CA1189163A

CA1189163A - Tactile sensor

Info

Publication number: CA1189163A
Application number: CA000422643A
Authority: CA
Inventors: Jack Rebman
Original assignee: Lord Corp
Current assignee: Lord Corp
Priority date: 1982-03-01
Filing date: 1983-03-01
Publication date: 1985-06-18
Also published as: JPS58192790A; GB2115935B; DE3307012A1; IT8347822A0; GB2115935A; FR2522407B1; DE3307112C2; US4521685A; IT1170305B; FR2522407A1; DE3307112A1; GB8305096D0

Abstract

Abstract A tactile sensing system is provided which consists of essentially four components including a touch surface having a plurality of mechanically and electrically isolated sensitive sites, transducer means associated with each of the sensitive sites for converting a mechanical response to an electrical signal, first signal processing means for scanning the signals produced by the transducer means and converting such signals to digital format, and second signal processing means including a computer for interpreting and displaying the data. The system of this invention is capable of providing high contrast, high normal load resolution, moderate spatial resolution and high sensitivity to determine such mechanical contact parameters as presence, pressure, pressure pattern, texture, hardness and topography of an object contacting the touch surface. In addition, separate means are included enabling the system to detect the location, magnitude and direction of shear forces applied to the touch surface.

Description

i3 Field of the Invention This invention relates to the field of tactile sensing, and, more parti.cularly, to a device capable of detect-ing, discriminating and recogniziny a number of mechanical contact phenomena including presence7 pressure, pressure pattern, incipient slip, slip, texture, hardness, and topo-graphy.
Bacqround of the Invention Many areas have been identified where it is desirable to have an artificial sense of touch~ The most commonly mentioned applications include the field of automation7 partic-ularly industrial robotry9 tele-operation as employed in remote manipulation underwater, in spacecraft, or with extra-terrestrial landing vehicles9 and also in the field of pros-thetic de~ices for amputees or those handicapped with loss of nerve function. In all of these applications9 information about an object being contacted or manipulated is necessary to make a characterization of the object such as size, shape, weight, orientation and other contact aspects 9 and then based on such characterization computer-controlled decisions can be made such as properly grasping~ moving, manipulating9 placing - and releasing the object7 Considering the area of industrial robotry9 which appears to be a particularly good candidate for devices having tactile sensing capability9 it is estimated that approximately 75% of the manufacturing conducted in the United States is low volume o~ batch operations performed by manual labor and accounting for approximately 30% of the gross national product.

Machine replacemen-t of human labor in a-t least a portion of such activities can result in improved accuracy, quality, speed, safety, efficiency and economy. It has been estimated that the cost of human labor in only the last decade has in-creased at a rate of more than five times the cost of robotic labor. In addition, this estimate does not take into consider-ation that robots can operate machine tools, for example, with a repeatable precision that may take a human worker many years to acquire. Manufacturing operations which potentially could be accomplished by devices having tactile sensing capabilities include assembly, fast adaptive grasping or the pick-up of randomly oriented parts from assembly lines, bin picking, grinding, deburring, polishing and welding among othersO
Tactile .sensing systems have been introduced in recent years but generally have met with little success and are of limited practical utility. For example, typical prior art tactile sensing systems include-U~ S. Patent No~ 4,014,217 to La~asse et al. The tactile pick-up system of Laqasse et al includes a continuous outer layer of material which has a variable electrical conductivity as a function of its state of compression. A matrix of measurin~ electrodes mounted to the layer of variable electric conductivity are operable to measure the electric field produced by compression of the layer in response to contact with an object. In this design, the continuous outer layer itself is electrically responsive to force exerted by contact with an object~ When compressed, the elec-trical conductivity of the layer is altered at and adjacent to the point of contact and this chanqed condition is detected by the electrodes.

- 2 -~39~

One problem of the Lagasse e~ al design is low contrast caused by the continuous nature of the pressure-sensing electrically conductive outer layer. While placement of an object on the outer layer will cause it to deflect and thus change the electrical conductivity of the layer immed-i.~tely beneath the object, ;uch deflection cannot be confined or iso]ated to the llmited area of the object's dimensions.
This is true because portions of the outer layer immediately 1 adjacent those port:ions contacting the object must also be J
deflected or compressed at least to some degree by the object.
The compression of adjoining or contiguous portions of the I
layer causes a current to be conducted there which is sensed by 1 the electrodes. Therefore, instead of sensIng current only at , those locations along the ollter layer where an object actually .
makes contact, prior art de~lces such as Lagasse et al tend to l produce false or incorrect signals from adjacent areas result-ing in relatively low resolution or inaccurate characterization of an object's presence, I~ressure, size, shape and similar i contact parameters. To the extent that such false signals or L
"cross-talk" may be circu~vented in Lagasse et 21, complex pattern recognition systems would be required.
For purposes of discussing the prior art and also the structure and advantages of this invention, the term contrast will be used in reference to the extent which a tactile sensing ~
system is capable of sensirg the boundaries of an object con- i tactin~ the scnsitive surface of the device. The term resolu- 1 tion will refer to the minimum change in load that can be detected, both in terms of the magnitude and location of such 1 load on the sensing surface. Therefore, in describing a tactile sensing system having high or low contrast, for e~

ample, such terms may be considered as an indication of the i3 system's ability or inability to accurately characterize the boundaries of an object contacting the sensing surface of the device.
~ tactile sensing system is also known in the art and which is similar to the ~ e et al system in that a layer or sheet of material is disposed over an array or matrix of measuring electrodes which are operable to produce a signal in response to contact of an ob~ect with the surface of the layer. ~ sheet of pressure sensitive conductive plastic forms the layer and the resistivity of the sheet changes in a known manner as a function of its deformation.
The array or matrix of measuring electrodes senses such change in resistivity and relays that information to electrical com-ponents for processing. For the same reasons as discussed in connection with the ~ et al patent, this approach suffers from a limited resolution capability since it is difficult to localize or isolate the strain imposed by con-tact with an object to be sensed to a limited area where a continuous sensing surface is utilized.
Additionally, a common limitation of the overlayer material used in the prior art is that such material is not rugged in construction and may be susceptible to failure particularly in the harsh environment found in many manufactur-ing operations. A cut, abrasion or other surface irregularity could easily alter the conductive or resistive properties of the outer layers in the known prior art. Since the sensing capability of these known systems is dependent on the integrity of the outer layer, which layer accomplishes the actual sensing function, it is axiomatic that change to the layer would render the entire system inoperableO More-over, electrically conductive or resistive elastomers or - 4 _ other polymers generally exhibit poor hysterisis, e~cessive set and poor mechanical strengtt1. All of these phvsical properties make such materials undesir~ble for use in many tactile sensing applications.
It has therefore been an object of ~his invention to provide a tactile sensing system which is capable of high contrast sensing of the magnitude and location of the deflec-tion caused by contact of an objec~ to be manipulated with the sensing surface of the system.
It is another object herein to provide a tactile sensing system capable of sensing parameters when contacting an object such as presence, pressure, size, shape, location and orientation among others.
It is a further object to provide a tactile sensing system havin~ the dual capability of sensing shear and normal loads imposed by contact with an object.
Another object herein is to provide a tactile sensing system having the combination of high contrast normal force detecting capability and separate moderate resolution shear force detecting capabilityO
It is still another object to provide a tactile sensing system having a touch surface with individual sensing means for contacting an object which are separate from one another and e~hibit little or no deflection ~hen adjacent sensin~ means contact an o})ject.
It is a still further object herein to provide a touch sur~ace oi- rugged ~onstruction which acts to transfer load in the form of mect~anical movement for meas~rement by sensing means.
It is another object of the invention ~o provide a sensing .system having a touch surface with sensitive sites c -5- _ .... .. ~

whose compliance may be controlled through material choice and/or geometrical configuration for varying the response of such sites to deflection by contact with an object.
Summar~ of the Inven-tion _ These objectives are accomplished, from a broad aspect of -the present invention, by providing a device for sensing contact parameters of an object, which device com~
prises a touch surface for contacti.ng the object. Mounting means is also provided for mounting the touch surface for substantially translational lateral movement in response to a shear force imposed thereon by contact with the object. A
plurality of sensitive sites are disposed in an array on the touch surface. The sensitive sites undergo a mechanical response to a normal force imposed thereon by contact with the object. Transducer means is associated with each of the sensitive sites. The transducer means includes magnetic means capable of producing a magnetic field and electro-magnetic sensing means operable to sense the intensity of the magnetic field produced by the magnetic means. Electro-magnetic sensing means is adapted to be disposed relative tothe magnetic means so that the mechanical response of the sensitive sites upon contact with an object causes a propor-tional change in the proximity and therefore intensity of the magnetic field sensed by the electromagnetic sensing means. The electromagnetic sensing means is operable to produce an electrical signal proportional to the change in intensity of the magnetic field. Signal processing means is operable to recei.ve the electrical signals from the electro-magnetic sensing means of the transducer means and provide information ident..ifying the contact parameters of the object.

According to a further broad aspect of the inven-tion, there is provided a tactile sensor device for sensing .~. - 6 -contac-t parameters of objects. The device comprises a -touch responsive rnember having an array of sensitive sites on an outer surface thereof. The surface of the member is engage-able with the objects. The sites are deflectable inwardly suhstantiaLly independently of each other in response to the imposition thereon of normaL forces produced by the engage-mentv A base member is also provided. Mounting means mounts the touch responsive member for substaIItially translational movement thereof generaLly paralle:L to the plane of the surface thereof in response to the imposi-tion thereon of shear forces produced by the said engagement. Transducer means is provided for sensing, and for producing data signal.s representative of, the deflection of the sites.
In one embodiment of the invention, this combination of components is operable to sense the deflection of the touch surface in response to normal forces induced by an object contacting the touch surface, and to ana;Lyze the magnitude and location of such deflection to determine such contact parameters as presence, pressure, pressure pattern, texture, hardness and topography of the object.
As discussed in detail below, an object placed on or against the touch surface of the tactile sensing sys-tem herein contacts a number of sensitive sites depending on the object's size, and causes such sensitive sites to deflect. The extent of this deflection or mechanicaL response is sensed by indivi-duaL transducer means associated with each of the sensitive sites, and an ana:Log signal is produced by each transducer means. The anaLoq signaLs are placed in digital format by circuitry located adjacent the transducer in a manner described below. The digit~L signals are then sent to external signaL
processing means including a computer where they are inter-preted and expressed on a visual display or other means to - 6a --indicate various mechanical contact parameters of the ob~ect as mentloned above.
In a further embodiment of thls invention, shear detection transducer means may be added to the tactile sensing system to detect with at least moderate contrast, the magnitude, location and direction of the shear force applied to the touch surface by an object. This provides the tactile sensing system herein with the additional capabilities needed to detect slip and incipient slip of an object contacting the touch surface~
Description of_the Drawinqs The structure, operation and advantages of this invention will become apparent upon consideration of the following discussion taken in conjunction with the accompanying drawings, wherein Figure 1 is a plan view of the tactile sensing system of the invention showing the touch surface and array of sensi-tive sites.
Figure 2 is a partial cross-sectional view in full elevation of the tactile sensing system taken generally along line 2-2 of Figure 1.
Figure 3 is an enlarged partial cross sectional view of one embodiment of the transducer means herein associated with a sensitive site in an undeflected position~
Figure 3a is a partlal view of the transducer means of Figure 3 with the sensitive site in a deflected position.
Figure 4 is a partial cross-sectional view of an alternate embodiment of the transducer means herein with the sensitive site in an undeflected position.
Figure 4a is a partial view of the transducer means of Figure 4 with the sensitive site in a deflected position.

~ -7-Figure 5 is a partial cross-sectional view of a still further embodlment of the transducer means with the sensitive site being in an undeflected position~
Figure 5a is a partial view of the transducer means of Figure 5 with the sensitive site in a deflected position.
Figure 6 is a view in partial cross-section taken generally along line 6-6 in Figure 2 of one embodiment of the shear detection transducer means herein~ with the touch surface being in a normal posi~ion.
Figure 6a is a view of the shear detection transducer means of Figure 6 with a shear force Sl acting on the touch surface.
Figure 6b is another view of Figure 6 shear detection transducer means with a shear force S2, perpendicular to Sl, acting on the touch surface.
Figure 7 is a view in partial cross-section of another embodiment of~the shear detection transducer means herein.
Figure 7a is a view of one foxm of the shear detec-tion transducer means of Figure 7 taken generally along line7a-7a thereof.
Figure 7b is a view of another form of Figure 7 shear detection transducer means taken along line 7a-7a of Figure 7.
Figure 8 is a ~iew in partial cross-section of a furthex embodiment of the shear detection transducer means.
Figure 8a is a view of the shear detection transducer means of Figure 8 taken gerlerally along line 8a-8a thereof.
Figure 9 is a still further embodiment of the shear detection transducer means of the invention~

~8-Figure 9a i9 a partial view of the Figure 9 emkodiment) taken generally along the line 9a-9a in Figure 9.
Figure 10 is a schematic view of the localized and remote data processing means herein.
Descr_~tion of the Inventio_ Referring now to the drawings and in particular to Figures 1 and 2, the tactile sensing system of this invention is labeled yenerally with the reference numeral 11. As mentioned above, the system 11 consists of essentially four componsnts including a touch surface having an array of sensi~
tive sites ? transducer means for detecting normal load9 local signal processing means and remote signal processing means.
Additionally, the system 11 may include separate shear detec-tion transducer means for ~roviding the cap~bility needed to detect such contact prameters as slip and incipient slipo Specifically, system 11 includes a top plate 12 and a support plate 13 which are secured together and formed with sixty-four chamfered openings 15 disposed in a matrix confi guration of eight rows and eight columns. It should be understood that while an 8 x 8 array is shown in Eigure 1, other matrices could be utilized depending on the space and size requirements of a particular application. A touch surface is provided, labeled generally with the reference 17, and it includes sensitive sites 19 disposed in a matrix configuration corresponding to that of the openings 15 in plates 12 and 13.
The touch surface 17 is a unitaxy element formed of resilient material such as elastomer or a ~uitable functional equivalent, which is rugged in construction and capable o-f withstanding harsh environments without appxeciable damage or deterioration.

_g_ ¦¦ ¦r Each of the sensitive sites l9 includes a raised section ~~0 of resilient mcl~erial which e~tends upwardly from the remainder of the touch surface 17. Integrally connected to each o~ the raised sections 20 is a pin structure 21 which ~, extends downwardly through the openings 15 in support pla~es 12 ~
and 13. The diameter of the pin structure 21 is less ~han that 'i of the raised section 20 forming an annular hollow section 22 ~, between the pin structure 21 and the adjacent opening in support plate 13. Once in place with all of the pin structures ¦~
21 in openings 15, the touch surface 17 is secured to top plate 12 by adhesives or any other sui-table means. j Each of the sensi~ive si~es 19 is resilient so that Is they undergo a vertical de~lection in response to the applica- ' tion of a normal force to the raised section 20, as would occur i~
for example when an object is placed on the touch surface 17.
Each of the sensitive sit~s l9 whioh the object cont~cts are b deflected downwardly, whic~, in turn, causes the pin structure ,3 21 of those affected sensitive sites l9 to move downwardly. ji For purposes of the present discussion 7 this deflection will be 1~1 called the mechanical response to the application of a normal force to the touch surface 17. The remainder of the components of system 11 include rneans of sensing this mechanical response, producing electrical signals as a measure of the existence, location and magnitude of the response, and then processing such signals so lhat contact parameters of the object causing the mechanical response can be interpreted and identified.
A base section 23 is disposed beneath plate 13 and is connected thereto by compliant mounts 25 attached at each of the four corners of the base 23 and plate 13~ The mounts 25 are moderately compliant in 5hear and relatively stiff in compression, thus permittin~ motion of the plate 13 relati~e to l -10-the base section 23 along ~ horizontal plane parallel to the plane of the plate 13 ! but very little motion of the plate 13 vertically with respect to base section 23. A transducer platform 27 disposed beneath the p.late 13y and an electronics platform 29 disposed between the transducer platform 27 and base Z3, are connected together and to the plate 13 by means of bolts 31 or other suitable structu:ral supports. Therefore, the platforms 27 and 29 are movable with the plate 13 as a unit relative to the fixed base section 23.
As mentioned above, an object placed on a sensitive site 19 will cause the pin structure 21 to deflect vertically downwardly~ The magnitude of such deflection or mechanical response is directly proportional to the weight of the object or the magnitude of the normal force applied. This mechanical response is measured by a plurality of transducers mounted to the transducer platform 27 in an array or matrix corresponding to that o~ the sensitive-sites--l9--so that each pin structure 21 is provided with an individual transducer~
In the embodiment of the invention shown in Figures 1-3j the pin structure 21 is essentially continuous~ except for an opening or window 35 formed at a discrete location along the length thereof. The transducers of this embodiment~
labeled generally with the reference 39, consist of a photo emitter 41 operable to produce a beam of light through a lens apertu.re 43 and a photo detector 45 which is capable of detect-ing the amount and intensity of light produced by the emitter 41. The detector 45 and emitter 43 are mounted to the trans~
ducer platform 27 such that the pin structure 21 extends in the gap 40 formecl therebetween. In an undeflected~ unloaded position as shown in Figure 3, the lowermost portion of pin structure 21 blo~ks the passage of light between the emitter 41 and detector X

3 w~_ , ;
,¦ 43. Ilowever, as the pin structure 21 moves downwardly in . response to contact of an Gbj~ct placed on the touch surface ; 17, the window 35 in pin structure 7~ moves in the path of the ~
light beam produced by emitter 41 allowing an amount of light .
directly propor~ional to the magnitude of the deflection D, for ~
example, to be detected by detector 43. See Figure 3a. In i turn, the detector 43 produces a signal which is directly , proportional to the intensity of light it senses, which signal i i is sent to the local electronic circuitry for processing as I discussed below. This method of detecting the mechanical response of the touch surface 17 may be termed interrupted l Il light transduction~ i l A second type of transduction means is shown in Figures 4 and 4a in which a transducer 50 is shown in combin-ation with a modified pin structure 51. In this embodiment, the bottom of pin structure 51 is formed with a reflecti~e ~
surface 53. Mounted side-by-side on the transducer platform 27 i, directly beneath the mirr~r 53 of pin structure 51 are a photo-emitter 55 and photo-detector 57. The emitter 55 is operable to produce a light beam, and the detector 57 produces .
a signal directly proportional to the intensity of light which i~ senses.
In an undeflected position, as shown in Figure 4, the mirror 53 is disposed a relatively large distance away from the ,.
emitter 55 so that a nomincll amount of light is reflected by the mirror 53 and detected ~y the detector 57. Downward rnotion of the pin structure 21 in response to contact of an object !~
placed on the touch surface 17, as shown in Figure 4a, causes the intensity of :Light reflected back bv the mirror 53 to the detector 57 to be increased in direct proportion to the proxim- ~
ity of the mirror 53. T~is method of transduction may be ¦
-12- ~

3 ~__ termed, for purposes of this discussion, reflected light transduction. -¦i A third embodiment of the transduction means for sensing the mechanical recponse of the touch surface 17 to , contact of an object placec thereon is shown in Fig~lres S and 6 Sa. A plurality of Hall e~fect txansducers 59 are mounted to ;
the transducer platform 2' ir~ediately beneath each of the -sensltive sites 19. Each of the sensi~ive sites 19 are formed with a pin structure 61 hav:Lng a magnet 63 attached or embedded i in its lower end adjacent ~he Hall effect transducers 59. As i noted above, the pin structure 61 moves downwardly in response c to a normal force applied by an object placed on the touch surface 17. The Hall effec~ transducer 59 is operable to sense the intensity of the magnetic field produced by the magnet 63 ;' er~bedded in the pin structure 61 in an undeflected or deflected .
position as shown in Figures 5 and 5a. The intensity of the magnetic field detected by the Hall efect ~ransducer 5~ is directly proportional to the pro~imity of the magnet 63, and, ~
in turn, the magnltude of the normal force applied to the touch ,, surface 17 which controls the relative position of the magnet t 63~
The transducers described above function to sense the mechanical response of the touch surface 17 to a normal load applied thereto clue to contact with an object. As discussed below, signals produced by the transducers are processed in J
both local and remote electronic circuitry to produce a visual display or written indicia of so-called rnechanical contact~
phenomena or parameters for an object. Such contact parameters~
include presence, pressure, texture, hardness and topography or shape among others. If the system 11 was adapted with the hand or grasping portion of an arm in an industrial robot, for 11 1'`

example, the mechanical contact parameters or information I L
provided by the invention would enable the robot to properly characterize the object so 1:hat decisions could be made about grasping, moving, manipulating, placing, releasing or otherwise h~ndl ing the object.
Particularly with respect to normal loading, the ~ystem ll is capable of providing high contrast or well defined characterization of an objeCt it contacts, high resolution of the magnitude of the normal load produced by such contact and at least moderate resolution of the shape or contour of the !
object. This is due primarily to the fact that normal loads imposed by an object contacting the touch surface 17 create a deflection of only those individual sensitiue sites l9 located .
immediately beneath the object, and this deflection or mechan~
ical response is sensed by separate transducer means associated with each affected sensitiv~ site l9. Due to the presence of plates 12 and 13 and the co~npartmentalized construction o the .
sensitive sites l9, normal loads applied by an object to the t touch surface 17 cause lit1:1e or no detectable deflection in i sensitive sites l9 which ~re no~ directly under load. In addition to this mechanical isolation of adjacent sensitive sites 19, the provision of ~ach sensitive site 19 with separate ' transducer means effectively isolates the electronic aspect of the transduction rneans herein preventing cross-talk and avoid-ing the need for complex pattern recognition systems. As a result, the co~figuration of this invention has been found to 7 provide much better contrast than prior art tactile sensors in ~
which a continuous touch surface is electrically responsive to I
contact with an object~ i Other advantages are inherent in the construction of the sensitive sites 19 of touch surface 17 which adds to the i 3 ~

¦ v satility of ystem ll. In the fig-lre the sens1tive sites 19 are shown having a frusto-conical shaped raised section 20 ~ith an annular hollow section 22 bet~Jeen the pin structure 21 and openings 15 in plates 12 and 13. Two factors affect the amount of deflection which a sensitive site 19 undergoes under the application of a given Load. These factors are the geomet-rical configuration of the sensitive site l9 and the type of material used to fabricate such site 19. Considered together, these factors determine th- compliance of the sensitive site 19. The compliance of a sensitive site may be altered, then, by changing the geometry of the sensitive site and/or using an elastomeric material of lower or higher modulus of elasticity.
The capability cf altering the compliance of the sensitive sites 19 is a valuable advantage of this invention over prior art devices because it allows the deflection and force sensitivity requirements of different applications to be accommodated equally well with a single system ll.
For example, assume that the system ll is to be utilized in a gripper hand for an industrial robot. Also assume that a heavy object is to be manipulated which will initially require a large grasping force to lift, and then recognition of the surface of the object is needed for proper handling and placement. ]n this application, the system ll would preferably provide relatively low sensitivity or resolu-tion up to the force required to lift the object, but high sensitivity at higher loadc so that the contours of the object could be detected.
To accommodate t~is requirement, the geometry of the scnsitive site 19 or the modulus of the material used to fabricate it could be alte~ed to produce minimal deflection of the pin structure 21, for example, up to the load imposed by the weight of the object, and then increased deflection in the pin structure 21 for forces of higher magnitude. As discussed above, the transducer means herein sense the deflection of the pin structure 21 and produce a siqnal directly proportional to such deflection. Minimum downward movement of the pin struc-ture 21 would produce a correspondin~ly minimal change in the signal produced by the transducer means. In the example above, the system 11 would thus provide low sensitivity in response to such minimal movements of the pin structure 21. However, AS
the pin structure 21 moves downwardly to a greater extent due to the increased load applied beyond the weight of the object, a correspondingly higher change in the signal is produced by the transducer means. Thus, the system 11 provides high sensitivity at such higher loads~
In another instance, it may be desirable to provide system 11 with a high sersitivity or resolution under rel~-tively small loading conditions, and then lesser sensitivity under lighter loads. The manipulation and characterization of lightweight objects or lightweight and heavyweight objects by a single device could fall into this category. The geometry of a sensitive site 19 could be altered by reducing the thickness of the elastomer in the raise~ section 20 so that rapid downward deflection of pin structu]-e 21 would occur under relatively small loads until the raised section 20 snubbed against the top plate 12, at which time minimal further deflection would occur.
The tran~ducer means wou]d thus detect a relatively larse change in deflection of pin structure 21 under small loads and producc a proportional change in their signal transmitted to the electronic circuitry. The system 11 would thus achieve high sensitivity under such loading conditions. However, once the raised section 20 snubbed out, only minimal deflection of -16~

`I 1-.' l pin structure 21 would occur and the sensitivity of the system ll would be relatively low.
'rhe various geome-trical and material variations, or ¦ ;
combinations of the t~70, in forming the sensitive sites 19 provide a wide range of options in obtaining a linear or various non-linear responses to t:he deflection of the pin structure 21 caused by contact of an object with the touch sur~ace o~ tne tactiLe se..sing systeJn ll. The sensitivity to the magnitude of nor~al loads applied to the system 11 may thus ;j be altered, as desired, to accommodate the requirements of a variety of applications.
In some instances, it may be desirable to detect shear forces applied by an object to the touch surface ll. For example, a robot arm may be required to grasp an object, J
recognize its configuration and then manipulate the object in ~' some manner such as by twisting or turning it prior to release.
While the detection of the normal forces will still be required for such an application to determine the presence, size and shape of the object, the ;hear forces developed between the object and the touch surface 17 of the system must be deter- i mined to detect incipient slip and slip as the object is being clamped, Iifted and then maripulated. 1 Another feature of the construction of sensitive ~
sites l9 should be noted in connection with the application of i shear forces to the touch surface 17. As shown in the figures, the pin structure of each sensitive site l9 is elongated and e~tends downwardly through the openings 15 formed in plates 12 J
and 13 n rrhe relatively close fit between the pin strucutures and opening 15 has the efiect of essentially eliminating any cocking motion of the base of the pin structures which could otherwise occur due to l~teral components of shear forces , ~8~

applied to the touch surface 17. Such cocking motion, if not eliminated, could adversely affect the accuracy of measurements of the pin struct-lre deflection taXen by the various transducer means disclosed herein. Therefore, the means for detection of !~
normal and shear loads is effectively decoupled with the construction of sensitive sltes ]9 :in accordance with this i!
invention. ;
Referring now to Figures 2 and 6a-b, one embodiment of the shear load letection transducer means of the system 11 ~
is shown. A pair of brackets 71 are mounted at either end of ,, the base section 23 and extend upwardly toward the plate 13. A ~
flange 73 is formed at the upper end of eaçh bracket 71 which t extends inwardly between a photo emitter ';5 mounted on the , lower surface of plate 13 near the middle and an array of photo , detectors ar~ mounted on the upper surface of the transducer platform 27 below the photo emitter 75. As shown in Figure 6, i there are four photo detectors, 79a, b/ c and d, disposed at i equal intervals apart. ~lthough four photo detectors are i shown, it should be underst~od that as little as two detectors or more could be utilized to accomplish the shear detection r concept described herein. ~ window 81 is formed in each of the .
flanges 73 to permit light ~rom the emitter 75 to be sensed by i the detectors 79a-d. 1, In the undeflected position, essentially all of the ¦j light produced by the emitters 75 passes through the window 81 in flanges 73, and is sense~ by the detectors 79a d. Assuming ¦1 a shear load Sl is applied ~o the touch surface 17 as shown in ¦ t ~igure 6a, the plate 13 and transducer platform 27 will move .
together causing detector 79c to be at least partially covered. i The reduction in the intensity of light sensed by the detect,or .
79c will be directly proportional to the magnitude of S1. ., .. I .
~ ~ .
Similarly, under the application of a shear load S2 to the touch surface 17, detector 79b will be at least partially covered with the light i~tensity it senses being directly proportional to the magnit~de of S2. Shear loads applied at oblique angles to the direction of shear forces S1 and S2 within the plane of plate 13 will create different maynitudes , of light intensity which c~ln be detected both as to magnitude l and direction by the detectors 79a-d and processed by the i electronic circuitry described below.
Further embodimellts of the transducer means for , detectir.g the magnitude and location of shear forces applied 'o i the touch surface 17 are shown in Figures 7-9aO Referring now to Figures 7 7b, a reflec-:ed-light shear detection means is illustrated. In Figure 7a, a single emitter 82 is surrounded by four equally spaced detectors 83a-d which axe all mounted at either end of the top surface of transducer platform 27. Only one of the emitter-detecto;- groups is shown in the drawings.
Mounted to the flange 73 of bracket 71 immediately above the .
emitter 82 is a reflective surface 84. Movement of the trans- , ducer platform 27 with the touch surface 17 in response to a shear force causes different ones of the detectors 83a-d to i receive more or less reflected light hack from the surface 84.
Such changes in the amount of light received causes proportion- t ately changed signals to be transmitted to the electronic circuitry herein. Figure 7b is a variation of Figure 7a wherein t~o detect:ors 85a,b are utilized to measure changes in the amount of light reflected back from surface 84.
A further variation of reflected light shear force transducer means is shown in Figures 8 and 8a. In this embodi-ment, a four-sided pin 86 having reflective surfaces 87a~d on 1 each side is mounted to the bottom surface on either side of i' Il -19- !

g~L~3 ~' ~
~ (- (- ., plate 13. Onlv one pin 86 is shown in the figures. Four blocks 88a d, each having an emitter 89 and detector 90 mounted thereto one over the other, are disposed directly across from respective reflective surfaces 87a-d of pin 86. The blocks r 88a-d are mounted at their lower end in the flange 73 of bracket 71. As can be appreciated from viewing Figure 8c, ,, lateral movement of the pin 86 with plate 13 in any direction will cause more or less lighl: to be reflected from the emitter t 89 to the detector 90 on recpective blocks 88a-d. The change in light intensity sensed by any of the detectors 90 causes a proportionately changed signal to be transmitted from the detectors 90 to the electronic circuitry herein.
Ano~her shear force transducer means is shown in Figures 9, 9a, wherein a magnetized pin 91 extends downwardly from the underside of plate 13 on each end thereof. Again, only one end of plate 13 is shown in the figures. Four Hall effect transducers 92a-d are mounted at intervals to the upper I~
surface of the 1ange 73 and extend upwardly about pin 91.
Thus, movement of pin 91 with plate 13 in response to a shear force causes one or more of the Hall effect transducers 91 to sense a changed magnetic fi~ld intensity. A signal propor-tional to such change is then transmitted by the respective ~all effect transducers to the circuitry for processing as described below.
Referring now to Figure 10, a schematic diagram of the electronic circuitry used in the tactile sensing system 11 of this invention i5 shown. As mentioned above, the circuitry herein consists oE components mounted to the el2ctronics platEorm 29 which has been identified a5 local circuitry, and external circuit~ry consisting of a computer, a buffer or peripheral interface and display means. The configuration and -2~-l ~ .~
f ~ ., ~perati.on of the circuitry described belo~ is not intended to be restrictive, and many modifications or substitutions could be made to satisfy the si~nal processiny requirements of the system 11.
The components mol~nted on the electronics platform 29 include a standard multiplexer 100, a signal conditioner 102, ~n analog to digi.tal (~/D~ convertor 104 and a controller 106.
The external circuitry includes a computer 108, a peripheral interface 110 which electrically connects the computer 108 to the components on the electtonics platform 29, mass storage 112 and a video display 114.
The electronics operate as follows. Each of the transducer means associated with the sensitive sites 19 produce a continuous signal, first in the form of a current and then after being dropped through resistors in the form of an analog voltage in the range of 0-1 volts. In the embodiment of system 11 shown in the drawings, t:here are sixty-four sensitive sites 19, so sixty-four signals, in parallel, ~re transmitted by an analog data line 116 to the mul~iplexer 100. The components on the electronics platform ~9 function to convert each of the siXty-four analog signals i.nto digital format for introduction into the computer 108.
The analog-to-digital conversion is accomplished as follows. A data strobe is transmitted from the computer 108 to the controller 106 through a data strobe line 118. The data strobe cor~ands the controller 106 to provide an address to the multiple~er 100, which then scans each of the sixty-four siynals from the s~nsitive sites 19 in serial fashion. For example, the signals from the sensitive site5 19 rnay be scanned beginning with the site 19' and moving left-to-right, top-to-bottom until all sites 19 are scanned.

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The multiplexer 10~) recognizes the address from the controller 106 as an instruction to scan the sixty-four signals in a manner such as suggestecl above, and to switch each analog signal scanned to the signal conditioner 102 through switching signal line 103. The signc~l conditioner 102 amplifies the si.gnals to a voltage in the r~nge of 1-10 volts from 0-1 volts, and presents the amplified si~nal to the A/D ~onvertor 104.
Each of the sixty-four signals from the sensitive sites is scanned as a result of a separate address sent to the multipleY~er 100 from the cor.troller 106. The controller 106 allows for the delay associat,~d with the scanning operation and the amplification of the sig~al in the signal conditioner 102, so that at t~e time the amplified signal is presented to the A/D convertor 104, a start convert signal is sent by the controller 106 through the start convert line 107 to the A/D
convertor 104. This signal instructs ~he A/D convertor to accept the amplified signal from the signal conditioner 102 through an amplified signal line 109, and convert it to diyital format. Once the conversion :~s complete, the A/D convertor 104 provides a conversion complete signal through con~ert cornplete line 111 to the controller 106. The controller 106 then in-structs the multiplexer 100 ~o scan the next signal, and the process is repeated for each of the slxty-four signals.
After converting an analog signal to digital format, which can be read by the computer 108, the A/D convertor 104 provïdes a data ready signal t:o the computer 108 through a data ready line 113. The computer 108 accepts the digital signal through digital data line llS. When all of the analog signals from the sensitive sites 13 have been serially selected, converted to digital form and transmitted to the computer 108, the controller 106 resets and waits for the next data probe.

~ -22-After reading the digi.tal da~ on each data ready signal, the computer 108 is operable to process such data in a variety of forms depending on the requiremen~s o~ an applica- !
tion. The computer 108 may be programmed using well known t~chni~ues to process the data and display it on a video displ.~y 114 or store such (~ata in ~ass s~orage 112 for future reference and use. Program~ have been written, for example, to display the data in numerical, gri.d format on a video display 114 with a number coxrespon~ing to the magnitude of the signal f from each sensitive site 19 being displayed on an 8 x 8 grid.
Many other display formats are possible.
The foregoing dis~ussion has indicated the manner in which signals produced by the transducer me~ns associated with sensitive sites 19 are pro~essed by the electronic circuitry herein~ With respect to signals produced by the shear detec-tion transducer means such as in Figures 6-~a, the processing is essentialiy the same wit~ some variation particularly in the program for computer 108.
Each signal produced by the detectors associated with the shear detection transducers herein is transmitted in parallel to the multiplexer 100, and the operation for con~ert-ing such si~nals from analc)g to digital format is conducted.
The digital signals are presented to the computer 108 serially, so that the computer 108 can ldentify which signal comes from each detector. A summation of the signals produced by the shear detection transducers on eacl side of touch surface 17 would pro-vide an output rep:resenting the translation of the touch surface 17 relative to the base section 23. The difference of the signals produced b:y the shea.~ detection transducers on each side of touch surface 17 would provide an output representing the rotation of the touch surface 17 relative to the base 23. Knowing _23-3 ~

the distance bef een t;he shear detection r lnsducers, programs may be written ior computer 108 to use the outputs, calculated by computer 108, representing the translation and rotation of the touch .surface 17 to determine the magnitude, location~ ~nd direction of shear forces applied to touch surface 17 with at least moderate resolution.
~ hi~e the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various chanl~es may be made and equivalents may il be substituted -for elements thereof without departing from the~ l~
scope of the inventior,. In ;lddition, many modifications may 1, be made to adapt a particula~ situation or material to the tea~hings of the invention w:lthout departing from the essential scope thereof. Therefore, it is intended that the inven~ion not be limited to the particular embodiment disclosed as the .
best mode contemplated for c~rrying out this invention, but .
that the invention will include all embodiments falling within the scope of the appended cl~ims.

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Claims

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

1. A device for sensing contact parameters of an object comprising:
a touch surface for contacting said object;
mounting means mounting said touch surface for substantially translational lateral movement in response to a shear force imposed thereon by contact with said object;
a plurality of sensitive sites disposed in an array on said touch surface, said sensitive sites undergoing a mechanical response to a normal force imposed thereon by contact with said object;
transducer means associated with each of said sensitive sites, said transducer means including magnetic means capable of producing a magnetic field and electro-magnetic sensing means operable to sense the intensity of said magnetic field produced by said magnetic means, said electromagnetic sensing means being adapted to be disposed relative to said magnetic means so that said mechanical response of said sensitive sites upon contact with an object causes a proportional change in the proximity and therefore intensity of said magnetic field sensed by said electro-magnetic sensing means, said electromagnetic sensing means being operable to produce an electrical signal proportional to said change in intensity of said magnetic field; and signal processing means operable to receive said electrical signals from said electromagnetic sensing means of said transducer means and provide information identifying said contact parameters of said object.

2. A device for sensing contact parameters of an object comprising:

a touch surface for contacting said object;
mounting means mounting said touch surface for substantially translational lateral movement in response to a shear force imposed thereon by contact with said object;
a plurality of sensitive sites disposed in an array on said touch surface, said sensitive sites undergoing a mechanical response to a normal force imposed thereon by contact with said object;
transducer means associated with each of said sensitive sites including light reflecting means, photoemitter means operable to direct a light beam to said light reflecting means, and photodetector means operable to receive light reflected by said light reflecting means from said photo-emitter means, said photoemitter means and said photodetector means being adapted to be disposed relative to said light reflecting means and said sensitive sites so that said mechan-ical response of said sensitive sites upon contact with an object causes a proportional change in the intensity of light reflected to said photodetector means by said light reflecting means from said photoemitter means, said photodetector means being operable to produce an electrical signal proportional to said change in intensity of light received from said photo-emitter means; and signal processing means operable to receive said electrical signals from said photodetector means of said transducer means and provide information identifying said contact parameters of said object.

3. A device for detecting, discriminating and identify-ing mechanical contact parameters when contacting an object comprising:

a generally horizontally extending touch surface for contacting said object, said touch surface being mounted for substantially translational horizontal movement in response to a shear force applied by contact with an object;
transducer means for sensing said movement of said touch surface and for producing an electrical signal propor-tional to said movement; and signal processing means for receiving electrical signals from said transducer means and for identifying the magnitude and direction of said shear force applied to said touch surface by contact with said object.

4. A tactile sensing system for detecting, discrimina-ting and identifying a number of mechanical contact phenomena when contacting an object including presence, pressure, topography and the like comprising:
a base section;
plate means formed with a plurality of openings in an array, said plate means being disposed above said base section and mounted for lateral movement relative thereto by resilient connectors;
a unitary touch surface overlying and affixed to said plate means and having a plurality of sensitive sites in an array corresponding to said array of said openings in said plate means, each of said sensitive sites including a raised section extending upwardly from said touch surface for contact with said object and a pin structure integrally connected with said raised section and extending downwardly through an underlying one of said openings in said plate means, said sensitive sites being flexible enabling said pin structures to deflect vertically downwardly in response to a normal force applied by contact of said object with said sensitive sites;

a lower platform disposed adjacent said base section and an upper platform disposed between said lower platform and said plate means, said upper and lower platforms being connected together and to said plate means for unitary move-ment;
a plurality of transducer means mounted in said array on said upper platform, one of said transducer means being disposed adjacent said downwardly extending pin struc-ture of each of said sensitive sites, said transducer means being operable to sense the magnitude of said deflection of said pin structures under the application of a normal force imposed by contact with said object and to produce a signal proportional to said magnitude of deflection;
local data processing means mounted on said lower platform, said local data processing means receiving said electrical signals produced by said transducer means, said local data processing means being operable to convert said electrical signal from each of said transducer means from analog to digital format in serial fashion; and remote data processing means electrically connected to said local data processing means, said remote data proces-sing means being operable to receive and process said digital signals from said local data processing means to provide information identifying said contact parameters of said object.

5. A tactile sensing system for detecing, discrimina-ting and identifying a number of mechanical contact phenomena when contacting an object including presence, pressure, pressure pattern, topography, slip, incipient slip and the like comprising:

a base section;

plate means formed with a plurality of openings in an array, said plate means being disposed above said base section and mounted for lateral movement relative thereto by resilient connectors;
a unitary touch surface formed overlying and affixed to said plate means and having a plurality of sensitive sites in an array corresponding to said array of said openings in said plate means, each of said sensitive sites including a raised section extending upwardly from said touch surface for contact with said object and a pin structure integrally con-nected with said raised section, said pin structures extending downwardly through said openings in said plate means, said sensitive sites being flexible enabling said pin structures to deflect vertically downwardly in response to a normal force applied by contact of said object with said sensitive sites, said touch surface and said plate means being laterally mov-able in response to shear force exerted on said touch surface by contact with said object;
a lower platform disposed adjacent said base section and an upper platform disposed between said lower platform and said plate means, said upper and lower platforms being connected together and to said plate means for unitary move-ment;
a plurality of normal force sensing transducer means mounted in said array on said upper platform, one of said transducer means being disposed adjacent said downwardly extending pin structure of each of said sensitive sites, said transducer means being operable to sense the magnitude of said deflection of said pin structures under the application of a normal force imposed by contact with said object and to produce a signal proportional to said magnitude of deflection;

shear detection transducer means for sensing said lateral movement of said touch surface in response to the application of a shear force thereto by contact with said object, said shear detection transducer means producing an electrical signal proportional to said lateral movement of said touch surface;
local data processing means mounted on said lower platform, said local data processing means receiving said electrical signals from said normal force sensing transducer means and said shear detection transducer means and being operable to convert said electrical signals from each of said transducer means from analog to digital format in serial fashion; and remote data processing means electrically connected to said local data processing means, said remote data proces-sing means being operable to receive and process said digital signals from said local data processing means to provide information identifying said contact parameters of said object.

6. A tactile sensor device for sensing contact para-meters of objects, comprising:
a touch responsive member having an array of sensi-tive sites on an outer surface thereof, said surface of said member being engageable with said objects, and said sites being deflectable inwardly substantially independently of each other in response to the imposition thereon of normal forces produced by said engagement;
a base member;
mounting means mounting said touch responsive member for substantially translational movement thereof generally parallel to the plane of said surface thereof in response to the imposition thereon of shear forces produced by said engagement;
transducer means for sensing, and for producing data signals representative of, said deflection of said sites.

7. A device as in claim 6, and further including trans-ducer means for sensing, and for producing data signals representative of, said lateral translatory movement of said touch responsive member.

8. A device as in claim 6, wherein said mounting means mounts said member for directionally universal movement generally parallel to said surface thereof.

9. A device as in claim 6, wherein said touch respon-sive member is formed of resilient and durable elastomeric material.