JPS63217241A - Contact tactile sensor - Google Patents

Abstract

PURPOSE:To obtain a sensor of small-sized, thin, and inexpensive constitution which can detect three components of force by arranging strain gauges in a sensor cell corresponding to the three components of force. CONSTITUTION:Connection terminals 22 and strain gauge 23 of silicon are formed in the sensor cell 21 made of silicon and force is received by a pressure reception part 24. The silicon strain gauges 23 are formed on the reverse surface of the sensor cell 21 by a semiconductor wafer process together with the connection terminals 22. The parts of the cell where the strain gauges are provided are made thin and the center recessed part of a pressure reception plate 25 made of ceramic is fitted onto the projection part of the pressure reception part 24 and joined with an adhesive 26. The projection part of the pressure reception part is formed by etching its periphery. Further, terminals 28 are provided to the upper part of a wiring board 27 matching with the positions of the terminals 22 of the cell, and the strain gauges 23 are connected to the wiring of the wiring board 27 through the terminals 22 and 28. Consequently, forces Fx and Fy which are parallel to the surface where the strain gauges are provided and cross each other at right angles and a force Fz perpendicular to the surface can be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Use) The present invention relates to a contact sensor that is attached to, for example, a robot's hand and detects force received from an object to be grasped.

[Conventional technology]

In recent years, technological advances in industrial robots have been remarkable. In particular, there is a growing trend to make robots more intelligent by attaching touch sensors to their hands.

The performance and conditions required for contact sensors include the following:

■High sensitivity High sensitivity for detecting two corners. It is desirable to be able to detect several grams with one element.

■High resolution: Sensor elements are desired to be small and highly dense.

■Wide dynamic range: The operating range should be as wide as possible.

■High reliability and durability: Can withstand harsh environments and long-term use.

■Linearity and hysteresis: Pressure and output should be proportional and there should be no hysteresis.

■Response speed: When an object is grasped, the signal is quickly transmitted to the control unit.

■Flexibility: It is preferable that the material be as soft as the skin of a human hand.

■Slip sensation: Detect not only pressure but also slip.

■Small and inexpensive: Thin, small, and inexpensive.

Several contact sensors that satisfy some of these requirements have been proposed or developed. For example, FIG. 15 shows a push button type sensor. 1 is a metal push button, 2 is an insulating plate, 3 is a spring coil, and 4.5 is an electrode. When the metal pushbutton 1 is not pressed, there is electrical continuity between the electrodes 4 and 5 through the spring coil 3, but when the hand grasps an object, the pushbutton 1 is recessed, so there is no continuity and the object is grasped. This is a method to detect that However, this method only knows the ON and OFF states, and has the drawback that it cannot continuously detect force.

Figure 16 shows one using conductive rubber, with 6 being something to grasp and 7 being something to grasp.
8 is an electrode, and 8 is a conductive rubber. 6 The conductivity (resistance) at the location where force is applied by the grasping object 6 changes, so the state of grasping can be known from this change. However, in this method, a substrate 12 on which non-linear elements 11 are arranged in a matrix is installed between the force and the conductivity. 13 is a light source. When the grasped object 14 presses the silicone rubber 9, the protrusion dents, and the light that was uniformly reflected within the acrylic plate 1O becomes diffusely reflected at this dent, changing the sensitivity of the light receiving element 11.
From now on, we will learn about the sense of touch. However, this method has a complex structure, nonlinearity and hysteresis, and
There are drawbacks such as.

Contact sensors that have been proposed other than these three examples each have their own merits and demerits, and not only are they not fully satisfactory, but all of them sense pressure in only one direction, that is, in the direction perpendicular to the contact surface. At present, there are almost no devices that can even detect forces parallel to a plane.

[Problem that the invention seeks to solve]

Recently, there has been a trend towards the development of contact sensors capable of detecting three component forces, but none of them satisfy all of the performance and conditions mentioned above, and there are none that are particularly thin and capable of measuring three component forces. The ability to detect forces not only perpendicular to the surface but also parallel to the surface is an essential requirement for detecting slip with high sensitivity, and expectations are high for future technological development.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned conventional drawbacks and provide a contact sensor that has a thin structure and can detect forces in three directions.

[Means for solving problems]

In order to achieve this object, the present invention includes a sensor cell in which three sets of strain gauges are arranged corresponding to forces in three directions, a pressure receiving plate fixed to the upper part of the cell, and a sensor cell mounted thereon. The device is characterized by comprising a wiring board which is placed on the ground and is electrically connected to three sets of strain gauges via a plurality of connection terminals.

(Function) According to the present invention, a 3-component force Fx,
Since the strain gauges are arranged in a simple structure corresponding to Fy%Fz, three component forces can be detected with a small, thin, and inexpensive structure.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to Examples.

FIGS. 1(A) and 1(B) are diagrams explaining the basic structure of the contact sensor according to the present invention, and FIG. 1(A) is a top view;
B) is a cross-sectional view. Sensor cell 21 made of silicon
is formed with a connecting terminal (knob-shaped solder) 22. The part of the cell where the strain gauge is installed is made thin inside. The central concave portion of the ceramic pressure receiving plate 25 is fitted into the convex portion of the pressure receiving portion 24 and bonded with an adhesive 26. The convex part of the pressure receiving part is made by etching around it. Since the wiring board 27 is required to have strength and heat resistance, a ceramic multilayer wiring board is desirable.

Terminals 28 are also provided on the upper part of this wiring board 27 in accordance with the positions of the terminals of the cells, and the strain gauge 23 is connected to the wiring of the wiring board 27 via the terminals 22.28.

FIG. 2 is a perspective view of the strain sensor. This sensor detects forces Fx and FM that are parallel to the plane on which the strain gauge is provided and perpendicular to each other, and a force Fz that is perpendicular to the plane.

Figure 3 shows an arrangement of strain gauges for detecting forces Fx and Fy%Fz in three directions. xl, ×2 is the force Fx in the X direction
These strain gauges are located on the same diameter of the cell thin section, and their longitudinal directions are aligned with the radial direction. Y
1 and Yl are strain gauges for detecting the force Fy, and are arranged in a direction perpendicular to the gauges x1 and x2. zl, zl are strain gauges for detecting the vertical force Fz, ×1,
xl, Yl, and Yl are arranged in directions of 45°, respectively.

4(8), (B), (C) and FIG. 5. Strain gauges (dummy gauges) 23G and 230 for temperature compensation are installed in the thick part, and gauge 23A1
23A in the longitudinal direction on the extension of the 23B array.
, 23B. Figure 4 (
When the load indicated by the arrow B) acts on the pressure receiving part 24, a compressive stress of -0 acts on the strain gauge 23A, and a tensile stress of 10 acts on the strain gauge 23B. FIG. 4(C) shows the stress distribution. Almost no stress acts on the strain gauges 23C and 23D in the longitudinal direction. Therefore, the resistances of the strain gauges 23A and 23B change, while the resistances of the strain gauges 23G and 23D hardly change. Figure 5 shows strain gauges 23A123B, 23C,
23D, resistors R1, R2, R3, and R4 are strain gauges 23A and 23A, respectively.
23B, 23fl: corresponds to 23D. When the forces shown in Figure 4 CB) and (C) act, R1 and R2 change, so when voltage E is input, a voltage change ■ is output according to the force, so the magnitude of the force is can be detected.

Figure 6 (A), (B), and (C) show the force Fx in the X direction.
It is a figure explaining the detection. In the same figure (A), Rx2 shown in FIG. 3 is a resistance of strain gauge x1 and x2. Strain gauges x1 and x2 form a half bridge. Figure 6 (C
) indicates the stress applied to each strain gauge in the longitudinal direction when the force Fx shown in FIG.

Figures 7 (A), (B), and (C) are diagrams explaining the detection of the force Fy in the Y direction, and (A) shows the strain gauge Y1%Y2.
Figure 6 (CB) shows the equivalent circuit of a half-bridge composed of gauges Y1%Y2, and Figure 6 (C) shows the stress that acts on each strain gauge when force Fy acts on the pressure receiving part 24. , 35 is an output terminal, RYI and RY2 are resistances of strain gauges Y1 and Yl, respectively, and vy is an output voltage.

Figures 8 (8), (B), and (C) are diagrams for explaining the detection of a force Fz perpendicular to the surface of the pressure receiving part 24 (perpendicular to the strain gauge installation surface). In addition to the strain gauges z1 and zl explained in Fig. 3,
Dummy gauges z3 and z4 having their longitudinal directions in the circumferential direction are arranged, and each of the gauges 21 to z4 constitutes a bridge as shown in FIG. 3(B). 36 is an output terminal, and returning to FIG. 6, when the force Fx is applied to the pressure receiving part 24, the strain gauge
I receives a compressive force (-〇), and its resistance value decreases.

On the other hand, the strain gauge x2 receives a tensile force (10), and its resistance value increases. Other four strain gauges Yl, Yl, zl
, zl d also generate a little stress as shown in FIG. 6(c) d. Naturally, the bridge output Vx is large, Vz is small, and vy is negligible. Since the output Vz is caused by the force of Fx, this must be corrected. Since this apparent output Vz is approximately proportional to Fx, that is, Vx, the correction formula for Vz is Vz -a-Vx (1). Here a is a proportionality constant.

In Fig. 7, when F31 is applied in the direction of the arrow, compressive force <-0> acts on strain gauge Y1, tensile force (10〇) acts on strain gauge Y2, and vy is output to the half bridge. be done. The stress of the strain gauge is as shown in Figure 7 (C), and the output of each bridge is maximum at vy, small at Vz,
Vx can be ignored. Since the apparent output Vz is approximately proportional to vy, Vz is corrected by the following formula, so the figure (B
), Vz is output to the red bridge. Since the stress at strain gauges z3 and 74 is small, it does not contribute to Vz.

Since the resistance changes of strain gauges x1 and x2 and Yl and Yl have the same sign and are equal, outputs Vx and vy are not generated, so there is no need to consider the influence of Fz on vx and vy.

FIG. 9 shows the stress acting in the longitudinal direction of each gauge when forces Fx and Fy are applied simultaneously. Strain gauges Xi and Yl have compressive stress due to forces Fx and Fy, respectively, and strain gauges x2 and Yl have compressive stress due to forces Fx and p, respectively.
A tensile stress due to y acts. Strain gauges XI, X2 are hardly affected by force py, and strain gauges Yl,
Yl is almost unaffected by force Fx.

Due to the forces Fx and FM, strain gauge L1 receives compressive stress, and strain gauge z2 receives tensile stress. As a result, each bridge has an output. Output VZ' is force F× and F31
The true output VZ is obtained by correcting the following equation.

Vz -Vz' -a-Vx -b-Vy
(3) When forces Fy and FZ are applied simultaneously to Figure 1O,
Compressive stress is applied to strain gauges Y1 and Zl from each strain, and strain gauge Y
2, the outputs Vx and vy are not produced.Therefore, when the forces FY and Fz act simultaneously, the pressure generated on each bridge is equal to the force F3/force y and the forces FY and F.
z is the output VZ'. The true output Vz is obtained by correcting the apparent output VZ' using the following equation.

Vz = Vz'-b-Vy (
4) Figure 11 shows the stress acting on each strain gauge when forces Fz and Fx are applied simultaneously. The situation is exactly the same as when the forces Fy and Fz act simultaneously, and each bridge has an output Vz due to the force Fx and an output Vz due to the forces Fx and Fz.
' will occur. In this case, the true output Vz can be obtained by correcting the apparent output VZ' using the following formula: νz −V
z' -a-Vx (5) Figure 12 shows the force F
It shows the stress acting on each strain gauge when x, Fy and Fz are applied simultaneously. As is clear from the explanation when forces in two directions act simultaneously, each bridge has an output vx due to force Fx, an output vy due to force ry, and forces Fx and Fy.
It is easy to find the relationship between the apparent force output and the force due to Fz. Further, it is easy to obtain the above-mentioned correction coefficients aa and b. Therefore, by finding these relationships and coefficients in advance, when arbitrary forces Fx, Fy, and Fz are applied, their magnitude can be determined as Vx by reading the cell bridge output Vx%vy%VZ. and V can be determined from their unchanged values, and Vz can be determined by performing a correction calculation from equation (6). Also, when force is applied in any direction, you can know the component forces in the three directions.

FIG. 13 shows that within one sensor cell, forces Fx in three directions,
Strain gauges, wiring and terminals compatible with Fy and FZ.

This shows the configuration. It goes without saying that signals from each terminal are transmitted to multilayer wiring built into a lower wiring board (not shown), and this manufacturing can be easily achieved by a known method. FIG. 14 is an equivalent circuit of the configuration shown in FIG. 13. Since each reference number in FIG. 13 and FIG. 14 is the same as in the previous example, the explanation is omitted. Further, the operation of the configuration example shown in FIG. 13 is also as described above.

〔Effect of the invention〕

As explained above, according to the present invention, the strain gauge is arranged in a simple structure in correspondence with the 3-component force Fx%Fy%Fz within the contact sensor cell, so it can be made smaller, thinner, and more dense.
Three component forces can be detected with an inexpensive configuration. For this reason, attaching this contact sensor to a robot's hand would be extremely effective in making the robot more intelligent.

[Brief explanation of the drawing]

1A and 1B are a top view and a cross-sectional view showing the basic structure of the contact sensor of the present invention, FIG. 2 is a perspective view of the sensor, FIG. 3 is a layout diagram of strain gauges, and FIG. Figures (A), (B), and (C) are diagrams for explaining the basics of the operation of the present invention, and Figures (A) and (B) are a top view and a cross-sectional view showing the arrangement of strain gauges, respectively. Figure 5 (C) shows the stress distribution of the strain gauge, Figure 5 is a Wheatstone bridge circuit diagram composed of strain gauges, Figure 6 (^), (B), and (C) shows the detection of force in the X direction. , Figures 7 (^), (B), and (C) are diagrams explaining the detection of force in the Y direction, and Figures 8 (^), (B), and (C) are diagrams explaining the detection of force in the Z direction. , Figure 6 (A), Figure 7 (
A) and FIG. 8(A) are diagrams showing the arrangement and wiring of strain gauges, and FIG. 6(B), FIG. 7(B), and FIG. 8(B) are Wheatstone bridge circuit diagrams configured with strain gauges. , Fig. 6(C), Fig. 7(C) and Fig. 8(C) are diagrams showing the stress of each strain gauge, Fig. 9, Fig. 10, Fig. 11 and Fig. 12 are respectively in the X direction. and Y direction, Y direction and Z direction, Z direction and X direction, and the stress of each strain gauge when force is applied in X direction, Y direction, and Z direction. Figure 13 shows the stress of strain gauge in cell. FIG. 14 is an equivalent circuit diagram of the configuration shown in FIG. 13, and FIGS. 15 to 17 are cross-sectional views showing the structure of a conventional contact sensor. 1... Metal push button, 2... Insulating plate, 3... Spring coil, 4.5... Electrode, 6... Gripping object, 7... Electrode, 8... Conductive rubber, 9... silicone rubber, lO... acrylic plate, 11... light receiving element, 12... substrate, 13... light source, 14... grasping object, 21... sensor cell, 22... Connection terminal, 23... Strain gauge, 24... Pressure receiving part, 25... Pressure receiving plate, 26... Adhesive, 27... Wiring board, 28... Terminal, 31... Wiring, 32... Input voltage terminal, 33... Earth terminal, 34.35.36... Output terminal, ×1, ×2
... Strain gauge for force in the X direction, Yl, Yl
... Strain gauge for force in the Y direction, Zl, Z2
... Strain gauge for force in Z direction, z3, z4
... Dummy gauge, E ... Input voltage, Vx, Vy, Vz ... Output voltage. Takekosen's Ajin Kogyo Rijutsu - Jisuke's Old House Koni 24th History and Ichiukou Shouting to Nasun (A) (B) Figure 6 (A) (C) Figure 7 (A) (B) (C) Figure 8 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 3+ is a gradient coil Figure 15 Figure 16

Claims (1)

[Scope of Claims] 1) A sensor cell in which three sets of strain gauges are arranged corresponding to forces in three directions, a pressure receiving plate fixed to the top of the cell, and the sensor cell placed therein; A contact sensor comprising a wiring board electrically connected to the three sets of strain gauges via a plurality of connection terminals. 2) The contact sensor according to claim 1, wherein the sensor cell is made of silicon, and each of the three sets of strain gauges is made of a high-resistance silicon layer. 3) The contact sensor according to claim 1 or 2, wherein at least one of the forces in the three directions is corrected by a linear expression of forces in other directions.