CA2075178C - Force feedback and texture simulating interface device - Google Patents

Abstract

A man-machine interface is dis-closed which provides force and texture information to sensing body parts. The interface is comprised of a force actuat-ing device (900) that produces a force which is transmitted to force applying de-vice (902). The force applying device ap-plies the generated force to a pressure sensing body part. A force sensor (909) on the force applying , device measures the actual force applied to the pressure sensing body part, while angle sensors (911) measure the angles of relevant joint body parts. A computing device (911) uses the,joint body part position informa-tion a determine a desired force value to be applied to pressure sensing body part.
The computing device combines the joint body part position information with the force sensor information to calculate the force command which is sent to the force actuating device. In this manner, the computing device may control the actual force applied to a pressure sensing body part to a desired force which depends upon the positions of related joint body parts. In addition, the interface is comprised of a displace-ment actuating device (901) which produces a displacement which is transmitted to a displacement applying device (902) (e:g.; a texture simulator). The displacement applying device applies the generated displacement to a pressure sensing body part. The for-ce applying device and displacement applying device may be combined to simultaneously provide force and displacement infor-mation to apressure sensing body part:

Description

207~v 78.
"'O 91 / 11775 PCT/ US91 /00632 A FORCE FEEDBACK AND TEXTURE SIMULATING INTERFACE
DEVICE
TECHhiICAL FIELD
This in~ntioa nelaoes to a man-machine inoafaoe and in pro an inoafaoe that measures body part positions and provides farce and tenure feedback to a user.
BACKGROUND OF THE INVF.N'I'ION
A new manner of computer interaction is now in its infancy. The words "virtual environment" or "viraial reality" will soon be oommonplax. A virtual environment is an enviroameat where some portion of the eavimameut is srtif~cislly simulated, most often via a computer. A aomputa may create a graphic simulation of an environment, complete with graphic images of chairs, windows, doors, walls, etc., and even images of other people.
The computer may also simulate environmental sounds. The generated objects may be viewed on a common two dimensional display, such as a computer scxzen, or, by viewing with special stereoscopic equipment, the objects may be made to appear three dimcnsionaL
The most nada~al way fac~ an individual to inoe~ux in a virtual environment is to directly control a graphical representation of himself. For example, if the individual turns his head, the display screen at which he is looking is appropriately updated.
Also, if the individual reaches out and cloxs his hand, the computer gentia~d image of his hand on the screen reaches out and closes. Such virtual environments have been discussed in the literature.
To creaoe the xnsation of a virtual reality, the computer should be able to generate and manipulate graphic images of Teak or imaginary objects in real time.
Although generating a graphic representation of an environment may be time consuming and non-trivial to implement, much of the theory has been explac~ed and is d 0 understood by those sldllod in the art of interactive 3-D computer graphics and solid modeling. ~
The invention described here pertains to the important rrlated ante in which relatively little research has been done, i.e., "How may a human uxr perceive grasping force and texture from his computer generated counterpart in the virtual environment?"
There are many peripheral devices which have been created to allow a uxr to enter SUBSTITUTE SHEET' WO 91/11775 ~ ~ PCT/US91/00632 information into the computer. The most notable of these is the standard QWERTY
keyboard. Besides the numerous modifications of this "key input" concept, there are many other devices with their assoaaood permutations. A partial list of such devices includes mice, joysticks, trackballs and Computer Aided Design (CAD) tablets. The main drawback of these computer input devices is that they don't perniit human users to enoer inf~nation in a manner which may be the most e~cient and nat<ual. For example, in a CAD
software program, the human designer may wish to rotate a 3-D graphic neprcsentation of a block on a computer screen to view and modify the hidden side. Using currently available input devices, the designer must select the axis or a sequence of axes about which the objoct must ~ m~~ ~ ~~~e ~e desired orientation and view. Afocr the desired axis is selocxd, the amount of angular rotation mnst be de~ined, usually by the Wrap motion of a mouse or by entering the desired amount of rxation as a decimal quantity via the keyboard. This whole proooduie seems very awkward and uniatuitive when compared to what a person would normally do when confronaod with a similar task in the "seal world,"
i.e., he would ~P1Y ~t~ P~ uP ~ tvtate the objoct! Providing feedback fa this mon nanasl approach to objcct/environment inoeracti~ is an objecx of this invention.
Insuumeaxd gloves which provide digit position information to the compuux have ban used w manipulaoe simulated objects in virtual environments. Such gloves have also ban used in telexobotics to control highly dextrous end effoctois to grasp real objects.
However, lack of force feodback to the glove wearer has reduced the effectiveness of these open-loop manipulation approaches. Imagine a 3-D graphic model of an egg on a computer screen. Suppose you are wearing a glove which maps your digit and hand motions to a graphic image of a hand on the same screen as the egg. As you move your hand and digits, ~c corncsponding graphic images of the hand and digits move in a similar manner. The task is to move your own hand and digits to control the gn;phic hand on the computer screen to pick up the egg. To accomplish this task you must provide enough force to reliably grasp and lift the virtual egg, but not so much force such that the egg is crushed Without some kind of grasping fotGt and tactile fxdback, this task would be extremely difficult.
Attempts have been made to provide information about simulated contact with virtual or tclemanipulated objects to senses other than tt~ corresponding tactile senses. One method of simulated feedback which has been testod uses audible cues. For example, the computer may beep when contact is made. Another simple method is to highlight the object once contact is made. Both these methods will require the user to re-learn hand-eye coordination. It may be frustrating and time consuming for the user to barn one of these "unnatural" methods of grasping an object, and the sensation of interacting in a virtual SUBSTITUTE SHEET

~O 91/11775 ~ ~' ~ ~n PfT/US91/00632 ent will be teduaod.
SLfMMARY OF TIC INVENZZON
An object of the invention is a man-aoschine ino~rfaee which may be employed in interaarva ootaputa applications.
Another object of the invention is a force feedback control system capable of ~oa~~g a sat force to a sel~ed part of the body, eg., the digit tip.
Still aaothes objoct of the invention is a man-machine sysxm capable of simulating textures on a selectod part of the body, e.g., the digit tip.
Yet another object of the iav~on is a man-machine interface comprised of a glove capable of sensing digit a~ hand positions aad head orientation, which may exert, measure a~ dymamicxlly vary and control the foaoea appliod ~ each digit, and which may vary the tactile stray ~tOem pmsantad oo each digit tip.
2p Another objoct of the iaveation is a digitial control sysoem capable of sensing the force applied to the digit tip and capable of using this signal to oontrnl the digit tip force to a desired force sat point which may vary as a function of digit position.
Still and objoct of the invention is a fame and texdae feedback system which may be employed in many different applications, such as virtual environments, telernanipulation and interactive 3-D graphics and Cozaputer Aidod Design (CAD).
A feature of the invanti~ is the use of a flexible housing which may comprise one or more concentric flexible casings which guide a force-transmitting flcxiblc elongaoed elemeat such as a flexible, low fricdon/stiction, low modules of elasticity thread or a shape memory allay wire which serves as a tendon and is used in tension to apply force to a sensing body part or to actuate texture simulating elements.
Another feature of the invention is the use of a flexible housing which may comprise one or more concentric inelastic tubes to guide a force transmitting flexible elongated element such as pneumatic or hydraulic fluid to a sensing body part to be used by a force applicator to apply force to the sensing body part.
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WO 91/11775 ~ ~ ~ " PCT/US91/00632 Still another feature of the invention is the use of forne acdiators to generate fot~ce which is asasmitted to the sensing body part via flexible tendon cables, err pneumatic or hydraulic tubes, and used by a force applicator to apply force to the sensing body part.
Yet another feature of the invention is the use of force or displacement actuators to gencta~e displace~nt which is transmitted to a sensing body part via flexible tendon cables, or pneumatic or hydraulic tubes, and used by a texture simulator to simulate textutzs on the sensing body part.
Yet ~~' feattme of the invention is the use of a support to which the flexible tendon cables or tubes are secured. The support may be a reinfonxd wrist-strap when the sensing body part is part of the hand.
Another feanat of the invention is the use of a pressure, tension and/or force sensor to measure the fence apliod to the force-sensing body part by the force acarator.
One embodiment of the invention pmseats, for the first time, the use of a glove incorporating not only sensors which provide analog values repr~ating digit and overall hand motion, but also true force feedback to the wearer's digit tips relating the amount of force . a corresponding graphic (or actual) device is applying to a given virtual (or telemanipulamd) object The invention also relates to a means whereby simulaxd texture and edge orientation may be presented to a user.
The invention, which senses one or make body part positions and provides force and texture feedback to one or mace body parts, pemnits a relatively "natural"
method of computer inoeraction. The subject device provides in a single unit: ( 1 ) controlling body part position-sensing means employing a plurality of signal producing means associated with individual movable controlling body parts, where the signal is ranted to controlling body part position, with the individual signals analyzed to define a composite signal The signal producing means may be anything which provides body part position and/or orientation, including strain gage, electromagnetic, ultrasonic, piezoelectric, hall effect, infrared emittcr/dctcctor pair, encodcr/potentiometer, laser scanning or other optical position (and/or orientation) sensors; (2) force-applying means which may be anything which provides force information to a sensing body part; and (3) force-sensing means w~oh may be anything which provides a force measurement signal; and (4) texture-applying means (e.g., an array of textia~e elements) which may be anything which pmvidcs surface pattern (e.g., texture) information to a sensing body part; and (5) force-generating means which may be any actuator which generates a force (or displacement), including SUBSTITUTE SHEET

~~'O 91/11775 ~ Q ~ ~ ~ ~ ~ '' PCT/US91/00632 elecarical, eloctromagnetic, elect~echanical, pneumatic; hydraulic, piemoelocaic, shape memory alloy (e.g., Nickel/ritaaium alloys). ~ pn~ actuators; and (~ force-tran~itting means (e.g., a fle~dble, inelastic tendon guided by a fleu'bk, incompressible housing, ac as inoomptessible fluid guidod by an inelastic housing) which may be anything which traa~mit$ a face signal 5~om a facno-,ga~tiug means to an applying means (e.g., a forco-applying means a a owrnao-applyin8 meaner and (~ signal collection and producing means (e.g., a prooessac or eomputa) which may be anything which collects signals (e.g., from the position-sensing sad/ac foroo-sensing mesas) and produce signals (e.g., far the forco-applyin8 and/or texdue-applying mesas); a~ (8) suppo:t stru~ae ('including clips, sue. clamps, guides, pocloets, material, etc.) used to support the body part sensing means, the fac~ec-applying means, the teacture-applying means, the foc~ce-generating means, the force-aansmitdng means and the signal collection and producing means.
The signal associaoed with the eant~dliag body past position-seasiag means may be ~ with the facve appliod to ~ a sensing body part and also with the ~xtea~e appliod to a sensing body past For eaam~ple. the signal pmduoed by the c~ntiolling body part position-sensing means may be used by a signal collection sad producing means to manipulate a multiaroiculasod ooh genemtod int~ve entity in a virtual environment The force-applying means may apply force to a sensing body part is relation to the ion between the intecactiv~e entity a~ a component of the virtual environment In addition, the t~ama~e-applying means may be assoQatod with a surface pattern informative signal and apply a to a sensing body part to futthGr enhance the sensation of reality in tzlation oo the inoeraction of the entity sad a component of the virtual environment A particular application for the invention is to sense and provide force and oexture feodback to the head. A useful embodiment for the invention when used for the hand is a "feedback glove: ' The feedback glove embodiment is comprised of means for measuring position and orientation of the hand, means far measuring individual joint angles, means for applying force to various parts of the hand, means for sensing the appliod force, and ~s for applying selocted oextures to various parts of the hand. Many of the specific descriptions of the invention will be centerod around the feedback glove, however, the sensing and structures described for the glove may be easily translated to other body parts (e.g., arms, legs, feet, head, neck, waist, etc.).
~ a pnfernd embodiment of the foedback glove, tt~ means for providing position and orientation of the hand is a PolhemusT~ electromagnetic position sensor.
The individual joint angle sensing means is comprised of two long flexible strain gages mounted back to back The strain gage assemblies reside in guiding poclaets sewn over SUBSTITUTE SHEET

5 ~ ' Pf;.'T/US91/00632 each joint. R~la~a a joint is flexed, one of the stZaia ~g~s of the corresponding pair of gages is in tension, while the otha~ strain gage is in compression. Each pair of two gain gages comprise the two legs of a half bridge of a common Wheatstone bridge configuration. An analog multiplexes is used to select, which of the half bridge voltages is to be sampled by an analog-to-digital converter. The maximum strain experienced by each gage is adjusted by varying the thiclmess and elastic modules of the backing to which the gages are mounted. The backing is selected to maximize the signal output without ~nificantly mduang the fatigue life of a gage. These joint aagle strain gage sensors are disclosed in the Krama et, al. patent application number 07lL58,204 and are inanpartatod hen byrfe~.
The means far applying force to parts of the hand is comprised of a means (e.g., an electric motor) for generating a desired force, a means (e.g., a flexible tendoNcasing assembly) for t<aasmitting the geaQated force to a farce-applying means, and a means (e.g., a fortx-applying Platform) foe transferring the face to a specific part of the hand (e.g., the digit tip). The feedback glove may also comprise a means (e.g., a force-sensing platform or load call) fa measuring the applied face. The means for applying oextae to parts of the hand is comprised of a means (e.g., an electromechanical solenoid) for generating a desired displacement, a means (e.g., a flexible ecadon/casirtg assembly) for ~~t~g the genaaud displacemeat to the hand, and a means (e.g., an array of texture elements) for applying a surface pattern to a specific part of the hand (e.g., the digit tip).
The embodiment includes scrucaue which supports both ends of the tetxions and casings, and also supports the force and texture-applying means.
The fax feedback glove, which embodies joint angle sensors and also the force and texture feedback apparanrs, ovr,~t:rornes many of the problems of joint sensing devices which do not embody forae and vext<a~e feedback. The feedback glove simulates contact and grasping information in a "nattusl" manner to a user and facilitaoes many tasks, such as those arising in interactive 3-D graphics and telerobotics. The feedback glove may be used to feedback texture information from "virwal" objects in a virtual environaxnt or from distal "real" objects when used in telerobotic applications.
When used with appropriate animation and control software, the feedback glove provides joint angle sensing and sufficient tactile feedback for a user to control an interactive entity, such as a computer generated graphic representation of his hand to reliably grasp a virtual object, such as a cup, or any object which appears as a graphic model on a display device. Some virnral objects are programmed to demonstrate physical properties similar to real objects, such as weight, contour, stiffness and texture. These, SUBSTITUTE SHEET

~'O 91/11775 '~ JC y ~ ~ PCT/US91/00632 and other feaarres, may be sensed and the virtual objects manipulated using the feedback glove. The force feedback incorporated into the glove relays the virtual grasping force infom0arion to the user, while a teuta~e simulaoor allows the nsa to sense orientation and motion of edges simply by "oorrchiag" virtual objects with his own computer simulated virtual digits.
The fxdback glove, which provides joint angle sensing and force and texture feedback, may also be used far telerobotics. For this application, the feedback glove provides joint angle infcarnation which is need to control an interactive entity, stick as a ~bot manipulator, oo grasp a distal real object: The force and texture feedback of the glove provide the user with the acwal gripping force and the object contours sensed by the robot's gripper, so the real object may be reliably grasped and manipulated without dropping or cnrshing.
A glue ~8 fame feedback may also be progc~amm~ to teach digit dexterity, digit timing and eves the motions no~sary m learn some musical instruments. Far example, if the user were learning dye piano, as digits are flexed, the user would receive digit tip piessia~c form vira~al laeys signifying to the uses that he had pressed the key. Tendons similar to those positioned on the da~al side of the digits ro digit flexure may also 2p be placed ~ the palm side of the hand. These palm-side tendons may be used to force the digits into the desired flexed positions or to restrict the digits from extending. These tendons would be used in the case when the user wanted to be "taught" to play the piano and wanted his digits to be prnpaiy positioned and flexed for him at the proper times. The idea of this example may be e~u~ndod from a virtual piano to other virtual instruments and non to other devices such as a virtual typewriter. The feedback glove could be used to teach someone to type, and when learned, to allow the user m generate text by "typing in the air."
More specifically, the invention is a man-machine system which, in addition to m~~g human joint angles, provides two feedback sensations to the user. The first sensation is force. In a preferred embodiment, a small device is attached to the digit tip of a joint-angle sensing glove and holds a force-applying platform in juxtaposition to the digit tip. The force-applying platform is displacxd from the digit tip (by about 4 mm) .by a retractable means (e.g., a leaf spring) when unactivated, but is capable of quickly o°n~~g ~ ~l~t tip and applying a dynamically selectable force when activated The sudden impact of the force-applying platform provides a sensation similar to that perceived when the actual digit tip contacts an objxt. Thereafter, the for~oe-applying platform prtsses against the digit tip with a progzammable force which may relate the amount of force that a SUBSTITUTE SHEET

WO 91/11775 ~, O ~ PCT/US91/0063Z

virtual digit is pressing against a virtual object.
In a pr~fecred embodiment, the force that is applied by the fa~oe-applying Platform to the digit tip is transmitted from a Entree generating actuator (a d.c.
servo motor) via a high tensile strength, flexible tendon enclosed in a flexible, non~ompnssible tubular casing.
The function of this assembly is similar to a bicycle brake cable. Other embodiments may employ force acwatacs based on eloctirical, electromagnetic, elecaomochanical, pneumatic, hydraulic, piezoelectric, shape memory alloy (e.g., Nickel/Titanium alloys), vapor pressure, or other suitable mchaaiogies. In choosing the appropriate actuator mchnology, v~ous factors should be considered, such as speed of response, force output, siu, weight, cost and power consumption.
One end of the tendon casing is secured near the force actuator and the ot>xr end is sc~a~d to a wristband near the feedback glove. As a tendon emerges from the end of the ~~g s~urrd to the wristband, it is guided by sections of casing axed to the glove material until the tendon reaches its designated final location. Tendons which are to provide a force to restrict the wearer from flexing a digit arz guided from the wristband across the back side of the hand to the final location. A preferred embodiment has these tendons passing across the back of each digit and has tea=m mechanically connected to the f~aPPlYulg P~o~ at the digit tip. In addition, a tendon may be terminated at any PAY m~~ uiurglove location.
As tension is increased, tendons which pass along the back side of a digit press against the joints and do not tend to pull the glove maoerisl away form the hand or digits.
The tension of the tendon restricts the joints over which the tendon passes from flexing in a direction which attempts to extend the tendon furt~r.
To provide a fomce w restiria the wearer from extending a digit or to actually drive a digit into a flexed position, tendons ate guided across the palm side of the glove by sections of casing. In a preferred embodiment, these tendons are guided to the digit tip where they are ultimately secured to a farce-applying Platform, but they may also germinate at properly minforced intermediate positions. Unlike the case where the tendons are guided along the back-side of the hand, when the tendons which art guided along the palm-side of the hand are in tension, they tend to pull the casing sections (and hence the glove material) away form the hand. Although not necessary, if it is dcsirzd to guide these tendons along the surface of the palm and digits as they pass fiom where the casings are securrd to the wristband to their final designated locations, the glove must be appropriately neinforood between each joint.
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"~'O 91/11775 ~'~ ~ ~ ~ PCT/US91/00632 Wlarre the oendoas ate routed and where they are ultimately seamed ~ the glove will determine the forces applied to the hand by the tendon. Forces and tongues applied m parts of the hand by a single tendon may not be controlled independently. Only dte fozne applied to one part of the hand ar the toque applied by the tendon to an individual joint may be controlled. In a preferred ennbodiment, the tendons are fastened to the foroe-applying platforms at the digit tips, and the forces at the digit tips ate measured and oont<ol1cd, not the torque applied to the jasats. To isolate the force and independendy restrict motion of a angle intermediate joint, a separate tendon is used Its casing is .1~ P~ m ~ Jo'~ sad the oeadon is fastened to a force-applying Platform just beyond ttar joint As pnrriously mendoned, the glove is properly reiaforood near the joint so the glove maurial doesn't unduly atcetch under the force of the tendon.
Whey farce is initially applied by a farce acxuaoar, the force will appear betaroen the d and the intended digit. lie, tlx wristband will tend to move toovards the digit as the "slacl~' in the skin an the wrist is taloen up. The taidency for this relative motion can be tnduood by inoorpa~iag a means which initially falser up the slack in this skin. Once this slack is taken up, the wristband will stop moving, and the digit will experience the full feeder force (except far frictional losses). If the slack in the wrist skin 2p is not initially takes up, to provide a reabsdc contact sensation, the farce acaiator must have sufficiently high bandwidth such that this aleck take-up time is insignificant when compared to the bandwidth of digit motion.
In a preferred embodiment, the actual farce at the digit tip is sensed and fed back to a servo control system. The control system conaols the output of the force actuator such that the force applied to the digit tip follows a desired force profile regardless of the undesireable compliance of the skin on the wrist. The force profile for any digit is a function which produces a desinxi force set point for any given digit and hand position.
That is. as either the digit or hand changes position, the force applied to the digits varies accordingly . For example, a face profile may be generated which simulates the force sensation of a push button switch that gradually increases its opposing force as the button is depressed until it reaches its toggle point, clicks, and pleases most of its resistive force.
In addition to providing object contact and force information, the invention ~~ a ~s whereby object textures and edge orientations may be penxivcd For one embodiaxnt, the previously described digit tip force applicator may be modified to include an array of small stimulators, railed texture elements. These elements produce a surface pattern (e.g., a simulated texture) in addition to providing force feedback Each SUBSTITUTE SHEET

tcaorme element may be individually selocood. The oraaae element may be a small pin which extends when selected and the amount of its extension may be pa~og~ram~od. The oexture element may also be a pair of electrodes, and tactile sensation produced via electnocutanoous stimulation.

In a preferred embodiment, the texture elements are driven by a texture displacement actuator. A flwcible bundle of foct~e feadbaclc and texture simulating oendons cannocx the glove to both the force and texture acdraoocs. The type of displa,oement actuator for a t~a~e element may vary. A pasricular embodiment may employ binary or linear 10 ~Pnt actuators sad the actuators may be based on elecaical, electromagnetic, electromechanical, pneumatic, hydraulic, piezoelecaic, shape memory alloy, vapor pressure and other suitable technologies. In choosing the appropriate actuatW
txhnology, various factors should be considered, such as speed of response, force output, size, weight, cost and power consumption If pnetrmati~s or hydraulic is used, a hermetically ~~d fleuble tubing assembly is usod to correct the textnne actuator to the texture element. Otherwise, the oonnoction may employ a cabling mesas com~s~ of a oendon inside a casing, similar to that used to t<an~it the facoe from the force actuator to the fa~oe applicanor:
If a binary actuator (e.g., a two-state solenoid) is usod, tlxn the texture element will either be fully exor fully nettactod. If a linear acd~ator. is chosen (e.g., a d.c. servo motor) then the exoension of the texturt element may be continuously variod.
The faex with which the texture is prtsentod to the digit tip is deoerminod by the fonx actuator. The paean of the texture array may be varied with time and reEloct changes in the position of ~e joints or hand. For example, by dynamically varying the texture array, a user may perceive his virtual digit moving over various (e.g., smoothhough) virtual surfaces. Using the time varying texturt array, a user may also determine the odge orientation of a virtual or tclemanipulated objoct.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. la is a perspective view of a tendon/casing assembly.
3S FIG. lb is a cross-section for the perspective view of FIG. la.
FIG. 2a is the side view of an embodiment of the invention showing the force-transmitting tendon assembly affixed to a glove.
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'~O 91/11775 ~ ~ ~ ~:~~,~ ~ PCT/US91/00632 FIG. 2b is a cxoss-suction vices of an embodiment of the invention which shows teadons affixed, via t~don guides, to material covering a digit: one tendon to the back side and one tendon to the palm side of the digit. . .
FIG. 2c is an embodiment ~ the invention which shows tendons affixed to provide force feedback to othar body parts (e.g., the arm).
FIG. 3 is the side view of an embodiment of the iavattion showing the trxt~a~e ~~ting tendon assembly affixed to a glove.
FIGS. 4a and 4b show an embodiment oaf the invention where force tendons are aced, via tendon casings, to both the palm and back side of the digit tip of a glove. One end of the tsndoa csaing is to a waist portion of the glove, and the other end is fastened to the force applicator assembly on the digit tip.
FIGs. Sa - Sh, and FIGS. Ga -6c show various fo~ee applicator embodiments.
FIGS. 7a and 7b show ttu ford applicator modified to simulate, in addition, texture information .
FIGs. 8a - 8m show various feature simulator embodiments.
FIG. 9 is a schematic elocaicalhmochanical signal propogation diagram.

FIG.10 is a control system block diagram for control of the digit tip force.
FIGs. l la - l ld show a fame applicator embodiment which employs a load cell to sense force applied to the digit tip.
FIGs. 12a and 12b show a force platform capable of pivoting to make the contact pressure between the platform and the digit tip uniform.
FIG. 13 is a side view of a force applying platform where the pressure distribution ~Y ~ m~~ by adjusting tendon tensions differentially.
FIGS. 14a and 14b show the side and plan views of an embodiment where the force applying platform is capable of pivoting in any direction and thus can move the location of SUBSTITUTE SHEET

W091/11775 ~y PCT/US91/0063Z

the centroid of pressuit.
FIG. 15 is a side view of an embodiment showing how the tension in the tendon may be measured prior to the platform contacqng the digit tip.
FIGs. 16a and 16b are side views of two more methods to measure tendon tension.
FIGS. 17a and 17b are side views of two embodiments of a structure which supports both a bend sensor and a force-aansmitting tendon.
FIGS. 18a and 18b an a perspective and plan view of an embodiment which provides a pre-tension between a force feodback glove and the casing support wristband.
FIG.19 is the block diagram of a threo-loop force control system.
DETAILED DESCltB'TION OF >LWSTRATIVE EMBODIMENT'S
FIGS. la aad lb show how the farce generated by a farce acwator may be aansmitted to a chosen location. More specifically, FIG. la shows a perspective view of a tendon assembly, and FIG. lb shows a doss-section view. The tendon assembly is comprised of a low friction, high modulus of elasticit3r and high tensile strength, flexible tendon cable 100 (e.g., Dacron'j'~ 20 lb. test fishing line or Kevlar'='M thread) inside an assembly employing one or more c~fleuble, low~ompressibility tubular casings 101 (e.g, TeflonTM tubing). One end 102 of the casing assembly is securod near the force actuator and the other end 103 of the casing is soctaed near the location where the force is to be applied (e.g., for a fudack glove, the casing may be secured to the wristband, and the farce applied to the digit tip). By using a plurality of concentric casings (e.g., a #20 Teflon tube inside a #14 tube) rather than simply increasing the thickness of the wall of a single casing, the rosulting tendon casing is more flexible (since the casings may slide relative to each other) and still produces an overall compressive strength nearly equal to that of a single casing of equivalent wall thickness.
FIG. 2a is a side view of a force feedback tendon assembly affixed to a glove 200.
In this embodiment, each tendon force is generated by a d.c. servo motor 201.
The motor is driven by a curncnt amplifier so that a motor torque is produced which is proportional to the amplifier current. This torque is converted to a tendon force by the tendon pulley 202 on which the tendon cable 203 is wound. By securing ono end 204 of the tendon casing SUBSTITUTE SHEET

""'~O 91/11775 ~ ~. ~ ~ ~ PCT/US91/00632 near the mota~r and tire other end 205 ~o the glove's teinfa~od wristband 206, the farce produced by the znoo~ may be transmito~d to the glove. In a preferred embodiment of the invention, the wristband is comprised of a sturdy, reinforced strap with Velcro backing wrapped around a thin, rubber (e.g" polytucthane) inxrmediate layer.
The rubber ~Y~ Provides a co~fortable inow~ffaoe between the ieinfoncing strap and the user's wrist.
The strap is made from a heavy-duty thttad (e.g., canvas) which is woven to allow it to be flWCed around a wrist, but to otbavvise provide a ataady support. In general, the wristband may be manufactumd from a v~iet~r of mataiala such as foam padded injection molded plastic. The wristband may be manufactiuod as part of the glove or made as a separate ~ ~t The tendon cable passes through a aeries of tendon guides 207 as it extends beyond the point whcrc the cauag is soc~and, oo the wristband on its way to the digit tip fomce applicaoor. In one embodument, the tendon guides for the back side of the hand art ~ ~ able, but inoomp~neessible cas;ag (eg., Teflon tubing) and fastened over the metacarpophalaagcal (lVIP) 208 and pro~cimal interphalangeal (PIP) 209 joints.
These guides prevent the oendons fivm moving )aterally and slipping off the sides of the joints as the lozuckles protrude during flexure. In the embodiment where the glove has tendons 210 on the palm side of the hand, and it is desitcd to have the tcadons remain close to the hand 2p when they are in tension, tendon guides 211 an loc~tod between the MP and PIP joints arxi also across the palm to loeep the tendon from pulling away fivm the glove. The glove is also reinfaacod in a variety of places oo prevent the glove from being pulled away fiom the hand by the tendon guides. Tendon guides may be axed to the glove by such mans as sewing or gluing, or the casings may be molded directly ontoltnto the glove.
The digit tip farce applicaooc 212 (shown gera~rically by the cross-hatched portion of the digit tip) applies both back-side and palm-side tendon forces directly to the digit tip.
Also on the digit tip force applicator assembly is a force transducer for each tec~on which senses the actual force applied to the digit tip. These force signals are fed back to the motor force control system which makes appropriate adjustments such that the dcsirc~
force profile is perceived by the user.
FIG. 2b is a cross-section view of an embodiment of the invention showing farce feedback tendons 216 passing through guides on both the back 213 and palm 214 sides of a glove digit. Both ters~ns are attached to the foroe applicator at the digit tip. In a pnefcmed embodiment, when the tendon guides are axed to an elastic glove, only the palm-side tendon guides need rtinforcement to ensure that they t~cmain against the digit when the tendon is in tension. One way to aa:omplish the reinforcement is to fasten SUBSTITUTE SHEET

PCT/US91/t10632 additi~octal material 215 of low elasticity (e.g., nylon, plastic, or axtal) around the digit at the base of the tendon guide.
FIG. 2c shows a force feedback tendon/casing assembly applied to the arm.
Casings 217 may be se~and to a rcinforoed atisp 218 worn around the bicep. The strap is s>milar in construction to the wristband previously described and also employed hen.
Both the tends shown exit tla~ casings on the bicep and are affixed to the wristband 219.
O~ tendon 220 p~rovid~es a force which resarxb the elbow from expending while the other uadon 221 provides a force which:tstricts the elbow from retracting.
Assemblies similar m ~ ones shown is FIG. 2a - 2c may be inoorparatod into a "feedback body suit," i.e., a suit which covers all, or portions of the body, and which can apply force and texture i~fo~oatioa to various parts of the body.
FIG. 3 is a silo view of a o~aoune simulaxing assembly axed to a glove.
T~ ~Pt in this embodiment is generated by a two-state cloctzomechanical solenoid 300 and is transmitted oo the digit tip via a oendon and casing assembly 301. The oendon assembly shown here is similar is function to the assembly described earlier far FIGS. la and lb, l~wevex, the diamarr of both the tendon and casing may be smaller sincx the forces these texnu~e tendons noel to exert one less than the forces exermd by the farce feedback tendons.
One end 302 of the tendon casing far the ~rataue simulator is secuzed near the displacameat actuator, and a point 303 near the other end of the casing is sociaed to the glove's ieinfo~rood wristband. After the casing is affixed to the wristband, it continues on ~d ~ f~~d ~ ~ Zd~'e at various locations 304 between the joints on its way to its designated final location, which in this embo~dimant is the digit tip oextuie simulator 305.
Casings may be af~ced to the glove by such means as sewing or gluing, or the casings may be molded directly onto/'moo the glove. In the embodiment shown, there is slack 306 in the casing betwxn points where it is aiBxod to the glove to allow for the tightening of ~ ~g win the digits are ben~ The casings may also be guided along the sides of the digits without allowing for slack since they won't be stressed when the digits are bent.
FIG. 4a shows a plurality of force feedback tendons 400 and their guides 401.
Although the texture feedback discussed in FIG. 3 may be used simultaneously with force 3$ feedback, the texture producing tetdosts have been omitted from this drawing for clarity.
The tendon casings 402 arc shown secured to the reinforced wristband 403. In this embodiment, there is one tendon on the back of each digit to control the force applied to the digit tip. In addition, the figure provides an example of an abduction force feedback tendon SUBSTITUTE SHEET

""v0 91 / 11775 404 on the thumb side of the index digit.
Force is imparted to each tendon from a force actuator. In the emboditncnt shown, forces are nnsasmitted to the glove via a tendon assembly similar to FIGS. la and 1 b. One end of the tendon casings is sxured near the farce actuaoor, and at the other end is fastened to the glove's reinfatcod wristband. Tendons 405 inoendod for the palm side of the glove extend around the wristband as shown. These tendons 400 intended for the back side of the hand urge from the casing on the wristband and are gttidod along the back surface of the glove by aectiona of casing 401 until they reach the desired final location. In the 10 ~bshown the final oendon location is the digit tip fence applicatac 406.
FIG. 4b shows a force feedback tendons 405 guided amend the wristband to the palm silo of a glove. The palm-side tendons then emerge from their casings on the wristband sad are guided through suctions of casing 407 on their way to the digit tip farce 15 aPP'.
One useful yet uncumbersome and inexpensive embodi~t of the invention employs force feedback tendons only along the back of the hand to the tips of the thumb and index digits, and employs texture elements only on the index digit tip.
This "reduced"
embodiment is in contrast to employing both face feodbadc and oetada~e simulation to each joint of all five digits. The rodttad embodiment prrnridea the wears with sufficient force feedback infacmation to grasp most virwal objects a~ also allows the wearer to sense virtual ua~m~ with the index finger Although, employing force feedback to all joints on all digits and texture simulation w all digits tips will provide the wearer with a mos,c realistic simulation of his virtual environment, the increase in realimn may not outweigh the added cost and complexity of the system.
FIGS. Sa-Se shows a digit tip fume fieedback applicator which is comprised of a force-applying platform and a force-sensing platform. FIG. Sa is a perspective view, FIG.
Sb is a front view, FIG. Sc is a bottom view, and FIGS. Sd and Se are side views.
Modifications may be made to this functional design without departing from the scope of the invention. The forte feedback applicator may be manufacriaod directly into the glove material (as might be done if the glove were molded fiom a type of plastic).
The applicator may also be affixed to the glove externally after both the applicator and glove are ~~~~ ~P~~IY. ~e force applicator tray also be a device which is simply clipped to the digit tip after the glove is put on.
In a preferned embodiment, a force tendon 500 is guided from the force actuator to SUBSTITUTE SHEET

the force feedback applicator, splits into two tendons, each oendon passing by the farce-applying platform SOl (e.g., though holes), and mechanically oonnecood to the ends of the force-sensing means, which is a force-sensing platform 502. The force feedback applicator suuc~at; S 19 provides support for holding the force-sensing and force-applying platforms in juxtaposiwn oo the digit tip. The farce-sensing platform is farad via the foc~ce of the tendon towsuds the digit tip. The fonx-sensing platform presses against the foroe-applying platform which they contacts and applies fence to the digit tip (FIG.Se). When there is little or no fomoe in the ~On, the farce-applying platform is displaced from the digit tip by about 4 mm sad is held away by a raractable means such as small springs (FIG. Sd). Leaf :Iutaga 503 are employed in the embodiment shown. By loxping the force-applying Platform displaced from the digit tip in sa uttactivated position unto fence is applied, bandwidth toqvimme~s of the farr,~ acarator are rnduood. For example, when the invention is used to provide feedback from a virtual environment and a virtual object is grasped, tile force-applying platform assumes an activated position and contacts the digit tip with a non-a~ro rzlative velocity, as would a real object when contacting the digit tip. If the force-applying platform were always in contact with the digit tip, very large tendon velocities and acoelerationa would have to be generated to provide the same contact scasation to the user.
The fonx-sensing platform may be simply a strain gage beam which bands across a S04 as force is applied. The fulcrum shown in FIGS. Sa - Sf is thin and concentrates the applied force over a small area such that the induced strain is easily meastm~d by the two strain gages SOS, S06 mounted differentially to either side of this force-sensing platform Alternative designs are possible such as shown in FIG. Sg. By modifying the fulcrum shape and contour, various stress vs. tendon force profiles may be obtained Far' example, the fulcnmn design of FIG. Sg will provide a higher strain "gain" for low strains than the fulcrum of FIG. Sf, i.e., the detected strain will be large for small forces, but the strain gain will decrease as the farce-sensing platform bends around the fulcrum.
As the force-sensing platform bends around the fulcrum, the measured strain includes not only a component from bending but also includes a component from tension in the platform. By varying the contour, and thus the strain sensitivity of the force-sensing platform, small forges arse detected with fine resolution, but the sensor will not saturate as q~~ldY f~ ~gher' strains. Further modifications of the fulcrum and platform geometries produce additional strain vs. farce profiles.
As shown in FIGS. Sa - Sg, when tension is applied to the tendon, strain gage SOS
SUBSTITUTE SHEET

""v0 91 / 11775 ~ ~ g PCT/ US91 /00632 is in tensi~ and strain gage: 506 is in compression. Both strain gages are active and cover the area of the platfa~m e~cpa~imcang atrmn. Together, the two strain gages form a half bridge for a common W6eetsooue bridge cirarit which provides temperature compensation.
The ftrkrum and all other parts of the forx applying platform that touch the force sensing platform are made from a thermally insulating material oo insulate the swain gages on the force-sensing platform from tire aturc flucdrations of the digit.
FiG. Sh shows a force-,easing means, comprised of two strain gages 507, 508, mounted to opp~ite tides of a fleuble a>zes$-sensing element 509 which is placed is w~ the tandon and wcpaieooes a tensile forx related to the oendon force. The stress-sensing element may be a flatxaed portion of the tendon itself. This stress-sewing element may be used to meaarnts the tendon tension and/or the joint angles.
One strain gage 507 is mounted to the top ssde of the element, while the second strain gage 508 is mounted to the bottom side. 1a the ~t~odimeat shown, the stress-sensing element is used ~ ~~ ~ ~ jet flextae. Therefore, the entire gage~element-gage "sandwich" is positioned in, and slides freely through, the casing guide 510, which has a rectangular cross-suction in this regiaa Both gages are covered with a smooth, flexible encapsulation 511 (e.g., a type of plastic) which provides the surface that slides against the casing. The differential signal from the two gages is used to deocrmine the joint angle, 2p while the common mode signal from the same two gages provides a measure of the tendon pension. The stress-sensing element may be made from a non-flexible material and located between joints when only a meastme of tendon tension is desired. The force in the tendon near the digit tip closely appraaamates the force applied by the force-applying platform to the digit tip. If the tendon ton is found using the stress-sensing eleme~
described here, the force-sensing platform previously described may be removed from the digit tip force applicator, and the mechanical design ~y be simplified to a single platform 512.
FIG. Si shows how a forx may be focused to restrict flexure of a single joint (e.g., the PIP joint as shown in this figure). The tendon casing 513 is sccurai to a first 30 n~~d section 514 of the glove just prior to the selected joint The tendon 515 exits the main casing and is guided over t~ joint by a section of casing 516, which is fastened to a second reinforced section 517 of the glove. The tendon exits the casing and forks into two tendon parts (as is shown 520 for the digit tip force-applying platform of FIG. Sa).
The two tendon parts pass arvuad opposite sides of the digit and arc affixed to opposite 35 ~~ of the force-applying platform 518, which is sociacd to the second reinforiced section of the glove. The platform assembly contacts and presses against the digit when the tendon 515 is in tension.
SUBSTITUTE SHEET

WO 91/11775 ~ = ~, - ' Pf'f/US91/t10632 The same method of operation can be applied ro restrict the joint from expending as was described above w restrict the joint fivm flexing, A second tendon casing 521 is affixed to the first reinforood suction of the glove. A accord oendon 522 emerges from the casing and forks into two tendon parts. The two tendon parts pass around opposite sides of the digit and are affixod to opposite ends of the force-applying platform 523. The platform assembly contacts and presses against the digit when the tendon 522 is in tension.
In the case where it is undesireable to rraaforee the glove to support sections such as 514 and 517, FIG. Sj shows a way to provide force foedback to an individual joint of ~ ~ glove. If the glove of FIG. Sh was not ninfarced near sections 514 and 517, then when tendon 515 was in tension, the two sections would be drawn towards each other. A possible soluti~ would be to place a hinge between the sections to puevent them from simply sliding together. I3,owever, since the bead axis of a digit may translate and change orientation with bend angle, a single hinge would be uncomfortable for a glove A preferrai alternative to the "fixed hinge" solution is shown in FIG. Sj, where sections S24 and 525 arc in contact with each other and produce a pivot surface 527 when tendon 526 (earerging from casing 530) is in tension. The pivot surface is seated Zp by the two mating flaps 528 acrd 529, which each have a characteristic surface contour designed to follow the average knuckle axis during flexure. As the tendon tension increases, the two sections press against each other sad section 525 is foroed to rotate clockwise, while section 524 rotates counter clockwise, each section rotating about the "moving" contact pivot point The two sections are able to slide axially relative to the digit so they may contact each other when tendon tension is applied, and also so the same surface contours for the two sections will accocnodate a variety of different knuckles. The two flaps, in addition to possessing a contour, may also have mating surfaces, such as mating groves, to prevent one surface from sliding off the other surface.
To keep the sections secured to the digits, the sections may be made from a solid, but elastic material (such as a plastic or spring metal), which is pm-fanned to clip around the digit, as shown in FIG. Sj. The frrm elastic strap 530 helps hold the two ends 531 of the clip together. One end of the elastic strap is permanently secured to ono side of the clip, while the other end 532 of the strap is secun~ to the other side of the clip by Velcro 533. The elasticity of the clip, together with the elastic strap, hold the section firmly to the digit, but, since the clip and strap are elastic, they allow the digit diameter to expand when the digit is flexed SUBSTITUTE SHEET

""''O 91/11775 ~~ '~ ~ ; Pl'T/US91/00632 In same instances, it may be preferred to have a linkage attached to ttie suctions, such as is shown is FIG. 51. For example, if a rotary goniometer (e.g., a potentiomeoer, an optical enooda, or a rotary Hall effecx sensor) were to the linkage at the joint S34 betvveea the two links 53S and 536, the value of the goniometa may be related to the joint angle of the knuckle. When the linkage is employed, the force feodback asxmbly of FIG. 5j may still be used, howewx, as shown in FIG. 51, the tendons may also be affixed directly no the linkage. A first casing 537 is affued ~ Iink 535 and tatdon 538 is affixed to link 536. Similarly, a xcond casing S39 is a~Ced to link 535 and taidaa 540 is affucod to link 536. When tendon 538 is in tension, link 536 is pulled to rotate ~Gl~x. fo~ng the digit ~ ~d. When oendon 540 is in tension, link 536 is pullod to mtaoe counter clockkwix, forcing the digit to flex Note that in FIG. 51, supporting actions similar to those used in FIG. Sj are shown. If the glove is appropriately reinforced, other support sections, such as shown in FIG. 5i, may be used. Also note that in FIGS. 5j-51, fonx-applying platforms may be employed to focus the applied foTx to a parbicnlar region of the digit In addition, for clarity, farce feodback tendons far the palm-side of the hand are not shown in FIGS. 5j-51, however, they may be employod in an obvious manner.
FIGS. 6a - tx show an embodiment of the force feedback applicator which produces force feedback from a tendon affiaced to the palm side of the glove.
This configtaation provides a force which nestticts floe digit joiars from essending and may also force them to flea. FIGS. 6a and 6b show side views, while FIG. 6c shows a top vices.
Fair clarity, only the apparatus specifically r~cquimd for palm-side tendons is shown, but the force applicator may additionally include the apparatus shown in FIGS. Sa -Se. Tendon forcx is generaood by an actuator and transmitted, as shown in FIGS. 1 and 2, to the force feedback applicator. As shown in FIG. Sa, the tendon ~ 600 is guided past the force applying platform 601 (e.g., through holes), and is aced to the farce-xnsing platform 602. The force-xnsing platform again has two strain gages oonnocted differentially in a half bridge configuration. The force-applying platform is also as before and has a stress concentrating, thermally insulating fukxum on the side opposite to the digit The insulating fulcrum prevents heat conduction from the digit to the gages on the force-sensing platform.
The force-applying platform is displaced above the digit nail by springs (FIG.
6a) and contacts the digit nail only when a force is applied to the tendon ,(FIG. 6b).
In the 3$ embodiment shown the springs are leaf springs 603. The applied tendon ford presses the force-xnsirtg platform into the fax-applying platform which then presses against the digit nail. As the force-xasing platform presses against the force-applying platform, the platform is bent around the fulcxum and produces a strain in the gages indicative of the SUBSTITUTE SHEET

WO 91/11775 ~ PCT/US91/00632 force applied to the digit nail.
FIGS. 7a and 7b show an embodiment of a digit tip texture simulator. FIG. 7a shows the top view, while FIG. 7b shows a view looking at the the texture simulator from the digit tip. The particular embodiment shows a 3x3 texture array 700, wheat the texture elements are space on 3 mm centers and extend 1 mm whey activated. Texture arrays employing various numbers of texture elements may lx constructed. The texture array is contained within a modified facno-applying platfoma 701 a~ held in juxtaposition to the digit tip by the supporting situcaat 519. As shown, this oexture simulator assembly may 10 ~ Pmt farce feedback by including the same force-sensing platform 702, fukxvm 703, and strain gages 704 as described in FIGS. 5 and 6. In FIGS. 7a and 7b, the actuating mechanism for the texwr~e elements is not shown.
Displacement may be delivered to the digit tip texture simulator from the 15 ~~~~g ~tuator as previously described in FIG. 3 via a tendon cableJcasing or tubing assembly, by elxtirc~tl wires, oz by pne~ or hydzaulic means. FIG. 8a is a cross-section view where a tendon 800 enters the digit tip oext~a~e simulator 801, and when actuated, pulls on the base of a corresponding spring-loaded texture elemeat 802 to raise it. When raised, t~ texture elemcat extends from within its enclosure and pnsscs 20 age ~ ~8it tip. When the u~ farce is reduced, the spring 803 causes the element to retract back into the digit tip texture simulating enclosure. Ia all of FIGS. 8a -8m, the diagram on the left shows the unactivated state and tile diagram on the right shows the activated state.
FIG 8b is a cross-section view of a digit tip texture simulator where a tendon pulls on the Irshaped bracket 804, rotating it counter clockwise. As it rotates, the bracket pushes on the texture element which then extends from the digit tip texture simulator enclosure and presses against the digit tip. When tendon pension is removed, the spring 805 returns the texture clement to its original, unextendcd position.
FIG. 8c is a cross-section view of a digit tip texture simulator when either pneumatics or hydraulics arc employed. A positive pneumatic or hydraulic pressure extends the texture element and a negative pressure retracts it.
~G. ~ ~ a mss-section view of a digit tip texture simulator where another type of pneumatic actuator is used. When actuated, air erects the device and exits through the nozzle 806. This focused air stream creates a tactile sensation on the digit tip.
SUBSTITUTE SHEET

P~./U891/00632 ''"O 91/11775 FIG. 8e is a exoss-socti~ view of a digit tip t~a~e simulator wl~re a tnidon pulls on the bar 808 ansing it 1o pit. The pivot may either be a hinge with a return spring err a living hinge 809 (as shown). A element 810 is attachod to the bar which protrudes from the eaclostrre and praises against the digit tip when the bar pivots.
FIG. 8f is a cress-section view of a digit tip texture simulaoor where a tendon 811 pulls on a wodge 812 causing it to slide underneath and raise the nwca>te element 813.
When tendon fomce is releasod, the spring 814 returns the wedge to its initial position.
FIG. 8g is a cross-suction view of a digit tip tr~ttue simulator where a tatdon 815 pulls on the middle hinge 816 of the linkage 81~, as shown, and raises the texture element 818. When tendon force is released, t~ spring 819 returns the hinge to its initial position.
FIG. 8h functions sim;latly to FIG. 8g, but the hinges and spring are~replacod by a flexible beam 820. The beaan is initially emceed, as shown. When a oendon force is applied, the beam straightens, forcing the texan~e elcmcnt up.
FIG. 8i is a cross-saxian view of a digit tip texture simulator wherz the texna~e e1~eat is raised by generating a pi~stae by hearing either vapor, liquid ac a combination of the two 821. (7~areat is passed through the resistive heating coil 822, causing the vapor (or liquid) to heat up and expand and raise the elemcat.
FIG. 8j is a cross-section view of a digit tip texture simulaoor where the texture ~~ ~ bY p~~~ ~ A voltage appliod to a pieaoeloctric element causes it to either expand err contract depending on the voltage polarity. In the figure, there are two scparaoc pieces of piezoeloccric matrrial oonnoctod to form a "bimorph". The two clement are wirod with opposite polarities such that when a single voltage is applied, one piezoelectric clement 823 expands while the other element 824 contracts. When one expands and the other contracts, the bimorph bends towards the direction of the clement which contracts. A texture element 825 is attachod to the free end of the bimorph and protrudes from the enclosure when the bimorph bends.
FIG. 8k is a cross-section view of a digit tip texture simulator where a texture ~~t 826 acts as tlx plunger of a elecaomechanical solenoid. As cuzzent is applied to the coil 827, the texture element is raised. A spring 828 retians the texture element to its initial position when the current is removed.

WO 91/11775 ~ a ~ ~ P~/US91/00632 -FIG. 81 is a doss-section view of a digit tip textum simulator where a flexible, relatively incompressible fiber 829 (similar to a fibs optic wine) is usod.
The fiber resides in a flexible, but incom4xrssible outer casing 830 (similar to the tendon/casing assembly).
The fiber transfers displao~meat genas~ed at one location (possibly by a bulky or heavy displacement actuator) to a second location (e.g., the digit tip) by sliding relative ~ to the outer casing. Tlsr principle of operation is similar to a catheter tube. The end of the fiber is the actual textiue clement which protrudes and presses against the digit tip.
The difference between this '~rber" m~hOd and tire oendoa method is that the tendon is "active" in tension while the fiber is "activd' in oomp~rssion.
FiG. 8m is a cross-section view of a digit tip teXture simulator where a magnetic amaction, in this embodiment gated by elocavmagnet 834, pulls on the metal bar causing it to pivot. The pivot may either be a hinge with a return spring or a living hinge 831 (as shown). A texture e)emau 833 is attached to the bar which protrudes from the eaclostme and presses against the digit tip when the bar pivots. This texture simulator embodiment can be realised with mi~cro~motoz/microactuator technology.
In the embodiments shown in FIGS. 8i, j, k and m, the actuation displacement for then texttme Simulator is genaatad in the digit tip force applicator enclosure itself. Any of these same acaratoz technologies may be ~ployod~, but positioned at an altanane locati~
(c.g., on the wristband ar at the same place as flee foroe actuator). The displacement may then be transfeand to the digit tip by a tendon or p~iDmatic/hydraulic tube and used by any appropriate texture simulator.
In addition to the acd~ator technologies shown in FIGS. 8i, j, k and m, other, mock standard force and displacement acwatacs such as elecaomechanical motors and pneumatic (hydraulic) compressors (pumps) may be used. Shape memory alloys (SMA, e.g., Nicke>/Titanium alloys) may also be used to generate the tensile foctx ar displacement of a tendon. SMA wire has the property that it contracts when heated. The wire may be heated simply by passing an clccuical cumcat through it FIG. 9 shows how the electrical and mechanical signals propogate through the force/texture feedback control system. FTG. 10 is a diagram of the force and texture feedback control system in standard control theory block diagram foam. The embodiment shown employs a d_c. servo motor 900 for force actuation and an electromechanical solenoid 901 to produce the displacement for a texture simulating element 902.
A
computer sends a digital value representing the desired force to a d.c.
servomotor contml circuit. In the embodiment shown in FIG. 9, the desired force is presented to the digital-to-SUBSTITUTE SHEET

~""'q'O 91/11775 ~,~ .. PCT/US91/00632 analog converter (DAC) 903. The analog output of the DAC is then amplified by a variable gain amplifier 904. This amplified foc~ec act point voltage is then converted into a current by a common voltage-to-curnent oonfiguratiou of a power operational amplifier 905. This current drives the servo motor at a deskod torque. Velocity damping of the servo control loop is performed by tachometer feedback 906.
Tcuq~ gGneraoed by the motor is eonvaood into a tensile fonx by a pulley 907 on the motor shaft. The diaaxta~ of this pulley is aela~od oo achieve the desirod force and apood of response for a given monor. In a ptef~Od embodiment; a pulley disanc~
of 1/4 inch was usod. The gen~od trrasik fozce is tsaasmitood to the digit tip farce applicator from the fac~ec acxuator via a oendon cab1t~casiag assembly 908. The force applied to the digit tip is sensod by the two attain gages 909 mouaood differentially to the strain sensing platform and wired into a half bridge oonfiguratioa. A full Wheatst~e bridge is usod to amplify the detected famce. This amplified signal is digitized by an analog-to-digital canvGroa 910 and n.ad into the computer 911.
The computer implements a farce control law 912 (c.g., Pmpordonal-Integral-Derivative or state fcodbaclc) using v~ll understood >xhniques from the field of digital control The control law incorporates the foedback face information 913, and servos the motor to produce a decked forx at the digit tip. Digitized values 914 from analog joint angle seasars provide the information the a~mpuna roods to deocrmine the force set point 915. In a preferred embodiment, the ooh oonva>s digit joint angles into acaral digit positions. If one of the digits is fouad to be inte=~saxing a virtual objoct, the computer calculaoes the farce to be applkd to that digit usiag knowledge of the virtual objoct's shape and compliance 916. In a preferznd embodiment, differential strain gage angle sensors 917, as disclosed in the Kramer et aL patent application, are used to determine joint angles.
As shown in FIG. 9, the computer also outputs commands to the displacement actuator of the texture simulating array. In the embodiment shown, the computer outputs digital values which control solenoid drive transistors 918. For example, a logical value of "1" turns the transistor "on," and a logical "0" turns the transistor "off."
When the transistor is on, the solenoid coil is energized, and the plunger 919 is retracted The retraction generates a displacement which is transmitted to the texture simulator 902 via a tendon cablekasing assembly 920. The texture simulator uses the displacement to extend ~~ ~xwn elements beyond the surface of the digit tip forioe-applicator platform against the digit.tip. When the transistor is turned off, the solenoid plunger is extended by the return spring and cable tension is released. When the tension is released, the texture element is rztracted back into the texture array platform housing by its own return mechanism.

WO 91/11775 ~ PCT/US91/00632 FTGa. l la l ld are functionally similar m FIGS. Sa-Se in that they all poses a foice-applying means and a foroe-sensing means. The diffet~nae is in ttte foc~ce-sensing means.
In FIGS. 5, the force-sensing means is shown as a force-sensing platform. In FIGS. 11 the force-sensing means is shown to include a load cell. The load cell 1100 may employ any of a wide variety of technologies, such as strain gage, capacitive or resistive sensing technologies, and the like. Besides the more common strain gage load calls, force sensor pads which use capacitive sensing technology ate discussed in the lioeradue by Fearing and resistive fac~ee sensing pads are available commercially by Interiink and TekScan. In FIGs.
11, the force-sensing means comprises part of the forcx-applying means: The force-sensi~pg/applying stinict<at comprises a platform 1101 which is affixed to support 1102.
Support 1102 is coanecoed to the digit tip clip 1103 by spring 1104. Force-transmitting tendon 1105 is affixed to platform 1101. Load cell 1100 is aB'vced to the digit side of platform 1101. For various masons, such as when the load cell surface is not rugged or if the load cell is tea~pastute sensitive, a proxctivdoemptratu:e insulating platform 1106 is axed bo the digit side of the load cell. When the tension in tendon 1105 is increased (FiG. l lc), platform 1101 presses on the load cell 1100 which in tur presses platform 1106 against the digit tip. The load cell measures the tension in tendon 1105 at the digit tip.
FIGS. 12a and 12b are side and plan views of a force-applying platform which is capable of pivoting to maloe the contact prrssute between the platform and the digit tip as uniform as possible. In this embodiment, platform 1200 pivots on hinge 1201 which is conn~ by support 1202 to return spring 1203, which in turn is axed to digit tip clip 1204. When tension is applyed w tendon 1205, platform 1200 contacts the digit tip and rotates on hinge 1201 to make the contact pressure uniform.
FIG. 13 is a side view of an extension of FIG. 12, with the addition that the contact pressure distribution between platform 1300 and the digit tip may be modified by adjusting the tension in tendons 1301 and 1302. If the tension in tendon 1301 is grratcr than in tendon 1302, then the digit tip will detect greatercontact force neaitr the fingernail than the bottom of the digit tip.
FIGs. 14a and 14b are the side and plan view of yet another embodiment which is used to modify the pressure distribution sensed by the digit tip. In this embodiment, platform 1400 is capable of pivoting in any direction due to the connection to support 1401 via ball joint 1402. By varying the tension in tendons 1403 and 140 . the centroid of pressure may be shifted vertically, whereas varying the tension in tendons SUBSTITUTE SHEET

~WO 91/11775 ~ ~ ~ ~ ~ ~ ~ PC'T/US91/00632 1405 and 1406, the oeatroid of pressure may be shifted laterally. By uniformly varying the tension in all oardoos, the magnitude of the pressure distribution may be changed accordingly without shifting the cent<vid. Although the embodiment provided only shows four tendons in a symmet<ic patoetn, the co<tcept obviously may be expanded to include more tendons and in more complex patterns.
FIG. 15 is a side view of an embodiment showing how the tension in the tendon may be measuczd giac to the platform cattacting the digit tip. Platform 1500 is affixed to support 1501 which is atmchod to to digit tip clip 1502 via flexible elastic m~ 1503.
10 The exxat of flexion of 1503 i: a measure of the forx appliod to platform 1500 by tends 1506 until the platform contacts the digit tip. With this capability, it can be sensed, among other things, whey the tendon is slack. In the embodiment shown, the flexion is measured via differential strain gages 1504 and 1505.
15 FIGS. 16a and 16b are side views of two more methods to measure tendon tension, and thus, fortx applied m the body part. In the embodiments provided, the oensioa is being measurod near the foreo-~atiag actuator. The same mra,stu~emont principles may be usod to sense ~cadoa tension at the force-sensing body part, for example, at a feedback glove. In FIG. 16a, tendon 1600 is wound on pulley 1601 which is in the shaft of force-20 generating actuator 1602, which in the embodiment provided is a motor The tendon passes over pulley 1603, nndGr fixed pulley 1604 and enters casing 1605.
Pulley 1603 is affixed to the free e~ of cantilever 1606, while the other end of the cantilever is anchored securely. When tendon tension is increased, pulley 1603 is displaced downward, causing the cantilever also to displace downward.. In the embodiment 25 providod, this caatil~r displacement is measuad via differential strain gages 1607 and 1608. Other displacement sensing technologies may be substituted.
FIG. 16b shows how the tendon tension may be measured by sensing the stass in the tendon casing. Tendon 1609 leaves the force-generating actuator 1610 and enters a tendon casing stress sensing sleeve 1611. This sleeve is affixed to casing support 1612 at one end, and not coanxtod to anything at the other end. At the foe end, the sleeve presses against a spacer 1613 which then passes against the main saction of the tendon casing 1614 which guides the oendon to its destination. The spacer is not connected to anything, but may rest idle on the tendon. Casing 1614 is guided and supported by structure 1615. The stress experienced by stress sensing sleeve 1611 is sensod, in the embodiment prrnrided, by differential strain gages 1616 and 1 b 17. The use of spacer 1613 and support 1615 rzducts the influence that lateral motion of casing 1614 would otherwise have on the sensod stress.

WO 91/11775 ~ ~ ~ ~ PCT/US91/00632 -FIGS. 17a and 17b are side views of two embodiments of a structure which supports both a bend sensor (e.g., the strain gage bend sensor of Kramer et aL) and a force-transmitting tendon. FIG. 17a shows a cross sectional view of an embodiment where bend sensor 1700 is in guiding pocket 1701 in support structure 1702.
The support structure is affixed in proximity do the joint whose angle is to be measured, shown in FIGS. 17a and 17b to be the PIP joint. Force-transmitting tendon 1703 is also supported over the body part by st<ucaue 1702. The tendon tray reside in a trough or pass through a hole in strucaue 1702. Structure 1702 should move in relation to the ~Y P~ ~g ~~ and may be made of a variay of materials including plastic, RTV
silicon rubber and the like.
FIG. 17b is a side view of a tendon/bend sensor support strucau~e similar to FIG.
17a but has portions of material removed 1704 from the strucaut 1705 to permit easier ~~& The shed line outlines where the bend sensor 1706 may be positioned in the support structure. Although, in both FIGs. 17a and 17b, the bend sensor is shown positioned in the support structure between tendon 1707 and the body part, other topologies may be used, such as the tendon between the bend sensor and the body part.
KGs. 18a and 18b are a perspective aad plan view of an embodiment which provides a pre-tension between a force feedback glove and the casing support wristband.
The embodiment provided is a schematic representation and a variety of details may be added to support the functional parts. ~In this embodiment, there are two pulleys mounoed on wristband 1800, one on the top 1801, one on the bottom 1802. T~ pulleys are able ~ ~s~~ ~ either direction along the axis of the forearm, optionally in a slotted guide, but arc pulled in the direction away from the glove by elastic members 1803 and 1804.
The pulleys may also be allowed to slide in a direction that is not parallel to, but has a component along the axis of the forearm The glove is reinforced on both the top 1805 and bottom 1806 (similar to top side reinforcement, but not shown). The reinforced 3p sections are connected to each other via pre-tension tendon 1807 which passes over pulley 1801, around the wrist (optionally over a bearing surface such as a series of roller bearings), and over pulley 1802. The reinforced glove sections serve to distribute the pre-tension force over the hand. The reinforcement may be extra material such as nylon, plastic or RTV silicon rubber. The wristband is strapped around the wrist at a location that places ~e elastic members in tension. The tension serves to draw the wristband toward the glove, without allowing the wristband to slide relative to the skin, and thus taking up the slack in the forearm skin so there is little motion of the wristband later when a force-transmitting tendon is placed in tension.

..~JVO 91/11775 ~ , : PhT/US91/00632 0 ~~1?~

FIG. 19 is the block diagram of a ttuoo-loop fore control system The diagram is very similar to FIG. 10 with the addition of an inner servo loop that controls the farce sensed at the output of the forx actuaooz This inner servo loop is a "fast loop" which may have a high gain to quickly adjust the force output by tlar fame actuator based on sensing the output force near the force actuator itself. A computing device 1900 which~~has knowledge of, for example, the environment, object shape, position and complance, determines a fartx set point 1901 far the control system based on additional knowledge of digit tip position which may be sensed by the Kramcr et aL strain gage bend sensors 1902 or suitable substitute. This farce set point is compared to acvual force sensed at the digit tip by a suitable sensor 1903, such as the force-sensing platform or appropriaoe load cell. The error is the force signal is input too the "slow loop" controller 1904 which may be running a standard control law. This is called the slow loop because the gain shouldn't be too high since then axe some nonlinear dynamics involved, if ~e cable force-transmission systan 1905 is employed.
The output of the slow loop contco~r is the force set point 1906 to the "fast loop"
control system. This fast loop set paint is compared to a force sensed (e.g., by the Pn~~Y ~~ sin gage cantilever 1907 of FIG. 1~ at the output of the force actuator 1908 which produces the error sigaal input for the fast loop controller 1909 which also may be running a standard control law. The gain of the fast loop may be large compared to the gain of the slow loop controller sirxe the dynamics of this loop are fairly linear and are relatively fast if a good quality servo motor were used.
Thcrtfort, the tension output of the motor can be c~trollod to a desired value very quickly, wherzas the force sensed at the digit tip cannot be servood to a desired value as quickly without increasing the possibility of oscillation due to the nonlinear transmission system.
BY aPPmPY ~~g commands to the texture array and the force applicator, innumerous sensations may be applied to the digit tip. For example, by extending thrte texture elements along a single column and then actuating the force platform to pass against the digit tip, the sensation of touching the digit tip to the vertical edge of a virtual object is simulated. If the thrcc extended texturt elements of the column are reaacted at the same time that the three elements of the adjacent column arc raised,, a sensation that the object edge is moving across the digit tip will be produced. This sensation may be used either when an objxt edge is moving and the digit tip is rtmaining stationary, or when the object position is fixed and the digit tip is moving across the edge. With appropriate modifications, force and texture may be simulated at ocher parts of the body besides the digit tip, such as is shown for the arm in FIG. 2c.

WO 91/11775 ~ PCT/US91/00632 --While the invention has been desa~od with refaeuee to specific embodiments, the description is illustrative of the invention and is not to be construed as limiting the invention. Thus, various modifications and amplifications may occur to those skilled in the art without departing foam the true spirit and scope of the invention as defined by the appended claims.

Claims (38)

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

1. A device for attachment to a body comprising a sensing body part connected to a second body part, said device producing a sensing signal at said sensing body part and comprising means for generating a force, said device further comprising at least one of the following:

(a) means for applying said generated force between said sensing body part and said second body part which serves as a non-sensing part;
(b) means for applying said generated force to said sensing body part, said applying means comprising a touching entity displaced from said sensing body part in a first unactivated position and touching said sensing body part in a second activated position;
(c) means for applying said generated force to produce a displacement of one or a plurality of texture elements, each texture element comprising an extendable and retractable pin or a focused fluid stream; and (d) means for applying said generated force to a sensing body part accomplished by at least one elongated element guided by an element guide over the surface of the body across a joint, which joint is acted upon as a result of said generated force applied to said elongated element.

2. A device according to Claim 1, said force-generating means comprising:
force actuating means;
transmitting means for transmitting force from said actuating means to at least one of said applying means, said transmitting means comprising:
at least one second flexible elongated element; and a second element guidefor guiding each said second flexible elongated element.

3. A device according to Claim 1, wherein said elongated element of part (d) is flexible and comprises a tendon or a fluid.

4. A device according to Claim 1, wherein said force generating means is a motor or solenoid.

5. A device for attachment to a body comprising a sensing body part, said device producing a sensing signal at said sensing body part according to Claim 1 and comprising means for generating a force, said device further comprising:
means for applying said generated force to said sensing body part, said applying means comprising a force-sensing element.

6. A device for attachment to a body comprising a sensing body part connected to a second body part, said device producing a sensing signal at said sensing body part and comprising means for generating a force, said device further comprising:
means for applying said generated force between said sensing body part and said second body part which serves as a non-sensing part.

7. A device for attachment to a body comprising a sensing body part, said device producing a sensing signal at said sensing body part and comprising means for generating a force, said device further comprising:
means for applying said generated force to said sensing body part, said applying means comprising an touching entity displaced from said sensing body part in a first unactivated position and touching said sensing body part in a second activated position.

8. A device according to Claim 7, said touching entity comprising a force-applying platform;
a supporting structure fog holding said force-applying platform in operative relation to said sensing body part; and retractable means for holding said force-applying platform in said first position.

9. A device for attachment to a body comprising a sensing body part, said device producing a sensing signal at said sensing body part and comprising means for generating a force, said device further comprising:
means for applying said generated force to said sensing body part, said applying means comprising a force-sensing element in proximity to said sensing body part.

10. A device according to Claim 9, wherein said force-sensing element comprises:
a force-sensing platform;
a force-applying platform;
a fulcrum mounted on said force-applying platform and supporting said force-sensing platform; and mechanical means connecting said force-sensing platform to said force-generating means, wherein actuation of said force-sensing platform by said generated force moves said force-applying platform into contact with said sensing body part.

11. A device for attachment to a body comprising a sensing body part, said device producing a sensing signal at said sensing body part and comprising means for generating a force, said device further comprising:
means for applying said generated force to produce a displacement of one or a plurality of texture elements, each texture element comprising an extendable and retractable pin or a focused fluid stream;
and means for holding said texture elements in operative relation to said sensing body part.

12. A device according to Claim 11, wherein said texture elements) is a 3 x 3 array of texture elements.

13. A device for attachment to a body comprising a sensing body part, said device producing a sensing signal at said sensing body part and comprising first and second force-generating means, said device further comprising:
means for applying said first generated force to said sensing body part, said applying means comprising a touching entity displaced from said sensing body part in a first unactivated position and touching said sensing body part in a second activated position; and means for applying said second generated force to produce a displacement of one or a plurality of texture elements, each texture element comprising an extendable and retractable pin or a focused fluid stream.

14. A device according to Claim 13, said applying means further comprising a force-sensing element.

15. A device according to Claim 13, wherein said applying means for said first generated force comprises:

transmitting means having the following components:
at least one flexible elongated element, said elongated element comprising a tendon or a fluid; and an element guide for guiding each said elongated element.

16. A device according to Claim 15, wherein said means for applying said second generated force comprises:
a force-applying platform including at least one texture element;
means for holding said force-applying platform in operative relation to said sensing body part;
retractable means for holding said force-applying platform in said first unactivated position;
a force-sensing platform;
a fulcrum mounted on said force-applying platform and supporting said force-sensing platform; and mechanical means connecting said force-sensing platform to said force-generating means, wherein actuation of said force-sensing platform by said generated force moves said force-applying platform into contact with said sensing body part.

17. A device for attachment to a body comprising a sensing body part, said device producing a sensing signal at said sensing body part and comprising means for generating a force, said device further comprising:
means for applying said generated force to said sensing body part by means of at least one elongated element guided by an element guide over the surface of the body across a joint, which joint is acted upon as a result of said generated force applied to said elongated element.

18. A device according to any of claims 1 to 17, further comprising at least one of:
(a) said sensing body part is a digit part;
(b) in claims 7 to 17 said sensing body part is connected to a second body part which serves as a non-sensing part;
(c) When said device comprises a second body part, said second body part comprises a wrist or is proximate to a wrist and forearm:
(d) a glove support structure supporting a means for applying said generated force; or said device operates with a controlling body part, wherein said device further comprises means for sensing position of said controlling body part and producing a controlling signal related to said position of said controlling body part; and signal collection producing means for receiving said controlling signal and actuating said generating means to produce said force in relation to said controlling signal; or (e) said sensing signal and said means for generating a force simulate an interaction between an interactive entity and a virtual or physical object.

19. A device according to claim 18, wherein said device comprises d) ii and e), and said signal collection and producing means further controls the interaction between said interactive entity and said virtual or physical object in relation to said controlling signal.

20. A device according to claim 18, wherein said device comprises e) and said means for generating a force simulates the contact force of said interactive entity interacting with said virtual or physical object.

21. A device according to claim 18, wherein said device comprises e) and said means for generating a force produces a surface pattern simulating a surface of said virtual or physical object.

22. A device for attachment to a body comprising, a controlling digit part and a sensing digit part connected to a second body part, said device producing a sensing signal at said sensing digit part and including means for generating a force;
a support for attaching to said digit part;
means for applying said generated force between said sensing digit part and said second body part which serves as a non-sensing part, said means for applying said generated force supported by said support;
means for sensing position of said controlling digit part and producing a controlling signal related to said position of said controlling digit part; and signal collection and producing means for receiving said controlling signal and actuating said generating means to produce said force in relation to said controlling signal.

23. A device according to Claim 22, wherein said support is a glove, said digit part is the digit tip, said force-generating means comprising a flexible elongated element and a housing for guiding said elongated element, and further comprising:
an element guide attached to said glove for directing said elongated element;
a wriststrap; and said housing attached at one end to said wriststrap and at the other end attached proximal to said force-generating means.

24. A device according to Claim 23, wherein said applying means comprises:
a force-applying platform movable from a first unactivated position to a second activated position in contact with said digit tip;
a supporting structure for holding said force applying platform in operative relation to said digit tip;
retractable means for holding said force-applying platform in said first position;
a force-sensing platform;
a fulcrum mounted on said force-applying platform and supporting said force-sensing platform; and mechanical means connecting said force-sensing platform to said force-generating means, wherein actuation of said force-sensing platform by said generated force moves said force-applying platform into contact with said sensing digit part.

25. A device for applying a force between first and second portions of an animate body, said device comprising:
first and second link assemblies associated with said first and second portions, respectively, each link assembly comprising:
a supporting section secured in position on a portion, each supporting section being a supporting link;
an articulated link attached through a joint to each of said supporting links and wherein each of said articulated links is attached to each other through a pivot joint;

a tendon extending through a casing and attached to a link in said first link assembly, with said casing attached to a link in said second link assembly;
whereby the tendon applies a force between the supporting sections resulting in applying a force between said first and second portions of said animate body.

26. A device according to Claim 25, wherein said casing is attached to the supporting section of said first link assembly.

27. A device according to Claim 26, wherein said tendon is attached to the supporting section of said second link assembly.

28. A device according to Claim 26, wherein said tendon is attached to the articulated link of said second link assembly.

29. A device according to Claim 25, wherein said casing is attached to the articulated link of said first link assembly.

30. A device according to Claim 29, wherein said tendon is attached to the supporting section of said second link assembly.

31. A device according to Claim 29, wherein said tendon is attached to the articulated link of said second link assembly.

32. A device according to Claim 25, further comprising a goniometer in functional relationship with a joint.

33. A device according to Claim 25, further comprising a force-generating means attached to said tendon for generating a force between the link-attached end of said tendon and said casing.

34. A device for applying a force between first and second portions of an animate body, said device comprising:
first and second link assemblies associated with said first and second portions, respectively, each link assembly comprising:
a supporting section secured in position on a portion, each supporting section being a supporting link;
an articulated link attached through a joint to each of said supporting links and wherein each of said articulated links is attached to each other through a pivot joint, with said articulated link of said first assembly extending beyond said pivot joint;
first and second tendons extending through first and second casings, respectively, each of said tendons attached to a link in said first link assembly, with each of said casings attached to a link in said second link assembly, wherein one of said tendons is attached beyond the pivot joint to said articulated link in said first assembly and the other tendon is attached to the link assembly on the other side of said pivot joint;
whereby each tendon applies a force between said first and second supporting sections resulting in applying a force between said first and second portions of said animate body.

35. A device according to Claim 34, further comprising a goniometer in functional relationship with a joint.

36. A device according to Claim 34, further comprising a force-generating means attached to a tendon for generating a force between the link-attached end of said tendon and associated casing.

37. A device according to claims 25 or 34, wherein said animate body is a hand.

38. A device for applying a force between first and second portions of a hand, one of said portions being a phalanx, said device comprising:
first and second link assemblies associated with said first and second portions, respectively, each link assembly comprising:
a supporting section secured in position on a portion, each supporting section being a supporting link;
an articulated link attached through a joint to each of said supporting links and wherein each of said articulated links is attached to each other through a pivot joint, with said articulated link of said first assembly extending beyond said pivot joint;
first and second tendons extending through first and second casings, respectively, said first and second casings attached to said second articulated link and said first and second tendons attached to said first articulated link on opposite sides of said pivot joint;
whereby each tendon applies a force between said first and second supporting sections resulting in applying a force between said first and second portions.