JPS6395332A - Distribution type tactile sensor - Google Patents

Abstract

PURPOSE:To enable fast processing, by providing a rectifying element for rectifying current flowing to a measuring point of a pressure-sensitive conducting rubber at each electrode to eliminate creeping current using a relatively simple scanning circuit. CONSTITUTION:Paired electrodes 4 and 5 are arranged at respective measuring points of pressing force working on a pressure-sensitive conducting rubber sheet 2 whose resistance varies with the pressing forces and a diode D as rectifying element is arranged for each electrode to rectify current flowing between the paired electrodes 4 and 5 through the rubber sheet 2. The paired electrodes 4 and 5 are set on the surface and back of the rubber sheet 2 facing each other. The electrodes are divided into a plurality of groups in each of which electrode units are arrayed linearly. The electrodes in each group are connected in parallel to one another with electrode lines X and Y while the dividing directions of the groups divided for each polarity cross one another at measuring points.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a tactile sensor that uses a pressure-sensitive conductive rubber to detect a pressing force that is distributed and acts on a certain area, and more specifically, the tactile sensor This invention relates to a tactile sensor with improved detection accuracy.

[Prior art]

When a robot or similar device handles an object, it is necessary to grasp the object with a moderate amount of force, or to use a sensor equivalent to the tactile sense on the contact surface between the robot hand and the object in order to recognize the shape by tactile sensation. It is being established.

Traditionally, elements for this sensor include semiconductors, ceramics,
Organic materials, optical fibers, etc. are known, but measurement systems using these have problems with flexibility, are difficult to make compact, lack the decomposition ability of each distributed part, and are not economical. The current situation is that people are not able to get enough satisfaction due to lack of sex.

Therefore, the present inventors used rubber (hereinafter referred to as pressure-sensitive conductive rubber), which is usually an insulator, but whose electrical resistance changes depending on the amount of deformation when force is applied to it, as the sensor element. Invented a distributed tactile sensor that can measure the force applied to each part of the sensor when it comes into contact with an object, and filed a patent application in 1986-2.
A patent application was filed as No. 1924'5.

This tactile sensor has two electrode wires that linearly connect each pair of electrodes placed at the pressing force measurement point of a thin sheet of pressure-sensitive conductive rubber, and are arranged so as to intersect with each other.
The force applied to the measurement point is detected as a change in the resistance value of the conductive rubber at that part, and is used as a tactile sensor for the gripping surface of a robot or the like.

In this way, the above-mentioned invention eliminates the need for arranging a sensor at each measurement point by combining a thin layer of flexible pressure-sensitive conductive rubber and an electrode wire. It is possible to use it as a functional sensor, and it can be used as a sensor for handling objects such as strength, weight, shape, etc.
In addition to controlling the gripping force depending on the purpose, it can be used for a wide range of purposes, including tactile shape recognition and slip detection.

However, in the configuration of the conventional tactile sensor, there is a problem that in addition to the current corresponding to the pressing force flowing to the electrode at the measurement point, there is an influence of a wraparound current flowing through other electrodes, and it is necessary to correct the detection signal. There was a problem.

This problem will be explained with reference to FIGS. 9 and 10 shown below. Note that FIG. 10 is an equivalent circuit diagram of the tactile sensor portion, and each resistance R in the figure represents an equivalent resistance due to current flowing through the shortest distance within the pressure-sensitive conductive rubber.

In order to simplify the explanation, the figure shows the electrode wire on the pressure receiving side XI,
X2, back side Y1. Y2, and the measurement point P+ which is the intersection
I, P +2 + R21, Q.

Now, let us assume that each point with the symbol P touches an object and applies a respective force, and that point Q does not touch the object, and we will explain the case where the resistance value at point Q is measured.

At this time, the resistance between the crossing points of the electrode wires is R11,
R12, R21, R22=” (oo indicates that the 1° resistance of the rubber is the resistance value of the insulator).

Now, when voltage E is applied between electrode wires X2 and Y2 as shown in FIG. 10, current does not flow through R, but through resistance R.
The loop current I (=E/ (R2+ +RB +R12)
) will flow, resulting in an erroneous judgment that a force is applied to point Q.

Since an actual tactile sensor has a large number of measurement points, such as 8×8, for example, there is a problem in that an accurate resistance value cannot be detected due to the influence of this wraparound current.

Therefore, although conventional sensors function well as tactile sensors when the distance between each measurement point is sufficiently large or under lower measurement conditions, improvements are still needed to obtain a tactile sensor with higher resolution and better performance. There is a need.

[Purpose of the invention]

The present invention has been made in view of the above problems, and it eliminates the above-mentioned wraparound current and more advantageously corrects the pressing force and resistance when using a pressure-sensitive conductive rubber sheet as a tactile sensor. The purpose is to provide a tactile sensor that enables high-speed processing.

[Structure of the invention]

In order to achieve the above object, the distributed tactile sensor of the present invention has a configuration in which a pair of electrodes is provided at each of a plurality of pressing force measuring points acting on a pressure-sensitive conductive rubber sheet whose resistance changes depending on the pressing force. a rectifying element arranged for each electrode to rectify the current flowing between the pair of electrodes via the rubber sheet,
The plurality of electrodes are divided into a plurality of groups for each polarity, such that the electrodes arranged in a line form one group, and the electrodes in each group are connected in parallel to each other by electrode wires, and the electrodes are divided for each polarity. The method is characterized in that the dividing directions of the groups intersect with each other at each of the measurement points.

That is, as can be understood from the above description, in the loop current circuit, there always occurs a portion where the current flowing in the pressure-sensitive conductive rubber flows in the opposite direction to the normal current direction, but the distributed tactile sensor of the present invention The rectifying element used in this function acts to cut the wraparound current by blocking the current flowing in the opposite direction.

The rectifying element used in the present invention can be a commercially available diode that is normally used in various electronic devices, but the diode is shaped like a flat plate with electrodes arranged on the front and back sides of the diode and attached to a pressure-sensitive conductive rubber sheet. By using a dedicated element that is integrated with the electrode, the sensor can have a more rational shape.

The pressure-sensitive conductive rubber sheet used in the present invention is a sheet of a known pressure-sensitive conductive rubber having an arbitrary thickness. They can be used in stacks, and since the detectable pressing force can be within the range of the force exerted by human fingers or palms, it is possible to approximate the human sense of touch.

The electrodes used in the present invention can be made by pasting precious metal foil, aluminum foil, metal foil with an anti-rust surface, etc. on the rubber surface, or by attaching conductive resin to a flexible, high-strength, insulating synthetic resin film such as polyethylene terephthalate. It can be attached by printing, coating the surface with carbon black, graphite, etc., and layering it on pressure-sensitive conductive rubber.

For the electrodes of the tactile sensor used in the present invention, a pair of electrodes may be arranged facing each other on the front and back sides of each measurement point of the pressure-sensitive conductive rubber sheet, or a pair of electrodes may be arranged at each measurement point on one side of the rubber sheet. Pair electrodes may be arranged with a predetermined spacing between them. In the latter case, a conductive film may be placed on the opposite rubber sheet surface in order to make the current distribution uniform.

The tactile sensor of the present invention has good detection accuracy and can perform high-speed processing, so it can be applied to a wide range of fields other than the robot hand, such as shape identification, slip detection, and tactile imaging systems.

〔Example〕

Hereinafter, the present invention will be specifically explained by way of an example in comparison with the drawings.

FIG. 1 is a three-dimensional equivalent circuit diagram of the sensor portion of the tactile detection circuit of the distributed tactile sensor of this embodiment, in which a diode D constituting a rectifying element according to the present invention is connected in series with a pressure-sensitive conductive rubber. You can see that it has been inserted. FIG. 1 is a diagram corresponding to FIG. 10, and the same symbols are used with similar meanings.

That is, as can be understood from a comparison between FIG. 1 and FIG. 10, the loop current flowing through Ru is blocked by the diode D, so that no loop circuit is formed.

FIG. 2 is a partial perspective view showing an exploded outline of the configuration of the 8×8 matrix tactile sensor 1 of this embodiment. In the figure, a printed wiring board 3 on which electrode wires X and electrodes 4 are printed is superimposed on the pressing surface side of the pressure-sensitive conductive rubber sheet 2. The dotted lines indicating the electrode lines indicate that they are printed on the side facing the pressure-sensitive conductive rubber sheet 2. The portion of the electrode wire X that becomes the electrode is provided with an electrode 4 coated with a conductive paint using carbon black, graphite, etc., and the surface thereof is provided with a corrosion-resistant finish.

On the back side of the pressure-sensitive conductive rubber sheet 2, a printed wiring board 7 is superimposed on which electrodes 5 with electrodes arranged in an 8×8 matrix are printed and electrode wires Y are printed on one side.
The electrode line Y and the electrode line X are arranged to cross each other (in this case, at right angles). The electrode 4 and the electrode line Y are connected by a diode D, which rectifies the current flowing therethrough.

FIG. 3 is an explanatory diagram showing the wiring between the diode D and the electrode 5 in a cross-sectional view to make it easier to understand. As mentioned above, the electrode 5 and the electrode wire Y are actually arranged on the front and back sides of the same printed wiring board 7.

As can be understood from the above explanation, there are 8×8 measurement point groups of the tactile sensor used in this example, and these are divided into 8 groups for each polarity, and each group has 8 electrode wires 8 electrodes 4 or 5 for each Y
are connected linearly and in parallel.

FIG. 4 and FIG. 5, which is a sectional view taken along the line A-A, show an example in which square comb-shaped electrodes are used and the electrodes are disposed only on one surface of the pressure-sensitive conductive rubber. Note that in FIG. 4, the printed wiring board 7 is omitted.

In the figure, electrodes 4 and 5 and electrode lines X and Y are each formed on a printed wiring board 7 by printed wiring. The electrodes 4 and 5 each have a comb-like shape and are arranged with a predetermined gap g between them so that their tally marks match, and the electrode 5 is formed by cutting out a part of the electrode wire Y. ing.

The electrode 4 is connected via the diode D to the electrode wire X printed on the opposite side of the printed wiring board 7, and the connection is made by printing from both sides of the through hole 6 made in the same film 7. By doing so, the tap 4' which is short-circuited through the hole 6 and the electrode wire X are connected by being connected to pins 8 of a commercially available flat diode D using solder 8'. The electrode wires 5 in FIG. 5 are arranged in a direction perpendicular to the paper surface. Note that b in FIG. 5 is a back-up material made of polyurethane, for example, and is used to flatten the back surface of the tactile sensor 1.

When the electrode is placed on one side of the pressure-sensitive conductive rubber 7 as in this modification, the current flows through the shortest path, so it may not be able to sufficiently respond to the deformation of the rubber 7 at the entire measurement point. There are cases. At this time, by arranging the conductive film 9 on the tactile sensing side, it is possible to prevent the current from drifting.

FIG. 6 is an example of a tactile sensor according to another embodiment. In this example, a flat diode D is attached directly to a printed electrode line Y, and an electrode 5 is provided on the surface of the diode D. In this case,
It is necessary to insulate the surface of the electrode wire Y so that it does not come into direct contact with the pressure-sensitive conductive rubber 2. This can be done by applying insulating paint or by utilizing the thickness of the diode D.
This can be achieved by overlapping insulating sheets with windows in the area.

Next, FIG. 7 is an explanatory diagram of a tactile detection circuit using the tactile sensor 1 of FIG. 2. In the figure, the tactile sensor l is of an 8×8 matrix as described above, and the eight electrode lines X and Y of each are connected to analog multiplexers 11 and 12 controlled by a logic circuit 10, The detection signals for each measurement point outputted from the multiplexers 11 and 12 are fed to the A/D converter 13, where they are converted into digital signals and fed to a control device consisting of a one-chip micro combinator (not shown) for the necessary signals. It is configured to perform calculations to perform the following operations.

The outline of the control device used in this example will be explained with reference to FIG. In the figure, a control device 14 is configured to simultaneously control a robot hand 15.
CPU, ROM.

It is composed of a central processing bag ff16 constituted by a RAM, an input/output device 17, an output D/A converter 18 for controlling the robot hand 15, etc., and receives feedback from the tactile sensor 1 to control the robot hand 15. It is used to perform the desired control. In the drawings, members and the like that have already been explained are given the same numbers and their explanations are omitted.

In the tactile sensor of the above embodiment, the detection lines are orthogonally arranged, but in addition, the electrode lines are arranged so that the intersection points, which serve as measurement points, are concentrated in places where it is necessary to sharpen the tactile sense, such as at the tip of a finger. Various layouts such as sparse and dense layouts can be used.

〔Effect of the invention〕

As described above, the present invention is configured to include an element that rectifies the current flowing at the measurement point of the pressure-sensitive conductive rubber used in the distributed tactile sensor, so that it is possible to eliminate the wraparound current flowing through the detection wire unrelated to measurement. can be done, so +11
Even if a relatively simple scan circuit is used, there is no interference due to sneak current, and (21) tactile sensation can be detected at high speed because no calculation processing is required to correct the detection signal. (3) For example, logic circuits, multiplexers, etc. Since the peripheral processing circuits are relatively IMIT!, the entire distributed tactile sensor system including the peripheral circuits can be made economical.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the equivalent circuit of the tactile sensor according to the present invention in three dimensions, Fig. 2 is an exploded explanatory diagram of the tactile sensor used in one embodiment, and Fig. 3 is a cross-sectional diagram of Fig. 2. figure,
FIG. 4 is an explanatory diagram of the main parts of another tactile sensor, FIG. 5 is a sectional view taken along the line A-A in FIG. 4, FIG. 6 is a perspective view of the main parts showing a modification of FIG. 2, and FIG. Fig. 2 is a block diagram of the tactile detection circuit of the embodiment using the tactile sensor, Fig. 8 is a block diagram of the control device shown in Fig. 7, Fig. 9 is an explanatory diagram of the detection line arrangement of the tactile sensor, and Fig. 10 is a block diagram of the control device. FIG. 3 is a perspective view for explaining a loop circuit. 1...Tactile sensor, 2...Pressure-sensitive conductive rubber, 4.5.
...electrode, D...diode, X, Y...detection line.

Claims (1)

[Scope of Claims] 1. A pair of electrodes is arranged at each of a plurality of pressing force measurement points acting on a pressure-sensitive conductive rubber sheet whose resistance changes depending on the pressing force, and A rectifying element for rectifying the current flowing between the electrodes is provided for each electrode, and each electrode is divided into a plurality of groups such that the electrodes arranged in a line form one group for each polarity of the plurality of electrodes. A distributed tactile sensor characterized in that electrodes within the sensor are connected in parallel to each other by electrode wires, and the division directions of the groups divided by polarity intersect with each other at each of the measurement points. 2. A pair of electrodes is placed on one side of the pressure-sensitive conductive rubber sheet.
The distributed tactile sensors according to claim 1, wherein the distributed tactile sensors are provided close to each other at a predetermined interval. 3. Paired electrodes are placed on the front and back surfaces of the pressure-sensitive conductive rubber sheet,
The distributed tactile sensor according to claim 1, wherein the distributed tactile sensors are provided facing each other.