2.1) ChecX the Xylene column. If xyle~e column steam is below l:he maximum, add steam here.
(1.2.2) If xylene column steam is maximum, the user cannot add steam. To get MFB on aim, feed to the column must reduced. Cut column feed.
(2) If cutting steam:
~2.1) First, check the xylene column. If xylene column steam is above the minimum, cut steam here.
(2.2) If xylene column steam is minimum, then (2.2.1) Check the MFB column. If MFB
columns steam is above minimum, cut steam here.
(2.2.2) If MFB column steam is minimum, the user cannot cut steam. To get MFB on aim, Feed to the column must be increased. Add column feed.
It is highly desirable that the decision tree being implemented should cover all the possible cases, and that the conclusions should be mutually exclusive. If it does not cover all the possible cases, the expert will sometimes be unable to come to a conclusion~ If the conclusions are not mutually exclusive, then more than one conclusion could exist. Although this might logically be possible, this condition ~ight mean unpredictability as to which conclusion will be reached, 80 that there would not be a reproducible basis for action.

Domain experts, in perfor~ing the analytic~ teps which the expert ~ystem should ideally emulate, will carry out many steps implicitly; but implementing a process in zl computer re~lires that eac:h 5tep be S expressly spelled out. To ~ake the decision, the u6er ~ust f irst 6pecify:
- what measurements will be used to evaluate the process condition (in this example, HFB_STEAM, XYL STEAM , DIRECTION OF C~NGE), - what ranges of value~ of the measurements (e.a. 40 > XYL STE~ match what status values for the measuremen~s (e.q_MID RANGE~;
- what combin~tions of status values (e.q.
~FB STEAM is MAX and XYL STEAM is MIN, and DIRECTION OF CHANGE is ADD) will result in what other conditio~s (e.q~ ACTION is CHANGE XYL STEAM);
- what must be done to make t~e desired action happen.
The det~iled specifications needed to bandle this proble~ are defi~ed ~s follows:
Measurements: For MFB column stea~, the goal on the computer loop f or MFB steam is a good measure. In the s~mple system referred to, thi~ i~ loop 30 in the "DMT PCS~ system. For xylene column ~team, the ~oal on the computer loop is a good measure. In th~ sample syste~ referred to, this is loop 5 in the "DMT PCS"
system. For t~e diraction of change, the best measure is the feedback error on the control block that will be changlng ~te2m (in this case, the third block in the ~upervisor procedure). For ~FB column ~team, we know the operat~ng li~its of ~team flow to the column (in thousands of pounds per hour (HPPH~):
~ 49.5;
MIN ~ 2805;
MID > 28 . 5 c 49 . 5 .

12~S5~3 And Ior the xylene column:
MA~ > 66 ~ 5 MIN < 4 0 . 5 MID > 40. 5 ~ 66. 5.
For the direction of action, we know that an of f aim high condition means a steam increase. our feedback block (in the supervisor pro~edure) is using the Shewhart deviation from aim as the measured variable, with an aim of 0. 0. Thus if the feedback error is positive, we increase steam:
ADD i f Feedback error > 0 CUT if Feedbac3c error < O or = O
For the analysis of these conditions, we need -to specify what combinations of conditions lead to what result. This expert provides only one result: it defines what the manipulated variable will be - xylene column steam ( "xyl col steam" ), MFB column steam ("MFB col steam"), or column feed ("column feed"). This logic results in the following rules:
Table 5 MANIPULATED VARIABLE is MFB COLUMN_STEAM While Direction of change is ADD
and MFB COL_STEAM is not MAX

MANIPULATED VARIABLE is XYL_COLUMN STEAM While Direction of change is ADD
and MFB_COL STEAM is MAX
and XYL COL STEAM is not MAX

MANIPULATED VARIABLE is COLUMN_FEED While Direction_of change is ADD
3 0 and MFB COL STEAM is MAX
and XYL COL STEAM is MAX

~75~

MANIPULATED V~RIABLE is XYL_COL~N S~EAM Whil~
Direction of_change is ~T
and XYL COL 5TEAM i5 not 2~IN

MANIPULATED_VARIABLE is MFB COI,UMN ST~AM while Direction_of change is CU~
and XYL_COL~STEAM is MIN
and MFB COL_STEAM is not MIN

MANIPULATED VARIABLE is COLUMN FEED While Direction of change is CUT
and XYL_COL_STEAM is MIN
and MFB_COL_STEAM is MIN

Note that: 1) some of the conditions are negated, i.e. it is specified that a rule or condition must NOT
have a certain value (MFB_COL_STEAM is ~OT MIN). 2) More than one test can set the value of the same condition (MANIPU~ATED_VARIABLE in this case). 3) More than one test can assign the same value to the same condition (i.e. the second and fourth both set MANIPULATED
VARIABLE to XYL_COL_STEAM, under different conditions).
By contrast, the retrieval rules each assign one of ~everal descriptors to a name which is unique to that specific rule.
Finally, the expert must do something with its conclusion to change the way the supervisor ~cts. In this case, assume that there are three feedback blocks in ~he supervisor procedure, all having the Shewhart ~FB
deviation as measured variable, with aims of 0Ø One (~3) manipulates xyl COL_steam, one (#4) MFB_column steam, and one (#5) column feed rate. The supervisor procedure includes a FORTRAN callable function na~ed ACS SELECT_9LOCX, which allows only one block out of a set to take action. The others are "de-selected'~ and ~2~3~58 stand ready to act if selected. When ACS select block is calle~, the first block number in the argument list becomes ~elected, the o~hers are deselected. ~railing zeros are ignored.
Thus, to enable the expert being built to çhan~e the control strategy, the following rules are added ::o the rule set:

While MANIPULATED VARIABLE is XYL_COL_ST~M Then do the FORTRAN statement:
ACS status - ACS select block ( 3, 4, 5, 0, 0, ) , While MANIPULATED VAXIABLE is~FB_COL_STEAM Then do the FORTRAN statement:
ACS status = ACS select_block ( 4, 3, 5, 0, 0, 0 ) .

While MANIPULATED VARIABLE isCOLUMN FEED Then do the FORTRAN statement:
ACS status - ACS select_block ( 5, 3, 4, 0, 0, 0 ) The foregoing data entries are all the inputs needed to define the expert ~ystem.
Within the supervisor procedure, an expert system can be developed for each block. Used in this way, the build-expert procedure will create the FORTRAN
subroutine Blockn expert system (where n is the block number, e. the subroutines will be named BLOCX2 EXPERT SYSTEM etc.), compile it, and place it in the proper library so that it can be called from within a supervisor block (by a user routine).

Ex~ert Rule Structure This ~ample embodiment provides an example which may help clarify what an expert procedure does. Some 1X~5~
more general teachings regarding expert system methods and structure will now be set forth.
Figure 2 is a schematic representation of the organization preferably used for ~he knowledge base.
Three main categories of rules are used, namely retrie-val rules 210, analysis rules 220, and action rules 230.

Retrieval Rules The retrieval rules 210 each will retrieve one or more quantitative inputs (which may be, e.~., sensor data 157 from one of the sensors 156, historical data 141 and/or laboratory measurements 162 from a historical data base 140, limits on variable values, goals 132 defined by the supervisor procedure 130, combinations of these, or other inputs). One of the significant advantages of the system described is that it provides a very convenient user interface for acces~ing quantitative inputs ~rom a very wide range of sources:
essentially any data object which can be reached by the host computer can be used. (The presently preferred emhodiment uses DECnet a~d serial communication lines to link the computer which will be running the expert system with the various computers it may be calling on for data, but of course a wide variety of other networking, multiprocessor, and/or multitasking schemes could be used instead.) In the presently preferred embodiment the retrieval rules are of two kinds: the simpler kind (referred to as "variable rules") will name one quantitative value (which may optionally be derived from several independently accessed quantitative inputs), and assign one of a predetermined set of descriptors (variable status values 222) to that name. Each of the more co~plex retrieval rules (referred to as "calculation rules~) per~its descriptors to ~e assigned selectively lX~7558 to a name in accor~ancP wi~h one or more calculated values (which may optionally be derived from a number of quantitative variables).
Figure 3 shows the template used for a retrieval rule in the presently preferred embodiment, together with a sample of a retrieval rule which has been entered into the te~plate. The areas in this drawing which are surrounded by do~ted lines indicate the parts o~ the template which the user can modify, and which are preferably highlighted to the user in some fashion, e.q.
by showing them in reverse video. In this example, the user has typed in the rule name as "xylene column steam." The build-expert software has automatically translated this rule name, by changing all the spaces in it to underscores, so that it appears as a one word name. (This can be conveniently used as part of a variable name in conventional computer languages.) Thus, the rule shown in Figure 3, when translated into an expert procedure by the build-expert procedure, will define a set of variables whose names each begin with "XYLENE_COL~MN_STEAM."
For example, in the presently preferred embodiment the rule shown will translate into the following set of variables:
"XYLENE COLUMN_STEAM STATUS" is a character variable (also known as a string or alphanumeric variable) which will have a string value which is either "MIN," "MAX," or "MID;"
"XYLENE_COLUMN STEAM VALUE" will be a real variable, representing the quantitative value originally retrieved for the parameter;
"XYLENE COLUMN_STEAM_AGE" will be an integer variable representing t~e age o~ the quantitative value originally retrieved;

~X~'7S~8 "XYLENE COLUMN STEAM ASTAT" will be a character variable which is defined to have values of "TOO OLD" or "OX," depending on whether the aqe value is within limits (note, for example, that this variable could easily be configured as a logical variable instead);
and "XYIENE COLUMN STEAM FIRED" will be a logical variable which indicates whether this particular rule has been fired (on a given pass).
In filling out the retrieval rule template, the user must fill in at least two of the classification blanks. However, in the presently preferred embodiment, only five classification ranges are permitted. (This limit could be changed, but there are significant advantages to permitting the user to input only a restricted number of ranges. Where the process control algorithm absolutely demands that the variable be classified into more ranges, two or more process variable rules could be used to label up to eight or more range Another constraint used in the presently preferred embodiment is that the user must enter at least the first two open ended ranges. He may enter up to three bounded ranges, to provide a complete coverage of all cases, but he must enter at least two open ended range specifications.
In the presently preferred embodiment, the build-expert procedure checks to see that the ranges defined are comprehensive and non-overlapping, before the rule is permitted to be added to the rule base.
Figure 4 shows an example of a different kind of retrieval rule, known as a calculation rule. The menu for ~his rule is (in the presently preferred embodiment) presented to the user as two screens. The user may specify up to ten quantitative inputs, of any of the 7~

types just referred to, as well as up to ten values arithmetically derived from these inputs (or constants).
By having some of the derived values refer back to other ones that are derived values, quite complex formulas may be implemented. (One advantageous use of such formulas may be to relate off-line time-stamped laboratory measurements with the continuously-measured values of the same (past) time era, ~g~ in a component material balance.) Moreover, notice that the variable values and calculated values thus assembled may be used not only :o define a "key value" to be categorized, but also ~-o de~ine the limits of the various categories against which the Xey value is sought to be tested.

Analvsis Rules Analysis rules generally are used to embed the natural lan~uage reasoning as practiced by the domain expert. One important distinction betwee~ retrieval rules and analysis rules is that each retrieval rule has a unique name, but the analysis condition names defined by analysis rules are not necessarily uni~ue. Figure 5 shows an example of an analysis rule 220. Again, the portions of the template which the user can modify are shown inside dashed boxes. Note that the template preferably used defines an analysis condition name and assigns a descriptor to that analysis condition name if specific conditions are met. In the presently preferred embodiment, the only tests permitted are ANDed combinations of no more than five logical terms, each of which can consist only of a test for identity (or non-identity) of two strings. Moreover, the string identity tests are preferably set up so that each of he com-parisons either tests a retrieval rule name to see if a certain variable status value 212 was assigned by that rule, or tests an analysis condition name to see if a 5~f~
certain analysis status value 222 was assigned by one of the analysis rules. That is, as seen schematically in Figure 2, there is pstential for recursion among ~he analysis rules 220 considered as a group, since some of S the analysis rules 220 can refer to the outputs of other analysis rules 220. Optionally the analysis rules could be sequenced so that there would never be any open-ended recursions, but in the presently preferred embodim~nt this extra constraint is not imposed.
Any one analysis condition name may (under various conditlons) ~e assigned values by more than one analysis rule. That is, each analysis rule is preferably set up as an IF statement, and multiple such IF statements will typically be needed to specify the various possible values for any one analysis condition name.
In the presently preferred embodiment, the status of every analysis condition name and variable rule name are initially defined to be "unknown," and the logical comparisons are implemented so that no test will give a "true" result if one term of the comparison has a value of "unknown."
The order in which the analysis rules are executed may be of importance where an analysis condition name is multiply de~ined. That is, it may in some configurations be useful to permit the conditions of the various analysis rules 220 to be overlapping, so that, under some circumstances, more than one analysis rule may find ~ true precondition and attempt to assign a status value to the same analysis condition name. In this case, the sequence of execution of the analysis rules 220 can optionally be allowed to determine priority as between analysis rules. However, as mentioned a~ove, this is not done in the presently preferred embodiment.
Moreover, more than one analysis rule may assign the same analysis status value 222 to the same analysis condition name, under different circumstances.
It can be advantagesus, for purposes of documenting the reasoning embedded in the expert system, to give names to the analysis rules which include bo~h the name and descriptor possibly linked by that rule: thus, for instance, a rule which is able to conclude that column operation is normal ~ight be named "COLUMN_OP NOP~L.'~

Action Rules Figure 6 shows the presently preferred embodiment of the template for action rules, and an example of on~
action rule which has been stated in this format. Again, the portions of the template which the user can modify are indicated by dashed boxes.
The user has chosen to name this particular action rule "Change Xylene Steam," which the build-expert software has translated into CHANGE XYLENE STEAM (for incorporation into various variable names such as "C~ANGE_XYT~NE STEAM FIRED"). The names assigned to action rules are primarily important for documentation, so that, when this user or another user looks back through the rule base, the use of clear rule names for action rules will help to understand what the structure of the expert system's inference chaining is. In fact, it may be advantageous, as in the example shown, to ~enerally pick analysis status values ~22 which have fairly descriptive names, and then, to the extent possible, name the action rules identically with the corresponding analysis status values.
Not~ also that the action rules can refer bacX to a variable status value 212 as well as to an analysis status value 222.
Thus, in the presently preferred embodiment the action rules embody an absolute minimum of logic. They ~.~97S~

are used primarily as a translat:ion from descriptive key words embedded within the inference chaining structure to the actual executable statements tor command procedures) which speci~y the action to be taken. Thus, one way to thinX about the advantages of the expert system organization preferably used is that the emulation of natural language reasoning i5 concentrated as much as possibl2 in the analysis rules, while ~he retrieval rules are used to provide translation from quantitative measurements into input usable with natural language inference rules, and the action rules are used almost exclusively to provide translation from the natural language inference process back to executable command procedures which fit in well with the computer system used.
Each of the action rule templates also gives the user several choices for the action to be taken to implement the action rule if its precondition is met.
The user can either insert an executable statement ~in FORTRAN, in the presently preferred embodiment) or insert a pointer to a command procedure, or simply have the action rule send advisory messages. The third option is useful for debugging, since the expert can be observed to see what actions it would have taken, without risking costly errors in the actual control of the system.
In the example shown, an executable FORTRAN
statement is used, but the statement specified merely passes an action code back to the supervisor process. In the example shown in Figure 6, the procedure call given will cause the ~upervisor procedure to turn on the block whose number is given first, and turn off all other blocks whose numbers are given. Thus, the statement acs status = acs select block ~3, 4, 5, 0, 0, 0) ~X9~7558 would change the status of block 3 to "on-selected"
(assu~ing that it did not need to be initialized), and would set the status values of blocks 4 and 5 to "on-deselected." Th~s, when the expert system has completed running, the supervisor procedure which called the expert procedure as a subroutine can selectively execute bluck functions depending on the values passed back to it by the subroutin~.
Thus, the action rules permit a very large variety of actions to be performed. For example, one optional altexnative embodiment provides synthetic-speech output;
optionally this can be combined with a telephone connection, to pe~mit dial out alert messages (e.~. to a telephone number which may be selected depending on the time of day shown by the system clock, so that appropriate people can be notified at home if appropriate).
Another optional embodiment permits an action rule to call up a further sub-expert. This might be useful, for example, if one expert subprocedure had been customized to handle emergency situations - who should be called, what should be shut down, what alarms should be sounded.

Generating the Exp~rt Procedure After the user has input as many rule statements as needed, or has modified as many of an existing set of rule templates as he wishes to, he can then call the generate code option to translate the set of templates 115, including the user inputs which have been made into the rule templates, to create the expert system 120.

GeDLeratina Source Code As a result of the constraints imposed in the various rule templates, the translation from the constrained format of the templates is so direct that the executable rules can be ~enerated simply by a series of appropriate string-equivalent tests, string-append operations, logical-equivalence tests, arithmetic operations, and fetches.
Preferably three passes are performed: the ~irst does appropriate character type declarations; the second loads the appropriate initializations for each rule; and the third translate~ the inference rules themselves.
An example of th initialization steps is seen in initialization of the analysis rules: an initial value such as "dont know" is assigned to each condition name, and the eguivalence tests are redefined slightly by the translation procedure, so that, until some other value is assigned to the name by another rule, the statement "name" = "descriptor"
will be evaluated as false, and the statement NOT("name" = "descriptor") will also be evaluated as false.
Sam~le Source Code A portion of the source code-for the procedure which actually performs this function, in the presently preferred embodiment, is as follows.

;58 ~k~

C****~*****************~*~***~*~*lt C

C Build expert.for C Routine to generate FORTRAN expert system code using C the process rulebase.
C
C

C*~*******~**********~*******~**~****,l.*
C

Subroutine Build expert C

Include 'pace$includes:Variable rule Params.inc' Include 'pace$includes:Expert data.inc' Include 'paceSincludes:Analysis commons.inc' Include 'paceSincludes:Analysis rule.inc' Include 'pace$includes:Action_commons.inc' Include 'pace$includes:Action rule.inc' Include 'pace~includes:Action params.inc' . C
Logical First Logical No more Character*25 Last cond Charaçter~80 code dir file Character*80 Directory Integer*2 L dir Character*39 Subroutine name Character*14 Subprocess_name Character~3 Cblock Integer*2 L sp Character*1 Search_string Integer~2 Srlen C

Call Fdv$Putl(' Generating Expert System code....') C

C...Rewind the code file C

d write(6,*~ ' will rewind code file' Rewind ( Unit = Code lun ) Next label = 2 C

C...Get the name of the expert system code file, pick out the C subr name from it C

d Call Fdv$putl ( 'Will translate logicals.') Call Lib$sys trnlog ( 'PACE$RULES' ,, Directory ,,,) Call Lib$sys trnlog ( 'PACESCODE' ,, Code dir file ,,,) d Call Fdv$putl ( 'Did translate logicals.') Istart = Index ( Code_dir file, ']' ) ~ X9~S5~1 Subroutine name = Code dir ~ile(Istart~1:80)//Blank d C~ll Fdv$putl ( 'Will get ~ndex of ~'.".') Iend = Index ( Subrsutine name, ~
d Call Fdv$putl ( 'Will clip subrout name~') If ( Ie~d .gt. 1 ) Then Subroutine name = Subroutine name(l:Iend-1)//BlanX
Else Subroutine name = 'Expert'~/BlanX
End If d Call Fd~$putl ( 'Will trim subroutine name.') Call Str$trim ( Subrou~ine name, Subroutine name, Srlen ) d Write ( 6, 100 ) Subroutine name Write ( Code lun, lOO ) Subroutine name C

C...construct a sub-process name C

If ( Subroutine name(l:5) .eq. 'BLOCX' ) Then d Call FdvSputl('Is block.') d Call Fdv$wait ( It ) Read ( Subroutine_name(6:8), '(I3)' ,err= 91 ) Iblock d Call Fdv5putl('Is ~ 99.') d Call FdvSwait ( It ) Liblock - 3 5O To 93 91 Read ( Subroutine name(6:7), '(I2)' ,err= 92 ) Iblock d Call Fdv$putl('Is > 9.') d Call FdvSwait ( It ) liblock = 2 Go To 93 92 Read ( Subroutine name(6:6), '(Il)' ,err= 93 ) Iblock d Call Fdv$putl('Is ~ 10.') d Call PdvSwait ( It ) Liblock - 1 Go To 93 93 Write ( Cblock, '(I3)' ) Iblock Istart = 4 - Liblock Subprocess name = 'B'//Cblock(Istart:3)//' ' L sp = 3 + Liblock Else L sp - l End If C

100 Format( 1 ' Options /Extend source', /, 'C***********************************~******~**~,/, 'C' ,/~
1 'C Expert System Code',/, 1 'C', /~
'C*****~*************~********~**********~****',/, 1 'C', /~
1 ' Subroutine ', A, /, 1 'C', /, 1 ' Include ''ACS~includes:ACSserV.inc'' ' , / , 1 ' Include ''ACS~includes:ACSstatus. inc" ~ , / , l ' Include ''ACSSincludes:Sys functions.inc'' ' , / , l ' Include ''($Jpidef)'' ' , / , l' Integer*4 VssS to ascii time' , / , 1 ' Integer This Pass-firesl , / , 1 ' Character~25 Unknown' , / , 1 ' Parameter ( Unknown = ''Unknown ")' l ' Character~25 GK' , / , 1 ' Parameter ( OK = ''OK ? 7 ~ /:
1 ' Character*25 Too old' , / , 1 ' Parameter ( Too old = ''Too old '')' l ' Integer~4 Now' , / , 1 ' Integer*4 Then' , / , 1 ' Cbaracter*18 C now' , / , 1 ' Integer~4 Itemlist~4)' , / , 1 ' Integer~2 Code(2)' , / , 1 ' Equivalence ( Itemlist(l) , Code(1) ~' , / , l ' Integer*4 Mode' , / , l ' Integer~2 Len' , / , 1 ' Character*80 Line' , / , 1 'C' 1 ) d write(6,~) ' wrote header info.' C

C..Make declaration code for variable rules C
C

First = .True.
1 Continue C
C..Read ~ rule C

Call Read var rule Params ( First , No more ) If ( No more ) Go To 200 C

C..Write out FORT~AN declarations C
Call Str$trim ( Rule name , Rule name , Len ) Write ( Code lun , 101 ) ~Rule name(l:len) , J=1,5 ) 101 Format ( 1 ' Real*4 ' , A , '_value' , ~ , 1 ' Integer*4 ' , A , ' age' , / , l ' Character*25 ' , A , ' stat' , / , 1 ' Logical*1 ' , A , ' fired' , / , 1 ' Character*10 ' , A , ' astat' , / , 1 'C' 1 ) C

Go To 1 C

200 Continue ~375~

C..Make declaration code for calculat:ion rules Call Declare calc rules C..Make declaration ~ode for analysis rules C

Last_cond = ' First = .True.
2 Continue C..Read A rule Call Read anal_rule arams ( First , No_more ) If ( No more ) Go To 201 C..Write out FORTRAN declarations Call Str$trim ( An_cond_name , An_cond_name , L2n ) Call StrStrim ( An rule name , An rule_name , ILen ) Write ( Code lun , 104 ) If ( An cond_name .ne. Last_cond ) 1 Write ( Code_lun , 102 ) (An_cond_name(l:len) ) Write ( Code_lun , 103 ) (An_rule name(l:Ilen) ) Last cond = An cond name 102 Format ( 1 ; Character*25 ' , A , '_stat' 103 Format ( 1 ' Logical*l ' , A , '_fired' 104 Format ( Go To 2 201 Continue C..Make declaration code for action rules CC
First = .True.
252 Continue C..Read A rule Call Read action rule Darams ( First , No more ) If ( No more ) Go To 251 C..Write out FORTRAN declarations 129~S5~3 Call Str$trim ( Ac rule name , Ac rule_name , Len ) Write ( Code_lun , 262 ) Ao rule_name(l.len) 262 Format ( 1 ' ~ogical*l ' , A , ' fired' , / , 1 'C' 1 ) Go To 252 C

251 Continue C
C

C...Now Write Init~alization code C

Write ( Code lun , 401 ~ Subroutine_name (l:Srlen) 401 Format ( 1 'C', / ~
1 'C Initialize the status values.' , / , 1 'C', /
1 ' Van status = VssS_from ascii_time ( ~ , Now )' , /
1 ' Van status = VssS_to_ascii_time ( Now , C_Now )' , / , 1 ' Code(1) = 4 ' , / , 1 ' Code(2) = jpiS mode' , / , 1 ' Itemlist(2) = %loc(Mode)' , / , 1 ' Itemlist(3) = %loc(Len)' , / , 1 ' Itemlist(4) - 0' , / , 1 ' sys status = sys$getjpiw ( ,,,Itemlist,,,)' , / , 1 'd Write(6,901) C now' , / , 1 '901 Format ( / , ~I Running ' , A , ' at ll , A )' , / , 1 'C
1 ) C.. ...Initialize variable rules - This will set logical flags false and : C retrieve the necessary data for the rule.
C
First = .True.
402 Continue C
C

C..Read A rule C

: Call Read var rule ~arams ( First , No more ) I f ( No more ) Go To 420 Call Str$trim ( Rule name , Rule_name , ~en ) Write ( Code lun , 403 ) ( Rule name(l:LRn) , J =1,4 ) 403 Format ( 1 'C', / ~
1 'C....' , A t I rule initialization' , / , 1 'C', / ~
1 ' ' , A , ' astat = Unknown' , / , lX975SB
1 ' I , A , ' stat = Unknown' , / , 1 ' ' , A , '_fired - .False.' If ( Ret_meth .eq. Current val ) Then Write ~ code lun , 404 ) Var num , (Rule name(l:len) ,J=l, 2) 404 Format ( 1 ' Call Get_cur data ( I , I4 , ' , i , A , '_value , ' '_age ) 1 ) Else If ( Ret_meth . q. Discrete avg ) Then Write ( code_lun , 405 ) Re~_time , ~Jar_n (Rule_name(l:len),J=1,2) 405 Format ( 1 'C' ~ / ~
1 ' Then = Now + ' , I12 , / , 1 ' Call Get_disc avg data ( ' , I4 , I , ' , ~ value A , ' age , Then , Now )' 1 ) Else If ( Ret meth .eq. Time_wt avg ) Then Write ( code lun , 406 ) Ret time , Var_n (Rule name(l:len), J=l, 2 ) 406 Format t 1 'C', / ~
1 ' Then = Now + ' , I12 , / , , A 1 ' Call Get_time wt avg data ( ' , I4 , ' , ' , A , ' val , ' age , Then , Now )' 1 ) Else If ( Ret meth .eq. Sec last vant Doint ) Then Write ( code lun , 411 ) Var num , 1 Rule name(l:len) 411 Format ( 1 'C', /, 1 ' Call Get sec last vant Point ( ' , I4 , ' , ' , A , ' , Itime stamp )' Else If ( Ret meth .eq. ACS ff delta ) Then Write ( code lun , 407 ) Var num , Rule name(l:len) 407 Format ( 1 'C', / ~
1 ' ACS status = ACS get FF delta ( I , I4 , ' , ' , A , ' ) ' 1 ) Else If ~ Ret meth .eq. ACS fb_error ) Then ~37S5i~

Write ~ code_lun , 408 ) Var_num , Rule name(l:len3 408 Format ( 1 'C' ~ / ~
1 ' ACS status a ACS get fb_error ( ' , I4 , ' , ' , A , ' ) Else If ( Ret meth .eq. PCS DMT loop goal ) Then Write ( code lun, 409 ) Var num , Rule name(l:len) 409 Format ( 1 'C', / ~
1 ' ~CS status = ACS get PCS soal ( ''DMT '' , ' , l I , ' , ' , A , ' value )' 1 ) Else If ( Ret meth .eq. PCS TPA loop goal ) Then Write ( ~ode lun , 410 ) Var num , Xule name(l:len) 410 Format ( 1 'C', ~, 1 ' ACS status = ACS get PCs goal ( ' 'TPA ' ', ', 1 I , ' , ' , A , ' value )' 1 ) ~ls~
Write( Code lun , * ) 'C....Bad retrieval method' ~nd If C
: Write ( Code lun , S10 ) (Rule name(l:len),J=1,2) 510 Format ( l 'd write~6~*) '' ' , A , ' value = '' , ' , A , '_value' C

Go To 402 C
420 Continue C
C....Initialize calculation rules C

Call Init calc_rules C

C....Initialize analysis rules C

Last cond = ' First = .True.
440 Continue C
C

C..Read A rule C

Call Read anal rule ~arams ( First , No_more ) If ( No more ~ Go To 450 C

Call Str$trim ( An cond name , An cond name , Len ) Call StrStrim ( An rule name , An_rule name , ILen ) Write ( Code lun , 441 ) ( An rule_name(l:ILen) , J =1,2 ) If ( An cond name .eq. Last cond ) Go To 440 .57 ~2~75~8 Last cond = ~n cond name ~ rite ( Code lun , 442 ) ( ~n_cond nam~ Len) , J =~,1 ) 441 Fsrmat ( 1 'C', /, 1 'C....' , A , ' rule initialization' , / , 1 ' ' , A , ' fired = .Fallse.' 442 Format ( 1 ' ' , A , '_stat = UnXnown' C
Go To 4 4 450 Continue C....Initialize action rules First = .True.
460 Continue C
C..Read A rule C

Call Read action rule params ( First , No_more ) If ( No_more ) Go To 490 Call Str$trim ( Ac rule name , Ac rule name , Len ) Write ( Code lun , 461 ) ( Ac rule name(l:Len) , J =1,2 461 Format ( 1 'C', / ~
1 'C....' , A , ' rule initialization' , / , 1 'C', /, 1 ' ' , A , ' fired = .False.' Go To 460 490 Continue 500 Continue C...Write the rule code ¦ Write ( Code lun , 501 ) 501 Format ( 1 'C', /, 1 ' 1 Continue' , / , 1 'C' ~ / ~
1 ' This Pass_fires = 0' , / , 1 'C' C
C...Write out variable rule code C

~ ~97558 First - .True.
502 Continue C

C..Read A rule C 11 Read_var_rule Params ( First , No_more ) If ( No more ) Gs To 600 C

Call Str$trim ( Rule name , Rule name , Len ) If ( Age limit .eq. Empty ) Age limit = -365*24*60*60 C

Write ( Code_lun , 299 ) ( Rule_name(l:len),J=1,3) , Abs(Age_ 1 ( Rule name(l:len),J=1,2) 299 Format ( 1 'C', /, 1 'C....' , A , ' Rules ' , / , 1 'C', / ~
1 ' If ( ' , /
1 ' 1 ( ' , A , '_astat .eq. Unknown ) .and. ' , / , 1 ' 1 ( ' , A , '_age .le. ' , I , ' ) ' , / , 1 ' 1 ) Then ' , / , 1 ' ' , A , '_astat = OK ' , / , 1 'd Write(6,*) ''' , A , ' age is OX. "' , / , 1 ' This Dass fires = This pass fires + 1' , / , 1 ' End If' 1 ) C

Write ( Code_lun ,Fmt=298 ) ( Rule_name(l:len),J=1 Abs(Age limit) , 1 ( Rule name(l:len),J=1,2) 298 Format ( 1 'C', / ~
1 ' If ( ' , / , 1 ' 1 ( ' , A , '_astat .eq. Unknown ) .and. ' , / , 1 ' 1 ( ' , A , ' age .gt. ' , I , ' ) ' , / , 1 ' 1 ) Then ' , / , 1 ' ' , A , ' astat = Too old' , / , 1 'd Write(6,*) ''' , A , ' age is Too old. "' , / , 1 ' This pass fires = This Pass_fires + 1' , / , 1 ' End If' 1 ) Write( code lun , 505 ) (Rule_name(l:len),J=1,3) , Log_opl , 1 Rule_name(l:len) , Statusl , Rule name(l:len) , 1 Statusl , Rule_name~l:len) 505 Format ( 1 'C', / ~

~L~97~i5~
1 ' I~ ( ' , / , 1 ' 1 ~ .not. ' , A , ' fired ) .and. ' , / , 1 ' 1 ( ' , A , ' astat .eq. OK ) .and. ' , / , 1 ' 1 ( ' , A , '_value ' , A4 , ' ' , F12.5 , ' ) ' , 1 ' 1 ) Then ' , / , 1 ' ' , A , ' stzt = ''', A25 ,'''' , / , 1 qd Write(6,~) '" , A , ' =tat is ' , A ,'''' , / , 1 ' ' , A , ' fired - .True~' , / , 1 ' This ~ass fires 2 This Pass fires + 1' , / , 1 ' End If' 1 ) C

Write( code lun , 506 ~ (Rule name(l:len),J=1,3) , ~og_op8 , 1 Rule name(l:len) , Status8 , Rule name(l:len) , 1 Status8 , Rule name(l:len) 506 Format ( 1 'C', / ~
1 ' If ( ' , / , 1 ' 1 ( .not. ' , A , ' fired ) .and. ' , / , 1 ' 1 ( ' , A , ' astat .eq. OK ) .and. 7 , / , 1 ' 1 ( ' , A , ' value ' , A4 , ' ' , F12.5 , ' ) ' , 1 ' 1 ) Then ' , / , 1 ' ' , A , ' stat = "', A25 ,'''' , / , 1 'd Write(6,*) ''' , A , ' stat is ' , A ,'''' , j , 1 ' ' , A , ' firsd = .True.' , / , 1 ' This_pass fires = This Pass fires + 1' , / , 1 ' End If' 1 ) C

If ( Status2 .neO ' ' ) Then C

Write~ code lun , 508 ) (Rule name(l:len),J=1,3) , Log op2 , 1 Rule name(l:len) , Log op3 , Limit3 , 1 Rule_name(l:len) , Status2 , Rule name(l:len) , 1 Status2 , Rule name(l:len) 508 Format ( 1 'C' ~ / ~
1 ' If ( ' , / , 1 ' 1 ( .not. ' , A , ' fired ) .and. ' , / , 1 ' 1 ( ' , A , '_astat .eq. OK ) .and. ' , / , 1 ' 1 ( ' , A , ' value ' , A4 , ' ' , F12.5 , ' ) .and 1 ' 1 ( ' , A , ' value ' , A4 , ' ' , F12.5 , ' ) ' , 1 ' 1 ) Then ' , / , 1 ' ' , A , ' stat = ''', A25 ,'''' , / , 1 'd Write(6,*) "' , A , ' stat is ' , A ,'''' , / , 1 ' ' , A , ' fired = .True.' , / , 1 ' This Pass_ fires = This pass_fires + 1' , / , 1 ' End If' 1 ) ~2~'755~3 End If C

If ( Status4 .ne. ' ' ) Then C

Write( code lun , 509 ) (Rule_name(l:len),J=1,3) , ~og_op4 , 1 Rule name(l len) , Lo~ op5 , Limit5 , 1 Rule~name(l:len) , Status4 , Rule_name(l:len) , 1 Status4 , Rule name(l:len) 509 Fo~mat ( 1 'C' ~ / ~
1 ' If ( ' , / , 1 ' 1 ( .not. ' , A , ' f ired ) . and. ' , / , 1 ' 1 ( ' , A , '_astat .eq. OK ) .and. ' , / , 1 ' 1 t ' , A , ' value ' , A4 , ' ' , F12.5 , ' ) .and 1 ' 1 ( ' , A , '_value ' , A4 , ' ' , F12.5 , ' ) ' , l ' l ) Then ' , / , l ' ' , A , ' stat = " ', A25 ,'''' , / , 1 'd Write(6,*) " ' , A , '_stat is ' , A ,'''' , / , 1 ' ' , A , ' fired = .True.' , / , l ' This Pass_fires - This Pass_fires + 1' , / , 1 ' End If' 1 ) End If C

If ( Status6 .ne. ' ' ) Then C

Write( code_lun , 511 ) (Rule_name(l:len),J=1,3) , Log_op6 , 1 Rule name(l:len) , Log_op7 , Limit7 , l Rule_name(l:len) , Status6 , Rule_name(l:len) , l Status6 , Rule name(l:len) 511 Format ( 1 'C', / ~
1 ' If ( ' , / , 1 ' l ( .not. ' , A , ' fired ) .and. ' , / , 1 ' 1 ( ' , A , ' astat .eq. OK ) .and. ' , / , l ' 1 ( ' , A , '_value ' , A4 , ' ' , F12.5 , ' ) .and 1 ' 1 ( ' , A , '_value ' , A4 , ' ' , F12.5 , ' ) ' , 1 ' 1 ) Then ' , / , 1 ' ' , A , '_stat = ''', A25 , " '' , / , 1 'd Write(6,*) " ' , A , ' stat is ~ ~ A
1 ' ' , A , '_fired = .True.' , / , 1 ' This Pass f ires = This Dass fires ~ 1 ' , / , 1 ' End If ' 1 ) End If C

Go To 502 C

'1 ~9755~
600 Continue C

C...Write out calculation rule code C

Call ~rite calc rules C...Write out analysis rule code First = .True.
C

602 Continue C

C~.Read A rule C

Call Read an 1 rule_params ( First , No_more ) If ( No more ) Go To 700 C

Call 5tr~trim ( An cond_name , An cond name , ,.en j Call StrStrim ( An rule name , An rule_name , ILen ) Write ( Code_lun , 699 ) (An_rule name(l:Ilen),j=1,2) 699 Format ( 1 '~', / ~
l 'C....' , A , ' Rules ' , / , 1 'C', /, 1 ' If ( ' , / , l ' 1 ( .not. ' , A , '_fired ) .and. ' 1 ) If ( An rulel .ne. ' ' ) Then Call Str~trim ( An_rulel , An rulel , Len ) C

If ( An notl .eq. '.NOT.' ) Then Write( code lun , 1001 ) An rulel(l:len) End If 1001 Format ( 1 ' 1 ( .not. ( ' , A , ' stat .EQ. Unknown ) ) .and.' Write( code lun , 608 ) An notl , An rulel(l:len) , 1 An statusl 608 Format ( 1 ' 1 ( ' , A , ' ( ' , A , ' stat .EQ. ' " , A , ' .and.' 1 ) End If C

If ( An rule2 .ne. ' ' ) Then Call StrStrim ( An rule2 , An rule2 , Len ) C

If ( An not2 .eq. '.NOT.' ) Then Write( code lun , 1001 ) An rule2(1:1en) ~297S5~3 End If Write( code_lun , 609 ) An_not2 , An_rule2(1:len) , 1 An_status2 609 Format ( 1 ' 1 ( ' , A , ' ( ' , A , ' stat .EQ. ''' , A , ' .and.' 1 ) ~nd If C

If ( An rule3 .ne. ' ' ) Then Call Str$trim ( An rule3 , An_rule3 , Len ) C
If ( An not3 .eq. '.NOT.' ) Then Write( code lun , 1001 ) An_rule3(1:len) End If Write( code lun , 610 ) An not3 , An rule3(1:1en) , 1 An status3 610 Format ( 1 ' 1 ( ' , A , ' ( ' , A , ' stat .EQ. ''' , A , ' .and.' 1 ) End If C

If ( An rule4 .ne. ' ' ) Then Call StrStrim ( An rule4 , An rule4 , Len ) ¦ If ( An not4 .eq. '.NOT.' ) Then j Write( code lun , 1001 ) An rule4(1:len) End If l Write( code lun , 611 ~ An_not4 , An_rule4(1:1en) , ¦ 1 An_status4 611 Format ( 1 ' 1 ( ' , A , ' ( ' , A , ' stat .EQ. ' " , A , ' .and.' I ' 1 ) I End If i C
I If ( An rule5 .ne. ' ' ) Then Call StrStrim ( An rule5 , An rule5 , Len ) C
If ( An not5 .eq. '.NOT.' ) Then Write( code lun , 1001 ) An_rule5(1:1en) End If Write( code lun , 612 ) An not5 , An_rule5(1:len) , 1 An status5 612 Format ( 1 ' 1 ( ' , A , ' ( ' , A , '_stat .EQ. ''' , A , ' .and.' ~2975t~8 1 ~
End If C

Call Str$trim ( An cond_name , An cond name , Len ) Write ( Code lun , 613 ) 1 (An_cond_name(l:len~,j=l,l) , An end_status , 1 ~n cond name(l:len),j=l,l) , An_end status , 1 (An_rule nametl:Ilen),j=1,1) 613 Format ( 1 ' 1 ( .True. ) ' , / , 1 ' 1 ) Then ' , / , 1 ' ' , A , ' stat = ''', A25 ,'' " , / , 1 'd Write(6,*) "' , A , ' stat is ' , A ,;''' , / , 1 ' This_pass fires = This Pass fires ' ' 7 ~ /, 1 ' End If' 1 ) C

Go To 602 C

700 Continue C
-C...Write out action rule code C

First = .True.
C

702 Continue C
C..Read A rule C

Call Read_action rule params ( First , No more ) If ( No_more ) Go To 800 C
Call Str~trim ( Ac rule_name , Ac_rule_name , Len ) Write ( Code_lun , 799 ) (Ac_rule_name(l:len),j=1,2) 799 Format ( 1 'C' ,~ / ~
1 'C....' , A , ' Rules ' , / , 1 'C', /
1 ' If ( ' , / ~
1 ' 1 ( .not. ' , A , '_fired ) .and. ' 1 ) C

Call Str~trim ( Ac rulel , Ac rulel , Len ) C

Write( code lun , 708 ) Ac rulel(l:len) , 1 Ac_statusl 708 Format ( 1 ' 1 ( ' , ' ( ' , A , '_stat .EQ. ' " , A , ''' ) ) ' 1 ) .
C

~ i~97S58 c Call StrStrim ( Ac_rule name , Ac rule name , Len ) Write ( Code lun , 713 ) (Ac_rule name(~:len),j=1,2) 71~ Format ( 1 ' 1 ) Then ' , / , 1 'd Write(6,~) " Doing astion rule ' , A , '''' , / , 1 ' ' , A , ' fired = .True.' , / , 1 ' This pass_fires = This ~ass fires + 1' C

Call Str$trim ( Ac data line , Ac_data line , Len ) If ( Iac_type .eq. Ex~c fort_statement ) Then Write ( code lun , 714 ) Ac data_line(l:Len) 714 Format ( 1 ' ' , A
Else ~f ( Iac type .eq. Exec_dcl procedure ) Th~n Subprocess name(L sp:l4) = Ac rule_name Call Str5trim ( Subprocess_name , Subprocess_name , ILen ) Write ( code_lun , 715 ) Ac_data_line~l:Len) , 1 Subprocess_name(l:Ilen) 715 Format ( - 1 ' Call Lib$spawn ( IIQ- , A , "',,,,''' , A , ''' , Else If ( Iac type .eq. Send vaxmail msg ) Then Call Str~trim ( Ac rule name , Ac_rule_name , Len ) Call Str$trim ( Directory , Directory , L_dir ) Subprocess name(L sp-l4) = Ac_rule_name Call Str$trim ( Subprocess_name , Subprocess_name , ILen ) Write(Code lun , 788 ) `
788 Format ( 1 ' If ( Mode .eq. Jpi~k other ) Then' Write ( code lun , 718 ) Directory(l:L_dir) , 1 Ac rule name(l:len) , 1 Subprocess name(l:Ilen) 718 Format ( 1 ' Call Lib$spawn ( "Q' , A , A , '.mailmsg'',,,,''' , A
, ) ' Write(Code_lun , 787 ) 787 Format ( 1 ' Else if ( Mode .eq. JpiSk interactive ) Then' 1 ) , Write ( Code lun , 789 ) Directory(l:L_dir) , 1 Ac rule name(l:len) , Next label, Next label Next label - Next label + 1 789 Format ( t Open(ll,File=''' , A , A , '.mailmsg'' ,Status=''old'' ~2975S~

1 ' Do J ~ 1,3 1 ,/, 1 ' Read ( 11 , ''SA~'I 3 Line' ,/, 1 ' ~nd ~o' ,/, Do ~ ~ 1;60 ~ /(A) " ~ E~d c ~ I4 1 ' Write(6,~ ~ine ' ,/, 1 ' End Dol ,/, 1 I4 ,' C~ntinue' ,/, 1 ' Close ( 11 ) ' Write(Code lun , 785 ) 786 Format ( 1 ' End If' 1 ) Else Write ( code_lun , 716 1 716 , Write(6,~) " Bad Action type End If Write ( Code lun , 717 ) 717 Format ( 1 ' End If' 1 ) Go To 702 800 Continue Wr~te( Code_lun ~ 9998 ) 9998 1 'd Write(6,~) ~his Pass_fires, " rules fired this pass.' 1 ' If ( This Pass-~ires .gt. 0 ) Go To 1' , / , 1 'C', / ~
1 ' Return' , / , 1 ' ~all Fdv$Putl(' Generating Expert System code..~. Done.l) Return End Copyright (c) 1987 E.I. DuPont de Nemo~rs ~ Co., all rights reserved ~Z~75~i8 Thus, steps such as those l:isted above will produce (in this example) FORTRAN source code which defines an expert system including rules as defined by the user.
This source code can then be compiled and linked, ~s described above, to provide an expert procedure which is ca'lable at run-time. This 4xpert procedure is tied into the supervisor procedure, as described above, by inserting an appropriate call into the user program section of one of the blocks in the supervisor procedure. Thus, the expert procedure can be called under specific circumstances (~ if selection among several possible manipulated variables must be made), or may optionally be called on every pass of the base cycle procedure, or at fixed time intervals, or according to any of the other options set forth above.
As will be recognized by those skilled in the art, the innovative concepts described in the present application can be modified and varied over a tremendous range of applications, and accordingly their scope is not limited except by the allowed claims.

Claims (61)

1. A computer-based method for operating a substantially continuous process, comprising the steps of:
(1) operating the process with one or more sensors connected to sense conditions in the process, and one or more actuators connected to change conditions in the process;
(2) controlling one or more of said actuators with a process controller in accordance with signals received from said sensors and in accordance with control parameters, said control parameters indicating a respective threshold, wherein attainment of said threshold as indicated by said signals creates an indicia for action; and (3) repeatedly running a process supervisor procedure for selectively defining one or more of said control parameters for said process controller;
(4) wherein, for each of said control parameters, said process supervisor procedure is constrained not to make changes to said control parameters unless the indicia for action exceed said respective threshold; and (5) wherein said process supervisor procedure reports every instance where it changes a control prameter.

2. A computer-based method for operating a substantially continuous process, comprising the steps of:
(1) operating the process with one or more sensors connected to sense conditions in the process, and one or more actuator connected to change conditions in the process;
(2) controlling one or more of said actuators with a process controller in accordance with signals received from said sensors and in accordance with control parameters;
and (3) repeatedly running a process supervisor procedure for selectively defining one or more of said control parameters for said process controller;
(4) wherein, for each of said control parameters, said process supervisor procedure is constrained not to make changes to said control parameters unless the amount of the change would exceed a certain threshold.

3. A computer-based method for operating a substantially continuous process, comprising the steps of:
(1) operating the process with one or more sensors connected to sense conditions in the process, and one or more actuators connected to change conditions in the process;
(2) controlling one or more of said actuators with a process controller in accordance with signals received from said sensors and in accordance with control parameters, said control parameters indicating a respective threshold, wherein attainment of said threshold as indicated by said signals creates an indicia for action; and (3) repeatedly running a process supervisor procedure for selectively defining one or more of said control parameters for said process controller;
(4) wherein, for each of said control parameters, said process supervisor procedure is constrained not to make changes to said control parameters unless the indicia for action exceed said respective threshold.

4. A computer-based method for operating a substantially continuous process, comprising the steps of:
(1) operating the process with one or more sensors connected to sense conditions in the process, and one or more actuators connected to change conditions in the process:
(2) controlling one or more of said actuators in accordance with signals received from said sensors and in accordance with control parameters;
(3) repeatedly running a process supervisor procedure for selectively defining one or more of said control parameters: and (4) wherein at least some of said actuators are controlled in a feedforward relation to respective measured variables, and wherein said feedforward relation includes a deadband.

5. A computer-based method for operating a substantially continuous process, comprising the steps of:
(1) operating the process with one or more sensors connected to sense conditions in the process, and one or more actuators connected to change conditions in the process; and (2) controlling one or more of said actuators in accordance with signals received from said sensors;
(3) wherein at least some of said actuators are controlled in a feedback relation with respective corresponding measured variables, and said feedback relation includes the use of statistical filtering, and/or deadband; and (4) wherein at least some of said actuators are controlled in a feedforward relation to respective measured variables, wherein said feedforward relation includes a deadband.

6. A computer-based process control system, comprising:
(a) one or more sensors connected to sense conditions in materials being processed, and one or more actuators connected to change conditions in the process.
(b) a plurality of process controllers, each connected to control one or more of said actuators in accordance with signals received from said sensors and in accordance with respective control parameters; and (c) a process supervisor means for selectively defining one or more of said control parameters for said process controllers (d) wherein, for each of said control parameters, said process supervisor means is constrained not to make changes to said control parameters unless the amount of the change would exceed a certain threshold; and (e) wherein said process supervisor means reports every instance where it changes a control parameter.

7. A computer-based process control system, comprising:
(a) one or more sensors connected to sense conditions in materials being processed, and one or more actuators connected to change conditions in the process;

(b) a plurality of process controllers, each connected to control one or more of said actuators in accordance with signals received from said sensors and in accordance with respective control parameters, said control parameters indicating a respective threshold, wherein attainment of said threshold as indicated by said signals creates an indicia for action; and (c) a process supervisor means for selectively defining one or more of said control parameters for said process controllers;
(d) wherein, for substantially all of said control parameters, said process supervisor means is constrained not to make changes to said control parameters unless the indicia for action exceed said respective threshold; and (e) wherein said process supervisor means reports every instance where it changes a control parameter.

8. The method of Claim 1, wherein said process controller of step (2) uses a cycling step, and said process supervisor procedure of step (3) uses a cycling step.

9. The method of Claim 1, wherein said process supervisor procedure uses a cycling step, and said process controller of step (2) operates in substantially real-time.

10. The method of Claim 1, wherein said process supervisor procedure of step (3) comprises the step of being implemented using a computer running one or more programs, including a cycling process which repeatedly samples a plurality of signals corresponding to inputs, forms inferences from said inputs according to a stored knowledge base, and provides outputs in accordance with said inferences, and then goes into a dormant state having a duration limited by timing;
wherein said duration of said dormant state is sufficiently large that said process does not on average occupy more than 50% of the available CPU time of the computer;
and wherein said duration of said dormant state is selected to be sufficiently short that process fluctuations cannot diverge to an out-of-control situation during the periods when said process is dormant.

11. The method of Claim 1, wherein said process supervisor procedure of step (3) comprises the step of defining parameters including parameters for a feedback control relation including a deadband on said control parameters.

12. The method of Claim 1, wherein said process supervisor procedure of step (3) comprises the step of having a maximum iteration period significantly longer than the maximum iteration period of said process controller of step (2).

13. The method of Claim 1, wherein said process controller of step (2) uses analog logic for controlling.

14. The method of Claim 1, wherein said step of repeatedly running a process supervisor procedure comprises the step of running said process supervisor procedure using a cycling step.

15. The method of Claim 1, wherein said control parameters of step (2) comprises the step of including goals of said process controller.

16. The method of Claim 1, wherein said respective threshold on said indicia for action of step (2) comprise the step of being dependent on the particular action in prospect.

17. The method of Claim 1, wherein said respective thresholds on said indicia for action of step (2) comprise the step of being different for at least some of said control parameters.

18. The method of Claim 1, wherein said process controller of step (2) and said process supervisor procedure of step (3) comprise processes running on the same computer system.

19. The method of Claim 1, wherein said process controller of step (2) and said process supervisor procedure of step (3) are both respective parts of the same software system.

20. The method of Claim 2, wherein said process supervisor procedure of step (3) uses a cycling step, and said process controller of step (2) operates in substantially real-time.

21. The method of Claim 2, wherein said process supervisor procedure of step (3) comprises the step of implementing a feedback control relation including a deadband on at least some of said control parameters.

22. The method of Claim 2, wherein said process supervisor procedure of step (3) comprises the step of having a maximum iteration period significantly longer than the maximum iteration period of said process controller of step (2).

23. The method of Claim 2, wherein said process controller uses analog logic for controlling.

24. The method of Claim 2, wherein said control parameters of step (2) comprise the step of including goals of said process controller.

25. The method of Claim 2, wherein said certain thresholds of step (2) comprise the step of being different for at least some of said control parameters.

26. The method of Claim 2, wherein said process controller of step (2) and said process supervisor procedure of step (3) comprise processes running on the same computer system.

27. The method of Claim 2, wherein said process controller of step (2) and said process supervisor procedure of step (3) are both respective parts of the same software system.

28. The method of Claim 3, wherein, for each of said control parameters, said process supervisor procedure of step (3) comprises the step of being constrained not to make changes to said control parameters unless the amount of the change would exceed said respective threshold: and wherein said process supervisor procedure reports every instance where it changes a control parameter.

29. The method of Claim 3, wherein, for each of said control parameters, said process supervisor procedure of step (3) comprises the step of being constrained not to make changes to said control parameters unless the amount of the change would exceed said respective threshold.

30. The method of Claim 3, wherein said process supervisor procedure of step (3) comprises the step of implementing at least one feedback control relation including a deadband on at least some of said control parameters.

31. The method of Claim 3, wherein said process supervisor procedure of step (3) comprises the step of having a maximum iteration period significantly longer than the maximum iteration period of said process controller of step (2).

32. The method of Claim 3, wherein said process controller of step (2) uses analog logic for controlling.

33. The method of Claim 3, wherein said control parameters of step (2) comprise the step of including goals of said process controller.

34. The method of Claim 3, wherein said respective thresholds on said indicia for action of step (2) comprise the step of being different for at least some of said control parameters.

35. The method of Claim 3, wherein said process controller of step (2) and said process supervisor procedure of step (3) comprise processes running on the same computer system.

36. The method of Claim 3, wherein said process controller of step (2) and said process supervisor procedure of step (3) are both respective parts of the same software system.

37. The method of Claim 4, wherein said process supervisor procedure of step (3) uses a cycling step, and said step (2) operates in substantially real-time.

38. The method of Claim 4, wherein said process supervisor procedure of step (3) implements at least one feedback control relation including a deadband on at least some of said control parameters.

39. The method of Claim 4, wherein said process supervisor procedure of step (3) has a maximum iteration period significantly longer than the maximum iteration period of said step (2) for controlling.

40. The method of Claim 4, wherein said step (2) uses analog logic for controlling.

41. The method of Claim 4, wherein said control parameters comprise the step of indicating a respective threshold, wherein attainment of said threshold as indicated by said signals creates an indicia for action, wherein said respective thresholds on said indicia for action comprise the step of being different for at least some of said control parameters.

42. The method of Claim 4, wherein said respective feedforward relation of step (4) comprises the step of including a deadband applied to a measured variable.

43. The method of Claim 4, wherein said step (2) for controlling and said process supervisor procedure of step (3) comprise processes running on the same computer system.

44. The method of Claim 4, wherein said step (2) for controlling and said process supervisor procedure of step (3) are both respective parts of the same software system.

45. The method of Claim 5, further comprising a process supervisor procedure step, implementing at least one feedback control relation including a deadband on at least some of said control parameters.

46. The method of Claim 5, further comprising a process supervisor procedure step having a maximum iteration period significantly longer than the maximum iteration period of said step (2) for controlling.

47. The method of Claim 5, wherein said step (2) uses analog logic for controlling.

48. The method of Claim 5, wherein said step (2) further comprises the step of using said control parameters comprise the step of indicating a respective threshold, wherein attainment of said threshold as indicated by said signals creates an indicia for action, wherein said respective thresholds on said indicia for action comprise the step of being different for at least some of said control parameters.

49. The method of Claim 5, further comprising a process supervisor procedure step, wherein said step (2) for controlling and said process supervisor procedure step comprise processes running on the same computer system.

50. The method of Claim 5, further comprising a process supervisor procedure step, wherein said step (2) for controlling and said process supervisor procedure step are both respective parts of the same software system.

51. The system of Claim 6, wherein said process supervisor means reports said control parameter change instances by means including voice messaging.

52. The system of Claim 6, wherein said process supervisor means implements at least one feedback control relation including a deadband on at least some of said control parameters.

53. The system of Claim 6, wherein said process supervisor means of element (c) has a maximum iteration period significantly longer than the maximum iteration period of said process controller of element (b).

54. The system of Claim 6, wherein at least one said process controller of element (b) is an analog controller.

55. The system of Claim 6, wherein one or more of said control parameters of element (b) goals of said process controller.

56. The system of claim 6, wherein said certain thresholds of element (d) are different for at least some of said control parameters of element (b).

57. The system of Claim 6, wherein Raid process controller of element (b) and said process supervisor means of element (c) comprise processes running on the same computer system.

58. The system of Claim 6, wherein said process controller of element (b) and said process supervisor means of element (c) are both respective parts of the same software system.

59. The system of Claim 7, wherein said process supervisor means of element (c) has a maximum iteration period significantly longer than the maximum iteration period of said process controller of element (b).

60. The system of Claim 7, wherein at least one said process controller of element (h) is an analog controller.

61. The system of Claim 7, wherein said respective thresholds on said indicia for action of element (b) are different for at least some of said control parameters of element (b).