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Description  |
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DESCRIPTION
1. Art Field
The present invention relates to a device for detecting contact pressures
distributed in a certain breadth of area, using a pressure sensitive
conductive rubber capable of changing the electrical resistance in
response to compression forces, and displaying the result of detection on
a display device in the form of an image or a drawing figure.
2. Background Art
To let a robot or the like handle objects, one practice is to provide a
sensor comparable to a tactile organ on the surface of a hand of the robot
or the like against which the objects to be handled are contacted so that
the objects can be held or gripped with an appropriate degree of force or
wherein their configurations can be recognized by the sensor.
Conventionally, materials such as semiconductors, ceramics, organic
material, optical fibers and so forth are known to be useful for sensor
elements. However, the known measurement systems made with use of such
materials have problems with their flexibility and/or involve difficulties
such that they cannot be made compact, they fail to provide sufficient
resolving power for analyzing respective forces, distributed over an area
and/or they are not economically feasible. Thus, it is the present status
of art that a satisfactory measurement system has not yet been provided.
With the above status of the art in mind, the inventors of the present
invention have previously invented a distribution type tactile sensor
which makes use, for the sensor element, of a rubber which normally is an
insulator but which, when subjected to deformation by an applied force,
changes its electrical resistance in response to a change in the amount of
the deformation (this rubber will hereinafter be referred to as pressure
sensitive conductive rubber). This sensor can determine the forces applied
on various contact points of the sensor at which the sensor is contacted
with an object. This invention formed the subject matter for a patent
application filed in Japan under the patent application No. 60-219245.
The above tactile sensor is of an arrangement in which electrodes are
provided in pairs at each measurement point for the measurement of
compression forces on a thin sheet-type pressure sensitive conductive
rubber, and by which the forces applied at the measurement points are
detected as changes in the electrical resistance of the conductive rubber
at such measurement points. This tactile sensor may be appllied to an
object holding surface of, for example, a robot and utilized as a tactile
detecting sensor. Electrodes may be provided in a sufficient number as
required for the holding of an object, and the number of electrodes to be
provided is, for example, on the order of 16 to 25.
The invention disclosed in the above cited Japanese patent application
makes a combined use of a thin layer of a flexible pressure sensitive
conductive rubber and electrode leads, and thereby dispenses with the need
of providing a sensor at each of the measurement points, thus making it
possible to provide a sensor device having a function closely resembling
the function of human hands. Thus, the touch or tactile sensor of the
invention referred to above can be widely utilized, not only in
controlling the force of holding or gripping depending on the strength,
the weight, the configuration and so forth of an object to be handled
and/or depending on the particular purpose of the handling, but also in
distinguishing shapes or configurations of objects and detecting slip or
slide, by contacting or touching.
In view of the above, it will be appreciated that by using a sensor device
having a number of touch or contact detecting points closely arranged in
longitudinal and transverse directions (hereinafter referred to as
distribution type tactile sensor), it is possible to display the
configuration of the object against which the sensor device is contacted,
and the distribution of the contact pressures on the object, in the form
of an image or a drawing figure. An attempt made in order to realize this
possibility is reported in the Report No. 4016 by Ishikawa et al of Seihin
Kagaku Kenkyusho (Industrial Products Research Institute), entitled
"Pressure Distribution Sensor Emitting Video Signals", entered in the
proceedings of the 28th Japan Joint Automatic Control Congeference under
the Society of Instrument and Control Engineers (Nov. 5 to 7, 1986).
The above Report carries a brief disclosure of the technique according to
which, now that it is necessary to provide a number of electrodes in order
to tell the configuration of an object by means of contact pressures with
which the sensor contacts the object, there are provided 4096 electrodes
arranged in 64 lines or rows in each of the longitudinal and transverse
directions, and an image of the palm of a hand is displayed on a
television tube, utilizing circuits detecting electrical resistance of a
pressure sensitive conductive rubber on respective electrodes.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide a sensing circuit in or
for a distribution type tactile sensor provided with a number, for
example, 4000 or more, of small electrodes for tactile sensing an object.
The contact pressures at which the object is contacted by the sensor can
be detected to display the configuration of the object in the form of an
image or a drawing figure. The sensing circuit of the present invention is
in that in comparison to the existing comparable circuits, it can detect
tactile signals at respective electrodes at a higher accuracy and a higher
speed and can reduce the required number of leads or wires and the
consumption of power.
Another object of the invention is to provide an image display system for
displaying images and/or drawing figures, using a distribution type
tactile sensor made with use of the above sensing circuit.
Yet another object of the invention is to provide various tactile sensing
parts having a tactile sensing surface, adapted to particular purposes of
detection or measurement.
The distribution type tactile sensor for attaining the above objects
according to the present invention makes use of a sensing circuit which is
characterized in that electrodes are provided in parts at respective
points for measurement of compression forces applied to a pressure
sensitive conductive rubber sheet capable of changing the electrical
resistance responsive to a change in the compression force, a rectifier
element being provided to respective electrodes for rectifying the current
flowing across each pair of electrodes through the rubber sheet, the
electrodes being divided into groups each comprising electrodes arranged
in a line or row for respective polarities of the electrodes, electrodes
in respective electrode groups being parallel connected to one another
through electrode leads, and directions of the division of electrode
groups divided for respective polarities being crossed with each other at
respective points for the measurement of compression forces.
According to the invention, it is possible to provide an image or figure
display system by processing by a computer the sensed tactile signals
outputted from the distribution type tactile sensor made with use of the
above sensing circuit, and then by displaying the processed signals on for
example a television tube.
Electrodes can be formed by means of attaching onto a surface of a pressure
sensitive conductive rubber any of such as rare metal foils, aluminium
foils and other metal foils the surface of which is treated for rust
prevention, or by laminating on the rubber an insulating film of a
synthetic resin having a flexibility and a high strength, for example
polyethylene terephthalate, after this film is applied with a printed
wiring and its surface is plated with gold or otherwise coated with any of
carbon black, graphite and so forth.
The pressure sensitive conductive rubber for use for or in the present
invention may be any of known pressure sensitive conductive rubbers
comprising conductive particles such as carbon particles dispersed in
rubber or an elastomer such as silicone rubber for example. Although this
conductive rubber is normally used in the form of a sheet, which may be
cut into pieces of the prescribed size, it is also possible to use a
rubber in the form of a coating material, which may be applied on
electrodes for example by coating and may then be solidified thereon.
The above described distribution type tactile sensor according to the
present invention and the image display system made with use of such a
tactile sensor can be applied to a variety of uses. For example, a use may
be made for measuring the weight applied on the sole of a foot or soles of
feet to then operate a diagnosis and/or to determine a guidance for
rehabilitation, of a handicapped person. Also, in the carrying out of
research work and/or designing activity in the field of human-factors
engineering, a use may be possibly made for obtaining data for the
designing of sporting shoes and other shoes or the designing of office
chairs by investigating the relationship between the manner in which a
wearer of shoes walks and the load distribution over various portions of
the shoes, or the relationship between the sitting posture of a user of a
chair and the distribution of loads over various portions of the chair. A
use may also be made in or for industrial robots which automatically
classify parts and members respectively having a characteristic shape or
configuration.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 show a view, taken for illustration of a sensing circuit in a
distribution type tactile sensor of the prior art, used in a robot's hand;
FIG. 2 is a view, taken for a brief illustration of a sensing circuit of a
distribution type tactile sensor in the prior art, used in an image
display system;
FIG. 3 shows a perspective view of electrodes used in the circuit of FIG.
1;
FIG. 4 is a circuit diagram, taken for illustration of a problem with the
circuit of FIG. 1;
FIG. 5 is a view, taken for illustration of the reason for the generation
of a stray current in the circuit of FIG. 4;
FIG. 6 is a perspective partial view, showing the structure of a sensing
part in a distribution type tactile sensor according to an embodiment of
the present invention, shown in a disassembled condition;
FIG. 7 shows a vertical sectional view through FIG. 6;
FIG. 8 is a view, taken for illustration of the reason for why the stray
current is not generated in the sensing part shown in FIG. 6;
FIG. 9 shows a view, taken for illustration of electrodes in a distribution
type tactile sensor according to another embodiment of the present
invention;
FIG. 10 is a partly broken-away perspective view, showing the distribution
type tactile sensor incorporating the electrodes shown in FIG. 9;
FIG. 11 shows a sectional view taken on the line XI--XI in FIG. 9;
FIG. 12 shows switching circuits in the contact sensing circuit;
FIGS 12A-12C show separate parts of FIG. 12;
FIG. 13 shows a sectional view of essential portions of the switching
circuits of FIG. 12;
FIG. 14 is a block diagram of a picture display system;
FIG. 15 is also a block diagram but shows an imaging unit in the image
display system of FIG. 14;
FIG. 16 is a view, showing a use condition of the image display system of
FIG. 14;
FIG. 17 depicts a block diagram of a control system used in a robot's hand;
FIG. 18 is a partly broken-away perspective view, showing a plate type
sensor device adapted to have mounted to thereon a human body or an
object;
FIG. 19 shows a pattern of electrodes for use in or for the distribution
type tactile sensor device shown in FIG. 18;
FIG. 20 shows a schematic view of a sensing circuit in or for a
distribution type tactile sensor adapted to curved surfaces;
FIG. 21 shows a partly broken-away perspective view of an example of unit
sensors for use in or for the distribution type tactile sensor shown in
FIG. 20;
FIG. 22 is a perspective view, showing an example of use of the
distribution type tactile sensor of FIG. 20;
FIG. 23 shows a partial plan view of an example of electrode leads in or
for the tactile sensor of FIG. 20;
FIG. 24 shows a stretched condition of the electrode lead of FIG. 23;
FIG. 25 shows a modified example of the unit sensor of FIG. 21;
FIG. 26 shows a connector portion in FIG. 25;
FIG. 27 is a partly broken-away perspective view, showing another modified
example of the unit sensor of FIG. 21;
FIG. 28 shows a sectional view, taken on the line IIXXX--IIXXX in FIG. 27;
FIG. 29 shows a perspective view of a shoe incorporating a distribution
type tactile sensor;
FIG. 30 is a partly broken-away perspective view of a unit sensor for use
in or for the tactile sensor of FIG. 29;
FIG. 31 is a plan view, showing essential portions in FIG. 30, in an
enlarged scale;
FIG. 32 is a sectional view, taken on the line XXXII--XXXII in FIG. 31;
FIG. 33 shows a sectional view of an adaptor for increasing the sensing
density; and
FIG. 34 is a sectional view of an adaptor for sensing convex and/or concave
surfaces in a recessed part or portion of an object.
BEST MODE OF CARRYING OUT THE INVENTION
Now, detailed descriptions will be successively provided of a tactile or
touch sensing circuit in or for the distribution type tactile sensors
according to the present invention (in what will follow, the sensors will
be referred to simply as tactile sensors unless misunderstanding is
likely), a picture display system made with use of one of the tactile
sensors utilizing the tactile sensing circuit, material structures and
methods of use of touch sensors respectively adapted to a particular use,
in the mentioned order.
FIG. 1 is a view, taken for illustration of circuits used in the electrode
part according to the invention disclosed in the before referred-to
Japanese patent application No. 60-219245, in which the distribution type
tactile sensor (touch sensor) indicated at 1, which is provided in a
robot's hand (not shown) comprises 16 electrodes Eij (i, j=0.about.4).
Four electrodes on the output side (hereinafter shown by Eo) are attached
to each of four parallel arranged output electrode leads 2.sub.0 to
2.sub.3 and disposed on a front surface of a sheet-type pressure sensitive
conductive rubber 3, and on the other, backside surface of the rubber 3,
four feed electrode leads 4.sub.0 to 4.sub.3 having feed-side electrodes
Ep (not shown) attached thereto at the points corresponding to the
locations of the electrodes Eo are so disposed as to cross the electrode
leads 2.sub.0 to 2.sub.3.
When a robot's hand having the above tactile sensor 1 is contacted against
an object to be held by the robot's hand, a contact pressure is applied to
the pressure sensitive conductive rubber 3 and its electrical resistance
undergoes a lowering, corresponding to which a current flow takes place
through electrodes Eij. Therefore, for example by connecting the electrode
lead 4.sub.0 to a power source and by taking the current successively from
each of the electrode leads 2.sub.0 to 2.sub.3, it is possible to detect
the contact pressure at each of the locations at which the 16 electrodes
Eij are provided. Accordingly, it is possible to control to a certain
value the forces applied at various portions of the object being gripped
or otherwise held by the robot's hand, so that the robot's hand can safely
hold various objects which cannot stand a strong force application, such
as eggs for example.
For the sensing of forces for purposes like that described above, generally
it is not required to provide a very large number of sensing points, but
if such sensing is for the purpose of detecting a shape or configuration
of an object by a tactile sensor, as in the before cited technical Report
by Ishikawa et al, it is necessary to considerably increase the number of
the sensing points.
Now, with reference to FIGS. 2 and 3, a brief explanation will be given the
distribution type tactile sensor according to the prior art made public by
the above referred-to technical Report by Ishikawa et al.
In FIG. 2, the distribution type tactile sensor 1 comprises pairs of
electrodes Eij (i=0 . . . 8 m.about.8 m+7 . . . 63, j=0 . . . n-1, n, n+1
. . . 63; 4096 electrodes in total), which are disposed on a backside of a
pressure sensitive conductive rubber (not shown) and to which respective
switches Sij comprising FET, a resistance and a diode (i=0 . . . 8
m.about.8 m+7 . . . 63; j=0 . . . n-1, n, n+1 . . . 63; 4096 switches in
total) are connected by electrode leads 2.
As shown in FIG. 3, the electrodes Eij comprise a square electrode having a
side length of about 5 mm, in which an electrode Ep and an electrode Eo
shaped in the form of comb teeth are assembled in a meshing arrangement
having a prescribed space therebetween. Electrodes Ep on the one hand and
electrodes Eo on the other hand make up electrodes for connection to a
power source side and electrodes for connection to an output side,
respectively. Further, on (the load bearing side of) the electrodes Eij,
the pressure sensitive conductive rubber 3 is placed. Although this rubber
3 is shown in FIG. 3 to be of a same size as the electrode, usually the
rubber 3 is in the form of a sheet, on which all the electrodes Eij are
attached.
In the tactile sensor 1, it is necessary to mount 4000 or more switches, as
stated above, on a square sensor board having a side length of about 32
cm, and to arrange electrode leads 4 for connecting all electrodes Ep to a
power source above the switches. Accordingly, a problem is posed that the
wiring cannot be performed with high efficiency. In view of this, and in
order to miniaturize switches and build them in the touch sensor 1 so as
to facilitate the wiring operation and also to reduce the overall size of
the device, in the case of the prior art example illustrated in FIG. 1, it
has been proposed that switching circuits made with use of FET's for the
switching elements are collectively formed on a single switch board to
provide a hybrid IC of 1.times.8 cells and of a pin pitch of 1.26 mm,
which is disposed on a backside of the touch sensor 1.
However, in the case of the sensing circuits of FIG. 2, it is necessary to
arrange 4096 electrode leads 2 for connecting together a sensor board
provided with all electrodes Eij and a switch board provided with all
switches Sij at a spacing of about 5 mm and, in addition, connect
electrode leads 4 above the electrode leads 2 (FIG. 2). In this case,
according to the above described prior art, a problem is met in that the
wiring operation and the assembling of the device can only be performed at
an extremely low operation efficiency.
In addition, according to the above described prior art, the switch board
has to be arranged on the backside of the tactile sensor 1 in a condition
in which a great number of electrode leads 2 project therefrom, so that no
means is made available for supporting the touch sensor 1 on the backside
thereof. A further problem is posed in that in order to effect a
reinforcement, it is indispensable that the sensor board itself to be very
stiff, whereby it becomes difficult to reduce the thickness and the weight
of the device.
It may possibly be made to apply the circuit of FIG. 1 to the sensing
circuit of the prior art shown in FIG. 2 to effectively reduce the number
of the output leads for the respective electrodes. It is provided,
however, that unless a compensating circuit is provided, the circuit of
FIG. 1 cannot operate to display the shape or configuration of an object
as described below. The reasons for this will be described with reference
to FIGS. 4 and 5. Further, FIG. 5 shows an equivalent circuit diagram, in
which respective resistances R show equivalent resistances with the
current flowing in a minimum flow path in the pressure sensitive
conductive rubber.
For avoiding complexity in the description, in FIGS. 4 and 5 electrode
leads are shown to simply comprise the electrode leads 4.sub.1 and 4.sub.2
of FIG. 1 on the pressure bearing side and the electrode leads 2.sub.1 and
2.sub.2 of FIG. 1 on the backside, and the sensing points, namely the
intersections of the leads, are shown to simply comprise P.sub.11,
P.sub.12, P.sub.21 and Q. For purposes of explanation, it may be
tentatively supposed that while respective points P are in contact with an
object and are exerting a contact pressure, the point Q is not in contact
with the object and that the electrical resistance at the point Q is to be
determined.
Electrical resistances between intersections of electrode leads 2 and 4 are
shown by R.sub.11, R.sub.12, R.sub.21 and R.sub.22 =.infin. (.infin.
denotes that the electrical resistance of the rubber corresponds to that
of an insulator). Now, as shown in FIG. 5, a voltage E may be impressed
across electrode leads 2.sub.2 and 4.sub.2, wherein, although no current
flow actually takes place across the resistance R.sub.22, a stray current
I [=E/(R.sub.21 +R.sub.11 +R.sub.12 ] flows through a stray current
circuit from the resistance R.sub.21 to the resistance R.sub.11 and
further to the resistance R.sub.12 (R.sub.21 .fwdarw.R.sub.11
.fwdarw.R.sub.12), whereby it is erroneously determined that a force is
applied at the point Q.
Actual tactile sensors have a number of sensing points, for example
8.times.8 or more, and it is a problem with them that due to the stray
current, it is impossible to detect accurate electrical resistance values.
As a consequence, conventional tactile or touch sensors may exhibit a
satisfactory function wherein a relatively large space can be provided
between sensing points or wherein the required conditions for the sensing
is relatively not severe, but they cannot provide a tactile sensor having
a relatively high power of resolution or analysis and an accordingly high
operation efficiency.
Now, with reference to FIGS. 6 and 7, a description will be provided of the
arrangement of the sensing part in the distribution type tactile sensors
according to the present invention.
FIG. 6 is a partial perspective view, showing essential portions of an
8.times.8 matrix distribution type tactile sensor according to the present
invention, in a disassembled condition. As shown, on the pressure bearing
side of the pressure sensitive conductive rubber 3, there is superposed a
printed circuit plate 6 having a printed wiring of electrode leads 4 and
feed-side electrodes Ep. Electrode leads 4 are shown by broken lines to
show that they are printed on the side of the plate 6 facing the pressure
sensitive conductive rubber 3. Electrodes forming parts of the electrode
leads 4 are provided with the electrodes Ep coated with a conductive
coating material such as carbon black and graphite, and the surface of the
plate 6 is made rust preventive.
On the other, or the backside, surface of the pressure sensitive conductive
rubber 3, a printed circuit plate 8 is disposed, which is printed, on a
front-side surface, with output-side electrodes Eo in an 8.times.8 matrix
arrangement and, on the backside, with electrode leads 2. The electrode
leads 2 and 4 are arranged to cross one another (in the illustrated
embodiment, they cross at right angles). Electrodes Eo and leads 2 are
connected together by diodes D.
FIG. 7 illustrates in section details of the wiring and connection together
of the diodes D and the electrodes Eo. As stated above, in actuality the
electrodes Eo and the diodes D are provided on a front-side and a backside
surfaces of the printed circuit plate 8.
As can be seen from the foregoing description, there are 8.times.8 sensing
points in the sensing part of the tactile sensor according to the present
invention, and these sensing points are divided into 8 groups, polarity by
polarity. On each of the 8 electrode leads 2, 8 electrodes Eo are
connected in a linear arrangement, and lines of electrodes Eo are parallel
arranged. Similarly, 8 electrodes Ep are connected in a linear arrangement
on each of the 8 electrode leads 4, and lines of electrodes Ep are
parallel arranged.
The tactile sensor 1 according to FIGS. 6 and 7 does not produce the stray
current described above in relation to FIG. 5, and can therefore exhibit a
drastically improved sensing accuracy. This will be now described with
reference, for comparison FIG. 8, which corresponds to purposes, with
prior art FIG. 5.
As can be seen from a comparison between FIG. 5 and FIG. 8, a diode D in
the tactile sensor 1 in FIG. 8 can prevent the stray current tending to
flow through R.sub.11, so that in this tactile sensor 1, a stray current
circuit of R.sub.21 .fwdarw.R.sub.11 .fwdarw.R.sub.12 is not formed.
Therefore, for example where a contact force is applied at each of
R.sub.11, R.sub.12 and R.sub.21 but not at R.sub.22, a voltage may be
applied to the electrode lead 4.sub.2 and current may be taken from the
electrode lead 2.sub.2, however, no output current will be produced as
opposed to the before considered case of the prior art. That is to say,
using the circuit shown in FIGS. 6 and 7, it is possible to accurately
detect the current flowing across the electrodes Eij at the intersections
of electrode leads 4 connected to a power source and the electrode leads 2
for taking out the current.
FIG. 9 shows a perspective view of electrodes used in another embodiment of
the tactile sensor according to the present invention, FIG. 10 being a
perspective view of a tactile sensor incorporating the electrodes shown in
FIG. 9, and FIG. 11 being a sectional view, taken on the line XI--XI in
FIG. 9.
Similar to the electrodes shown in FIG. 3 (prior art), the electrodes shown
in FIG. 9 comprise square comb-tooth shaped electrodes, which are provided
on just one of the two surfaces of a pressure sensitive conductive rubber.
Electrodes Eo and Ep, and electrode leads 2 and 4, are printed on a printed
circuit plate shown at 17 in FIGS. 10 and 11, and the electrode parts are
formed by plating with gold. Electrodes Eo and electrodes Ep, each of
which takes a comb-like shape, are assembled in a meshing arrangement with
the prescribed gaps g maintained as shown. Electrodes Ep and leads 4 are
integrally formed.
Electrodes Ep are connected to leads 2 printed on the other side surface of
the printed circuit plate 6 through diodes D which form rectifier elements
according to the present invention. As best seen from FIG. 11, taps t
applied in thorugh-holes h formed in the printed circuit plate 6 and
electrode leads 2 are connected to pins 13 of commercially obtained diodes
D of a flat-plate type by soldering 13'. Further, the electrode leads 2
extend at right angles to the plane of the drawing sheet of FIG. 11. Also
in FIG. 11, the reference symbol b denotes a backing-up sheet of, for
example, polyurethane, which is applied to provide a flat surface,
compensating for irregularities formed by diodes on the backside of the
contact sensor 1.
Then, as best seen from FIG. 10, on the electrodes Eo and Ep, a sheet-type
pressure sensitive conductive rubber 3 is placed, on which superposed is a
touch or contact member (surface forming member) 14 which may be referred
to as a skin. This surface forming member 14 comprises a sheet formed by
laminating on a fabric a soft foamed sheet capable of closely contacting
an object to be handled, and under this surface forming member 14, an
upper-side conductive film 16 is further disposed. The electrodes Eij
(pairs of Eo and Ep) are provided, wherein a number of 4096 electrodes is
provided within an area of about 32 cm.times.32 cm in a square net-work or
a chessboard arrangement.
Now, referring to FIGS. 12 and 13, a description will be provided of the
output circuits for outputting the data on touch or contact from the above
described tactile sensing circuits.
FIG. 12 shows output circuits in or of a touch sensing system, which were
made with use of CMOS-IC for the output switches and which are applicable
to the tacticle sensor shown in FIGS. 6 and 7 and the tactile sensor shown
in FIGS. 9, 10 and 11. Further, FIGS. 12 and 13 illustrate the instance in
which 64 electrodes Eij are used in each of the vertical and transverse
directions (4096 electrodes in total).
For the multiplexor shown at 18, for operating 64 output switches Si
comprising FETS shown in FIGS. 12 and 13, use was made of a high signal
output CMOS-IC, type 74HC238 (a surface mounting device, a product of NEC
Corporation; this same description is applicable also to the below
appearing CMOS-IC's.) as M.sub.1 to M.sub.8, and for the multiplexor shown
by 20 for operating feed-side switches Sj, use was made as N.sub.1 to
N.sub.8 of a low siganl output CMOS-IC's, type 74HC 138. In each of the
CMOS-IC's, the elements comprise a 3-to-8 decoder, decoding one of 8
output lines under the condition of 3 selection inputs and 3 enabling
inputs.
Thus, in order to operate 64 switches Si and 64 switches Sj, it is
necessary to use 8 each of 74HC138 and 74HC 238. Therefore, for decoders
for controlling 8 IC's, 74HC138, M.sub.9 and M.sub.10, were used for the
multiplexors 20 and 18, respectively. Further, for the feed switches Sj
for the illustrated embodiment, widely used digital transistors (DTB) were
used.
In the circuit Ci for operating the output switches Si in the touch sensor
1, the No. i output pin of the 64 pins in the multiplexor 18 and the gate
of FET of the switch Si were connected together by a capacitor C, and as
shown in FIGS. 12 and 13, a bias voltage of -3 V was impressed through a
voltage divider circuit comprising resistances R.sub.2 and R.sub.3.
For the operation of the switch Si, it is sufficient only if a voltage
capacity enough to produce a switching level for the FET is provided
therefore, the voltage (-3 V) to be impressed to the gate of FET was
obtained from a 5-V power source for operating the tactile sensor 1. That
is to say, by a voltage of 5 V supplied from the 24th and 25th pins of
output terminals of a control device (not shown), an RC oscillation
circuit was excited, and the negative voltage of the alternating voltage
thus obtained was supplied through a constant-voltage circuit 22 for
obtaining -3 V, composed of a transistor and a constant-voltage diode.
One of the characteristics of the sensing circuit of the present embodiment
resides in that all of the required power, including the bias voltage of
-3 V for operating the gate of FET, can be supplied by a single power
source as described above.
The above described embodiment operates as follows. From the 11th to 16th
pins and the 19th pin (for enabling input) of the terminal 22 of the
control device, address signals for operating feed switches Sj are sent to
the feed multiplexor 20 for the electrodes Eij. Also, from the 1st to 6th
pins and the 9th pin (for enabling input), address signals for operating
output switches Si are sent to the output multiplexor 18. The respective
signals are modified to operation signals through receiver circuits 24 and
26 and then transmitted to A to C pins of respective decoders M.sub.1 to
M.sub.8 and N.sub.1 to N.sub.8, and signals for operating the decoders
M.sub.1 to M.sub.8 and N.sub.1 to N.sub.8 are imparted to A to C pins of
the decoders M.sub.9 and M.sub.10.
Decoders M.sub.9 and M.sub.10 issue signals for operating one of decoders
M.sub.1 to M.sub.9 and N.sub.1 to N.sub.9, successively. To these decoders
M.sub.1 to M.sub.9 and N.sub.1 to N.sub.9, and from the decoder M.sub.1 .
. . or M.sub.8 or the decoder N.sub.1 . . . or N.sub.8 that is put into
operation by the above signals, high signals are outputted for opening
switches Sj and Si to be successively operated, whereby a voltage is
impressed successively to the electrodes Eij, whereupon the current
corresponding to the degree of compression force is taken out from the
output terminal 28.
The output switches Si according to the present invention may comprise the
switching circuits Sij shown in FIG. 2, in place of the driving or
operating circuit shown in FIG. 12. In the following, a description will
be entered into the characteristics of the switching circuit Si shown in
FIG. 12, in comparison to the conventional switching circuit Sij.
When an FET is used for the output switch element, the switching operation
of gates in the case of FIG. 2 relies upon the H of the open collector of
TTL, and it is further necessary to lower the impedance of the gates, so
that it is required to effect a pulling up by the resistance R.sub.1 (for
example, 1 k.OMEGA.). In this case, the length of time for outputting high
signals because opening a gate is 1/64 of a total length of time (for
there are 64 electrode leads i), and the output is L for the remaining
63/64 length of time, whereby a power of, for example, on the order of 10
mA flows to the resistance of 1 k.OMEGA.. A same situation as the above
applies to the remaining 63 electrode leads, and as a whole, a power of
640 mA will flow in total, whereby a considerable heat generation takes
place.
In contrast to the above, in the output switching circuit Si shown in FIG.
12, it is possible to lower the required operation current to the order of
.mu. amperes. Therefore, it is possible to considerably suppress the
current capacity as a whole, reduce the feed power capacity, and suppress
the heat generation, so that it is possible to miniaturize the sensor
circuit.
Further, using the sensor circuit of FIG. 12, as before indicated, the
current capacity required for switching operation of the FETS can be
extremely small, so that the bias voltage (-3 V) to be imparted to the
gate of the FETS can be taken from the 5-V feed voltage for the sensor
circuit. The switching circuits used in the prior art (for example the one
shown in FIG. 2) require two power sources, a +5 V power source and a -5 V
power source. As opposed to this, the circuit of FIG. 12 is characterized
further in that it can lower the power consumption and simplify the
circuit only with the need of a single power source, so that it becomes
possible to provide a compact device.
Advantages brought about because of the sensor circuit of the above
described embodiment may be summarized as follows. The 4096 output
switches required in the prior art could be reduced only to 64; the sensor
circuit could be operated only with a 5V-power source alone; therefore,
the required number of parts could be reduced and it became possible to
simplify the circuit; the current value flowing through the output
switching circuits could be reduced; and a tactile sensing part and sensor
circuits could be mounted on a single sensor board, whereby it was
possible to effect a reduction in size and weight and an increase in
strength of the device.
As can be perceived from the foregoing description, in the tactile sensor 1
according to the present embodiment, 64 electrodes Eo and 64 electrodes Ep
are parallel connected on each of 64 leads 2 and 64 leads 4 respectively.
According to this arrangement, it is possible to reduce the 4096
high-speed switching elements required in the prior art to only 128,
whereby it is possible to lower the production cost and simplify the
arrangement of circuits around the sensing part.
Image Display System
Now, a description will be given to the image display system according to
the present invention, with reference to an embodiment thereof as
illustrated in FIG. 14. It is possible to arrange such a system so that
signals of the detected compression force (touch) at each of the sensing
points in the distribution type tactile sensor or a tactile image sensor 1
according to the present invention are sent to an imaging unit 30 and
therein converted to imaging signals, which are inputted through an image
input device 32 to a personal computer 34, in which the signals are
subjected to a prescribed processing. According to this system, it is
possible to display the tactile detected detail of an object sensed by the
tactile image sensor 1 in the form of an image on an image display unit
36, in which two monitors, comprising a monochrome (black and white)
television tube and an RGB three-primary-color television tube, are used
in the illustrated embodiment.
The image input device 32 used in the present embodiment had a
pseudo-color-through function for displaying the input image wherein the
image shape is changed with the lapse of time, comprising a 64-level
gradient tone display function and a 4 stationary image display function.
For the personal computer 34, use was made of a 640 KB NEC-PC9801 machine
equipped with software providing main menus which enable image freezing,
pseudo-colouring, image processing, enlargement/reduction, inter-image
processing, histogram processing, image saving/loading, and so on.
Next, with reference to the block diagram of FIG. 15, a description will be
given of an example of the imaging unit 30. FIG. 15 represents the system
in which the plane shape of an object against which the tactile sensor 1
is contacted is displayed intact on the display device 36.
In the system illustrated in FIG. 15, the tactile sensor 1 is operated by
the imaging unit 30 to scan respective electrode leads 2 and 4, and a
voltage is applied successively to electrodes at the sensing points. The
control in this respect is made as follows. Pulsed signals, which are
generated from a synchronous signalling circuit 37 on the (vertical) side
of the leads 2 and a synchronous signalling circuit 38 on the (horizontal)
side of the leads 4, are subjected to a timing regulation by timing
controllers 39 and 40 | | |
