CA1237471A

CA1237471A - Control system for an electronically commuted motor used in a laundering apparatus and method of operating

Info

Publication number: CA1237471A
Application number: CA000469645A
Authority: CA
Inventors: Glen C. Young
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1983-12-13
Filing date: 1984-12-07
Publication date: 1988-05-31
Also published as: US4642537A; BR8406537A

Abstract

Abstract of the Disclosure Control system for an electronically commutated motor includes circuitry for integrating the back emf of an unenergized motor winding to determine motor rotor position.
However, integration should not occur on a field collapse voltage which precedes the back emf. A zero-approaching detector enables the integration of the back emf only when a zero-approach occurs at the ending of the field collapse voltage. The integration is also inhibited from being spuri-ously enabled by zero approaches for a predetermined length of time after commutation and prior to the ending of the field collapse voltage. A system for controlling the average volt-age cyclically applied to a load such as an electronically commutated DC motor includes circuitry for generating a direct function of the applied voltage. The function is compared to a reference by a comparator which indicates when the function reaches the reference. The end of each voltage cycle is sig-naled when the function of the applied voltage reaches a pre-determined value. The external application of voltage to the load is terminated when the function of the applied voltage reaches the reference, and each voltage cycle is terminated when the function of the applied voltage reaches the predeter-mined value.

Description

Field of the Invention This invention relates in general to dynamoelectric machines and domestic appliances and more particularly to a control system with special applicability to an electronic-ally commutated motor, a method of operating an electronic-ally commutated motor, and a laundering apparatus.
Ba`c~ground of the Invention While conventional brush-commutated DC motors may have numerous advantageous characteristics such as con-venience of changing operational speeds and direction ofrotation, it is believed that there may be disadvantages, such as brush wear, electrical noise or RF interference caused by sparking between the brushes and the segmented commutator, that may limit the applicability of such brush-commutated DC motors in some fields such as the domesticappliance field. Electronically commutated motors, such as brushless D~ motors and permanent magnet motors with electronic commutation, have now been developed and generally are believed to have the above discussed advantageous characteristics of the brush-commutated DC motors without many of the disadvantages thereof while also having other important advantages. Such electronically commu-tated motors are disclosed in U.S. Patents 4,005, 347, issued January 25, 1977 to Erdman, 4,169,990, issued October 2, 1979 to Erdman, and 4,162,435, issued July 24, 1979 to Wright. These electronically commutated motors may be advantageously employed in many di~ferent fields or motor applications among

- 2 - 03-I,0-5724 which are domestic appliances, e.g., automatic washing or laundry machines such as disclosed in U.S. Patent 4,449,079, issued May 15, l9S4 to Erdman; U.S. Patent 4,528,485, issued July 9, 1985 to Boyd, Jr.; U.S. Patent No. 4,532,459, issued July 30, 1985 to Erdman et al; U.S. Patent 4,459,519, issued July 10, 1984 to Erdman; Canadian Patent 1,140,658, issued February 1, 1983 to ~rdman et al, U.S. Patent 4,327,302, issued April 27, 1982 to Erdman et al and Canadian Patent No. 1,199,997, issued January 28, 1986 to Erdman.
Laundry machines as disclosed in the above patents are believed to have many significant advantages over the prior art laundry machines which employ various types of transmissions and mechanisms to convert rotary motion into oscillatory motion to selectively actuate the machine in its agitation or washing mode and in its spin extraction mode. Such prior art laundry machines are believed to be more costly and/or complicated to manufacture, consume more energy, and require more servicing. Laundry machines with electronically commutated motors require no mechanical means, other than mere speed reducing means, to effect oscillatory action of the agitator, and in some applications, it is believed that the spin basket might be directly driven by such a motor.
~hile the past control systems, such as those discosed in the aforementioned patents for instance, undoubtedly illustrated many features, it is believed that the control system for electronically commutated motors in general, and for such motors utili~ed in laundry machines, could be improved. In some of the past con~rol systems, the position of the rotat-able assembly (i.e., the rotor) of the electronically com-mutated motor was located by sensing the back emf of one of the winding stages on the stationery assembly (i.e., the stator) thereof. More particularly ~he back emf of an unenergi~ed winding stage was sensed and integrated to determine rotor position. However, the voltage measured at the terminal ~`

7~
03-Lo-s724 of an unenergized winding has several components other than that induced by the rotation of the rotor. Immediately after a winding is commutated off, the voltage at the terminal of the now unenergized windinq crosses zero. Thereafter the voltage is of the same polarity as the anticipated back emf at the enB of the commutation period, but it is not due to back emf. Rather, current which had -been in the winding while it was energized induces this field collapse voltage, so it is not an accurate measure of rotor position~ This field col-lapse voltage ~ay last for several electrical degrees, but itsactual duration is highly motor and load dependent. Some of the previous applications disclose locking out the integrator for a predetermined number of electrical degrees of rotation, e.g., 20, to prevent the current-induced voltage from being-integrated. This has been done successfully by basing themeasurement of the lockout interval upon the i~mediately pre-vious interval between commutations, However, during rapid speed changes, it is believed that this approach can result in lockout times which are longer ~han 60 electrical degrees or less than the commutation current interval, both of which may result in a loss of position sensing and in less than desir-able motor operation. A system which ignores these commuta-tion current-induced voltages and avoids the problems which may result from locking out the integrator for a supposedly constant number of electrical degrees would be desirable~
The speed sf an electrically commutated motor is ~irectly correlated to the average voltage appli~d to the windings, which in turn is determined by the unregulated DC
voltage ~pplie~ to the motor windings and the duty cycle o the pulse wiath modulation used to apply the voltage. The duty cycle is in turn a function of the total time the wind-ings are energized each cycle divided by the length of each cycle. The windings are typically energized until some func-tion of the supply voltage, such a~ the integral~ equals some preset reference selected to give the desired averaye voltage.

~3~
o3-Lo-s724 When this reference is reached, the winding drive is shut off.
The length of the cycle has been separately dete~mined, usual-ly by a separate clock circuit. In economical circuits, both the generation of the function of applied voltage and the measurement of the cycle length are believed to introduce error into the average voltage applied. Use of inexpensive low precision capacitors for each function in some cases may result in significant error in average voltage applied, and hence in motor speed. Converselyr higher precision capacitors are undesirably expensive for use in a control system which is to be widely and economically used. Thus, it would be desir-able to have a control system which uses relatively low preci-sion components yet which accurately controls average applied voltage and motor speed.

Summary of the Invention Among the several objects and features of this invention may ~e noted the provision of an improved electron-ically commutated motor (ECM), an improved method of operating an ECM, an improved laundry machine~ and an improved control system for an ECM which overcome the above discussed disadvan-tageous features, as well as others, of the prior art; the provision of such improved ECM, method of operating such ECM, improved laundry machine, and improved control system which mor~ accurately and reliably effects the sensing and control of rotor position in such ECM~ the provision of such improved ECM, improved method of operating an ECM, improved laundry machine and improved control system for an ECM which reliably controls such`motors and laundry machines at very low rotor speeas as upon startup and reversal when rapîd speed changes occur; the ~rovision o~ such improved ECM, improved method of operating an ECM, improved laundry machine, and Improved con-trol system for an ECM which operates with a wide variety of 7~
03-Lo-5724 motors and over a wide range of loads; the provision of meth-ods an~ systems for accurately controlling the average voltage cyclically applied to a load such methods and systems being applicable in an improved ECM~ an improved method of operating S an ECM, an improved laundry machine, and an improved control system for an ECM; the provision of such methods and systems in which either high or low precision components can be em ployea; the provision of an ECM and an improved laundry machine, an improved method of operating an ECM and an improved control system for an ECM which is relatively effi-cient over a wide range of loads; the provision of such improved ECM, improved method of operating an ECM, an improved laundry machine, and an improved control system for an EC~
which operates at an accurate speed; the provision of an improved ECM, an improved method of operating an ECM, an improved laundry machine, and an improved control system for an EC~ which operates at accurately controlled rates and which is relatively economical in cost; and the provision of an improve~ ECM, an improved method of operating an ECM, an improved laundry machine, and an improved control system for an ECM which accurately controls speed and rotor position.
These as well as other objects and advantageous eatures of the present invention will be in part apparent and in part pointed out hereinafter.
In general, the inventive control system for an electronically commutated motor adapted to be energized from a DC power source and including a stationary assembly having a plurality of winding stages adapted to be electronically com-mutated in a~ least one preselected sequence, and a rotatable assembly as~ciated in selective magnetic coupling relation with the winding stages, each winding stage having a terminal associa~ed therewith, in ~ne form of the inven~ion, comprises circuitry operable for electronic commutation of at least one at a time of the winding stages of tle electronically commu-tated motor by applying thereto a DC voltage from the power . . _ . ~

~ ;~3~
03-Lo-5724 source in the at least one preselected sequence to effect the energization of the electronically commutated motor and the rotation of the rotatable assembly. At least one other of the winding stages during any one commutation exhibits a terminal voltage including a back emf and a field collapse voltage end-ing prior to appearance of the back emf. In a~dition, cir-cuitry is provided for receiving and integrating the terminal voltage in response to its first approach to zero at the end-ing of the field collapse voltage and effecting the operation of the ele~tronic commutation circuitry when a predetermined level is reached in the integrating.
In another form o the invention the control system for an electronically commutated motor adapted to be energized from a DC power source and inrluding a stationary assembly having a plurality of winding stages adapted to be electron-ically commutated in at least one preselected sequence, and a rotatable assembly associated in selective magnetic coupling relation with the winding stages, each winding stage having a terminal associated therewith comprises circuitry operable generally for electronic commutation of at least some of the winding stages of the electronically commutated motor by applying thereto a DC voltage from the power source in the at least one preselected s quence to e~fect the energization of the electronically commutated motor and the rotation of the rotatable assembly. Circuitry is provided operable generally for receiving and integrating the terminal voltage of at least one of the winding stages. The terminal voltage inc~udes at least the ~ack emf of the at least one winding stage and a field collapse signal ending prior to appearance of the back emf. Circuitry responsive to a predetermined output level of the integrating circuitry generates a commutation signal for a predetermined length of time, the predetermined len~th of time expiring before the ending of the field collapse signal D
Additional circuitry responsive to the commutation signal ef~ects the operation of the electronic commutatio~ circuit o3-Lo-s724 and inhibits the operation of the integrating circuit for the preaetèrmined length o~ time and initiates the operation of the integrating circuit when the terminal voltage of the at least one winding stage first approaches zero after the prede-termined length o time.
The invention also involves a control system for anelectronically commutated motor adapted to be energized from a DC power source and including a stationary assembly having a plurality of winding stages adapted to be electronically com-mutated in at least one preselected sequence, and a rotatableassembly associated in selective magnetic coupling relation with the winding stages, each winding stage having a terminal associated therewith, comprising ~ircuitry operable generally for electronic commutation of at least one at a time of the winding stages of the electronically commutated motor by applying thereto a ~C voltage from the power source in the at least one preselected sequence to effect the energization of the electronically commutated motor and the rotation of the rotatable assembly. At least one other of the winding s~ages during any one commutation exhibits a terminal v~ltage includ-iny a back emf. Also circuitry is provided operable generally for integrating the terminal voltage of the at least one other winding stage during any one commutation. Another circuit responds to a predetermined output level of the integrating means for generating a commutation signal. Logic circuitry under programmed control and responsive ~o the commutation signal effects the operation of the electronic commutation circuit and inhibits the operation of the integrating circuit for a predetermined length of time after commutation.

3~ A method of operating an electronically commutated motor adapted to be energized from a DC power source and in-cluding`a stationary assembly having a plurality of winding stages adapted to be electronically commutated in at least one prese~ected se~uence, and a rotatable assembly associated in selective magnetic coupling relation with the winding stages, . .

~3~7L~
03-Lo-s724 each winding stage having a terminal associated therewith, comprises the steps of commutating in response to a commutat-ing signal at least some of the winding stages by applying a DC voltage thereto in the at least one preselec~ed sequence to effect the energization of the electronically commutated motor and the rotation of the rotatable assembly; generally inte-grating the terminal voltage of at least one of the winding stages, the terminal voltage including at least the back emf of the at least one winding stage and also including a field collapse voltage ending prior to appearance of the hack emf;
generating the commutation signal when the integrating reaches a predetermined level; and initiating the integrating in response to a first approach to zero at the ending of the field collapse voltage~
lS An electronically commutated motor according to the invention adapted to be energized rom a DC power source com-prises a stationary assembly having a plurality o~ winding stages adapted to be electronically commutated in at least one preselected sequenceO a rotatable assembly associated in selective magnetic coupling relation with the winding stages, and a-control system including circuitry operable ~enerally for electronic commutation of at least some of the winding stages of the electronically commutated motor by applying thereto a DC voltage from the power source in the at least one preselected sequence to effect the energiæation of the elec-tronically commutated motor and the rotation of the rotatable assembly. Also circuitry is provided operable generally for integratiny a voltage across an unenergized one o~ the winding stages in each commutation period~ The unenergized winding voltage includes a back emf and a field collapse voltage end-ing prior to the back emf. In addition, circuitry is provided respons~ve to a predetermined output level of the integrating circuit for effecting the operation of the electronic commuta-tion Gircuitry and for preventing the operation of the inte-grating circuitry after the commencement of comm~tation of the .

~3~
03-Lo-s724 at least some winding stages until the ending of the field collapse signal.
A launder ing apparatus according to the invention comprises in combination equipment for agitating water and fabrics to be laundered thereby to wash the fabrics and for thereafter spinning the fabrics to effect centrifugal dis-placement of water from the fabrics; an electronically commu-tated motor adapted to be energized from a DC power source, the motor comprising a stationary assembly having a plurality of win~ing stages adapted to be electronically commutated in at least one preselected sequence, each winding stage having a terminal associated therewith, and a rotatable assembly asso-ciated in selective magnetic coupling relation with the wind-ing stages f or driving the equipment for agitating and spin-lS ning; a control system connected to the motor; and a circuitfor applying a DC voltage to the control system. The control system includes circuitry operable generally for effecting the electronic commutation of at least some of the winding stages of the electronically commutated motor by applying the DC
voltage thereto in the at least one preselected se~uence to effect the energization of the electronically commutated ~.otor and the rotation of the rotatable assembly; circuitry operable generally for integrating the terminal voltage of at least one of the winding stages, the terminal voltage including at least the back emf of the at least one winding stage; circuitry responsive to a predetermined output level o~ the integrating means for generating a commuta~ion signal, circultry respon sive to the commutation signal for effecting the operation of the electronic commutation effecting circuitry and for inhi-biting the operation of the integrating circuitry for a prede-termined length of time after the commutatîon of the at least some winding stages; and circuitry for initiating the opera tion of the integratiny circuitry when the terminal voltage of the at least one winding stage at least approaches zero a f ter commutation.

03-Lo-5724 Another form of inventive control system for an electronically commutated motor adapted to be energized from a DC power source and including a stationary assembly having a plurality of winding stages adapted to be electronically com-mutate~ in at least one preselected sequence, and a rotatableassembly associated in selective magnetic coupling relation with the windin~,stages, each winding stage having a terminal associatea therewith, comprises circuitry operable generally for effecting the electronic commutation o at least some of the winding stages of the electronically commutated motor by applying thereto a DC voltage from the power source in the at least one preselected sequence to effect the energization of the electronically commutated motor and the rotation of the rotatable assembly whereby a motoring condition is achievable.
Circuitry is also provided operable generally for integrating the terminal voltage of at least one of the winding stages, the terminal voltage having a higher magnitude part followed by a lower magnitude back emf part under the motoring condi-tion. Also circuitry responds to a predetermined output level of the integrating circuitry for generating a commutation sig-nal, and additional circuitry inhibits the operation of the integrating circuitry until the terminal voltage of the at least one winding stage falls in magnitude below a selected level selected to exceed that of the back emf under the motor-ing condition.
An inventive system for controllirlg the averagevoltage cyclic~lly applied to a load comprises circuitry for generating a direct function of the applied voltage, circuitry for comparing the function of the applied voltage to a refer-ence and for indicating when the function reaches.the reer-encet circuitry for signaling the end of each voltage cycle when the function of the applied voltage reaches a predeter-mined value, and circuitry responsive to the comparing cir-cuitry and to the signaling circuitry for terminating applica-tion of voltage to the load when the function of the applied ~ ~7i~
03-Lo-s724 voltage reaches the reference and for terminating each voltage cycle when he function of the applied voltage reaches the predetermined value.
A method of controlling the average voltage cycli-cally applied to a load comprises the steps of generating adirect function of the applied voltage, terminating applîca-tion of voltage to the load when the function of the applied voltage reaches a first predetermined value selected to repre-sent a desired average voltage, and terminating each voltage cycle when the function of the applied voltage reaches a second predetermined value.
A control system for an electronically commutated DC
motor having a stationary assembly with a plurality of winding stages and a rotatable assembly arranged in selective magnetic coupling relation therewith comprises circuitry respon~ive to a set of control signals for commutating the winding stages by cyclically applying a DC voltage thereto in at least one pre-selected sequence to cause rotation of the rotatable assembly, circuitry for generating a direct function of the applied voltage, circuitry for comparing the function of the applied voltage to a reference and for indicating when the function reaches a reference, circuitry for signaling the end of each voltage cycle when the function of the applied voltage reaches a predetermi~ed value, and circuitry responsive to the compar-ing circuitry and to the signaling circuitry for terminating application of voltage to the motor when ~he function of the applied vo~tage reaches the reference and for terminating each voltage cycle when the function o~ the applied voltage reaches the predetermined value.
A method of controlling the average voItage cycli-cally applied to an electronically commutated mo~or compriseS
the steps of generating a direct function of the applied volt-age, terminating application of voltage to the motor when the function o the applied voltage reaches a firs~ predetermined value selected to represent a desired average voltage, and .

03-Lo-s724 terminating each voltage cycle when the function of the applied voltage reaches a second predetermined value.
Another form of the inventive laundering apparatus comprise~ in combination equipment for agitating water and fabrics to be laundered thereby ~o wash the fabrics and for thereafter spinning the fabrics to eff~ct centrifugal dis-placement of water from the fabrics; an electronically commu-tated DC motor, the motor comprising a stationary assembly having a plurality of winding s~ages adapted to be electron-ically commutated in at least one preselected sequence, and arotatable assembly associated in selective magnetic coupling relation with the winding stages for driving the equipment for agitating and spinning; a control system connected to the motor; and a circuit for applying a DC voltage to the controi system. The control system includes circuitry operable gener-ally for effecting the electronic commuta~ion of at l~ast some of the winding stages of the electronically commutated motor by applying the DC voltage thereto in the at least one prese-lected sequence to effect the energization of the electron-ically commutated motor and the rstation of the rotatableassembly. Circuitry is also provided for generating a direct function of the applied voltage. Also circuitry oompares the function of the applied voltage to a reference and indicates when the function reaches the reference. Circuitry sign~ls the end of each voltage cycle when the function of the applied voltage reaches a predetermined value. Additional circuitry responds to the comparing circuitxy and to the signaling cir-cuitry foE terminating application of voltage to the motor when the function of the applied voltage reaches the reference and terminates each voltage cycle when the function of the applied~voltage reaches the predetermined value.

. _ _ . . . . . .. . . . , ... , _ _ _ _ _ _ , Brief DescriEtion of the Drawings FIG. 1 is a block-diagrammatic schematic showing the major components of the control system of this invention in . combination with an electronically commutated motor driving a laundry machine;
FIG. 2 is an exploded, perspective view of the main elements oE an electronically commutated DC motor which is controllable by the control sy~tem of the present .invention;
FIG~ 3 is a schematic diagram showin~ the winding stages and terminals of the motor of FIG. 2;
FIG. 4 is a block diagram showing in greater detail than FIG. 1 the major components of the control system of this invention;
FIG. 5 is a schema~ic diagram of part o~ the posi-tion sensing circuitry of the control system of this invention for use with the circuitry of FIG. 6;
FIG. 5A is a schematic diagram showing an alterna-tive embodiment of the position sensing circuitry o the con trol system of this invention;
FIG. 6 is a schematic and waveform timing dia~ram of zero approach detection and integrator inhibit circuitry for the position sensing circuit of FIG. 5 utilizing a method of this invention;
FIG. 6A is a schematic diagram of another embodiment of position sensing circuitry according to the invention.
FIG. 7 is a schematic diagram o~ alternative posi-~ion sensing circuitry of the control system of this invention;
FIG. 8 is a schematic diagram of average voltage control~ing circuitry o~ the present invention; and FIG. 9 is a graph of terminal voltage output versus time for illustrating zero approach detection and integration aspects of methods and apparatus of the invention employed in ~IGS. 5, 5A, 6 t 6A and 7.

03-~0-5724 FIG~ 10 is two graphs of wid~h modulated pulses for illus~rating average voltage control aspects of methods and apparatus employed in FIG. 8.
Corresponding re~erence characters refer to corre-sponding parts throughou~ ~he ~ev~ral views ~f the d~awings.
The exemplifications set ou herein illustrate pre-ferred embodiments of the invention in one form thereof~ and such exemplifications are not to be construed as limiting the scope of the invention in any manner.

Detailed Description o the Preferred Embodiment Referring now to the drawings, and more particularly to FIG. 1, a laundry machine 11 in one form of the invention is illustrated schema~ically. Laundry machine or laundering apparatus 11 includes an electronically commutated motor (ECM~
M adapted to be energized from a DC power source and havin~
(see FIG. 2) a stationary assembly including a stator or core 13 and a rotatable assembly including a permanent mags~et rotor 15 and a shaft 17. Stator 13 includes a plurality (eOg., ~hree) of winding stages Sl, S2 and S~ tFIG. 3) adapted to be electronically commutated in at least one preselected se-quence, although the invention is not limited to that particu~
lar number o~ winding stages. Two sets of terminals Ilt I2,I3 and Tl,T2,T3 for two different speed ranges of operation of motor M ~re shown, there being at least one ~Pr-minal associated with each winding sta~e.
When the winding stages Sl,S2jS3 are energized in atemporal sequence, six sets of eight ma~netic poles are established that will provide a radial magnetic field which moves clockwise or counterclockwise around the stator bore 30 depending on the preselected sequence or order in which the stages are energized. This moving field intersects with the flux field of the permanent magnet rotor to cause the rotor lS

1~37~L
03-Lo-s724 to ro~ate relative to the stator 13 in the desired direction to develop a torque which is a ~irect function of the intensi-ties or strengths of the magnetic fields,. If a more detailed description of the construction of elect,ronically commutated motor M is desired, reference may be had to the aforementioned Canadian Application Serial No. 406,028, filed ~une 25, 1982 to John. H. Boyd, Jr.
Further, while electronically commutated motor M i5 ~llustrated herein for purposes of disclosure, it is contem-plated that other such motors of different constructionsand~or different winding arrangements may be utilized in one or another form of the invention so as to meet at least some of the ob~ects thereof.
The winding stages o motor M, as explained in the-aforementioned David M. Erdman Can. Ser. No. 432,524,filed July 15, 19~3, are commutated without brushes by sensing the rotational position of the rotatable assembly or rotor 15 as it rotates within the bore of stator 13 and uti-lizing electrical signals generated as a function of the rota-tional position of the rotor to sequentially apply a DC vol~-age to each of the winding stages in different preselected orders or seque~ces that determine the direction of the rota-tion of the rotor. Position sensing may be accomplished by a position-detecting ~ircuit responsive to the back emf of the 25 ECM to provide a simulated signal indicative of the rotational position of the motor's rotor to control the timed sequential application of voltage to the winding stages of the motor.
Referring back to FIG. 1, machine 11 comprises a basket 23 which is rotatable within a tub (not shown) which holds the water for washing the'fabrics to be laundered t and a coaxially mounted agitator 25, both of which are rotatable independently or jointly about their common axis. Agitator 25 and basket 23 together comprise means for agitating water and fabrios to be laundered thereby to wash them and Eor there-after spinning the fabrics to effect centrifugal displacement of water therefrom; however~ it is contemplated tha such means may also include only such basket~ as provided in a typical tumbler laundry machine, for instance, within the scope of the inven~ion so as to meet at least some of th~
objects thereof. Motor M is coupled selectively ~o the agita-tor alone during the wash cycle or mode and to both the basket and the agitator in the spin cycle hrough a connection mecha-nism 27 which may comprise a fixed ratio speed reducer, such as a gear box or a pulley arrangement for instance, or in some applications, it is believed that the shaft 17 of motor M
could be directly coupled to the agitator and the basket.
Mechanism 27 therefore comprises means for driving the agitat-ing and spinning means. Power supplied from a llS V 60 Hz AC
line is rectified by a rectifier circuit 29 which defines a DC
power source and ~pplied to a power switching circuit 31 which constitutes means for controlling the application of the DC
voltage to the winding stages to provide a resultant effective voltage thereto. Power switching circuit 31 responds to a set of control signals from a control signal circuit 33 for commu-ta~ing the winding stages by applying the DC voltage theretoin at least one preselected sequence to cause rotation of the rotor iS. Control signal circuit 33 thu~ constitutes means operable for electronic commutation of at least one at a time of the winding stages of the electronically commutated motor M
by applying a DC voltage thereto from ~he power source in the at least one preselected sequenc~ to effect the energization of the electronically commut~ted motor and the rotation o the rotatable assembly. The motion of ro~or lS is selectively coupled as discussed above to at least one rotatab9e component of the laundry machine 11, namely basket 23, agitator 25 or both, to cause rotation of the ro~atable componen~O The set of control signals of control signal circuit 33 are a function of rotor position -- which is derived from a position sensing circuit 35 -- and selected conditions and parameters, such as 03-Lo-5724 - 17 ' ap~lied voltage (as represen~ed in part by an applied command signal).
Position sensing circuit 35 (see FIG. 4) includes a set of voltage dividers 51 for sensing the terminal voltages of the windin~ stages, which terminal voltages include a back emf and a field collapse voltage caused by commutation current and ending prior to appearance of the back emf. The particu~
lar output o the voltage dividers needed in any parti~ular commutation period is the terminal voltage of the one winding stage which is not having DC voltage applied during that com-mutation period compared to neutral N. The terminal voltage of such unenergized winding stage is selected by a signal selector ~3, which is responsive to the system's particular place in the commutation sequence at that time to'supply the desired output of the voltage dividers to a position sensor circuit 55. The position sensor circuit 55 inventively and advantageously supplies a more accurate signal indicative of the angular position of the rotor, even under rapid rotor speea changes, to a commutation control circuit 57 whose out-puts are the set of control,signals Bl,B3,B5,B7,B3,Bll topower switching circuit 31. Upon the rotor reaching a prede-termined angular position, the commutation control circuit 57 (see FIG. 9 of said Erdman application) cAanges the control signals which are supplied to the power switching circuit 31 to commutate the winding stages. The commuta~ion control cir-cuit 57 also has an input from a non-commutation control cir-cuit 59 which input represents a number of external commands such as an ON/OFF signal, a direction of rotation signal, and a slow/fast commutation signal.
FIG. 9 illustrates a simplified view o~ the terminal voltages 101~Sl)tjust ending~, 101(S2), and 101~S3~ seen by the position sensor circuit 55 during successive commutation perioas. The terminal voltages are derived from a different windiffg stage Sl, S2 and S3 during each respective commutation ~3~
03~Lo-s724 period, indicated as repetitively extending from zero degrees ~hrough 60 degrees. Immediately following the commencement of a commutation at zero degrees (time 112) th~ voltage crosses zero while a winding stage S2 is being switched into a sense connection. Next follows an illustrated lOD interval when the portion 103~S2~ of terminal voltage lOl(S2) is of the same polarity as the anticipated back emf 105~S2) at the end of the commu~ation period. However, portion 103(S2) is not due to back emf. This field collapse voltage 103(S2) results from current which had been in the winding stage S2 while energiæed in the previous commutation period. While the field collapse voltage 103(S2) is illustrated as persisting for 10 degrees, the angular duration is actually highly motor and load depen-dent. The angular duration is also dependent on which tran-sistors are pulse width modulated in power switching circuit31, because of differences in the conditions that extract energy from the commutating current to produce field collapse voltage 103.
All this serves to suggest the difficulty in pre-dictinq the interval of time that a position integrator must be lockea out to avoid sensing this commutating voltage or field collapse voltage 103 and forcing commutation to the next winding prematurely. Reset interval timers have been used successfully for locking the position integrator out for 20 electrical degrees based on the previous commutation interval.
However, during periods of rapid speed change, reset interval timers can either produce reset times longer than 60 rotation-al degrees or less than the duration of the field collapse voltage 103. Either condition ~esults in a loss of position, torque, and consequent high current in the switchin~ transis-tors and flyback rectifiers.
. For an illustration of the dilemma that arises in using a lockout period based on the previous commutation interyal, consi~er long and short lockout periods TL and .
, .. . . . . . .. .. .

7~ . 0 3-LO- 5 7 2 4 TS in FIG. 9. Terminal voltage lûl (S33 is generated through 6û in a much shorter time than terminal voltage 101 ~S2) in the previous commutation interval due to acceleration o the rotor. Such acceleration occursr for instance, in startup and reversal of the rotor.
If the long locko~t period TL i~ selected on the basis of the duration of the field collapse voltage 103 (S2), then the entire 60 of terminal voltage 101(S3~ will be locked out~ On the other hand, suppose some shorter lockout period TS is selected so that under acceleration at lol~S3?, at least the positive part of the back emf 105~S3) is able to be integrated. Then such period TS will ~isadvantageously expose the integrator to field collapse voltage when decelera-tion occurs.
In solving this dilemma, a conceptual beginning is to provide a zero crossing detector to find the zero crossing at point 107 and then enable the integrator~ However, the terminal voltage 101 is relatively complex and leads to the need for a more sophisticated approach. First of all, there is very little back emf 115 when the rotor is just beginning to turn a~ start up. In production, real circuits f~r detect-ing a zero crossing exhibit error variat~on in their ability to detect the zero crossing in emf curve 115. Also, produc-tion variations in the voltage dividers 51 of FI~. 4 ~ntroduce a zone of error 117 in the zero crossing because the neutral voltage VN is synthesized imperfectly and the terminal volt~
age 101 is a less-than-perfect replica of the actual winding stage voltage relative to actual neutral N. Because of the zone of error 117, a zero crossing detector may entirely fail to initiate the integrating of the back emf at the very low rotor speeds relative to which acceleration and deceieration are particularly important~
Accordi~gly~ it is preferable to provide for detec-tion of a voltage such as at zero approach 10g and not zero . .

7~.

crossing 107. The detection of zero approach 109 as the field collapse voltage descends from peak to zero is then satlsfao-tory for detecting the ending of the field collapse voltage whether the rotor is moving fast or very slowly.
The terminal voltage 101 can evidence.zero voltage or zero approach occurences 120 caused by the use of pulse width modulation (PWM). When PWM is used in combination with a series inauctance to limit inrush currents to the power switches, this voltage 120 can erroneously set the flip-flop FFA (described below in FIG. 6) for integra~ion before the completion of the field collapse voltage, unless ampliier Al and comparator 78 are slow enough to ignore this relatively rapid transient. Usually adequate inrush protection will be obtained with an inductor that will cause a transient o less than five microseconds duration, which will be ignored by most discrete component operational amplifiers and comparators.
Of longer duration, however, are zero approach volt-ages which are the consequence of selecting a power switch for PWM purposes that allows the voltage across the sense winding ~o collapse for the duration of PW~ off period. If the pow.r device that is turned off is of the same polarity as the device th~t had been driving ~he sensed winding prior to com-mutation, then the consequence of turning this device off is to allow the terminal voltages of all three windings to go to near the same potential as current ~s sust~ined in the one remaining on power device and the flyback diode of the alter-nate powered windingO If, however, the opposite polarity power device is selected for PWM, the voltage across the sensed winding will increase as the remaining on device will be of the opposite polarity to that a~ the terminal of the sensed winding. The first method of PWM device selection is referred to as slow commutation due to the reduced rate of energy extraction during PWM off, and the second described method is referred to as fast commutation due to the greater rate of energy extraction.

Because of the zero approach that occurs during slow commutation, fast commutation is the preferred method of PWM
control to be employed with the circuits of FIGS. 6, 6A and 7. F G. 5A (to be discussed later~ would be suitable for use with slow commutation. Albeit not shown or purposes of brevity, methods of voltage sampling keyed to the PWM on period may be utilized with the circuits of FIGS. 6, ~A and 7 to maintain proper function ~uring slow commutation within the scope of the invention so as to meet at least some of the objects thereo~; however, the benefits of slow commutation (no diverting of c~mmutating current into the supply capacitor, and some reduction in audio noise) may not warrant the added complexity.
Another complication is that the terminal voltage 101 evidences an initial zero voltage or zero approach occur-rence 119 reflecting switching in the signal selector 53.
This zero crossing and zero approach condition occurs just after the commencement of co~mutation at point 112. Accord-ingly, in the preferred embodiment, the detection of zero crossings and zero approaches or integration resulting there-from is inhibited for a predetermined time interval 111 begin-ning at or after ~he commencement of commutation 112 and expiring at point 113 before the ending of the field collapse voltage 103. The duration of predetermined time interval 111 is in general selected by the skilled worker so as to avoid any spurious detection of a zero approach or zero crossing.
This interval 111 is so short compared to the duration TL f any field collapse voltage curve 103(S2)~ 103~S3) that accele-ration and deceleration result in no dilemma.
In FIG. 4 the signal selector 53 has outputs V~l and Vc2 for providinq the waveform illustrated in FIG. 9 ~o position sensor ~ircuit 55. Position sensor circuit 55 is shown in greater detail in FIGS. 5 and 6. Outputs Vcl and Vc2 are connected to the negative and positive input or _ _ _ _ . . ...... . . . . . . . . . . .

~ 03-LO-5724 receiving terminals respectively of a difference amplifier Al (FIG. 5) having an offset which is correctable by means of a potentiometer R19. A 1.5V reference voltage VR is ~lso sup-plied via a lOK resistor R21 by means of the diode drops o two forward biased diodes to the p~sitive input of amplifier Al to prevent out of ~ange errors. Inasmuch as the voltage on one of outputs Vcl or Vc2 is the actual or approximated neutral conducto~ voltage and the voltage on the other termi-nal is the terminal voltage of the stage not then being ener-gized, difference amplifier Al constitutes means for receivingand comparing thP terminal voltage of at least one of the winding stages (namely the unenergized winding stage) with a reference (namely the neutral conductor voltage). It has been found that the output of amplifier Al is a signal which can be used to determine the angular position of the rotor or rotat-able assembly of the motor, Specifically, after the commuta-tion currents die out, the output of amplifier A1 is a voltage 121 (FIG. 9) with an initial negative value proportional to speed, followed by a positive slope. The output VT of amplifier Al is supplied~through an electronically controlled switch 71 to an integrator 73 which constitutes means operable generally for integrating the output of amplifier Al and which operates so as to ignore the output of difference amplifier Al when the amplifier Al output has a polarlty opposite to the field collapse voltage. Switch 71 has three independently actua~le switch units 71aJ 71b and 71c, only the first two of which are connected to the output of difference amplifier Al, switch unit 71a being connected to said output through resis-tor R23 and unit 71b bein~ so connec~ed through resistor ~25.
Two switch units are used because it is desir~ble for integra, tor 73 to have two different time constants, one for each winding tap when a ~apped motsr winding is used. When ~he motor-is operating in the High speed winding mode, i.e., when external command signal SPEED i5 a logic High, switch unit 71b is closed and the output of difference amplifier Al is applied to the integrator through resistor R25, which resistor deter-mines the integrator ' s time constantO When signal SPEED is a logic Low, switch unit 71a is closed instead, and the input to the integrator occurs through resistor R23, which provides a second time constant for the integrator~ By this change in the integrator's time constant, a proper commutation angle can be maintained by compensating for the change in back emf per RPM that results from ~he use of a tapped motor windingO
Clearly other means for compensation are available; such as altering the voltage threshold at the output vf integrator 73 at which commutation is initiated. The SPEED command signal is applied to one input of an AND gate Gl and through an inverter 75 to one input of a second AND gate G3 The other inputs of gates Gl and G3 are connected to an internal command signal U, discus-~ed below, which when High is the integrate signal. When command signal U is Highr both logic gates are ena~led. However, the output of o~ly one goes High. Because of the presence of inverter 75, the other signals at the inputs to qates Gl and G3, labelled H and L respectively, can-not both be High at once. Hence only one can have a High out-put at any given time and so only one of switch units 71a or 71b can be closed at a given time.
The other switch unit of electronically controlled switch 71, namely unit 71c is controlled by an internal com-mand signal D which is the complement o~ command signal U.
When this switch unit is closed, which occurs from the begin ning of commutation for at lea~t a predetermined time of from approximat~ly 50 to approximately 100 microseconds, the inte-grator is initialized by being reset to the limit voltageestablished by zener diode Dl70 Integration is also inhibi'ced during this time because command signal U lthe complement of signai D) is Low at this time. As a result the ~utpu~s of gates Gl and G3 are bo h Low, switch units 71a and 71b are , . . . . . . . . ..

03-Lo-5724 2~ .
both open, and integration is inhibited so that no portion of field collapse voltage 103 is mistakenly integrated by the inte~rator~
Integrator 73, as is explained below, only starts integrating, or being exposed to ~erminal voltage at least, after the terminal voltage of the winaing stage being examined at least approaches zero at the ending of the field collapse voltage. Inte~rator 73 ignores the negative portion 11~ (FIG.
9) in the back emf tthe part opposite in polarity to field collapse voltage 103~ by virtue of zener diode D17. When zero point 122 of FIG. 9 is reachedt a physical reference rotor position in motor M is also reached and integration now devel-ops values of voltage interpretable as rotor angle relative to the physical reference rotor position. Once integrator 73 starts integrating in this way, it inte~rates down from a voltage output of about 9 volts to a predetermined voltage level of about 3 volts, which latter output is indicative o~
an angular position (selected by the skilled worker) of the rotor when the commutation period should be terminated. The output is applied to a comparator 77 and when the output reaches 3 volts, th~ output of comparator 77, labelled C~ goes High, which High is a commutation signal or pulse which repre-sents the fact that the rotor is at the proper position for commutation of the winding stages. Thus, comparator 77 con-stitutes means respon~ive to a predetermined output level ofintegrator 73 for generat~ng a commutation signal.
In FIG. 6 the output C of comparator 77 is supplied ~o OR gate GS and flip-flop FFA which, together with compara-tor 78 and inverter NGl, constitute means responsive to the commutation signal for inhibiting the integrator for the pre-determined length of time, initiating inte~ration u~ h~
first approach to xero at the ending of the field collapse signal ana providing the commutation pulses CP to effect the operation of the commutation con rvl circuit 57 to commu~ate .

, . . .... ... . . . . . . .. .. . ..

03-Lo-5724 the winding stagPs when the rotor reaches a predetermined angular position. Commutation signal C advantageously termi nates the same commutation period as the commutation period auring whic~ the endiny of Eield collapse voltage 103 occurred and initiated the operation of the integrator so as to result in the commutation signal in the first place. More specif-ically, the comparator 77 commutation signal C is applied to one input of an OR gate G5 (FIG. 6) driving a reset input of flip-flop FFA and providing control signal U directly and con-trol signal D ~also called CP) through inverter NG1. The cir-cuitry of FIG. 6 differs principally from the circuitry of said Erdman application in that control signal D is generated differently. In FIG. 8 o the Erdman application a pair of -divide-~y-16 counters 83~ 85 were used to keep command signal D High for approximately twenty electrical degrees. In the present work, command signal D stays High until the ending of the field collapse voltage in each commutation period.
Circuit 56 (which is the FIG. 6 portion of position sensor circuit 55) is seen to constitute means responsive to the commutation signal for ef~ecting by signal CP the opera-tion of the electronic commu~ation means and for inhibiting the operation of the integrator 73 for a predetermined length of time after a commencement of commutation of the at least some electronically commutated winding stages and before the ending of the field collapse voltage and for initiating the operation of the integrator when the terminal voltage of the at least on~ electronically commutated winding stage first . approaches zero after the predetermined len~th o~ time and at the ending of the ~ield collapse voltage.
In FIGo 5, integrator 73 and comparator 77 cooperate to provide the commutation signai, which is a pulse having a duration equal to the predetermined time period. When a com-mutatê pulse C is produced, the leading edge thereof produces through 1ip-flop FFA signals ~ and U which in turn inhibit ..

.

the integrator 73 throuyh switch 71. Integrator 73 now sees its noninverting input at reference VR forcing its output to rise to High. However, the ~.C network R73,C73 requires time to chzrge. In the meantime, comparator 77 stays on until the hysteresis or positive feedback provided b~ 100K resistor R77 is insufficient to keep comparator 77 from turning back off.
The time factors result in commutation signal C being on for the 50 to 100 microsecond predetermined time period durin~
which the integrator 73 is to be inhibited and reset~
"Inhibit" as the term is used herein denotes the action of flip-flop FFA keeping the inte~ra or from being exposed to the terminal voltage VT, in such manner that even if a zero crossing be detected, the integrator is not enabled.
The integrator is inhibited by flip-flop FFA during the prede-termined time period by action of commutation signal C, because even if comparator 78 goes high during signal C, flip-flop FFA prevents the integrator from respo~ding. If a zero approach is not detected by comparator 78 for a while after the predetermined time period expires, the integrator 73 is prevented from operation until the ending of the field col-lapse signal but not inhibited because the first approach to ~ero will enable it by action of comparatox 78 setting flip-flop F~A and exposing integrator 73 to terminal voltage VT
through switch 71.
Ou~put C is connected (FIG. 6) through OR gate G5 to the reset input of a NOR gate flip~flop FFA. The set input of flip-flop FFA is connected to the output of comparator 78 which is confi~u~ed as a zero-approaching detector and consti-~utes mean~ for initiating the operation of integrator 73 when the terminal voltage of the at least one electronically commu-tated winding stage firs~ approaches zero after commutation, ,and sp.ecifically after the predetermined length of time after commutation and at the ending of the field collapse voltage.
More specifical1yt the inverting input of comparator 78 is ~L~3~

connected to the output of amplifier Al, which output is the terminal voltage signal VT from the unenergized winding.
When the field collapse voltage of the unenergized winding crosses or closely approaches zero, the output of comparator 78 goes High. The approach reference level is set at about 100 millivolts above the offset reference VR, for example, by choice of resistors at the noninverting input o comparator 78. Thus, the zero approach reference is at least approxi-mately one percent of the ten volt peak value of the terminal voltage produced as voltage VT.
Zero crossings or approaches occurring during the predetermined 50 to 100 microseconds length o time after commence.~ent of commutation do not cause a change in the out- `
put of flip-flop FFA because the reset input of the flip-flop is held High by commutation signal C. The predetermined length of time is selected to allow any voltage behavior 11~
(FIG. 9) to end and the integrator to reset before flip-flop FFA can be set by zero-crossing or zero approaching detector 78. Then commutation signal C goes Low and stays Low until the next commutation. Because of the presence of field col-lapse voltage 103, the output of zero-crossing or approaching detec~or 78 is Low by this time and stays Low until the volt-age 103 crosses or closely approaches zero~ which indicates that the commutation currents have dissipated and the ending of the field collapse voltage has occurred. At that time flip-flop FFA is set and its output as signal ~ goes ~igh.
The High output of the flip-flop is inverted by inverter NGl and the resulting Low output i5 ~upplied as the trailing edge of command signal D and commutation pulse CP of FI~. 4. Sig-nal U initiates and enables integrator 73 by closing theappropriate one of electronically controlled swi~ches 71a and 71b, and signal D being Low opens switch 71c.

7~ 0 3 -Lo- 5 7 2 4 Note that during the predetermined length of time ater commutation, signal C is High, so the output of flip-flop FFA is Low. This inhibits AND gates Gl and ~3 and keeps switches 71a and 71b open for the duration of the predeter-mine~ length of time after commencement of commutationOFurthermore, signal D keeps switch 71c closed, resetting inte-grator 73. Signal C additionally keeps flip-flop FF~ reset during the predetermined length of time after commutation, so that zero crossings during the predetermined length of time are ignored by inte~rator 73.
The selection of component values for this network will include numerous consiaerations well known to those skille~ in the art. A set of component values consistent with the ob~ectives of this circuit are:
C73 = 0.001 microfarad D17 = 8.2 volts R23 = 33 ~ ohms R25 = 15 K ohms R73 = 10 K ohms R77 = 100 K ohms R78 = 220 K ohms R79 = 560 K ohms 50 KHz Oscillator 85 and resettable divide by 4096 counter 87 act as a motor starting circuit for the system by providing a start pulse about every 80 milliseconds. The requirement for this sta~t pulse only occurs when the random alignment of the permanent magnet rotor 15 is such that no torque is developed. The start pulse then forces commutation to the next drive state which will develop torque and conse-quent rotor movementO ~hen the rotor begins to turn, commutate pulses C produce the D output which resets the counter 87 more fre~uently than the 80 milliseconds, thereby avoiding any undesired pulses from counter 87 after starting.
An alternative appeoach to that illustrated in FIGS.
5 and 6 is shown in FIG. 5A, and while the circui~ of FIG. SA
meets at least some of the obje~ts set out hereinbefore, it is 7~ 0 3 - Lo- 5 7 2 4 believed that suoh circuit may have indigenous objects and advantageous features as will be in part apparent and in part pointed out hereinafter. Rather than wait for the terminal voltage of the unenergized win~ing to approach ~ero, the cir-cuit of FIG. 5A enables the integrator once the terminal volt-age falls below the rail or supply voltage. In normal, loaded motoring conditions, the terminal voltage of ~he unenergized winding is clamped to the positive or negative supply voltage VAcT during the collapse of the field in that winding after commutation. Thus the terminal voltage is the higher magni-tude field collapse voltage portion beginning with commence-ment of commutation and ending prior to appearance of the lower magnitude back emf portion. Once this field collapses, the terminal voltage of the unenergized winding is simply the back emf portion of that winding which is normally signif-icantly below the supply voltage in magnitude. Specifically, the circuit o~ FIG. 5A includes a voltage divider 51a con~
nected between the terminals of the winding stages and the reference voltage VR. The proper terminal voltage (i.e., the one corresponding to the unenergized winding) is selected by circuit 53a as describea above and supplied to an amplifier Ul. The output of amplifier ~1 is supplied not only to a position determining integrator U~ but also to the inverting input of an operational amplifier U3. The other input of amplifier U3 is set at a reference ~oltage derived from the supply voltage VAcT by a voltage divider 51b. While the terminal voltage of the unenergized winding stays near the supply voltage~ the output of amplifier U3 inhibits and resets the integrator U~. But when the terminal voltage falls below the referencer amplifier U3 enables integrator U2 and integra-tion of the back emf proceeds as described above~ Thus, it can be seen that amplifier U3 constitutes means for inhibiting the operation of the integrating means until the terminal voltage of one of the at least some electronically commu~ated -~;3 7`~
. 03-LO-5724 winding stages falls in magnitude below a preselected level selected to exceed that ~f the back emf of a winding stage under motoring conditions. ~urther, the consequence of slow commutation is minimal~ as during the PWM off period little integration will take place due to the low voltage that will occur, and subsequently the integrator will be reset when the PhM returns to ~he on period.
In FIG. 6A, alternative position sensing circuitry 55' has some numerals primed to suggest circuit portions per-forming ~unctions corresponding to those in FIGS~ 5 and 6.
The circuit 55' is contemplated for implementation on a singleintegrated circuit chip. While the circuit of FIG. 6A meets at least some of the objects set out hereinbefore, it is believed that.such circuit may have indigenous objects and advantageous features as will be in 2art apparent and in part pointed out hereinafter.
Integrator 73' utilizes a transconductance amplifier providing current IoUt proportioned to the terminal voltage difrerence VT appearing between voltag~s V~l and Vc2.
The current IoUt is provided to the capacitor C73', which integrates from the supply voltage down to a predetermined voltage V3. Then circuit 77' operates to generate a commu-tation signal, with the comparator therein driving an inverter w i th hys te resis~
~lipflop FFA' provides the U and D pulses and is set by zero-approach detector comparator 7R ' and reset by commuta~
tion signal generating circuit 77 ' . An inhibit High signal is provided to NOR-gate G6 by delay circuit DLl in response to the commutation signal C-bar. The inhibiting High isolates 30 zero approach detector ?8' from flipflop FFA' and integrator 73'. Signals U and D cont~ol analog switches 71a' and 71b' to disconnect capacitor C73' from the transconductance amplifier and connect it to the positive supply rail or vice versa.
Thus. signals U and D reset and enable the integrator 73~

.. . ~ . . .. . ... . ... ... . . . .. .

~2;3t~
~ 31 - 03-LO-572~

Zero approach detector 78' is a differential mode comparator with fixed internal offset voltage VOF
at which the zero approach 109 is detected. The voltage VOF is provided in a CMOS (complementary metal oxide semiconductor) chip as by an intentional current injected to develop a voltage drop equal to VoF~ Inhibit gate G6 keeps zero approach detector 78' from setting flipflop FFA' during the nominally 50 to 100 microsecond time period set b~ circuit DLl.
Circuit DLl develops the minimum reset time through RS flipflop FFD, gates G7, G8, G9 and the two `'D" flipflops LTl and LT2 fed by a nominal 10I~Hz. PWM
oscillator for the motor. The initial pulse SR arrives as a logic one resetting flipflop FFA'. Pulse SR appears at NAND-gate G5' in response to commutation signal generating circuit 77' or the motor-start counter circuit including a 5KHz. oscillator, counter 87' and NAND-gate G4. In circuit DLl, signal D has been low, which has kept latches LTl and LT2 reset through gates G7 and G8.
Pulse SR se~s flipflop FED High. Signal D rapidly goes High at flipflop FFA' in response to pulse SR being High, thereby removing the forced reset input from latches LTl and LT2. Neither of these devices will change state, however, until a positive going signal is applied to the respective C clock input of LTl or LT2. The first positive-going edge from the PWM oscillator drives latch LTl output Q High. Inverter G9 takes the clock input to latch LT2 Low. The second positive going edge from the PWM oscillator drives latch LTl Low. Inverter G9 takes the clock input to latch LT2 High. The high-going clock input to latch LT2 drives its output Q high, which in turn resets flipflop FFD. Flipflop FFD thereby removes the High input to NOR-gate G6 which had been ultimate-ly inhibiting integrator 73' through flipflop FFA', and the inhibit ceases after the predetermined length of time 111.

;7~
03-Lo-s724 Optional zero approach comparator speed compensation CSC is providable by means of an external capacitor or Yolt-age~ Compensation CSC provides for slow down of the very fast operation achievable by the comparator in circuit 78' when implemented on an integrated circuit chip. If very fast noise pulses come into the circuit 55', too fast a response as dur-ing time period 111 or at other times could defeat the func~
tion of the circuit. The circuit DLl operates to inhibit false detections o zero crossings during the time period lllo It is contemplated, however, ~hat circuit DLl can be omitted when compensation CSC is provided so that the detector circuit 78' is slow enough to only detect zero approaches that last in excess of the predetermined time interval of 50 to 100 micro-seconds.
.~nother alternative em~odiment of the circuit of FIG~ 5 is shown in FIG. 7, and while the circuit of FIG. 7 meets at least some of the objects set out hereinbefore, it is believed that such circuit may have indigenous objects and advantageous features as will be in part apparent and in part pointed out hereinafter. See Alley U.S. patent 4,250,544 for disclosure of programming of microcomputer circuitry to obtain terminal voltage and provide currents in a preselected sequence to the electronically controlled motor, and for other purposes. The FIG. 7 embodiment includes a logic circuit under programmed control, namely a microcomputer MCl for, inter alia, receiving the commutation signal Cl and ~or sup-plying an integrator inhibit signal on port Pl line 3. The inhibit signal on Pl }ine 3 is supplie~ for the predetermined 50 to 100 microseconds leng'ch of time after receipt of the commutation signal C' by programming the microcomputer with an interrup~ routine usiny a technique familiar to the skilled worker so as to accomplish the production of the inhibit sig-n~l in the ma~ner o~ a one~shot. For instance, as soon as the interrupt routine is commenced in response to commutation sig-nal C', the program sets Pl line 3 high and then tests a ~imer , .

~ ~7~

so that when the predetermined ~ime interval has been exceeded, the line is set low.
Microcompu~er ~Cl has three Pl outputs 1, 0 and 2 connected to the A, B and C select pins of a 4053-type triple 1-of-2 switch STl. The t~ree inputs of switch STl are con-nected to a voltage divider DVl in such a manner that one input represents the terminal voltage VA of one winding stage of the electronically commutated motor, a second input repre-sents the terminal voltage VB of a second motor winding stage, and the third input represents the terminal voltage VC of the third winding stage. Switch STl has two outputs OPl and OP3.
The microcomputer MCl is programmed to control switch STl dur-ing each commutation period so that the signal on one of the two outputs is proportional to the terminal voltage of the unenergi~ed winding by switching from the leg of divider DVl connected to tha~- winding, e.g., Ain to OP3. The siynal on the other output is an approximated neutral conductor voltage obtzined by programming microcomputer MCl to switch both of the other two inputs, e.g~, Bin and Cin to output OPl.
The signals are assigned to OPl and OP3 so that the voltage difference between them i5 as shown in FIG. 9, for successive commutation periods.
The signals on outputs OPl and OP3 are supplied through a pair of unity gain amplifiers UAl and UA3 which con-stitute means for providing a high impedance to outputs OPland OP3 of switch STl and a low impedance to the inputs of an amplifier AAl. Amplifier AAl is analogous to amplifier Al o~
FIGr 5 in that it~ output represents the terminal voltage ~inverted in polarity so that field collapse vol~age outp~ i5 negative~ of the unenergized winding stage. The output o~
ampli~ier AAl is supplied to an integrator 71A similar to the integrator 71 of ~G. 5 except that integrator 71A integrates in the direction of more positive magnitudes and has an 3~7~

03~Lo~s724 adjustable reference at the noninverting input. The adjust-able reference provides compensation for manufacturing varia-tions in divider DVl and other components. In this way inte gration error at slow rotor speeds is adjustably minimized.
The output of amplifier AAl also feeds a zero crossing or approaching detector 78A. Because the amplifier AAl ~ield collapse voltage is negative, a negative voltage divider reference is provided at the inverting input of detector 78A.
The output of the ~ero crossing or approaching detector 78A is connected to the set input o~ a NOR gate flip-flop ~FB~ whose reset input is connected to the Pl93 output of microcomputer MCl. The reerence voltage for detector 78A is preferably set to be at least one percent of the peak value of the field col-lapse voltage provided to detector 78A.
The output of integrator 71A, which is the inte-grated back emf of the unenergize~ winding, is supplied to a comparator 77A having its comparator input diode-protec~ed.
When the integration increases to and reaches a positive pre-set value representative of the desired rotor position for commutation, the output of comparator 77A goes Low, which is a commutation signal C', analogous to but opposite in polari~y from, commutation signal C of FIG~ 5. The outpu~f~compara-~~ tor 77A is connected to an interrupt pin P3,2 ~a-b~ (low active3 of the microcompu~er MCl. When the output of the com-parator 77A goes Low, which si~nif ies the beginning of co~u-tation, the microcomputer is directed by ~ts program to supply a ~ligh signal on line Pl,3 to the set input s:~f flip-flop FFB
for the predetermined length o~ time, which again is from approximately 50 microseconds to approximately 100 micro-seconds. During this time the output of flip-flop FFB is held Low by the High on pin P1,3. This Low t~rns on a PNP transis-tor QA, which resets integr~tor 71A during the pxedetermined length of time to p~event unintended integration of field col-lapse voltage of the unener~ized winding. Trans~s~or Q~ thus .

~7'~

constitutes means -to prevent or inhibit integration during the predetermined length of time after receipt of the commutation signal. After the predetermined length of time has passed, the microcomputer causes pin Pl,3 to go back Low, thereby removing the inhibition signal from the flip-flop FFB and the integrator 71A.
The first subsequent zero crossing or approach (which occurs at the end of the field collapse voltage) causes the output of comparator 78A to go High, causes flip-flop FFB to be set high, transistor Q~ to be turned off, and in-tegrator 71A to be thereby enabled.
Upon receipt of the commutation signal C', microcomputer MCl is also programmed to supply at port PO, pins 0-5, the necessary control signals Bl, B3, B5, B7, B9 and Bll ~see Fig. 8) to commutate the proper winding stages to cause rotation of the rotor.
In FIG. 8, microcomputer MCl is again shown, this time with emphasis on an additional set o-f outputs, as for an Intel 8051 unit. The microcomputer MCl is programmed to use these outputs to control the peak motor current and the average pulse width modulated (PWM) voltage applied to the winding stages, as well as for commutating the winding stages. The actual available power supply voltage applied at any given time to the winding stages is labelled VAcT and is an input to the circuitry of FIG. ~, as is the voltage across motor current sensing shunt resistor Rs (see also FIG. ~).
The microcomputer MCl supplies a two bit signal at port 1 representing the maximum desired peak motor current IREF on pins ~ and 7 (pin 7 representing the most significant bit MSB) through an adder network AN
of resistors to the non-inverting input of an op-amp A5.
The voltage across shunt resistor Rs is applied through a pair of matched resistors R~l and a filter FTl across the inputs of op-amp A5, so the output of amplifler A5 represents whether or not the actual peak motor current exceeds the reference peak motor current IREF set by the signals on pins 6 and 7 of themicrocomputer.
Amplifier A5 thus constitutes means for comparing the peak motor current with the microcomputer-set current reference. During operation, if different motor current levels are desired at different points in the operation of the motor, the motor current can be changed directly by the microcomputer at the desired time by changing the signals on Pl pins 6 and 7. Of course, if finer gradations of motor current are desired than are available with only two bits, additional output pins of the microcomputer could be used to output a desired motor current word consisting of mroe bits. In such a case, the use of a digital-to-analog converter to convert the microcomputer output to analog form could be desirable.
When the actual motor current exceeds the micro-computer's reference motor current, the output of amplifier A5 goes Low. This Low is supplied to the low active reset-bar input of a D-type latch LTH, which causes the Q-bar output labelled QZ to go High. Output Q~ is supplied to a pair of NAND gates NDl and ND3 whose other inputs are signals from port PO pins 6 and 7 respectively of the micro-computer. PO pins 6 and 7 determine which set of transistors (either the upper (U-bar) or the lower (L-bar)) in power switching circuit 31 are to be left on when power is cut off, to allow current in the windings to circulate, as is explained in the aforementioned Canadian Patent No.
1,199,997. The signals on PO pins 6 and 7 are complementary, so when output QZ goes High, it causes the output of one ; 30 of gates NDl and ND3 to go High and the other to stay Low.
The output of gate NDl is connected through an inverter to a set of three NOR gates NG5 whose outputs are the lower transistor control signals B3, B7 and Bll corresponding to ; winding state connections A-, Band C-. Likewise the output of gate ND3 is connected through an inverter to a set of three NOR gates NG7 whose outputs are the upper transistor control signals Bl, B5 and ~9 corresponding . .

to ~inding stage connections A+, B+ and C+. When the output of gate NDl goes Low because output QZ is ~igh and P0 pin 6 is High, gates NG5 are disabled~ This breaks the circuit from VAcT ~hrough the energized windings to ground and thereby reduces motor current. 1ikewise, when the output of gate ND3 goes Low because output ~Z is High and P0 pin 7 is Hiyh, sates NG7 are disabled, which again breaks the circuit but at a dif-ferent point therein. In either case, the excess motor cur-rent signal from amplifier A5 causes the external application of voltage to the windings to cease. Application of voltage to the windings is resumed when the PW~ oscillator at UA7 clocks the latch LTH back on.
Microcomputer ~Cl also controls the average voltage applied to the windings over a nominally lO to 20 KHz. PWM
cycle, by supplying an 8-bit word representing a reference voltage over P2 pins 7-0 to a digital-to-analog converter DAC.
As in the case of the peak current reference, the average voltage reference may be changed from cycle to cycle, or con-ceivably even within a cycle, as re~uired to obtain the desired operating characteristics of motor M. The analog out-put VAcT REF of converter DAC is supplied through an ampli-ier Al3 configured as an inverter to the non-inverting input of a comparator UA5 which compares the VAcT REF reference voltage set by the microcomputer with a function of the actual DC power supply volt~ge VAcT being supplied to ~he motor windings. Specifically, the reference voltage V~cT REF is compared by amplifier UA5 with the integral of the actual applied vol~age as approximated by a resistor-capacitor cir-cuit R87.,R89,C9l generally designated RCl which constitutes means for generating a direct function of the applied voltage~
When the voltage on the capacitor o~ circuit RCl reaches the reference ~oltage, the output of amplifier UA5 goes Low.
Thus, amplifier UA5 constitutes means for comparing the func-tion of the applied voltage to a refe~ence and for indicating . .

"3,~

03-Lo-5724 .

when the function reaches the reference. Since the output of amplifier UA5 is connected to the reset-bar input of latch LTH, the Q-bar output of the latch goes High when the integral of the voltage reaches the voltage reference, which stops the application of external power to the winding stages as explained above in connection with motor current control.
Note that when the integral of the applied voltage reaches the reference the voltage on the capacitor of circuit RCl is not reset (e.g., made to be zero). Rather the integra-tion is allowed to continue even though the external a~plica-tion of power has ceased. In other words~ the cycle for power being applied to the windings is not stopped because the inte-gral reaches the reference value. Rather, the cycle length is controlled by a voltage divider DV3 and a second comparator lS UA7. The inverting input of comparator UA7 ist li~e that of comparator UA5, connected to the integral approximating cir-cuit RCl. The non-inverting input, however, is connected to voltage divider DV3.
Divider DV3, circuit RCl, and comparators UA7 and 20 UA9 amount to a sawtooth oscillator circuit. Comparator UA7 signals when capacitor C9l should start charging and subse-quently stop charging. Variations in the cycle length of the sawtooth oscillations which might occur in respons~ to varia-tions in the DC supply voltage VAcT are minimized or elimi~
25 nated by applying VAcT both to divider DV3 and to ch~rging circuit RCl . Potential cycle shor tening which might occur due to a r ise in V~cT causing c:apacitor Cgl to charge to a given volta~e in a shorter time i~ compensated by dividër DV3 pre-senting a hi~her voltage to which C91 must charge before com-parator'UA7 changes state. The values of ~he resistors R81,R82,RS5 in divider DV3 and components R87,R89 and C91 of cir-cuit RCl are selected so as to 8et the cycle length for the application of voltage to the windings at a predet~?rmined value. Examples of component values are: R81 - l.37 megohmr ~ ~3 7L~ ~

1~; R83 - 13K, 1%; R85 - 13K~ 1%; R87 - 5.5 megohm, 5~; R89 -1.8K, C91 - 0.001 microfarad. The actual applied voltage VAcT i~ supplied to the top of divider DV3 and the predeter-mined fraction thereof is supplied to the noninverting input of comparator UA7~
When the function of the applied voltage represented by the voltage o~ the capacitor C91 of circuit RCl reaches the p~edetermined fraction of the applied voltage, the output of comparator UA7 goes Low. Thus, comparator UA7 constitutes lQ means for signaling the end of each voltage cycle when the function of the applied voltage reaches the predetermined value~ UA7 going low causes transistor QN to momentarily drive reset~bar of latch LTH low until output Q of LTH
responds by going low. Transistor QN thus acts as an elec-tronic~lly controlled switch for connecting the output of com-parator UA7 to the input of latch LTH, the ba~e of transistor QN being connected to the Q output of the latch. Q-bar output goes High which, as above, rssults in the cessation of th~
applica~ion of external power to the winding stages if this has not already occurred. Latch LT~ thus constitutes means for terminating the external application of voltage to the load when the function of the applied voltage reaches the reference and for terminating the present cycle.
The output of comp~rator UA7 is also connected to the non-inverting input of compa~ator UA9, whose other input is held at approximately 2.5V~ When the output of comparator UA7 goes Low, diode D9 pulls down the DV3 divider voltage and the output o~ comparator UA9 goès Low as w~ll, controllably discharging the capacitor C91 of circuit RCl through R89.
When the capacitor is discharged the output of comparator UA7 goes High again because a DV3 voltage e~ual to about ~alf the diode~D9 diode drop is fed to the noninverting input of UA7.
When comparator UA7 goes ~igh, divider DV3 is restored since ~ 3~

,~o diode D9 becomes reversed biased. Also at this time compara-tor UA9 goes high so that VAcT resumes charging the capaci-tor C91, and a new cycle is begun. UA7 going high clocks LT~
Q-bar output low which restores the application of external power to the winding stages. Comparator UA9 t because it con-trollably discharges the capacitor, thus ensures that the min-imum off period at the end of each cycle is of sufficient length to allow the op-amp A5 to clear of a sensed peak cur-rent condition before a new cycle is begun. Failure to pro-vide this feature results in a discontinuity of motor controlas increasing current load first approaches the peak current regulate point.
From the above, it can be seen that the same cir-cuit, namely circuit RCl, provides the integral of the applied voltage for comparison with the VAcT_REF g and the timing for terminating each cycle~ Such an arrange-ment permits the use of low precision ~e.g., ~ 10%) capacitors for C91 because the error in the capacitance of that capacitor of circuit RCl cancels out from the caiculation of the average voltage applied in a cycle to the winding stages. If separate resistor-capacitor circuits were used to calculate the inte-gral and to determine the cycle length, the error in average voltage (which is their ratio~ caused by the use of low preci-sion capacitors in each circuit could be significant. ~ow-ever, with the present arrangement, the error in the integralvalue and the error in the cycle length caused by manufactur-ing variations in the capacitance of the capacitor of circuit RCl in effect . cancel out/ resulting in much better accuracy.
FIG. 10 graphs A and B each show voltage-versus-time illustrations of pulse width modulated cycles for Motor M cor-responding in timing to FIG. 8 latch output Q, the cornplement of QZ; It is noted in passing that the time axis of FIGo 10 is much magnified hecause the cycle lengkh of th~ PW~ cycl2s of FIG. 10 is the same as the interYal ~etween cycles showing ~:3~
03-Lo-5724 ~1 .
in the voltage behavior 120 of FIG~ 9. Graph A shows success-ful average voltage control utili~îng a first value of capaci-tance of capacitor C91. Graph B corresponas to equaliy suc-cessful average voltage control with a larger value of capaci-tance of capacitor C91 than in graph A.
Suppose, for example, that an average 25 voltsVAcT RE~ is ordered by microcomputer MCl, and that a presently occurring level of VAcT is S0 volts. Then, as shown in sraph A of FIG. 10, the 50 volt pulses tsolid lines) have cycle length to and a pulse length tp during which VAcT is applied to the load. The FIG. 8 circuit sets pulse length tp half as long as cycle length to, so that the average voltage is half of S0 in this example. If voltage VAcT subsequently rises from its first level of S0 to a higher level shown by the dotted pulses, the circuit of FIG. 8 reduces pulse length tp without changing cycle length to, so as to keep the average voltage VACT x ~p /~O equal to VAcT_REF~
In graph B, the larger capacitor C91 merely increases the cycle length to'. Then the circuit of FIG~ 8 provides the pulse length tp' sufficiently lon~ to achieve the same ratio tp'~to' as was needed in graph A to main~
tain the average voltage.
From the foregoing, it is now apparent that novel forms of a control system for an electronically commutated motor (ECM3, novel methods of operating an ECM, novel ECMs ~
novel laundering apparatus~ novel systems for controlling the average voltage cyclically applied to a Ioad, novel methods of controlling the average voltage cyclica}ly applied to a load, and novol methods o~ controlling the average voltage cyclical-ly applied to an ECM have been disclosed for accomplishlng the objec~s set forth hereinbefore, as well as others~ and that change as to the precise arrangements, shapes, details and connections of the component parts~ as ~ell as the steps of .

methods, may be made by those having ordinary skill in the art without departing from ~he spirit of the invention or ~he scope thereof as set out in the claims which followO

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A control system for an electronically commutated motor adapted to be energized from a DC power source and including a stationary assembly having a plurality of winding stages adapted to be electronically commutated in at least one preselected sequence, and a rotatable assembly associated in selective magnetic coupling relation with the winding stages, each winding stage having a terminal associated therewith, the control system comprising:
first means operable for electronic commutation and energization of at least one at a time of the winding stages of the electronically commutated motor by applying thereto a DC voltage from the power source in the at least one preselected sequence to effect the energization of the electronically commutated motor and the rotation of the rotatable assembly, at least one unenergized other of the winding stages during any one commutation exhibiting a terminal voltage including a back emf and a field collapse voltage ending prior to appearance of the back emf; and second means for receiving and integrating the terminal voltage in response to its first approach to zero at the ending of the field collapse voltage and effecting the operation of said electronic commutation means when a predetermined level is reached in the integrating.

2. The control system claimed in claim 1 wherein said second means for receiving, integrating and effecting comprises:
third means operable generally for receiving and integrating the terminal voltage;
means, responsive to a predetermined output level of said third means, for generating a commutation signal; and fourth means responsive to the commutation signal for effecting the operation of said electronic commutation means and for inhibiting the operation of said third means for a predetermined length of time after a commencement of commutation and before the ending of the field collapse voltage and for initiating the operation of said third means when the terminal voltage first approaches zero after the predetermined length of time and at the ending of the field collapse voltage.

3. The control system claimed in claim 2 wherein said third means operates so as to ignore the terminal voltage when the terminal voltage has a polarity opposite to the field collapse voltage, and the commutation signal terminates the same commutation period as the commutation period during which the ending of the field collapse voltage occurred and initiated the operation of said third means so as to result in the commutation signal.

4. A control system for an electronically commutated motor adapted to be energized from a DC
power source and including a stationary assembly having a plurality of winding stages adapted to be electronically commutated in at least one preselected sequence, and a rotatable assembly associated in selective magnetic coupling relation with the winding stages, each winding stage having a terminal associated therewith, the control system comprising:
electronic commutation means operable generally for electronic commutation of at least some of the winding stages of the electronically commutated motor by applying thereto a DC voltage from the power source in the at least one preselected sequence to effect the energization of the electronically commutated motor and the rotation of the rotatable assembly;
receiving and integrating means operable generally for receiving and integrating the terminal voltage of at least one of the winding stages, the terminal voltage including at least the back emf of the at least one winding stage and a field collapse signal ending prior to appearance of the back emf;
commutation signal generating means responsive to a predetermined output level of said integrating means for generating a commutation signal for a predetermined length of time, the predetermined length of time expiring before the ending of the field collapse signal; and means responsive to the commutation signal for effecting the operating of said electronic commutation means and for inhibiting the operation of said integrating means for the predetermined length of time and initiating the operation of said integrating means when the terminal voltage of the at least one winding stage first approaches zero after the predetermined length of time.

5. The control system as set forth in claim 4 wherein said receiving and integrating means comprises at least one electronically controlled switch means for receiving the terminal voltage, said electronically controlled switch means being controlled in its opening and closing by said means for effecting, inhibiting and initiating thereby to inhibit and initiate the integrating.

6. The control system as set forth in claim 4 wherein the means for effecting, inhibiting and initiating comprises flip-flop means for coupling with said integrating means, and comparator means for coupling with an input of said flip-flop means and responsive to the terminal voltage to initiate integration when the terminal voltage approaches zero.

7. The control system as set forth in claim 6 wherein said flip-flop means has a second input coupled to said commutation signal generating means so as to inhibit integration upon occurrence of the commutation signal.

8. A control system for an electronically commutated motor adapted to be energized from a DC power source and including a stationary assembly having a plurality of winding stages adapted to be electronically commutated in at least one preselected sequence, and a rotatable assembly associated in selective magnetic coupling relation with the winding stages, each winding stage having a terminal associated therewith, the control system comprising:
means operable generally for electronic commu-tation and energization of at least one at a time of the winding stages of the electronically commutated motor by applying thereto a DC voltage from the power source in the at least one preselected sequence to effect the energization of the electronically commutated motor and the rotation of the rotatable assembly, at least one unenergized other of the winding stages during any one commutation exhibiting a terminal voltage including a back emf and a field collapse voltage ending prior to appearance of the back emf;
integrating means operable generally for inte-grating the terminal voltage of the at least one unener-gized winding stage during any one commutation;
means responsive to a predetermined output level of said integrating means for generating a commutation signal for effecting the operation of said electronic commutation means;
controlling means for controlling said integration means, said integration controlling means being responsive to the commutation signal to disable said integrating means; and comparing means for comparing the field collapse voltage with a predetermined level and, upon the field collapse voltage falling below the predeter-mined level, causing said controlling means to enable the operation of said integrating means.

9. The control system as set forth in claim 8 wherein said controlling means includes flip-flop means for connection to said integrating means to prevent integration at least during a predetermined length of time, the predetermined length of time expiring prior to the ending of the field collapse voltage.

10. The control system as set forth in claim 9 wherein said comparing means includes means for initiating the operation of said integrating means substantially when the terminal voltage first approaches zero after the predetermined length of time, the output of said operation initiating means being connected to an input of said flip-flop means to initiate integration.

11. The control system as set forth in claim 10 wherein the field collapse voltage has a peak value, the predetermined level for said comparing means being at least equal to a preselected percentage of the peak value.

12. The control system as set forth in claim 8 further including an electronically controlled switch having one input for each winding stage, each input being connected to its respective winding stage, and having at least two outputs, and logic circuit means being programmed to control said electronically controlled switch so that one output represents a neutral voltage and a second output represents the terminal voltage of the one of the windings.

13. A method of operating an electronically commutated motor adapted to be energized from a DC
power source and including a stationary assembly having a plurality of winding stages adapted to be electronically commutated in at least one preselected sequence, and a rotatable assembly associated in selective magnetic coupling relation with the winding stages, each winding stage having a terminal associated therewith, the method comprising the steps of:
commutating in response to a commutating signal at least some of the winding stages by applying a DC voltage thereto in the at least one preselected sequence to effect the energization of the electronically commutated motor and the rotation of the rotatable assembly;
generally integrating the terminal voltage of at least one of the winding stages, the terminal voltage including at least the back emf of the at least one winding stage and also including a field collapse voltage ending prior to appearance of the back emf;
generating the commutation signal when the integrating reaches a predetermined level; and initiating the integrating in response to a first approach to zero at the ending of the field collapse voltage.

14. The method as set forth in claim 13 comprising the intermediate steps of:
inhibiting the integrating for a predtermined length of time after the commutation of the at least some winding stages and prior to the initiating step; and ignoring any part of the terminal voltage opposite in polarity to the field collapse voltage during the integrating.

15. The method as set forth in claim 14 comprising the preliminary step of programming a logic circuit to supply an inhibit signal for the predetermined length of time after receipt of the commutation signal.

16. The method as set forth in claim 14 wherein the predetermined length of time is between approximately 50 microseconds and approximately 100 microseconds.

17. The method as set forth in claim 16 wherein the predetermined length of time is approximately 70 microseconds.

18. An electronically commutated motor adapted to be energized from a DC power source comprising:
a stationary assembly having a plurality of winding stages adapted to be electronically commutated in at least one preselected sequence;
a rotatable assembly associated in selective magnetic coupling relation with said winding stages;
and a control system including:
electronic commutation means operable generally for electronic commutation of at least some of the winding stages of the electronically commutated motor by applying thereto a DC voltage from the power source in the at least one preselected sequence to effect the energization of the electronically commutated motor and the rotation of said rotatable assembly;
integrating means operable generally for integrating a voltage across an unenergized one of the winding stages in each commutation period, the unenergized winding voltage including a back emf and a field collapse voltage ending prior to the back emf; and effecting and preventing means responsive to a predetermined output level of said integrating means for effecting the operation of said electronic commutation means and for preventing the operation of said integrating means after the commencement of commutation of said at least some winding stages until the ending of the field collapse signal.

19. The electronically commutated motor as set forth in claim 18 wherein said effecting and prevent-ing means comprises means for generating a commutation signal in response to the predetermined output level of said integrating means and electronic means responsive to the commutation signal for effecting the operation of said electronic commutation means and responsive to the field collapse signal for preventing the operation of said integrating means only until the ending of the field collapse signal.

20. The electronically commutated motor as set forth in claim 18 wherein the unenergized winding voltage is connected through at least one electronically controlled switch to said integrating means, an output of said effecting and preventing means being connected to said electronically controlled switch to control its opening and closing.

21. The electronically commutated motor as set forth in claim 18 wherein said effecting and preventing means includes means responsive to the predetermined output level of said integrating means for generating a commutation signal, and a logic circuit under programmed control, said logic circuit having as one input the output of said commutation signal generating means and being programmed to supply an inhibit signal for a predetermined length of time after receipt of the commutation signal.

22. The electronically commutated motor as set forth in claim 21 further including an electronically controlled switch having one input for each winding stage, each input being connected to its respective winding stage, and having at least two outputs, said logic circuit being programmed to control said electronically controlled switch so that one output represents a neutral voltage and another output represents a terminal voltage of said unenergized one winding stage, said integrating means being coupled to said winding stages by said electronically controlled switch.

23. The electronically commutated motor as set forth in claim 21 wherein the predetermined length of time is between approximately 50 microseconds and approximately 100 microseconds.

24. The electronically commutated motor as set forth in claim 23 wherein the predetermined length of time is approximately 70 microseconds.

25. A laundering apparatus comprising in combination:
agitating and spinning means for agitating fluid and fabrics to be laundered thereby to launder the fabrics and for thereafter spinning the fabrics to effect centrifugal displacement of fluid from the fabrics;
an electronically commutated motor adapted to be energized from a DC power source, said motor comprising a stationary assembly having a plurality of winding stages adapted to be electronically commutated in at least one preselected sequence, each winding stage having a terminal associated therewith, and rotatable assembly means associated in selective magnetic coupling relation with said winding stages for driving said agitating and spinning means;
a control system connected to said motor; and means for applying a DC voltage to said control system;
said control system including:
electronic commutation means operable generally for electronic commutation of at least some of said winding stages of said electronically commutated motor by applying the DC voltage thereto in the at least one preselected sequence to effect the energization of said electronically commutated motor and the rotation of said rotatable assembly means;
integrating means operable generally for integrating the terminal voltage of at least one of said winding stages, the terminal voltage including at least the back emf of said at least one winding stage and a field collapse signal ending prior to appearance of the back emf;

commutation signal generating means responsive to a predetermined output level of said integrating means for generating a commutation signal for a predetermined length of time, the predetermined length of time expiring before the ending of the field collapse signal;
effecting and inhibiting means responsive to the commutation signal for effecting the operation of said electronic commutation means and for inhibiting the operation of said integrating means for the predetermined length of time ; and initiating means for initiating the operation of said integrating means when the terminal voltage of said at least one winding stage at least first approaches zero after the predetermined length of time.

26. The laundering apparatus as set forth in claim 25 wherein said effecting and inhibiting means is a logic circuit under programmed control, said logic circuit having as one input the output of said commutation signal generating means and being programmed to supply an inhibit signal for the predetermined length of time after receipt of the commutation signal.

27. The laundering apparatus as set forth in claim 26 further including an electronically controlled switch having one input for each winding stage, each input being connected to its respective winding stage, and having at least two outputs, one output representing a neutral voltage and one output representing the voltage of said at least one winding stage, said logic circuit being programmed to control said electronically controlled switch to provide the terminal voltage of said at least one winding stage to said integrating means and to said initiating means.

28. The laundering apparatus as set forth in claim 25 wherein the predetermined length of time is between approximately 50 microseconds and approximately 100 microseconds.

29. The laundering apparatus as set forth in claim 28 wherein the predetermined length of time is approximately 70 microseconds.

30. A control system for an electronically commutated motor adapted to be energized from a DC
power source and including a stationary assembly having a plurality of winding stages adapted to be electronically commutated in at least one preselected sequence, and a rotatable assembly associated in selective magnetic coupling relation with the winding stages, each winding stage having a terminal associated therewith, the control system comprising:
means operable generally for effecting the electronic commutation of at least some of the winding stages of the electronically commutated motor by applying thereto a DC voltage from the power source in the at least one preselected sequence to effect the energization of the electronically commutated motor and the rotation of the rotatable assembly whereby a motoring condition is achievable;
integrating means operable generally for integrating the terminal voltage of at least one of the winding stages the terminal voltage having a higher magnitude portion followed by a lower magnitude back emf portion under the motoring condition;
means responsive to a predetermined output level of said integrating means for generating a commutation signal; and inhibiting means for inhibiting the operation of said integrating means until the terminal voltage of the at least one winding stage falls in magnitude below a selected level selected to exceed that of the back emf under the motoring condition.

31. The control system as set forth in claim 30 wherein the inhibiting means includes a comparator having one input being coupled to the terminal voltage, another input connected to an electrical reference, and an output connected to an enable input of the integrating means.

32. The control system as set forth in claim 31 wherein the reference is derived from the DC
voltage.

33. A system for controlling the average voltage cyclically applied to a load comprising:
function and generating means for generating a direct function of the applied voltage;
comparing means for comparing the function of the applied voltage to an electrical reference and for indicating when the function reaches the reference;
voltage cycle signaling means for signaling the end of each voltage cycle when the function of the applied voltage reaches a predetermined value; and terminating means responsive to said comparing means and to said signaling means for terminating application of voltage to the load when the function of the applied voltage reaches the reference and for terminating each voltage cycle when the function of the applied voltage reaches the predetermined value.

34. The system as set forth in claim 33 wherein the function generating means provides an output that approximates said integral of the applied voltage.

35. The system as set forth in claim 34 wherein said function generating means includes a series resis-tor-capacitor circuit.

36. The system as set forth in claim 35 wherein said series resistor-capacitor circuit includes a low precision capacitor.

37. The system as set forth in claim 33 further including a logic circuit under programmed control for supplying the reference for said comparing means, the reference being changeable by said logic circuit.

38. The system as set forth in claim 37 wherein said logic circuit also includes an output for supplying a current reference, said system further including means for comparing the load current with the current reference, said terminating means being responsive to the load current exceeding the current reference to terminate the external application of voltage to the load.

39. The system as set forth in claim 33 wherein said terminating means includes a latch having a clock input connected to said voltage cycle signaling means and a reset input connected to said comparing means.

40. The system as set forth in claim 39 further including an electronically controlled switch means for connecting the output of said comparing means to the reset input of said latch, said electronically controlled switch means.

41. The system as set forth in claim 33 further including means connected to theoutput of said voltage cycle signaling means for resetting said function generating means at the end of each cycle.

42. A method of controlling the average voltage cyclically applied to a load, comprising the steps of:
generating a direct function of the applied voltage;
terminating application of voltage to the load when the function of the applied voltage reaches a first predetermined value selected to represent a desired average voltage; and terminating each voltage cycle when the function of the applied voltage reaches a second predetermined value.

43. The method as set forth in claim 42 wherein the generated function approximates the integral of the applied voltage.

44. The method as set forth in claim 42 including the further step of programming a logic circuit to supply the first predetermined value to a comparing circuit, the first value being changeable by the logic circuit.

45. The method as set forth in claim 42 wherein the voltage causes a current to flow in the load and the method includes the further step of terminat-ing the external application of voltage to the load when the load current exceeds a current reference, the current reference being set by a logic circuit under programmed control.

46. A control system for an electronically commutated DC motor having a stationary assembly with a plurality of winding stages and a rotatable assembly arranged in selective magnetic coupling relation therewith, the control system comprising:
means responsive to a set of control signals for commutating the winding stages by cyclically applying a DC voltage thereto in at least one preselected sequence to cause rotation of the rotatable assembly;
function generating means for generating a direct function of the applied voltage;
comparing means for comparing the function of the applied voltage to a reference and for indicating when the function reaches the reference;
cycle signalling means for signaling the end of each voltage cycle when the function of the applied voltage reaches a predetermined value; and terminating means responsive to said comparing means and to said signaling means for terminating application of voltage to the motor when the function of the applied voltage reaches the reference and for terminating each voltage cycle when the function of the applied voltage reaches the predetermined value.

47. The control system as set forth in claim 46 wherein said function generating means provides an output that approximates the integral of the applied voltage.

48. The control system as set forth in claim 47 wherein said function generating means includes a series resistor-capacitor circuit.

49. The control system as set forth in claim 48 wherein said resistor-capacitor circuit includes a low precision capacitor.

50. The control system as set forth in claim 46 further including a logic circuit under programmed control for supplying the reference for said comparing means, the reference being changeable by said logic circuit.

51. The control system as set forth in claim 50 wherein said logic circuit also includes an output for supplying a current reference, said control system further including means for comparing the motor current with the current reference, said terminating means being responsive to the motor current exceeding the current reference to terminate application of voltage to the motor.

52. The control system as set forth in claim 46 wherein said terminating means includes a latch whose clock input is connected to said cycle signaling means and whose reset input is connected to said comparing means.

53. The control system as set forth in claim 52 further including electronic means for connecting the output of said comparing means to the reset input of said latch, said electronic means having an input terminal coupled to an output of said latch whereby the output of said latch is reset at the end of each voltage cycle.

54. The control system as set forth in claim 46 further including means connected to said cycle signaling means for resetting said function generating means at the end of each voltage cycle.

55. A method of controlling the average voltage cyclically applied to an electronically commutated motor, comprising the steps of:
generating a direct function of the applied voltage;
terminating application of voltage to the motor when the function of the applied voltage reaches a first predetermined value selected to represent a desired average voltage; and terminating each voltage cycle when the function of the applied voltage reaches a second predetermined value.

56. The method as set forth in claim 55 wherein the generated function approximates the integral of the applied voltage.

57. The method as set forth in claim 55 including the further step of programming a logic circuit to supply the first predetermined value to a comparing circuit, the first value being changeable by the logic circuit.

58. The method as set forth in claim 55 including the further step of terminating the external application of voltage to the motor when the motor current exceeds a current reference, the current reference being set by a logic circuit under programmed control.
59. A laundering apparatus comprising in combination:
agitating and spinning means for agitating fluid and fabrics to be laundered thereby to launder the fabrics and for thereafter spinning the fabrics to effect centrifugal displacement of fluid from the fabrics;

Claim 59 continued:
an electronically commutated motor, said motor comprising a stationary assembly having a plurality of winding stages adapted to be electronically commutated in at least one preselected sequence, and rotatable assembly means associated in selective magnetic coupling relation with said winding stages for driving said agitating and spinning means;
a control system connected to said motor; and means for applying a DC voltage to said control system;
said control system including:
means operable generally for effecting the electronic commutation of at least some of said winding stages of said electronically commutated motor by applying the DC voltage thereto in the at least one preselected sequence to effect the energization of said electronically commutated motor and the rotation of said rotatable assembly means;
function generating means for generating a function of the applied voltage;
comparing means for comparing the function of the applied voltage to a reference and for indicating when the function reaches the reference;
cycle signaling means for signaling the end of each voltage cycle when the function of the applied voltage reaches a predetermined value; and terminating means responsive to said comparing means and to said cycle signaling means for terminating application of voltage to said motor when the function of the applied voltage reaches the reference and for terminating each voltage cycle when the function of the applied voltage reaches the predetermined value.

60. The laundering apparatus as set forth in claim 59 wherein said function generating means provides an output that approximates the integral of the applied voltage.

61. The laundering apparatus as set forth in claim 60 wherein said function generating means includes a series resistor-capacitor circuit.

62. The laundering apparatus as set forth in claim 61 wherein said series resistor-capacitor circuit includes a low precision capacitor.

63. The laundering apparatus as set forth in claim 59 further including a logic circuit under programmed control for supplying the reference for said comparing means, the reference being changeable by said logic circuit.

64. The laundering apparatus as set forth in claim 63 wherein said logic circuit also includes an output for supplying a current reference, said control system further including means for comparing the motor current with the current reference, said terminating means being responsive to the motor current exceeding the current reference to terminate the external application of voltage to the motor.

65. The laundering apparatus as set forth in claim 59 further including means connected to the output of said cycle signaling means for rapidly resetting said function generating means at the end of each voltage cycle.

66. A control system for an electronically commutated motor adapted to be energized from a DC
power source and including a stationary assembly having a plurality of winding stages adapted to be electronically commutated in at least one preselected sequence, and a rotatable assembly associated in selective magnetic coupling relation with the winding stages, each winding stage having a terminal associated therewith, the control system comprising:
electronic commutation means operable for electronic commutation of at least one at a time of the winding stages of the electronically commutated motor by applying thereto a DC voltage from the power source in the at least one preselected sequence to effect the energization of the electronically commutated motor and the rotation of the rotatable assembly, at least one other of the winding stages during any one commutation exhibiting a terminal voltage including a back emf and a field collapse voltage ending prior to appearance of the back emf; and means for generating a direct function of the terminal voltage during each commutation in response to its first approach to zero at the ending of the field collapse voltage and effecting the operation of said electronic commutation means when the direct function of the terminal voltage thereafter reaches a predetermined level during each same commutation.

67. The control system as set forth in claim 66 for an electronically commutated motor having only three winding stages wherein said commutation means comprises means operable for electronic commutation of pairs of the winding stages of the electronically commutated motor by applying a DC voltage from the power source to pairs of the terminals of the winding stages in the at least one preselected sequence to effect the energization of the electronically commutated motor and the rotation of the rotatable assembly, the third winding stage during any one commutation exhibiting the terminal voltage including the back emf and the field collapse voltage ending prior to appearance of the back emf.

68. A control system foran electronically commutated motor adapted to be energized from a DC power source and including a stationary assembly having a plurality of winding stages adapted to be electronically commutated in at least one preselected sequence, and a rotatable assembly associated in selective magnetic coupling relation with the winding stages, each winding stage having a terminal associated therewith, the control system comprising:

commutation means operable for electronic commutation of at least one at a time of the winding stages of the electronically commutated motor by applying thereto a DC voltage from the power source in the at least one rpeselected sequence to effect the energization of the electronically commutated motor and the rotation of the rotatable assembly; and means connected to said commutation means for causing said commutation means to apply the DC voltage during each commutation in pulse width modulated cycles, including means for supplying a reference voltage which is independent of the DC voltage and further including an oscillator circuit having a resistor connected to a capacitor that is charged from the DC voltage, said oscillator circuit having a cycle time which approximately equals the length of time in which a current flowing between said resistor and said capacitor causes the voltage across said capacitor to reach a second voltage, and means for signalling said commutation means to apply the DC voltage to the winding stages in any one cycle only until the capacitor voltage reaches the reference voltage, so that the average voltage of the pulse width modulated cycles is substantially independent of the capacitance of said capacitor.

69. The control system as set forth in claim 68 further comprising means for deriving the second voltage as a predetermined fraction of the DC voltage from which said capacitor is charged so that the cycle time of said oscillator circuit is substantially independent of the magnitude of the DC voltage.

70. The control system as set forth in claim 69 wherein said oscillator circuit further has means for comparing the voltage across said capacitor to the second voltage, and upon the voltage across said capacitor reaching the second voltage, resetting the voltage across said capacitor to begin another voltage cycle.

71. The control system as set forth in claim 68 wherein said means for supplying the reference voltage comprises a digital computer and a digital-to-analog converter.

72. The control system as set forth in claim 68 wherein said means for signalling said commuta-tion means comprises means for comparing the voltage across said capacitor to the reference voltage and, upon the voltage across said capacitor reaching the reference voltage, terminating application of voltage to the motor until the next cycle of said oscillator circuit.

73. The control system as set forth in claim 68 wherein said means for signalling said commuta-tion means comprises a latch connected to said oscillator circuit for producing an output which is set to a first logic level at the end of each cycle and, upon the voltage across said capacitor reaching the reference voltage, reset to a complementary logic level, the output of said latch being connected to the commutation means so that said commutation means is caused to apply the DC voltage only when the latch output is at the first logic level.

74. The control system as set forth in claim 73 further comprising electronically controlled switch means connected to the output of said latch for resetting said latch just prior to the end of each cycle if it has not already been reset during the same cycle.

75. A laundering apparatus comprising in combination:
agitating and spinning means for agitating fluid and fabrics to be laundered thereby to launder the fabrics and for thereafter spinning the fabrics to effect centrifugal displacement of fluid from the fabrics;

an electronically commutated motor, said motor comprising a stationary assembly having a plurality of winding stages adapted to be electronically commutated in at least one preselected sequence, and rotatable assembly means associated in selective magnetic coupling relation with said winding stages for driving said agitating and spinning means;
commutation means operable generally for effecting the electronic commutation of at least some of said winding stages of said electronically commutated motor by applying a DC voltage thereto in the at least one preselected sequence to effect the energization of said electronically commutated motor and the rotation of said rotatable assembly; and means connected to said commutation means for causing said commutation means to apply the DC voltage during each commutation in pulse width modulated cycles, including means for supplying a reference voltage which is independent of the DC voltage and further including an oscillator circuit having a resistor connected to a capacitor that is charged from the DC voltage, said oscillator circuit having a cycle time which approximately equals the length of time in which a current flowing between said resistor and said capacitor causes the voltage across said capacitor to reach a second voltage, and means for signalling said commutation means to apply the DC voltage to said winding stages in any one cycle only until the capacitor voltage reaches the reference voltage, so that the average voltage of the pulse width modulated cycles is substantially independent of the capacitance of said capacitor.

76. The laundering apparatus as set forth in claim 75 further comprising means for deriving the second voltage as a predetermined fraction of the DC
voltage from which said capacitor is charged so that the cycle time of said oscillator circuit is substantially independent of the magnitude of the DC voltage.

77. The laundering apparatus as set forth in claim 76 wherein said oscillator circuit further has means for comparing the voltage across said capacitor to the second voltage, and upon the voltage across said capacitor reaching the second voltage, resetting the voltage across said capacitor to begin another voltage cycle.

78. The laundering apparatus as set forth in claim 75 wherein said means for supplying a reference voltage comprises a digital computer and a digital-to-analog converter.

79. The laundering apparatus as set forth in claim 75 wherein said means for signalling said commutation means comprises means for comparing the vol-tage across said capacitor to the reference voltage and, upon the voltage across said capacitor reaching the reference voltage, terminating application of vol-tage to said electronically commutated motor until the next cycle of said oscillator circuit.

80. The laundering apparatus as set forth in claim 75 wherein said means for signalling said commutation means comprises a latch connected to said oscillator circuit for producing an output which is set to a first logic level at the end of each cycle and, upon the voltage across said capacitor reaching the reference voltage, reset to a complementary logic level, the output of said latch being connected to said commu-tation means so that said commutation means is caused to apply the DC voltage only when the latch output is at the first logic level.

81. The laundering apparatus as set forth in claim 80 further comprising electronically controlled switch means connected to the output of said latch for resetting said latch just prior to the end of each cycle if it has not already been reset during the same cycle.

82. A laundering apparatus comprising in combination:
agitating and spinning means for agitating fluid and fabrics to be laundered thereby to launder the fabrics and for thereafter spinning the fabrics to effect centrifugal displacement of fluid from the fabrics;
an electronically commutated motor, said motor comprising a stationary assembly having a plurality of winding stages adapted to be electronically commutated in at least one preselected sequence, and rotatable assembly means associated in selective magnetic coupling relation with said winding stages for driving said agitating and spinning means;
commutation means operable generally for effecting the electronic commutation of at least some of said winding stages of said electronically commutated motor by applying a DC voltage thereto in the at least one preselected sequence to effect the energization of said electronically commutated motor and the rotation of said rotatable assembly; and means connected to said commutation means for causing said commutation means to apply the DC voltage during each commutation in pulse width modulated cycles, including a logic circuit for supplying a reference voltage which is independent of the DC voltage, a resistor connected in series with a capacitor that is charged from the DC voltage through said resistor, means connected to the same DC voltage for deriving another voltage value which is a predetermined fraction of the same DC voltage from said capacitor is charged, comparing means for controllably discharging said capacitor to begin another cycle upon the voltage across said capacitor reaching the other voltage value, and signalling means for signalling said commutation means to apply the DC
voltage to said winding stages in any one cycle only until the capacitor charges to the reference voltage, so that the average voltage of the pulse width modulated cycles is substantially independent of variations in the DC voltage and substantially independent of the capacitance of said capacitor.

83. The laundering apparatus as set forth in claim 82 further comprising a second resistor connected between said capacitor and said first-named resistor, said deriving means including first, second, and third voltage divider resistors connected in series across said DC voltage, and said comparing means including a first comparator having a first input connected to said capacitor to sense the capacitor voltage, a second input connected to the junction of said first and second voltage divider resistors, and an output connected by a diode to the junction of said second and third voltage divider resistors, said comparing means further including a second comparator having a first input connected to the output of said first comparator, a second input supplied with a second reference voltage, and an output connected to the junction of said first-named resistor and said second resistor through which said capacitor is charged.

84. The laundering apparatus as set forth in claim 83 wherein said signalling means includes a third comparator having a first input connected to the reference voltage supplying circuit, a second input connected to said capacitor, and an output, and further includes a latch having a clock input connected to said first comparator output, a reset input connected to said third comparator output, and an output connected to said commutation means.

85. The laundering apparatus as set forth in claim 84 further comprising means for comparing the current flowing in said winding stages of said electron-ically commutated motor with another reference voltage from said logic circuit, said current comparing means having an output connected to said reset input of said latch.

86. A laundering apparatus comprising in combination:
agitating and spinning means for agitating fluid and fabrics to be laundered thereby to launder the fabrics and for thereafter spinning the fabrics to effect centrifugal displacement of fluid from the fabrics;
an electronically commutated motor comprising a stationary assembly having a plurality of winding stages adapted to be electronically commutated in at least one preselected sequence, and rotatable means associated in selective magnetic coupling relation with said winding stages for driving said agitating and spinning means;
electronic commutation means operable generally for effecting the electronic commutation of at least some of said winding stages of said electronically commutated motor by applying a DC voltage thereto in the at least one preselected sequence to effect the energization of said electronically commutated motor and the rotation of said rotatable means, at least one of said winding stages during any one commutation exhibiting a terminal voltage including a back emf and a field collapse voltage ending prior to appearance of the back emf; and generating means for generating a function of the terminal voltage during each commutation in response to its first approach to zero at the ending of the field collapse voltage and thereafter effecting the operation of said electronic commutation means when the function of the terminal voltage thereafter reaches a predeter-mined level during each same commutation.

87. The laundering apparatus as set forth in claim 86 wherein said generating means includes integrating means for integrating the terminal voltage in response to its first approach to zero at the ending of the field collapse voltage and effecting the operation of said electronic commutation means when the predetermined level is reached in the integrating.

88. The laundering apparatus as set forth in claim 87 wherein said integrating means includes means for preventing the terminal voltage from affecting the integrating when the terminal voltage has a polarity opposite to the field collapse voltage.

89. The laundering apparatus as set forth in claim 86 wherein said winding stages have at least one terminal each and said commutation means includes means operable for electronic commutation of at least two of said winding stages at a time by applying the DC voltage to said terminals thereof in the at least one preselected sequence to effect the energization of said electronically commutated motor and the rotation of said rotatable means.