WO2000053950A1

WO2000053950A1 - Controllable pneumatic apparatus including matrix medium retaining structure and braking devices utilized therein

Info

Publication number: WO2000053950A1
Application number: PCT/US2000/005474
Authority: WO
Inventors: Mark R. Jolly; J. David Carlson
Original assignee: Lord Corporation
Priority date: 1999-03-08
Filing date: 2000-03-02
Publication date: 2000-09-14

Abstract

A controllable pneumatic apparatus (400), comprising a braking device (420) coupled to a pneumatic actuator (27) for allowing precise motion control (e.g., stopping at any point along its stroke). The braking device includes a working space having a preferably porous matrix structure (30) disposed therein. A field responsive medium (28) is retained in the matrix structure. In operation, activation of a field generator (80) in the device generates a field to act on the field responsive medium to change its apparent viscosity thereby producing a braking force to control motion of the pneumatic actuator. A braking device is also described which has spacing means for maintaining a constant gap dimension of the working space, thus preventing excessive compression of the matrix.

Description

CONTROLLABLE PNEUMATIC APPARATUS INCLUDING MATRIX MEDIUM RETAINING STRUCTURE AND BRAKING DEVICES UTILIZED

THEREIN

Field of the Invention

The invention relates to the area of damping, resistance generating, and motion control devices. Specifically, it relates to devices employing a controllable medium for damping, resistance generating and motion control. More particularly, the invention relates to controllable pneumatic apparatus including a controllable medium.

Background of the Invention

Dampers and shock-absorbers are known which use a hydraulic fluid as the working medium to create damping forces to control or minimize shock and /or vibration. Typically, the damping forces are generated by a pressures resisting movement between operative components of the damper or shock absorber. One class of these devices includes magnetorheological (MR) fluid devices. MR fluid devices may be of the "rotary-acting" or "linear-acting" variety. Known MR fluid devices include linear dampers, rotary brakes and rotary clutches. Each MR fluid device employs a Magnetorheological (MR) fluid comprised of soft-magnetic particles dispersed within a liquid carrier. Typical particles include carbonyl iron, and the like, having various shapes, but which are preferably spherical and have mean diameters of between about 0.1 μm to about 500 μm. The carrier fluids include low viscosity hydraulic oils, and the like. In operation, these MR fluids exhibit a thickening behavior (a rheology change) upon being exposed to a magnetic field. The higher the magnetic field strength exposed to the fluid, the higher the damping/restraining force or torque that can be achieved within the MR device. MR fluid devices are disclosed in U.S. Patent No. 5,816,372 entitled

"Magnetorheological Fluid Devices And Process Of Controlling Force In Exercise Equipment Utilizing Same", U.S. Patent No. 5,711,746 entitled "Portable Controllable Fluid Rehabilitation Devices", U.S. Patent No. 5,842,547 entitled" Controllable Brake", U.S. Patent Application No. 08/674,179 now US Pat. No. 5,878,871 entitled "Controllable Vibration Apparatus" and U.S. Patent Nos. 5,547,049, 5,492,312, 5,398,917, 5,284,330, and 5,277,281, all of which are commonly assigned to the assignee of the present invention.

Known MR devices advantageously can provide controllable forces or torques, as the case may be, but, as currently designed, such devices are comparatively expensive to manufacture. These devices typically include a housing or chamber that contains a quantity magnetically controllable fluid, with a movable member, a piston or rotor, mounted for movement through the fluid in the housing. The housing and the movable member both include a magnetically permeable pole piece. A magnetic field generator produces a magnetic field across both pole pieces for directing the magnetic flux to desired regions of the controllable fluid. Such devices require precisely toleranced components, expensive seals, expensive bearings, and relatively large volumes of magnetically controllable fluid. The costs associated with such devices may be prohibitive to their use in certain applications, for example, washing machines and home exercise devices. Therefore, there is a long felt, and unmet, need for a simple and cost effective MR fluid device for providing variable forces and /or torques.

For industrial applications, it is sometimes desired to accurately position items in assembly or manufacturing processes, such as in a packaging, tensioning, positioning, stacking, guiding, pick-and-place or other industrial automation applications. Many times, pneumatic actuators are used to provide the motive force for such applications. In simple operations, certain simple pneumatic actuators are utilized. The simplest types are 2-position pneumatic actuators only capable of stopping at the end positions, i.e., all the way to one end or all the way to the other end of the stroke. Although cost effective, they are only useful in a very limited set of automation applications. More sophisticated pneumatic actuators, such as the TOM THUMB® 3- position pneumatic actuator sold by PHD, Inc. of Fort Wayne, Indiana, include the ability to stop at an intermediate position. Although more flexible than 2- position actuators, these 3-position actuators are still very inflexible, in that, once designed, the intermediate position is largely unchangeable.

In the next level of sophistication, pneumatic actuators are available which can stop at any intermediate position. For example, SMC Corporation of Tokyo, Japan manufactures a rod-less pneumatic cylinder with an internal brake and positioning scale (e.g. model ML2B). This system includes a piston moveable within a housing, an integral position sensor and a friction brake. The position sensor provides a position signal to the controller. By comparing the instantaneous position with inputted desired position data, the brake is actuated via air pressure to move a brake shoe into contact with a brake plate, thereby stopping the piston at the predetermined intermediate point. The system includes the ability to learn the distance from application of the brake to the actual stopping point, and makes adjustments to improve the accuracy for each subsequent commanded stop. Adding the ability to stop at an intermediate position in such pneumatic systems is very desirable, however, such friction braking tends to add significant mechanical and pneumatic complexity and significant additional expense to the system. Moreover, such friction brakes in the systems are only actuated "full on" or "full off" at any position along the actuator stroke, thus, by their very nature they are inflexible. Moreover, such systems tend have good accuracy only at low speeds.

Robohand, Inc. of Monroe, CT, manufactures pneumatic position controlling systems under the tradename POSITIONEX™. These systems include a pneumatic servo-actuator having a piston moveable in, and subdividing, a cylinder into first and second chambers. They also include an output shaft coupled to the piston, a position transducer providing a signal of a position of the output shaft and a servo-valve controlled by a control system to apply the appropriate pressure to position the output shaft at the appropriate predetermined position. Problematically, such systems tend to overshoot and hunt (oscillate about) the desired stopping position. Moreover, the servo-valves tend to be complex and expensive. Accordingly there has been a long felt, and unmet need for a cost effective pneumatic actuator and motion control system which is capable of accurately stopping at any point along its stroke and /or which is capable of programmable motion profiles.

Related Applications

The present invention is a continuation-in-part of US Application Serial Number 08/959,775 to J. David Carlson entitled "CONTROLLABLE MEDIUM DEVICE AND APPARATUS UTILIZING SAME" filed October 29, 1997.

Summary of the Invention

The present invention provides a controllable medium device which uses a vastly reduced quantity of controllable rheological medium as compared to prior art devices, and which eliminates the need for expensive seals, bearings, and precisely toleranced components. As a result, the cost to manufacture such devices is dramatically reduced.

According to the invention, a small amount of controllable medium, preferably in fluid form, is entirely contained in a working space between relatively movable members subjected to the magnetic field by a fluid-retaining means, for example, an absorbent matrix (preferably an open cell foam or the like) or a wicking member. The inventor herein discovered that an absorbent member can hold a sufficient amount of fluid to produce a significant rheological effect between a first pole member and a relatively movable second pole member. The invention may be incorporated in various physical embodiments such as linear dampers, rotary dampers such as brakes, mountings, pneumatic devices and applications therefor.

In particular, the present invention is a magnetorheological medium device which comprises first and second members coupled for relative movement and having a working space therebetween, means for producing a magnetic field that acts on the first and second members and the working space and a field controllable medium contained substantially entirely in the working space. A working space is provided by spacing the first and second members using structural supporting means. In a piston and cylinder device, for example, a working space is provided by selecting a piston head to have an outer dimension that is smaller than an inner dimension of the cylinder by a predetermined amount. The difference in size provides the working space when the piston head is assembled in the cylinder. In a piston and cylinder device, the structural support to maintain the spacing may conveniently be provided by a fluid retaining material surrounding and preferably fixed to the piston head. In a disk brake device, the working space is provided by mounting the rotor and caliper yoke in such a way as to space apart the surface of the rotor and the inner surfaces of the calipers. In other devices, spacing means for maintaining a constant gap dimension of the working space are positioned at a first and second end of the matrix structure. Preferably, the spacing means comprises at least one disc and may be integral with a first member. According to a preferred embodiment of the invention, a controllable fluid is contained in the working space by a material providing an absorbent matrix disposed in the working space. Absorbent matrix is used here to indicate a material that has the ability to pick up and hold a fluid by wicking or capillary action. In a particularly preferred embodiment, the absorbent matrix is a sponge-like material, for example, an open-celled or partly open-celled foam. Polyurethane foam and rubber foam are examples of particularly suitable materials. Foams made of other materials are also suitable, and examples include silicone rubber, polyamide, viton rubber, neoprene, loner rubber, melamine, a polyimide high temperature foam and metal foams. An absorbent matrix can also be formed of other material structures, such as an unwoven material (e.g. a mineral wool), or a felt, for example, Nomex brand aramid fiber felt or a compressed carbon fiber felt. In addition, a woven fabric could be used, made from materials such as Kevlar brand fiber, graphite, silica, Nomex brand aramid fiber, polybenzimadazole, Teflon brand fiber and Gore-Tex brand fiber. Alternatively, a mesh material, such as a metal mesh, could be used. Other structures that can contain a fluid, for example, brushes, flocked surface materials, wipers, and gaskets are also suitable.

The absorbent matrix need not entirely fill the working space, as long as the field controllable medium is contained in the working space. Thus, the absorbent matrix may be formed as a structure having a plurality of cavities, such as a honeycomb or other network structure, to contain the medium in the working space.

By containing an effective amount of controllable medium only in the working space of the device, no expensive seals are needed to contain the controllable medium as in the prior art.

It is another advantage of the invention that the amount of controllable medium needed to accomplish the rheology-based resistance effect is dramatically reduced to only the amount contained in the working space.

Another advantage of the invention, is providing a linear damper that requires no seals or bearings.

Another advantage of the invention, is providing a linear damper that doesn't require precisely toleranced components, i.e., non-ground piston rods and loosely toleranced outer member tubes and pistons.

Another advantage of the invention, is providing a linear damper that may be utilized to provide a cost effective pneumatic motion control apparatus.

According to the invention, means for generating a field in the first and second member and the working space is mounted to either of the first or second members in proximity with the working space. For example, in a piston/cylinder damper, the generating means can be at least one coil circumferentially wrapped on the piston head. In a rotary damper, the generating means can be at least one coil mounted to a yoke having arms between which the rotor turns.

A damping device in accordance with the invention can be incorporated in a number of apparatuses where it previously was cost-prohibitive to use controllable dampers. For example, the dampers of the invention can be used in washing machines to control vibration during various cycles. A resistance device of the invention can also be incorporated in exercise devices, such as bicycles, step machines, and treadmills to provide variable resistance. Moreover, such resistance devices may be employed in pneumatic apparatus, for example, a controllable pneumatic motion control apparatus.

Accordingly, in another aspect, the present invention is a controllable pneumatic apparatus, comprising a braking device coupled to a pneumatic actuator for allowing precise motion control (e.g. stopping at any point along its stroke) of the pneumatic actuator. The braking device includes a working space having a preferably porous matrix structure disposed therein. A field responsive medium is retained in the matrix structure. In operation, activation of a field generator in the device generates a field to act on the field responsive medium to change its apparent viscosity thereby producing a braking force to control motion of the pneumatic actuator.

More specifically, the controllable pneumatic apparatus according to the invention, comprises a pneumatic actuator having a gas containing chamber and an output member moveable in response to pressure changes in the gas containing chamber, a braking device coupled to the pneumatic actuator, the braking device including a first member, a second member disposed in spaced relation to the first member to form a working space therebetween, a matrix structure disposed in the working space, a field responsive medium retained in the matrix structure and a field generator that upon energizing generates a field that acts upon the field responsive medium to change the apparent viscosity of the medium thereby producing a braking force to control motion of the output member.

The above-mentioned and further features, advantages, and characteristics of the present invention will become apparent from the accompanying descriptions of the preferred embodiments and attached drawings. Brief Description of the Drawings

The accompanying drawings which form a part of the specification, illustrate several key embodiments of the present invention. The drawings and description together, serve to fully explain the invention. In the drawings,

Fig. 1 is a schematic side view of a magnetorheological linear resistance device in accordance with the present invention,

Fig. 2 is a partial isometric view of an absorbent matrix material for the resistive device, Fig. 3 is a cross sectional view of a damper having an alternative fluid retaining structure,

Fig. 4 is a cross sectional side view of a passive linear damper, Fig. 5 is a cross-sectioned side view of a controllable linear damper, Fig. 6 illustrates an alternative embodiment of the damper of Fig. 5 having a multiple coil field generator,

Fig. 7 a cross-sectioned side view of a linear rod damper embodiment of MR device,

Fig. 8 is a perspective side view of a controllable linear damper having a movable strip and a stationary yoke, Fig. 9 is a perspective side view of an alternative yoke member for the device of Fig. 8,

Fig. 10a is a perspective cross-sectioned view from the front of an alternative linear strip damper or brake,

Fig. 10b illustrates a field generating coil for the linear strip damper of Fig. 10a,

Fig. 10c is a pole piece used in connection with the linear strip damper of Fig. 10a,

Fig. 11 is a front view of a brake device for a continuous belt, Fig. 12 is a side perspective view of a brake device for a rotor disc, Fig. 13 illustrates a device for replenishing controllable medium to a device as in Fig. 12, Fig. 14 illustrates a nipple arrangement for supplying or replenishing controllable medium to a device,

Fig. 15 is a perspective view from the side of a pivoting damper arrangement, Fig. 16 is a perspective, cross-sectioned view of a two rotor brake system,

Fig. 17 is an alternative structure for the brake elements with a rotor,

Fig. 18 is an exploded view of the brake elements of Fig. 17,

Fig. 19 is a front sectional view of a front loading washing machine including controllable dampers, Fig. 20 is a graph of rotation speed of a washing machine tub during a washing cycle,

Fig. 21 is a graph of transmitted forces from a washing machine tub during a spin cycle,

Fig. 22 is a side sectional view of a damper with an integrated spring; Fig. 23 is a side sectional view of a top loading washing machine include a damper with an integrated spring;

Fig. 24 is a side sectional view of a damper incorporated in an air spring supported leveling table for providing vertical damping;

Fig. 25 is a side view of a step machine incorporating a resistance device, Fig. 26 is a side view of a stationary exercise bicycle incorporating a resistance device,

Fig. 27 is a side sectional view of a treadmill having a damper in accordance with the invention to control the impact conditions at the deck,

Fig. 28 is a side sectional view of a rotary brake in accordance with the invention,

Fig. 29 is a side sectional view of an embodiment of controllable pneumatic apparatus in accordance with the invention,

Fig. 30 is a side partially sectioned view of another embodiment of controllable pneumatic apparatus in accordance with the invention, Fig. 31a is a side partially sectioned view of another embodiment of controllable pneumatic apparatus in accordance with the invention, Fig. 31b is an enlarged side sectioned view of the brake device of controllable pneumatic apparatus of Fig. 31a,

Fig. 32 is a side sectioned view of another embodiment of controllable pneumatic apparatus in accordance with the invention, Fig. 33 is a side view of another embodiment of controllable pneumatic apparatus in accordance with the invention,

Fig. 34 is an end sectioned view of the embodiment of controllable pneumatic apparatus taken along line 34-34 of Fig. 33 with the control schematics removed for clarity, Fig. 35 is a bottom view of the controllable pneumatic apparatus of Fig.

33 with the control schematics removed for clarity,

Fig. 36 is a partially sectioned view of another embodiment of controllable pneumatic apparatus including multiple brake devices,

Fig. 37 is a partially sectioned view of another embodiment of controllable pneumatic apparatus including multiple brake devices,

Fig. 38 is an end view of the bracket of Fig. 37,

Fig. 39 is a sectioned side view along line 39-39 of the brake device of Fig. 37,

Fig. 40 is a plot of the velocity versus displacement profile for a simple control method,

Fig. 41 is a block diagram for a simple control method, and

Fig. 42 is partially sectioned view of another embodiment of controllable pneumatic apparatus including multiple brake devices.

Detailed Description of the Preferred Embodiments

Referring now to the Drawings where like numerals denote like elements, in Fig. 1, shown generally at 20, is a schematic illustration of a device for providing preferably controllable resistance between two relatively movable structures (not shown). The device 20 includes a first member 22 and a second member 24 that are disposed in spaced relation or coupled for relative movement along the mating surfaces. A working space 26 is provided between the coupled portions by spacing the mating surfaces apart. Means for generating a field, indicated by the vertical arrows, produces a field that preferably acts on the first member 22 and the second member 24 and (generally across) the working space 26.

According to the invention, the field generating means can be an electric field generator or a magnetic field generator. For reasons relating to cost, power requirements, and field strength, it is preferred to use a magnetic field generating means. The first 22 and second 24 members each preferably include magnetically permeable material (such as a soft magnetic steel), which can be done by forming each of the members 22, 24 entirely from such a material, or including such material as a component part or integrated portion of the member 22, 24. A field responsive controllable medium 28, such as a controllable fluid, compatible with the field generating means is contained in the working space 26 by fluid retaining means 30. Magnetorheological controllable fluids as contemplated for the present invention are disclosed in, for example, U.S. Patent No. 5,382,373 to Carlson et al. and U.S. Patent No. 5,578,238 to Weiss et al. For use with an electric field generator (not illustrated), an electrical conducting material, such as aluminum, is incorporated in the first 22 and second 24 members, and is used with an Electrorheological (ER) fluid.

The field generating means alters the rheology of the controllable medium 28 in proportion to the strength of the field. The controllable medium 28 becomes increasingly viscous with increasing field strength, and provides a shear force to resist movement between the members 22, 24. The members 22, 24 are preferably fixedly secured to relatively moveable structures (not shown) to provide resistance to movement therebetween.

The inventor has discovered that a significant shear force for resisting relative movement can be obtained with a small amount of controllable medium 28, such as MR fluid, contained in the working space between the movable members. Thus, a variety of relative movements, rotational, linear, pivoting, that include shear movement between two structural members can be controlled by a device according to the invention. By containing substantially the entire amount of controllable medium or fluid at the working space, the present invention avoids the need to provide a large quantity of medium or fluid, and the associated seals and containing devices of the prior art, and accordingly reduces the tight tolerances formerly needed on all components.

Any suitable means for containing the medium or fluid at the working space can be used. According to a preferred embodiment of the invention, means for containing the controllable medium in the working space comprises an absorbent matrix material, that is, a material that can take up and hold the controllable medium by wicking or capillary action. The absorbent matrix preferably provides a structure having open spaces for containing the medium, and the material forming the matrix may or may not be absorbent itself. A particularly preferred absorbent material is a sponge-like material, for example, an open-celled or partly open-celled foam. Examples of materials suitable for making a foam are polyurethane, rubber, silicone rubber, polyamide, neoprene, loner, melamine, polyimide high temperature foam, and metal foam. By way of example, if the absorbent material is, for example, a foam, it is desirable to have the foam compressed between about 30% and 50% from a resting state in its installed state.

In addition, other exemplary absorbent matrix materials include felts, including felts made of materials such as Nomex brand aramid fiber, compressed carbon fiber, or other materials, loose weave fabrics, mineral wool, cloths made from graphite, silica, Nomex brand aramid fiber, polybenzimadazole fiber, Teflon brand fiber, and Gore-Tex brand fiber, fiberglass wicking, and woven brake or clutch lining material. Other materials and structures are also suitable, for example, a metal mesh, a brush, or a flocked surface material.

The medium or fluid retaining means 30 is preferably fixed to one of the relatively moving members to ensure that it remains disposed in the working space 26. According to a preferred embodiment, a fluid retaining means is adhesively bonded to one member, for example, by a pressure sensitive adhesive. A preferred material is a polyurethane foam having a pressure sensitive adhesive on one side. The foam may be readily attached to one member by the adhesive. Alternatively, the fluid retaining means can be shaped so that it is held in place by the structure of the member, for example, a tubular shaped foam material may be fitted on a piston head as a sleeve.

The retaining means need not fill the working space. An absorbent matrix such as that illustrated in Fig. 2, having a plurality of cavities 32 for holding the controllable medium may be placed in the working space. In a linearly acting damper, for example, a piston and cylinder arrangement as illustrated in Fig. 3, the medium or fluid retaining means 30 alternatively can be formed as dams 34 at the boundaries of the working space 26, either inside or outside the working space 26, to trap the medium or fluid in the space 26 in proximity to the magnetic poles 54, 54'. As may be understood, in a piston 50 and cylinder 40 arrangement, the working space 26 are defined between cylindrical portions of the of the piston 50, and localized portions of the inner wall of the cylinder 40. As the piston 50 slides in the cylinder 40, the working space 26 moves with the piston 50. The field generating means 80 is conveniently carried and mounted on the piston 50. The dams 34 slide with the piston head 50 as it slides relative to the cylinder 40 to retain controllable fluid

28 in the moving working space 26 and in proximity the field generating means. Thus, when the poles 54, 54' are energized, the controllable fluid 28 changes rheology in the space 26. The dams 34 can be formed of elastomer, felt, or foam materials, as is convenient. Alternatively, packing material or gasket material could be used to form the dams. Other structures that may occur to those skilled in the art could also be used. As will be understood by those skilled in the art, any suitable fluid retaining means could be used in the embodiments described below, and the embodiments are not limited to the particular, preferred fluid retaining means described. A controllable fluid made from a suspension of iron alloy particles suspended in a carrier, as disclosed in, for example, U.S. Patents No. 5,382,373 to Carlson et al. and No. 5,578,238 Weiss et al. may be used in the present invention. Preferably, the controllable fluid for the present invention has the consistency of a grease or paste to aid in containing the fluid in the retaining means. One such grease is described in PCT/US97/02743, entitled

"Magnetorheological Fluid Seismic Damper."

The invention can be incorporated in a wide range of devices for resisting relative movement between members, including linear dampers, rotary dampers, resistance devices for exercise equipment, braking devices, and others, as will be understood from the following descriptions.

Fig. 4 illustrates a passive linear damper 38 in the form of a piston and cylinder arrangement. The damper of Fig. 4 includes a cylinder 40 and a piston 50 disposed in the cylinder for sliding movement. The piston 50 is preferably supported in the cylinder 40 by fluid retaining means, here, an absorbent matrix material 30, for example, an open cell foam. The absorbent matrix material 30 is wrapped around circumference of the piston 50, and is fastened to the piston 50 by pressure sensitive adhesive. The absorbent matrix material 30 spaces and supports the piston 50 from the inner surface 42 of the cylinder 40, thus providing a working space 26 between the piston 50 and cylinder 40. The absorbent matrix material 30 also eliminates the need for bearings to support the piston 50, which reduces the cost of the damper. A controllable fluid 28 is contained in the absorbent matrix material 30. To prevent an air spring effect, the cylinder 40 is preferably provided with vents 44 to relieve air pressure during movement of the piston 50. The cylinder 40 and the piston 50 include pole pieces 54, 54', which are parts formed of soft-magnetic, magnetically permeable material. The cylinder 40 can be formed entirely out of a magnetically permeable metal or formed with an inner metallic sleeve as the pole piece 54'. The piston 50 may similarly be formed entirely out of metal or, as illustrated, to have end pole pieces 54 formed of magnetically permeable material.

In this embodiment, a permanent magnet 60 including axially directed north n and south s poles is carried on the piston 50 and produces a magnetic field, indicated by the flux lines 62. The magnetic field acts on the pole pieces 54 of the piston 50, the pole piece 54' of the adjacent portion of the cylinder 40, and the working space 26. By selecting the field strength of the magnet 60, the force resisting movement of the piston 50 in the cylinder 40 can be selected. Those skilled in the art will recognize that the magnetic field and controllable fluid will resist linear, that is sliding, movement of the piston, and also rotation of the piston about the shaft axis. A piston rod 56 is fixedly secured to the piston 50. Suitable means for connecting to the relatively moveable structures (not shown) are provided, such as rod end 51 and bushing 52. A controllable linear damper 70 in the form of a piston and cylinder is illustrated in Fig. 5. The damper 70 includes a piston 50 disposed in a cylinder 40. Each of the piston 50 and the cylinder 40 includes a pole piece 54, 54', the cylinder 40 in this case being formed entirely of a magnetically permeable material, and the piston 50 having a core of magnetically permeable material. The piston head is wrapped with an absorbent matrix material 30 which functions as the means for containing a controllable fluid 28 in the working space 26. Magnetic field generating means in the form of a coil 80 is mounted on the piston 50, and is connected to a controller and power supply (not shown) by wires 82 (shown graphically as a single line) that preferably pass through a hollow interior of the piston rod 56. The resistive force produced can be varied by changing the magnetic field strength which is controlled by the amount of current supplied to the coil 80 by the controller (not shown). The controllable damper 70 may be adjusted from low resistance to high resistance to restrain relative movement between the piston 50 and the cylinder 40. Fig. 6 illustrates an alternative embodiment of the damper of Fig. 5, in which a plurality of coils 80a, 80b, and 80c are wound on the piston 50. The cylinder 40 includes a sleeve 46 of magnetically permeable material to serve as the cylinder pole piece. Multiple coils are advantageous in situations where the cylinder pole is subject to magnetic saturation, such as where the cylinder wall is thin or a sleeve 46, as illustrated, is used as the magnetically permeable member. As in the damper of Fig. 5, wires 82 connect the field generating coils 80a, 80b, and 80c to a controller. The coils 80a, 80b, and 80c are alternately wound so that the fields produced are additive. Elastomer bushings 52 may be added as the means to attach to the structural members (not shown), the elastomer helping to reduce the harshness in any control algorithm utilized.

The device of Fig. 7 is useful for motion control or guide mechanisms, or in a braking device. Pole pieces 54 are supported on a shaft 56 by an absorbent matrix material 30 for sliding and /or rotational movement, as illustrated by arrows A and B, respectively. The absorbent matrix material 30 supports the pole pieces 54 relative to shaft 56 and at a distance to provide the working space 26. Thus, in this embodiment, no bearings are necessary to support relative movement of the pole pieces 54 relative to shaft 56. The pole pieces 54 may be part of a moving component 49 and the shaft 56 may be part of a fixed frame 48. Alternatively, the pole pieces 54 may be the fixed element. A controllable fluid medium 28 is contained in the absorbent matrix material 30. A coil 80 is circumferentially wound and generates a magnetic field acting on the shaft 56, the pole pieces 54 and the working space 26 as indicated by the dotted field lines shown.

Other linear movement devices could advantageously incorporate the resistance device of the invention. Fig. 8 illustrates a device 120 in which a strip 100 is coupled for linear movement in a yoke member 110. The yoke 110 is C- shaped and includes two opposed jaws 112, 114 defining a working space 26 in which the strip 100 is disposed for sliding movement. Fluid retaining means 30, such as an absorbent matrix, is carried on the jaws 112, 114 in the working space 26 to hold the controllable fluid 28. A coil 80 is mounted on a shoulder 116 of the yoke 110 between the jaws 112, 114 to generate a magnetic field that acts on the yoke jaws 112, 114, and across the strip 100 and the working space 26.

Fittings 166 as shown in Fig. 14 allow controllable fluid to be replenished in the working space 26 and absorbent matrix 30. As shown in Fig. 9, the yoke 110 may be alternatively formed from a stack of magnetically permeable layers laminated together. The strip 100 and yoke 110 are preferably formed of a soft magnetic ferrous metals. Bracket 115 attaches the yoke 110 to a stationary structure 148. Means such as bolt hole 152 shown are used for attaching strip 100 to a movable structure (not shown)

An alternative linear strip device 120' is illustrated in Fig. 10a. In this embodiment, a strip 100 is disposed between the opposed walls 122 of a U- shaped yoke 110. Fluid medium retaining means 30 is disposed in the working space 26 between the walls 122 and the strip 100. In this embodiment, a field generating means in the form of a square-shaped coil 80, illustrated separately in Fig. 10b, is disposed to surround a magnetically soft pole piece 124, illustrated separately in Fig. 10c, mounted between the walls.

A linear acting brake is illustrated in Fig. 11. In this device an endless metal belt 130, for example, a drive belt, of a soft magnetic /magnetically permeable material is driven by one or more of the rollers 132. The belt 130 passes through working space 26 provided between an upper pole 134 and a lower pole 136 of the brake. An absorbent material 30 is disposed in the working space 26 on both sides of the belt 130. Field generating means 80 (shown in back of the belt 130) is provided as a coil that surrounds a shoulder member (not shown) interconnecting the poles 134, 136. The field generating means 80 creates a magnetic field (indicated by the arrows) that acts on the plates, the belt 130, and controllable fluid 28 in the working space 26. The device acts at the maximum radius of the rollers 132, which provides very effective braking. The device could also readily be used as a brake for a metal cable or wire, or other like drive member, as will readily understood, by replacing the endless belt with a cable, wire or other like drive member. Notably, in the case of a metal belt the brake only need act on a small lateral (into and out of the paper) portion of the belt 130, thus leaving the majority of the belt free from a medium film. Appropriate shrouding may be added to cover the portion of belt including a film on its surface.

Fig. 12 illustrates a rotary braking device. A rotor element 140, which could be a flywheel of an exercise machine, for example a stationary bicycle (see Fig. 26), is mounted for rotation on a shaft 142. The rotor element 140 is preferably formed entirely of a magnetically permeable material. A yoke 110, similar to that shown and described in Fig. 8 or 9, is mounted so that the outer portion of the rotor element 140 passes between the jaws 112, 114 of the yoke 110. The fluid retaining means 30, in this embodiment formed of an absorbent matrix material, is carried in a working space 26 between the jaws 112, 114 to retain the controllable fluid 28 in the working space. A coil 80 for generating a magnetic field is mounted on the yoke 110. The device may be variably activated to provide adjustable resistance to rotation of the rotor 140. The device of Fig. 12 may be used for large diameter rotors. In addition, the rotor 140 may be formed with sufficient inertial mass to act as a flywheel, as may be used in an exercise bicycle, ski machine, or step machine. Additional brake devices may be provided to increase the braking force.

The controllable fluid 28 is retained, for the most part, in the absorbent matrix material 30, and a small amount will form a thin layer on the surface of the contacting outer portion of the rotor element 140. Under normal conditions, the controllable fluid 28 is not consumed, and spreading of a thin layer on the rotor 140 presents no problem. Should the use conditions require that the controllable fluid 28 be replenished, for example, at high rotation speed where the fluid film on the rotor 140 is spun off by centrifugal effects, a device as shown in Fig. 13 provides a controllable fluid replenishment source 150, a pan container, in communication with the outer portion of the rotor element 140. As the rotor element 140 turns through the pan 150, controllable fluid is picked up on the outer portion of the rotor element 140 and carried into the working space 26 to be absorbed by the absorbent matrix material 30. Appropriate shrouding may be used.

Fig. 14 illustrates an alternative embodiment for supplying and replenishing a controllable fluid medium 28 to the working spaces 26. A moving element 153 (plate, strip, disc, etc.) is positioned in working spaces 26 between two pole piece jaws 160, 162 which carry magnetic flux therein. Fluid retaining means 30 is disposed in the working spaces 26. This structure can be included within a linear or rotary acting device, as will be readily understood. The pole jaws 160, 162 have passages 164 that communicate with the working space 26, and fittings 166 (similar to grease fittings) are mounted to the passages 164 to allow controllable fluid 28 to be introduced to the working space 26. Although not shown, the fittings 166 may include means to prevent escape of the medium from the fitting 166 once filled, i.e., spring-loaded ball mechanisms or caps.

The yoke 110 as previously described can also be used for other apparatuses, for example, a reciprocating pivot apparatus as shown in Fig. 15, in which a pivoting element 170 mounted with a shaft 172 has an outer portion that moves between the jaws 112, 114 of the yoke 110. Shaft 172 is interconnected to a machine (not shown). Other applications will be apparent to those of ordinary skill in the art.

Fig. 16 illustrates, in perspective sectional view, a device in which two parallel disc-like rotors 180, 182 are mounted for rotation with a shaft 184. The shaft 184 being rotatably attached to other rotating componentry of a machine

(not shown). A U-shaped pole bracket 190 having a center spacing piece 192 is positioned adjacent to and straddling a radially outer portion of the rotors 180, 182. Multiple working spaces 26 are provided between legs 194, 196 of the bracket and the center piece 192. The rotors 180, 182 are positioned so that a portion rotates through the working spaces 26. Fluid retaining means 30 includes an absorbent material disposed in the working spaces 26. Field generating means includes a single annular coil 80 mounted in the center piece 192, which produced a field which acts on the pole bracket 190 and the working spaces 26. A puck-shaped center pole 154 having disc-like end poles 154' in contact therewith focus the magnetic field across the working spaces 26.

Fig. 17 and Fig. 18 illustrate another braking device 200. Fig. 17 is a sectional view of a rotor 140 mounted for rotation with a shaft 142. Shaft 142 being rotatably mounted relative to stationary frame 148. Rigidly connected to shaft 142 is pulley 265. Pulley 265 is interconnected to a machine (not shown), such as an exercise machine, in this embodiment by cable 267 doubled about pulley 265. The braking device 200, shown in exploded view in Fig. 18, includes a U-shaped pole bracket 202 that defines a space for receiving the rotor 140. Mounted to both inner surfaces of the legs of the pole bracket 202 are annular wound coils 80, soft magnetic puck-shaped core 204 which supports the coils 80, disc-shaped pole pieces 206 and a fluid retaining member 30, such as a molded foam absorber. Each of the coils 80 generates a field that acts on the pole bracket 202, pole pieces 206, cores 204, and fluid retaining member 30 and across the working spaces 26. The coils 80 are wound in the same directions so that the generated magnetic fields are aligned. The approximate magnetic field lines are illustrated by the dotted line in Fig. 17.

One particularly advantageous application for a linear damper of the invention is in washing machines. Fig. 19 illustrates controllable linear dampers

70, such as those described with reference to Fig. 6, mounted in a front loading washing machine 210 as components of the suspension and damping system. The front loading machine 210 has a horizontally-mounted drum 212 including a rotational portion 213 rotationally fixed and drivable relative to drum 212 by a motor (not shown). The drum 212 (and rotational portion 213) are flexibly suspended relative to a cabinet 214 by flexible springs 216. Dampers 70 provide control of radial vibrations of the drum 212.

Controllable dampers according to the invention can be used in top- loading washing machines also to superior advantage, as illustrated in Fig 23. A damper 70' with an integrated spring 47, such as a coil spring, is illustrated in sectional view in Fig. 22. The damper 70' is similar to that shown in Fig. 6, and includes a soft magnetic cylinder 40 in which is mounted a piston 50 for relative axial sliding movement. The piston 50 carries a circumferentially wound annular coil 80, soft magnetic piston head including poles 54, and a fluid retaining absorbent matrix material 30, such as a open-celled polyurethane foam is wrapped around the piston head. The spring 47 acts between the piston 50 and the cylinder 40 to provide vertical and radial support to the drum 212' (Fig. 23). Suitable means for securing to the drum 212' and cabinet 214' are provided such as rod end 51 and bushing 52. Fig. 23 illustrates a plurality (preferably four) of the dampers 70' of Fig.

22 mounted in a top-loading washing machine 220. Dampers 70' including integral springs 47 are used to suspend the drum 212' from the washing machine cabinet 214'.

Controllable dampers (ex. 70, 70') allow for adjusting the damping of the washing machine system to the different washing cycles. A typical wash cycle for a front loading machine is illustrated in Fig. 20 in terms of drum rotational speed in Revolutions Per Minute (RPM) over time. The cycle from Tl to T2 represents an agitation/wash cycle in which the rotating member 213, 213' executes reciprocal rotations. As the rotation accelerates into the spin cycle, represented by the period T3 to T4, the drum assembly 213, 213' passes through a resonance condition, which is shown in Fig. 21 between speed points A and B.

By activating the damper 70, 70' during this acceleration period T3 to T4, damping can be imparted to the system and the transmitted force can be reduced. The washing machine cycle includes a second agitation T6 to T7 during the rinse cycle, and a second spin T9 to T10, which includes a second resonance condition during the associated acceleration T8 to T9. The damper

70, 70' would be activated during this time also. The damper 70, 70' is also preferably used at the end of the spin cycles when the drum decelerates through the resonance condition.

From Fig. 21, it can be seen that while increased damping is advantageous during the resonance condition between spin speeds A and B, increased damping will cause more force to be transmitted after the drum reaches spin speed than will low damping. Thus, the controllable dampers are preferably turned off after the drum leaves the resonance condition. The system of the invention advantageously allows damping to be adjusted for minimal force transmission throughout the washing machine cycle, which is a vast improvement over passive systems, in which a single, constant damping value must be chosen for all conditions.

Control of the dampers 70, 70' may be through a timer coordinated with the washing machine control timer, or through a speed sensor monitoring the drum rotation and set to activate the dampers 70, 70' at predetermined speeds, or through a vibration sensor 218, 218' (Fig. 19, 23), for example, an accelerometer, monitoring drum vibration. Alternatively, vibration in the cabinet 214, 214' may be monitored.

Fig. 24 illustrates another application for damper in accordance with the invention, in a air-spring leveling table. A table 240 is illustrated in part, and one supporting leg 242 (one of four) of the table is shown in the figure. The leg

242 encloses an air chamber 244 divided by a wall 246 having vents 248. A damper 70" includes a soft magnetic cylinder 40 mounted to the wall 246 by weldments or the like, and a piston 50 having a rod 56 connected to the table 240. A bellows or rolling diaphragm 250 closes the upper portion of the chamber 244 and allows the table 240 to be supported and levitated by the air in the chamber 244. The rod 56 is connected to pole 241 having permanent magnet 242 secured thereto. A field produced by the magnet 243 causes the pole 241 to be attracted to the table piston 247 made form a ferromagnetic material. This avoids having to cut a hole in bellows 250. The damper 70" helps control the motion of the table 240 when air is added to or removed from the chamber 244, by quickly damping the transient motions which cause the table 240 to oscillate.

Dampers and resistance devices in accordance with the invention can also be advantageously incorporated in exercise apparatus, as previously mentioned. Fig. 25 shows a simplified step machine 260 which includes a flywheel 140 and a resistance device 220 as described in connection with Figs. 12, 16, or Fig. 17. The resistance device 220 may be controlled to adjust the resistance to rotation of the flywheel according to the user's preference. The device 220 according to the invention can generate high torque with a relatively small flywheel.

A similar rotary resistance device 220', such as described in connection with Figs. 12, 16 and 17, can be mounted in an exercise bicycle 270, shown in Fig. 26. The resistance device 220' is mounted on the bicycle flywheel 140.

Fig. 27 shows a treadmill 280 having a damper 220" including a linear strip 100 and a yoke 110 mounted between the deck 282 and frame.

Alternatively, a linear piston and cylinder damper as in Fig. 5, 6, or 22 can be used. The damper 220" can be controlled to provide a stiffer or softer running

97 surface. For example, for slow running, that is, low foot strike frequency, a runner may prefer a softer, springier surface, and for fast running, a stiffer surface. The damper can also adjust the damping of the deck surface 282 for the weight of the user, to increase damping for heavier users and decrease it for lighter weight users.

Fig. 28 illustrates a rotary brake 300 in accordance with the invention. The brake 300 includes a fixed member, or stator 302, which forms an outer member. The stator 302 is formed of magnetically permeable material to act as a pole piece, and includes an interior space 304. A disc-shaped rotor 306 is disposed in the interior space 304, and is rigidly connected to a shaft 310 for rotation in the interior space 304. The rotor 306 is spaced from the inner surfaces of the stator 302 that define the interior space 304, which provides a working space 26 between the stator 302 and the rotor 306. An absorbent material 30 is disposed in the working space 26 to surround the radially outer portion of the rotor 306. A controllable medium 28 is contained by the absorbent material 30. A circumferentially wound field generating coil 80 is mounted between halves 303 of the stator 302 and preferably radially surrounds the rotor 306. The coil 80 is connected by wires 82 to a controller and power source (not shown). As shown by the field lines 312, the coil 80 produces a field that acts on the stator 302, the rotor 306 and across the working space 26. Activation of the field causes resistance to rotation of the rotor 306. The absorbent material 30 eliminates the need to seal the interior space 304 of the stator. Further, no bearings are required. Figs. 29-30, 31a, 32-37 and 42 illustrate various embodiments of the controllable pneumatic apparatus 400 in accordance with the invention. The apparatus 400 is a controllable pneumatic motion control apparatus. The apparatus 400 comprises a pneumatic actuator device 27 and a primary brake device 420, and may also include a secondary brake device 420'. The pneumatic device 27 includes a housing 29 including at least one gas containing chamber

244, and more preferably, two gas chambers 244, 244' separated by a moveable puck-shaped piston 31. An output member 35 of the pneumatic device 27 is moveable in response to pressure changes in the at least one gas containing chamber 244, and more preferably two gas chambers 244, 244' caused by the pneumatic control system 33.

As illustrated in Figs. 29-30, 31b, 32-37, 39 and 42 each of the primary brake devices 420, 420' of the apparatus 400 includes a first member 22, a second member 24, a fluid retaining matrix structure 30, a field responsive medium 28, and field generator 80. The first member 22 of the brake 420, 420* is coupled to, or integral with, the housing 29 of the actuator 27. For example, in the Figs. 29 and 32 embodiments, the first member 22 is formed of a soft-magnetic material and is integral with the housing 29. In Figs. 29, the first member 22 is the tubular sleeve of the housing 29, whereas in Fig. 32, the first member 22 comprises the end cap of the housing 29. In Figs. 30, 31a and 33 embodiments the first member 22 is coupled to the housing 29. For example, in Figs. 30, 31a and 31b the coupling means 37 are bolts or other fastening means which secure and mount the first member 22 to the end of the end cap of housing 29. In the

Fig. 33 embodiment, the first member 22 comprises a plate-like member secured to the body of housing 29 by coupling means 37 such as fasteners, adhesive or other suitable fastening means. In the Figs. 36 and 37 embodiments, the first member 22 comprises a tubular member coupled to the housing 29 by coupling means 37 such as the end cap bracket (Fig. 36) or clevis (Fig. 37) shown. In the

Fig. 42 embodiment, the orientation of the brakes 420, 420' of Fig. 37 are reversed such that the wires do not move. In this embodiment, the shaft 57 and bracket 37 provide the coupling means to interconnect the first member 22 (the metal portions of piston) of the brake 420, 420' to the housing 29 of pneumatic actuator 27. The second member 24 of the brake 420 of Fig. 42 comprises the outer housing. This is opposite of that illustrated in Fig. 39.

Likewise, in each embodiment, the second member 24 is coupled to, or integral with, the output member 35. The second member 24 is disposed in a spaced relationship to the first member 22 to form a working space 26 therebetween. For example, in the Fig. 29 embodiment, the second member 24 is coupled by the coupling means 59 to the output member 35 (the output shaft). The coupling means comprises the piston 31 secured to output member 35 and the bolt 64 and washers 61a, 61b shown securing the second member 24 to the piston 31. In particular, the piston 31 is threaded onto the output member 35, and multi-piece second member 24 is secured to the other end of piston 31 by bolt 64 such that it moves axially therewith along the axis A-A. In the Fig. 30 embodiment, the second member 24 is another shaft coupled to the output member 35. The coupling means 59 to the output member 35 (the output shaft) is the piston 31, where the second member 24 is threaded into one end of the piston 31 and the output member 35 is threaded into the other.

In the Figs. 31a and 36 embodiments, the second member 24 comprises another shaft coupled to the output member 35 via coupling means 59 such as the pusher block connecting member shown. In the Fig. 32 embodiment, the second member 24 is integral with output member 35 (shaft). In the Fig. 33 embodiment, the second member 24 is coupled to the output member 35 directly by coupling means 59 such as bolts. In the Fig. 37 embodiment, the second member 24 is coupled to the output member 35 via coupling means 59 which comprise a coupling pusher block and an interconnected shaft 57. In the Fig. 42 embodiment, the second member 24 is coupled to the output member 35 via coupling means 59 such as the block member shown.

In each of the embodiments of Fig. 29-42, a matrix structure 30, such as an absorbent matrix as described above herein, is disposed in the working space

26. Preferably, the matrix 30 comprises a open cell polyurethane foam adhered to the first 22 or second 24 member by adhesive, such as a pressure sensitive adhesive. Preferably, the foam comprises a reticulated open cell foam having a pore structure of between about 40-80 pores/inch (1.57-3.15 pores/mm). A field responsive medium 28, such as a magnetorheological fluid or grease, is retained in the matrix structure 30. One such grease is described in PCT/US97/02743, entitled "Magnetorheological Fluid Seismic Damper." The field generator 80, which is preferably a wound coil, upon energizing, generates a magnetic field which acts upon the field responsive medium 28 to change its rheology (apparent viscosity). This produces a variable braking force to control motion of the output member 35. In the Fig. 29, 36 and 39 embodiments, multiple field generators 80 are used to enhance the available braking force. Alternatively, the field generator 80 may include a permanent magnet.

In each of the Fig. 29-31a, 32-33, 36-37 and 42 embodiments, a pneumatic control system 33 is provided for controlling the pressure PI, P2 at the input ports of the actuator device 27 which is the pressure applied to the internal chambers 244, 244'. Preferably, the system 33 includes a pneumatic control 53, a pneumatic valve 55 and a pressure supply 58. The pneumatic valve 55 is preferably a 3-position solenoid valve such as model SY5440 manufactured by SMC Corporation of Tokyo, Japan. Alternatively, the valve function may be derived from two 2-position valves. Other types of valves such as pneumatic servo-valves could be used as well. The pressure supply 58 preferably comprises a pneumatic pump which supplies a pressure of between about 30 psi tol20 psi (207 kPa to 827 kPa). The pump (not shown) may supply a gas canister or reservoir (not shown) which supplies the pressure to the valve 55. Preferably, the pressure in the reservoir is regulated. Accordingly, it should be recognized that the valve 55, and, thus, the pressures PI, P2 which move the piston 31, are controlled via a pneumatic control 53.

The pneumatic control 53 is operated to dictate the direction of travel of the piston 31 and, thus, the output member 35. Based upon input data 21b from the input 21 and motion information (e.g. position) from the sensor 39 passed through data interconnection 23, the pneumatic control 53 actuates the valve 55 to move the output member 35 from its initial position towards the desired position x_des. Upon nearing the desired position, the pneumatic control 53 again actuates the valve 55 to its neutral position (as opposed to the positions which cause right or left travel). If no brake were applied, the output member 35 would drift to a stop, probably some distance from the desired stopping position, and likely at the end of the stroke, depending upon the parasitic friction in the system. Adding rheological braking, allows the output member 35 to be stopped accurately at any desired point along its stroke. A simple control method for controlling all the apparatus 400 mentioned herein is illustrated in Figs. 40-41. According to the method, control logic in the pneumatic control 53 turns off the pneumatic device 27 upon sensing a signal 41 from sensor 39 which is approximately equal to the desired position x_dcs. This accomplished by sending an appropriate signal(s) 53a from the control 53 to the valve 55. The motion control 43 then activates the brake device 420 or devices 420, 420' (Figs. 36-37 and 42) to generate a braking force and decelerate the output device 35 and stop its motion. In actuality, the turning off of the pneumatic actuator 27 and activation of the brake device 420 both occur preferably simultaneously upon entering a predetermined tolerance band 71 (+/- Δx) surrounding the desired and predetermined stopping position x_des. This braking force controls the motion, as desired, of the output member 35 at any desired point along its stroke.

Referring to Fig. 40, the output device 35 is initially positioned at some point, for example, at the far left end of the travel (at zero) labeled point a. The pneumatic control 53, based on an input signal 41 derived from the sensor 39 and signals 21b of the desired position x_des input from the input 21, via control logic commands the valve 55 to move the member 35 to the right. System dynamics and flow capacity/characteristics determine the slope and rate of acceleration to a maximum velocity between points a and b in Fig. 40. Notably, this may also be controlled by application of low level braking forces. Upon reaching the desired speed, application of a low level control signal 45 by the motion control 43 will set the actual velocity v from points b to c to a value υ_des commanded by the input 21a. Upon entering the tolerance band 71 at point c, the control logic of motion control 43 generates a higher level control signal 45 to further energize the coil(s) 80. This creates a strong magnetic field that acts upon and changes the rheology (apparent viscosity) of the medium 28 retained in the matrix 30 and produces a braking force that acts between the first 22 and second 24 members, thus stopping the output member 35 almost instantaneously.

In the case where the inertia of the system is low and the braking force is adequate, the output device 35 comes to a stop within the band 71 at point d following a direct path 74. However, if the system inertia is high or the braking force available is inadequate, then the apparatus 400 may hunt, i.e., exceed the tolerance band 71 on the right side and cause the pneumatic control 53 to be momentarily actuated to drive the output member 35 back to the left along indirect path 75 and back into the tolerance band 71, thus again bringing the member 35 to rest within the tolerance band at point d. Moreover, as suggested above, it may be desirable under some circumstances to control the acceleration /deceleration, i.e., the velocity profiles between points a-b and c-d.

In this case, the desired velocity profile is input via the input 21. By way of example, the input 21 may be manual input from a programmer on a PC, a key pad or programmable logic controller (PLC). The various controls 43, 53 may be implemented in separate logic modules, in one single unit or by any other suitable means.

It is desirable in all braking devices 420 described herein to include soft- magnetic pole pieces 54 adjacent to the field generator 80 which carry the magnetic flux and focuses the field across the working space 26 (see for example, Fig. 31b). The coil 80 is preferably formed by circumferentially winding a plurality of winds of conductive wire 65 about a plastic bobbin 67.

By way of example, 100 to 300 winds of 29 gauge copper magnet wire have been found to be effective for many applications.

The braking device 420 may include means for spacing 69 the first member 22 relative to the second member 24 such that an appropriate gap thickness is maintained. This is desirable to account for manufacturing tolerances and any side loads present, such that the compression of the matrix 30 is substantially constant through the working space 26. This also prevents over compression of the matrix should side or cocking loads be present. By way of example, a gap in the working space 26 of about 0.5 mm - 1mm is appropriate with the matrix 30 being precompressed by about 30%-50%, and most preferably about 35%. The means for spacing 69 may include one or more plastic discs as in the Figs. 29-31b and 39 embodiments, a seal 69 such as in the Fig. 32 embodiment, pins 69 which ride against the outer surface of the first member 22 as in the Fig. 33 embodiment or sealed roller bearings 69 as in the Fig. 36 embodiment.

Preferably, the sensor 39 comprises a linear position sensor. However, any type of sensor may be utilized from which displacement information may be derived, such as, for example, a rotary or linear potentiometer. Further, a resistive strip position sensor may be built into the body of the device 27 as in the Fig. 32, 36 and 37 embodiments as are known to persons of ordinary skill in the art. Velocity information may be obtained, if required, for the controls 43, 53 via differentiating the position signal 41, for example, in the differentiator 76

(Fig. 41). Alternatively, a velocity sensor may be employed.

In a more sophisticated control, the brake device 420 is turned on to a high level at a shut down point x₀ = c just before the desired stopping point x_des based upon the kinetic energy in the system and the braking energy available from the braking device(s) 420, 420'. In essence, if the kinetic energy and the braking forces available are known quantities, then the exact position to shut down the pneumatics and apply the brake is easily and readily determined for any desired position x_des. In a preferred embodiment, the activation of the braking device(s) 420, 420' is based upon velocity of the output member 35, the mass (inertia) of the moving components in the system, and /or braking force available, and most preferably based upon all three. This hereinafter will be referred to as "kinetic energy control."

Kinetic energy control virtually eliminates overshoot and hunting associated with prior art methods, especially on systems where the inertia is large. In particular, according to the kinetic energy control method, the kinetic energy of the system is equated with the braking energy available in the system (see equations 4-6 below) to provide an intelligent tradeoff between accuracy and speed.

The energy associated with the controllable brake 420 is given by:

E_mr = JF„ dx ^ F_mr (x_lk, - x₀) (1)

where

E_m, is the braking energy available,

F_mr is the braking force available, x^ is the desired stopping position, and

39 x_Q is a shut down point where, if the force available were applied, it would bring the output member 35 to a stop at the position x _e .

The kinetic energy of the system at x₀ is:

E_k = -mv² (2)

where

E_t is the kinetic energy at x₀ , m is the mass of any moving system components including any payload article (article being moved) present, and v is the velocity of the output member 35 at .v₀ .

In order to bring the mass m to a stop at the target position χ_des , the kinetic energy E_κ must be equal to the braking energy E_mr . Setting the values equal to each other provides:

E = E_mr (3) and substitution provides:

1

-mv- = F_mr (x_Jn - x₀) (4)

and

Δ* = ^XJ ^{~ X}0 (5) and, finally

Ax = (6)

2E mr rearranging into another form gives:

Thus, it can be readily seen that Λ-v can be regarded as a position tolerance, and it is easily recognized that there is a tradeoff between positioning accuracy and positioning speed. Equation 7 becomes the basis for the kinetic energy control method, where the inputs provided via the input 21 are the desired accuracy Ax , the braking force available F_mr and the mass _m . Thus, the point-to-point (e.g. point b to c of Fig. 40) velocity v can be controlled such that the resultant actual stopping position is substantially at x_des without any substantial overshoot. Optionally, the user may input the mass _m and the braking force available F_mr via the input 21 and the velocity v may be derived from the motion signal 33 to calculate the value Ax according to equation 6 above; the value Ax corresponding to where the pneumatic actuator 27 is shut down and the brake 420 is applied. In this case, the velocity v may be derived via differentiating the position signal in differentiator 76 (Fig. 41).

In summary, it should be apparent from the foregoing that the present invention comprises a novel controllable device (either rotary or linear acting) which includes a controllable medium retaining means for holding medium (ex. a magnetically controllable fluid) in a working space between relatively moving components. The invention provides controllable devices and apparatus that are simpler to design and manufacture, and less costly, than prior devices.

While several embodiments including the preferred embodiment of the present invention have been described in detail, various modifications, alterations, changes, and adaptations to the aforementioned may be made without departing from the spirit and scope of the present invention defined in the appended claims. It is intended that all such modifications, alterations, and changes be considered part of the present invention.

Claims

CLAIMSWhat is claimed is:

1. A controllable device, comprising: first and second members arranged for relative movement with a working space therebetween; means for producing a field which acts on said working space; absorbent means disposed in said working space; a quantity of controllable medium contained substantially entirely within said working space by said absorbent means, said controllable medium having a rheology variably responsive to being energized by a field for providing resistance forces between said first member and second member.

2. A controllable pneumatic apparatus (400), comprising: (a) a pneumatic actuator (27) including; a housing (29) having at least one gas containing chamber (244), an output member (35) moveable in response to pressure changes in the at least one gas containing chamber (244), (b) a primary brake device (420) including; a first member (22) coupled to, or integral with, the housing (29), a second member (24) coupled to, or integral with, the output member (35) and disposed in spaced relation to the first member (22) to form a working space (26) therebetween, a matrix structure (30) disposed in the working space (26), a field responsive medium (28) retained within the matrix structure (30), and field generator (80) which upon energizing generates a field that acts upon the field responsive medium (28) to change a rheology of the medium and produce a braking force to control motion of the output member (35).

3. The pneumatic apparatus (400) of claim 2 further comprising a pneumatic control system (33) for controlling the pressure, the system including a pneumatic control (53), a pneumatic valve (55), and a pressure supply (58).

4. The apparatus (400) of claim 2 wherein a braking force generated by the brake device (420) is controlled by a motion control (43) which generates a control signal (45) responsive to a motion signal (41) derived from a motion sensor (39).

5. The apparatus (400) of claim 4 wherein the motion sensor (39) comprises a displacement sensor measuring relative displacement between the first (22) and second (24) members.

6. The apparatus (400) of claim 2 wherein the field generator comprises at least one wound coil.

7. The apparatus (400) of claim 6 wherein the coil surrounds a portion of the matrix structure.

8. The apparatus (400) of claim 6 further comprising a plurality of coils.

9. The apparatus (400) of claim 2 wherein a motion control (43) for controlling the brake device (420) interacts with the pneumatic control system (33).

10. The apparatus (400) of claim 2 wherein at least one gas containing chamber (244) further comprises first (244) and second chambers (244') formed within the housing (29) and separated by a piston (31).

11. The apparatus (400) of claim 2 wherein the output member (35) comprises a shaft.

12. The apparatus (400) of claim 2 wherein the first member (22) comprises a cylinder of magnetically soft material.

13. The apparatus (400) of claim 2 wherein the first member (22) comprises a plate of magnetically soft material.

14. The apparatus (400) of claim 2 wherein the first member (22) comprises a pole piece (54) manufactured from a magnetically soft material for focusing the field onto the working space (26).

15. The apparatus (400) of claim 2 wherein the second member (24) comprises a pole piece (54) manufactured from a magnetically soft material for focusing the field onto the working space (26).

16. The apparatus (400) of claim 2 wherein the matrix structure (30) comprises an annular shape.

17. The apparatus (400) of claim 2 further comprising spacing means for maintaining a substantially constant gap dimension of the working space

(26).

18. The apparatus (400) of claim 2 further comprising a second brake device 20 coupled to the output member (35).

19. The apparatus (400) of claim 18 wherein the first brake device 20 is disposed on a first side of the pneumatic device and the second brake device 20 is disposed on a second side of the pneumatic device generally opposed to the first side.

20. The apparatus (400) of claim 18 wherein the field generator produces a magnetic field.

21. The apparatus (400) of claim 2 wherein the motion controlled comprises a position, velocity or acceleration of the output member (35).

22. The apparatus (400) of claim 2 wherein the field responsive medium (28) comprises a magnetically controllable fluid.

23. The apparatus (400) of claim 2 wherein the pneumatic actuator (27) is shut off and the braking device (420) is activated within a tolerance band about a desired position.

24. A controllable pneumatic apparatus (400), comprising:

(a) a pneumatic actuator (27), including: a housing (29), a piston (31) disposed in the housing (29) and moveable in response to an applied pneumatic pressure, an output member (35) coupled to the piston (31),

(b) a brake device (420), including: a first member (22), a second member (40) spaced from, and moveable relative to, the first member (22) and defining a working space (26) therebetween, a fluid retaining matrix structure (30) disposed in the working space (26), a field generator (80) for producing a magnetic field, a magnetic field responsive medium (28) retained in the matrix structure whose rheology is changeable responsive to application of the field to restrict motion between the members, c) means for coupling the brake device (420) to the output member (35), d) a sensor (39) for providing a signal (41) representative of a motion of a moveable element of the apparatus, and e) control means for processing the motion signal (41) and desired motion information and providing control signals to the generator (80) and the pneumatic actuator (27) thereby controlling at least one selected from a group consisting of a position, velocity and acceleration of the output member (35).

25. A controllable pneumatic apparatus (400), comprising:

(a) a pneumatic actuator (27), including: a housing (29), a piston (31) disposed in the housing (29) and moveable along an axis in response to an applied pneumatic pressure, an output member (35) coupled to and moveable with the piston (31),

(b) a brake device (420), including: a first member (22) coupled to, or integral with the housing, a second member (40) spaced from, and moveable relative to, the first member (22) and defining a working space (26) therebetween, the second member being coupled to or integral with the output member (35), a fluid retaining porous matrix structure (30) disposed in the working space (26), a wound coil field generator (80) for producing a magnetic field, a magnetic field responsive fluid (28) retained in the matrix structure whose apparent viscosity is changeable responsive to application of the field to restrict motion between the members, c) a sensor (39) for providing a signal (41) representative of a motion of a moveable element of the apparatus, d) means for inputting desired motion information, d) control means for processing the motion signal (41) and the desired motion information and providing control signals to the generator

(80) and to the pneumatic actuator (27) to control at least one selected from a group consisting of a position, velocity and acceleration of the output member (35).

26. A controllable pneumatic apparatus (400), comprising: (a) a pneumatic actuator (27) including a gas containing chamber (244) and an output member (35) moveable responsive to pressure changes in the gas containing chamber (244), and

(b) a braking device (420) coupled to the pneumatic actuator, the braking device including a first member (22), a second member (24) disposed in spaced relation to the first member (22) to form a working space (26) therebetween, a matrix structure (30) disposed in the working space (26), a field responsive medium (28) retained in the matrix structure (30), and a field generator (80) which upon energizing generates a field which acts upon the field responsive medium (28) to change an apparent viscosity of the medium thereby producing a braking force to control motion of the output member (35).

27. A braking device (420), comprising: a first member (22), a second member (24) disposed in spaced relation to the first member (22) to form a working space (26) therebetween, a matrix structure (30) disposed in the working space (26), spacing means for maintaining a constant gap dimension of the working space (26), a field responsive medium (28) retained in the matrix structure (30), and field generator (80) which upon energizing generates a field which acts upon the field responsive medium (28) to change a rheology of the medium thereby producing a braking force between the first and second members.

28. A braking device (420) of claim 27 wherein the spacing means are positioned at a first and second end of the matrix structure.

29. A braking device (420) of claim 27 wherein the spacing means comprises at least one disc.

30. A braking device (420) of claim 27 wherein the spacing means are integral with the first member.

31. A braking device (420) of claim 27 wherein the spacing means are integral with the first member.