JP2017187399A - Tactile sensor and shearing force detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tactile sensor and a shearing force detection method capable of detecting a shearing force in a rotation axis direction.SOLUTION: The tactile sensor includes: a pair of force detection elements each of which is disposed, in a periphery of a predetermined area of a predetermined plane, at a position different from each other in a circumferential direction of the predetermined area; and a detect circuit that detects changes of state of the pair of force detection elements as an electric signal. The detect circuit is configured so as, when a shearing force is applied in a rotation direction of a vertical axis with respect to the predetermined plane in the predetermined area, to change the strength of the electric signal depending on the shearing force.SELECTED DRAWING: Figure 4

Description

  The present case relates to a tactile sensor and a shearing force detection method.

  Many sensors are required for controlling the robot so as not to damage humans and surrounding objects. Among them, a tactile sensor that detects pressure and shear force applied to a contact surface with an object is important. For example, a tactile sensor that detects a shear force using a piezoresistive element is disclosed (for example, see Non-Patent Document 1).

“Research on 3-axis tactile sensor using piezoresistive doubly supported beam”, Tateishi Science and Technology Foundation, Grant-in-Aid for Scientific Research (No. 22), 2013

  However, the above technique cannot detect the shear force in the direction of the rotation axis.

  In one aspect, an object of the present invention is to provide a tactile sensor and a shearing force detection method capable of detecting a shearing force in the rotation axis direction.

  In one aspect, the tactile sensor has a pair of force detection elements arranged at different positions in the circumferential direction of the predetermined area and a state change of the pair of force detection elements around the predetermined area of the predetermined plane. A detection circuit configured to detect an electrical signal, wherein the detection circuit converts the strength of the electrical signal to the shear force when a shear force is applied in a rotation direction of a vertical axis with respect to the predetermined plane in the predetermined region. It is comprised so that it may change according to it.

  A shearing force in the direction of the rotation axis can be detected.

(A) is a figure which illustrates the whole structure of the robot system which concerns on Example 1, (b) is a figure which illustrates a shear force. (A) is a schematic perspective view of a tactile sensor element, (b) is a schematic plan view of a tactile sensor element, (c) is an enlarged view of (b). (A)-(c) is a figure for demonstrating the detail of a force detection element. It is the figure which extracted and drawn the piezoresistive element in FIG.2 (c). It is a Wheatstone bridge for acquiring a detection result of a piezoresistive element. It is a figure which illustrates a detection circuit. (A) And (b) is a figure illustrated about the detection of the shearing force by a tactile sensor element. (A) is a schematic perspective view of the tactile sensor element according to the second embodiment, (b) is a schematic plan view of the tactile sensor element, and (c) is an enlarged view of (b). It is a figure which illustrates LC circuit. It is the figure which extracted and drawn the capacitor in FIG.8 (c). FIG. 6 is a diagram illustrating a detection circuit according to a second embodiment. (A) And (b) is a figure illustrated about the detection of the shearing force by a tactile sensor element. (A) is a figure which illustrates detection of a capacitor when external force is applied to a tactile sensor element, (b) is a figure which illustrates detection of a capacitor when rotational force is applied to a tactile sensor element. (C) is a figure which illustrates a capacitor, (d) And (e) is the sectional view on the AA line of (c). (A) And (b) is a figure for demonstrating the modification 1. FIG. It is a figure which illustrates about the robot system concerning the modification 2.

  Hereinafter, embodiments will be described with reference to the drawings.

  FIG. 1A is a diagram illustrating the overall configuration of the robot system 100 according to the first embodiment. As illustrated in FIG. 1A, the robot system 100 includes a robot hand 10, a tactile sensor element 20, a detection circuit 30, a control unit 40, and the like. The tactile sensor element 20 and the detection circuit 30 function as a tactile sensor.

  The robot hand 10 performs an operation by holding the object with the holding unit 11 and releasing it. For example, the robot hand 10 performs movement in three axis directions, horizontal turning, vertical turning, and the like. In FIG. 1A, as an example, a robot hand 10 viewed from above is drawn.

  The tactile sensor element 20 is disposed on the contact surface of the gripper 11 with the object. As illustrated in FIG. 1B, the tactile sensor element 20 includes a contact force (pressure in the Z-axis direction) on the contact surface 21, a shear force in the X-axis direction, a shear force in the Y-axis direction, and a rotation axis direction. Detect shear force. The shearing force in the direction of the rotational axis is a rotational shearing force about the Z axis. When the robot hand 10 grips an object, a shearing force in the direction of the rotation axis acts when the robot hand 10 grips a portion that is off the center of gravity of the object. Therefore, it is important to detect the shearing force in the rotation axis direction. The detection circuit 30 is a circuit that detects a change in the state of the tactile sensor element 20 as an electrical signal. The detection result of the detection circuit 30 is transmitted to the control unit 40. The control unit 40 controls the operation of the robot hand 10 based on the detection result of the detection circuit 30.

  FIG. 2A is a schematic perspective view of the tactile sensor element 20. As illustrated in FIG. 2A, an elastic body 22 may be provided on the contact surface 21 of the tactile sensor element 20. FIG. 2B is a schematic plan view of the tactile sensor element 20. 2A and 2B, the elastic body 22 is transmitted. FIG.2 (c) is an enlarged view of FIG.2 (b).

  As illustrated in FIG. 2C, the center portion of the contact surface 21 of the tactile sensor element 20 is a contact portion 23 that comes into contact with an object. The contact surface 21 corresponds to the XY plane. On the contact surface 21, a plurality of types of force detection elements are arranged radially with the contact portion 23 as the center.

  Here, details of the force detection element will be described. As illustrated in FIG. 3A, the force detection element includes a pair of piezoresistive elements 30a and 30b. The piezoresistive elements 30a and 30b include beams having a longitudinal direction in the Y-axis direction, for example. In the beam of the piezoresistive element 30a, for example, an elastic body 31 is disposed on the X axis minus side, and a piezoresistive layer 32 is disposed on the X axis plus side. For example, the elastic body 31 is a silicone resin or the like. The piezoresistive layer 32 is formed, for example, by doping an impurity into a Si single crystal by ion implantation, thermal diffusion, or the like. The elastic body 31 and the piezoresistive layer 32 are joined. In the beam of the piezoresistive element 30b, a piezoresistive layer 32 is arranged on the X axis minus side, and an elastic body 31 is arranged on the X axis plus side. The piezoresistive layer 32 and the elastic body 31 are joined.

  When a force in the X-axis plus direction is applied to the force detection element and the beam is distorted, as illustrated in FIG. 3B, the beams of the piezoresistive element 30a and the piezoresistive element 30b are curved and the X-axis plus Bends to extend sideways. In this case, the piezoresistive layer 32 is pulled in the piezoresistive element 30a. On the other hand, in the piezoresistive element 30b, the piezoresistive layer 32 is compressed. Thus, in the pair of piezoresistive elements 30a and 30b, the piezoresistive layer 32 receives a tensile force and a compressive force, respectively. That is, the resistance value of each piezoresistive layer 32 increases and decreases in the positive and negative directions. By measuring this change in resistance value with a bridge circuit as shown in FIG. 3C, the shearing force can be detected.

  FIG. 4 is a diagram illustrating the piezoresistive element extracted from FIG. Each piezoresistive element is arranged on the contact surface 21 around the contact portion 23 at a different position in the circumferential direction. As illustrated in FIG. 4, on the contact surface 21, the X axis is set so that the beam formed by the elastic body 31 and the piezoresistive layer 32 extends radially in a point symmetry with respect to the contact portion 23 along the Y axis direction. A pair of piezoresistive elements 30xa and 30xb for detecting the shear force in the direction are arranged. The piezoresistive element 30xa is arranged on the Y axis plus side, and the piezoresistive element 30xb is arranged on the Y axis minus side.

  In the piezoresistive element 30xa, the elastic body 31 is disposed on the X axis minus side, and the piezoresistive layer 32 is disposed on the X axis plus side. In the piezoresistive element 30xb, the elastic body 31 is disposed on the X axis plus side, and the piezoresistive layer 32 is disposed on the X axis minus side. That is, in the same circumferential direction, the arrangement side of the elastic body 31 and the piezoresistive layer 32 of the pair of piezoresistive elements 30xa and 30xb is the same. The same circumferential direction means a circumferential direction when unified in either the clockwise direction or the counterclockwise direction. In the pair of piezoresistive elements 30xa and 30xb, when a shearing force in the X-axis direction is applied, each piezoresistive layer 32 receives a tensile force and a compressive force, so the shearing force in the X-axis direction is detected. be able to.

  On the contact surface 21, a shear force in the Y-axis direction is detected so that the beam formed by the elastic body 31 and the piezoresistive layer 32 extends radially in a point-symmetric manner with respect to the contact portion 23 along the X-axis direction. A pair of piezoresistive elements 30ya and 30yb are arranged. The piezoresistive element 30ya is arranged on the X axis plus side, and the piezoresistive element 30yb is arranged on the X axis minus side.

  In the piezoresistive element 30ya, the elastic body 31 is disposed on the Y axis plus side, and the piezoresistive layer 32 is disposed on the Y axis minus side. In the piezoresistive element 30yb, the elastic body 31 is disposed on the Y axis minus side, and the piezoresistive layer 32 is disposed on the Y axis plus side. That is, in the same circumferential direction, the arrangement side of the elastic body 31 and the piezoresistive layer 32 of the pair of piezoresistive elements 30ya and 30yb is the same. In the pair of piezoresistive elements 30ya and 30yb, each piezoresistive layer 32 receives a tensile force and a compressive force when a shearing force in the Y-axis direction is applied, so that the shearing force in the Y-axis direction is detected. be able to.

  A pair of piezoresistive elements 30za and 30zb are arranged at any location on the contact surface 21 so that the beam formed by the elastic body 31 and the piezoresistive layer 32 extends radially with respect to the contact portion 23. ing. In the piezoresistive element 30za, the elastic body 31 is disposed on the Z axis plus side, and the piezoresistive layer 32 is disposed on the Z axis minus side. In the piezoresistive element 30zb, the elastic body 31 is disposed on the Z axis minus side, and the piezoresistive layer 32 is disposed on the Z axis plus side. That is, in the Z-axis direction, the arrangement side of the elastic body 31 and the piezoresistive layer 32 of the pair of piezoresistive elements 30za and 30zb is reversed. In this pair of piezoresistive elements 30za and 30zb, when a shear force in the Z-axis direction is applied, each piezoresistive layer 32 receives a tensile force and a compressive force, and thus the shear force in the Z-axis direction is detected. be able to.

  A pair of piezoresistive elements 30ra and 30rb are arranged at any location on the contact surface 21 so that the beam formed by the elastic body 31 and the piezoresistive layer 32 extends radially with respect to the contact portion 23. ing. In any of the piezoresistive elements 30ra and 30rb, when the contact surface 21 is divided by a line connecting the piezoresistive elements 30ra and 30rb, the elastic body 31 is disposed on the same side, and the piezoresistive layer 32 is disposed on the opposite side. Yes. That is, in the same circumferential direction, the arrangement side of the elastic body 31 and the piezoresistive layer 32 of the pair of piezoresistive elements 30ra and 30rb is reversed. In the present embodiment, as an example, the piezoresistive element 30ra is disposed between the piezoresistive element 30xa and the piezoresistive element 30yb, and the piezoresistive element 30rb is disposed between the piezoresistive element 30xb and the piezoresistive element 30ya. ing. The detection of shearing force by the piezoresistive elements 30ra and 30rb will be described later.

  In addition, as illustrated in FIG. 2C, the contact portion 23 side end of the piezoresistive elements 30xa, 30xb, 30ya, 30yb, 30za, 30zb, 30ra, and 30rb is connected to the reference electrode 24 connected to the reference voltage Vs. It is connected. The other end of each piezoresistive element is connected to an individual electrode 25.

  FIG. 5 shows, for example, a Wheatstone bridge for obtaining detection results of the piezoresistive elements 30xa and 30xb. The Wheatstone bridge is a part of the detection circuit 30. As illustrated in FIG. 5, the reference voltage Vs is applied between the piezoresistive element 30xa and the piezoresistive element 30xb. The piezoresistive elements 30xa and 30xb together with two fixed resistors R constitute a Wheatstone bridge. The shearing force can be detected by detecting the voltage value that changes due to the resistance change of the piezoresistive elements 30xa and 30xb. With respect to the piezoresistive elements 30ya, 30yb, 30za, 30zb, 30ra, and 30rb, each shear force can be detected by configuring a similar Wheatstone bridge.

  FIG. 6 is a diagram illustrating the detection circuit 30. The detection circuit 30 includes a bridge circuit for detecting each shear force. A Wheatstone bridge is configured for each of the piezoresistive elements 30xa and 30xb, the piezoresistive elements 30ya and 30yb, the piezoresistive elements 30za and 30zb, and the piezoresistive elements 30ra and 30rb. The variable resistor Rp_x1 corresponds to the piezoresistive element 30xa, and the variable resistor Rp_x2 corresponds to the piezoresistive element 30xb. The variable resistor Rp_y1 corresponds to the piezoresistive element 30ya, and the variable resistor Rp_y2 corresponds to the piezoresistive element 30yb. The variable resistor Rp_z1 corresponds to the piezoresistive element 30za, and the variable resistor Rp_z2 corresponds to the piezoresistive element 30zb. The variable resistor Rp_r1 corresponds to the piezoresistive element 30ra, and the variable resistor Rp_r2 corresponds to the piezoresistive element 30rb.

  The Amp_x output Vx_out of the Wheatstone bridge amplifier formed by the piezoresistive elements 30xa and 30xb is a value corresponding to the shearing force in the X-axis direction. The Amp_y output Vy_out of the Wheatstone bridge amplifier formed by the piezoresistive elements 30ya and 30yb is a value corresponding to the shearing force in the Y-axis direction. The Amp_z output Vz_out of the Wheatstone bridge amplifier formed by the piezoresistive elements 30za and 30zb is a value corresponding to the shearing force in the Z-axis direction. The output Vr_out of Amp_r of the Wheatstone bridge amplifier formed by the piezoresistive elements 30ra and 30rb is a value corresponding to the shearing force in the Z-axis rotation direction.

  FIG. 7A and FIG. 7B are diagrams illustrating the detection of shear force by the tactile sensor element 20. FIG. 7A is a diagram illustrating a case where an external force F is applied to the tactile sensor element 20 from the X axis minus side and the Y axis minus side to the X axis plus side and the Y axis plus side. That is, the external force F includes an external force component Fx toward the X axis plus side and an external force component Fy toward the Y axis plus side.

  As illustrated in FIG. 7A, when an external force F is applied to the tactile sensor element 20, in the piezoresistive elements 30xa and 30xb, the piezoresistive layer 32 receives a tensile force and a compressive force by the external force component Fx, respectively. Therefore, the piezoresistive elements 30xa and 30xb detect the shear force toward the X axis plus side. In the piezoresistive elements 30ya and 30yb, the piezoresistive layer 32 receives a tensile force and a compressive force by the external force component Fy, respectively. Therefore, the piezoresistive elements 30ya and 30yb detect the shearing force toward the Y axis plus side.

  In the piezoresistive elements 30ra and 30rb, both piezoresistive layers 32 receive a tensile force. Therefore, the piezoresistive elements 30ra and 30rb do not detect a shear force.

  FIG. 7B is a diagram illustrating a case where a rotational force R is applied as an external force around the Z axis. As an example, a case where a clockwise rotational force R is applied in a plan view with respect to the contact surface 21 will be considered.

  As illustrated in FIG. 7B, when the rotational force R is applied to the tactile sensor element 20, in the piezoresistive elements 30xa and 30xb, both the piezoresistive layers 32 are each subjected to a tensile force by the rotational force R. Therefore, the piezoresistive elements 30xa and 30xb do not detect a shear force. Also in the piezoresistive elements 30ya and 30yb, both piezoresistive layers 32 receive a tensile force due to the rotational force R. Therefore, the piezoresistive elements 30ya and 30yb also do not detect shear force.

  On the other hand, in the piezoresistive elements 30ra and 30rb, the piezoresistive layer 32 receives a tensile force and a compressive force, respectively. Therefore, the piezoresistive elements 30ra and 30rb detect the shear force in the Z-axis rotation direction.

  According to the present embodiment, the piezoresistive elements 30 ra and 30 rb are arranged at different positions in the circumferential direction of the contact portion 23 around the contact portion 23 of the contact surface 21. In addition, a detection circuit 30 that detects a change in the state of the piezoresistive elements 30ra and 30rb as an electrical signal is provided. The detection circuit 30 is configured to change the intensity of the electric signal according to the shearing force when a shearing force is applied in the rotation direction of the vertical axis (Z axis) with respect to the contact surface 21 in the contact portion 23. ing. Thereby, the shear force in the direction of the rotation axis can be detected. In addition, since changes in the resistance values of the piezoresistive elements 30ra and 30rb are detected, temperature changes and interference with other axes can be canceled, and a stable output value can be obtained. The same applies to the piezoresistive elements 30xa, 30xb, 30ya, 30yb, 30za, and 30zb.

  In the present embodiment, the piezoresistive elements 30ra and 30rb are arranged point-symmetrically with respect to the contact portion 23, but are not limited thereto. The piezoresistive elements 30 ra and 30 rb need only be arranged at different positions in the circumferential direction of the contact portion 23 around the contact portion 23 of the contact surface 21. The piezoresistive elements 30xa and 30xb are arranged point-symmetrically with respect to the contact portion 23, but are not limited thereto. The piezoresistive elements 30xa and 30xb may be arranged so as not to be parallel to the X axis with the contact portion 23 of the contact surface 21 interposed therebetween. The piezoresistive elements 30ya and 30yb are arranged point-symmetrically with respect to the contact portion 23, but are not limited thereto. The piezoresistive elements 30ya and 30yb may be arranged so as not to be parallel to the Y axis with the contact portion 23 of the contact surface 21 interposed therebetween.

  In the first embodiment, the shear force is detected using a piezoresistive element, but the present invention is not limited to this. The shearing force may be detected by using a capacitor whose capacitance value changes when an external force is applied. In the second embodiment, an example in which a capacitor is used as a force detection element will be described.

  FIG. 8A is a schematic perspective view of the tactile sensor element 20a according to the second embodiment. As illustrated in FIG. 8A, an elastic body 22 is provided on the contact surface 21 of the touch sensor element 20a. FIG. 8B is a schematic plan view of the tactile sensor element 20a. 8A and 8B, the elastic body 22 is transmitted. FIG. 8C is an enlarged view of FIG.

  As illustrated in FIG. 8C, the central portion of the contact surface 21 of the tactile sensor element 20a is the contact portion 23 that contacts the object. The contact surface 21 corresponds to the XY plane. On the contact surface 21, a plurality of types of force detection elements are arranged radially with the contact portion 23 as the center.

  Here, details of the force detection element will be described. As illustrated in FIG. 9, the force detection element includes a pair of capacitors 40a and 40b. In the capacitors 40a and 40b, the electrode 41 and the electrode 42 are spaced apart from each other. Thereby, the capacitors 40a and 40b have electric capacity. As the electrode 41 and the electrode 42 approach each other, the electric capacity increases. On the other hand, when the electrode 41 and the electrode 42 are separated from each other, the electric capacity is reduced. By detecting the electric capacitance obtained by changing the distance between the electrode 41 and the electrode 42 by the shearing force, the magnitude of the shearing force can be detected.

  For example, in the LC circuit illustrated in FIG. 9, the total electric capacity C of the capacitors 40a and 40b can be detected by detecting the output of the oscillation / frequency detection circuit.

  FIG. 10 is a diagram illustrating the capacitor extracted from FIG. As illustrated in FIG. 10, on the contact surface 21, a pair of capacitors 40 xa and 40 xb are arranged so as to extend radially in a point symmetry with respect to the contact portion 23 along the Y-axis direction. The capacitor 40xa is disposed on the Y axis plus side, and the capacitor 40xb is disposed on the Y axis minus side.

  In the capacitors 40xa and 40xb, the X-axis plus side electrode 41 is fixed, and the X-axis minus side electrode 42 is arranged so as to be bent in the Y-axis direction. That is, with respect to the same circumferential direction, the capacitors 40xa and xb have the arrangement side of the electrode 41 and the electrode 42 reversed. In the pair of capacitors 40xa and 40xb, when the shearing force in the X-axis plus direction is applied, the electrode 42 approaches the electrode 41 side, so that the electric capacities of the capacitors 40xa and 40xb increase. On the other hand, since the electrode 42 is separated from the electrode 41 when a shearing force in the X-axis minus direction is applied, the electric capacities of the capacitors 40xa and 40xb are reduced. That is, the shear force in the X-axis direction can be detected.

  On the contact surface 21, a pair of capacitors 40 ya and 40 yb are arranged so as to extend radially in a point-symmetric manner with respect to the contact portion 23 along the X-axis direction. In the capacitors 40ya and 40yb, the Y-axis plus side electrode 41 is fixed, and the Y-axis minus side electrode 42 is arranged to be bendable in the Y-axis direction. That is, with respect to the same circumferential direction, the capacitors 40ya and yb have the arrangement side of the electrode 41 and the electrode 42 reversed. In this pair of capacitors 40ya and 40yb, when a shearing force in the Y-axis plus direction is applied, the electrode 42 approaches the electrode 41 side, so that the electric capacities of the capacitors 40ya and 40yb increase. On the other hand, since the electrode 42 is separated from the electrode 41 when a shearing force in the negative Y-axis direction is applied, the electric capacities of the capacitors 40ya and 40yb are reduced. That is, the shear force in the Y-axis direction can be detected.

  A pair of capacitors 40za and 40zb are arranged at any location on the contact surface 21 so as to extend radially in a point-symmetric manner with respect to the contact portion 23. In the capacitors 40za and 40zb, the electrodes 41 and 42 are fixed, and the electrode 43 disposed between the electrodes 41 and 42 is disposed so as to be bent in the Z-axis direction. That is, with respect to the Z axis, the capacitors 40za and 40zb have the same arrangement side of the first electrode and the second electrode. In the pair of capacitors 40za and 40zb, when a shearing force is applied in the Z-axis minus direction, the electrode 43 is bent in the Z-axis minus direction, so that the opposing area between the electrode 41 and the electrode 43 and the electrode 42 The area facing the electrode 43 is reduced. Thereby, the electric capacities of the capacitors 40za and 40zb are reduced. That is, the shear force in the Z-axis direction can be detected.

  A pair of capacitors 40ra and 40rb is arranged at any location on the contact surface 21 so as to extend radially in a point-symmetric manner with respect to the contact portion 23. In the capacitor 40ra, when the contact surface 21 is divided by a line connecting the capacitors 40ra and 40rb, the electrode 41 is fixed on one side, and the electrode 42 is arranged on the other side so as to bend. In the capacitor 40rb, the electrode 41 is fixed on the other side, and the electrode 42 is arranged on the other side so as to bend. That is, in the same circumferential direction, the capacitors 40ra and 40rb have the same arrangement side of the electrode 41 and the electrode 42. In the present embodiment, as an example, the capacitor 40ra is disposed between the capacitor 40xa and the capacitor 40yb, and the capacitor 40rb is disposed between the capacitor 40xb and the capacitor 40ya. The detection of the shearing force of the capacitors 40ra and 40rb will be described later.

  FIG. 11 is a diagram illustrating the detection circuit 30 according to the present embodiment. As illustrated in FIG. 11, the detection circuit 30 includes an LC circuit for detecting each shear force. LC circuits are respectively configured for the capacitors 40xa and 40xb, the capacitors 40ya and 40yb, the capacitors 40za and 40zb, and the capacitors 40ra and 40rb. The variable capacitance Cx1 corresponds to the electric capacitance of the capacitor 40xa, and the variable capacitance Cx2 corresponds to the electric capacitance of the capacitor 40xb. The variable capacitor Cy1 corresponds to the electric capacity of the capacitor 40ya, and the variable capacity Cy2 corresponds to the electric capacity of the capacitor 40yb. The variable capacitance resistor Cr1 corresponds to the electric capacitance of the capacitor 40ra, and the variable capacitance Cr2 corresponds to the electric capacitance of the capacitor 40rb. The variable capacitor Cz1a corresponds to the electric capacity between the electrode 41 and the electrode 43 of the capacitor 40za. The variable capacitor Cz1b corresponds to the electric capacity between the electrode 42 and the electrode 43 of the capacitor 40za. The variable capacitor Cz2a corresponds to the electric capacity between the electrode 41 and the electrode 43 of the capacitor 40zb. The variable capacitor Cz2b corresponds to the electric capacity between the electrode 42 and the electrode 43 of the capacitor 40zb.

  The output Vx_out of the oscillation / frequency detection circuit of the LC circuit of the capacitors 40xa and 40xb is a value corresponding to the shearing force in the X-axis direction. The output Vy_out of the oscillation / frequency detection circuit of the LC circuit of the capacitors 40ya and 40yb is a value corresponding to the shearing force in the Y-axis direction. The output Vz_out of the oscillation / frequency detection circuit of the LC circuit of the capacitors 40za and 40zb is a value corresponding to the shearing force in the Z-axis direction. The output Vr_out of the oscillation / frequency detection circuit of the LC circuit of the capacitors 40ra and 40rb is a value corresponding to the shearing force in the Z-axis rotation direction.

  FIGS. 12A and 12B are diagrams illustrating the detection of shear force by the tactile sensor element 20a. FIG. 12A is a diagram illustrating a case where an external force F is applied to the tactile sensor element 20a from the X axis minus side and the Y axis minus side to the X axis plus side and the Y axis plus side. That is, the external force F includes an external force component Fx toward the X axis plus side and an external force component Fy toward the Y axis plus side.

  As illustrated in FIG. 12A, when the external force F is applied to the tactile sensor element 20a, the electrode 42 is curved toward the electrode 41 in the capacitor 40xa, so that the capacitance Cx1 increases (Cx1 + ΔCx1). Also in the capacitor 40xb, the electrode 42 is bent toward the electrode 41, so that the capacitance Cx2 is increased (Cx2 + ΔCx2). Since ΔCx1 + ΔCx2 is a large value, the capacitors 40xa and 40xb detect the shearing force to the X axis plus side.

  In the capacitor 40ya, the electrode 42 is curved toward the electrode 41, so that the capacitance Cy1 increases (Cy1 + ΔCy1). Also in the capacitor 40yb, the electrode 42 is bent toward the electrode 41, so that the capacitance Cy2 increases (Cy2 + ΔCy2). Since ΔCy1 + ΔCy2 is a large value, the capacitors 40ya and 40yb detect the shearing force to the Y axis plus side.

  In the capacitor 40ra, the electric capacity Cr1 is increased (Cr1 + ΔCr1) by bending the electrode 42 toward the electrode 41. On the other hand, in the capacitor 40rb, the electric capacity Cr2 becomes small (Cr2-ΔCr2) when the electrode 42 is bent to the opposite side to the electrode 41. Since ΔCr1 and ΔCr2 are substantially the same, the capacitors 40ra and 40rb do not detect the shearing force.

  FIG. 12B is a diagram illustrating a case where a rotational force R is applied as an external force around the Z axis. As an example, consider a case where a clockwise rotational force is applied in a plan view with respect to the contact surface 21.

  As illustrated in FIG. 12B, when the rotational force R is applied to the tactile sensor element 20a, in the capacitor 40xa, the electrode 42 is bent toward the electrode 41 by the rotational force R. As a result, the electric capacity Cx1 increases (Cx1 + ΔCx1). In the capacitor 40xb, the electrode 42 is bent to the side opposite to the electrode 41 by the rotational force R. As a result, the electric capacity Cx2 is reduced (Cx2-ΔCx2). Since ΔCx1 and ΔCx2 are substantially the same, the capacitors 40xa and 40xb do not detect the shear force.

  In the capacitor 40ya, the electrode 42 is bent to the opposite side to the electrode 41 by the rotational force R. As a result, the electric capacity Cy1 is reduced (Cy1-ΔCy1). In the capacitor 40yb, the electrode 42 is bent toward the electrode 41 by the rotational force R. As a result, the electric capacity Cy2 increases (Cy2 + ΔCy2). Since ΔCy1 and ΔCy2 are substantially the same, the capacitors 40ya and 40yb do not detect the shearing force.

  In the capacitor 40ra, the electrode 42 is bent toward the electrode 41 by the rotational force R. Thereby, the electric capacity Cr1 increases (Cr1 + ΔCr1). In capacitor 40rb, electrode 42 is bent toward electrode 41 by rotational force R. Thereby, the electric capacity Cr2 also increases (Cr2 + ΔCr2). Since ΔCr1 + ΔCr2 has a large value, the capacitors 40ra and 40rb detect the shearing force.

  FIG. 13A is a diagram illustrating detection of the capacitors 40za and 40zb when an external force F is applied to the tactile sensor element 20a. In FIG. 13A, the external force F is a force from the X axis minus side and the Y axis plus side to the X axis plus side and the Y axis minus side.

  As illustrated in FIG. 13A, when the external force F is applied to the tactile sensor element 20a, in the capacitor 40za, the electrode 43 is curved toward the electrode 42, so that the electric capacity between the electrode 41 and the electrode 42 is increased. Cz1a decreases (Cz1a−ΔCz1a), and the capacitance Cz1b between the electrode 42 and the electrode 43 increases (Cz1b + ΔCz1b). In the capacitor 40zb, since the electrode 43 is curved toward the electrode 41, the electric capacity Cz2a between the electrode 41 and the electrode 43 is large (Cz2a + ΔCz2a), and the electric capacity Cz2b between the electrode 42 and the electrode 43 is small. (Cz2b−ΔCz2b). Since ΔCz1a, ΔCz1b, ΔCz1a, and ΔCz1b are substantially the same, the capacitors 40za and 40zb do not detect the shearing force.

  FIG. 13B is a diagram illustrating detection of the capacitors 40za and 40zb when the rotational force R is applied to the tactile sensor element 20a. As illustrated in FIG. 13B, when the rotational force R is applied to the tactile sensor element 20a, in the capacitor 40za, since the electrode 43 is curved toward the electrode 42, the electric current between the electrode 41 and the electrode 43 is The capacitance Cz1a decreases (Cz1a−ΔCz1a), and the electric capacitance Cz1b between the electrode 42 and the electrode 43 increases (Cz1b + ΔCz1b). In the capacitor 40zb, since the electrode 43 is curved toward the electrode 42, the electric capacitance Cz2a between the electrode 41 and the electrode 43 is reduced (Cz2a−ΔCz2a), and the electric capacitance Cz2b between the electrode 42 and the electrode 43 is reduced. Becomes larger (Cz2b + ΔCz2b). Since ΔCz1a, ΔCz1b, ΔCz1a, and ΔCz1b are substantially the same, the capacitors 40za and 40zb do not detect the shearing force.

  FIGS. 13D and 13E are cross-sectional views taken along line AA of the capacitor 40za in FIG. If no external force is applied in the Z-axis direction, the electrode 43 is not bent. Thereby, as illustrated in FIG. 13D, the capacitance of the capacitor 40za does not change. As illustrated in FIG. 13E, when an external force is applied in the negative Z-axis direction, the electrode 43 is bent in the negative Z-axis direction. As a result, the facing area between the electrode 41 and the electrode 42 is reduced, so that the capacitance Cz1a is reduced (Cz1a−ΔCz1a), and the facing area between the electrode 43 and the electrode 42 is reduced, so that the capacitance Cz1b is also reduced. (Cz1b−ΔCz1b). Similarly, in the capacitor 40zb, the electric capacity between the electrode 41 and the electrode 43 and the electric capacity between the electrode 42 and the electrode 43 are reduced. Therefore, the shear force in the Z-axis direction can be detected.

  According to the present embodiment, the capacitors 40 ra and 40 rb are arranged at different positions in the circumferential direction of the contact portion 23 around the contact portion 23 of the contact surface 21. In addition, a detection circuit 30 that detects a change in the state of the capacitors 40ra and 40rb as an electrical signal is provided. The detection circuit 30 is configured to change the intensity of the electric signal according to the shearing force when a shearing force is applied in the rotation direction of the vertical axis (Z axis) with respect to the contact surface 21 in the contact portion 23. ing. Thereby, the shear force in the direction of the rotation axis can be detected. In addition, since changes in the capacitance of the capacitors 40ra and 40rb are detected, temperature changes and interference with other axes can be canceled, and a stable output value can be obtained. The same applies to the capacitors 40xa, 40xb, 40ya, 40yb, 40za, and 40zb.

  In the present embodiment, the capacitors 40ra and 40rb are arranged point-symmetrically with respect to the contact portion 23, but are not limited thereto. Capacitors 40ra and 40rb may be arranged at different positions in the circumferential direction of contact portion 23 around contact portion 23 of contact surface 21. The capacitors 40xa and 40xb are arranged point-symmetrically with respect to the contact portion 23, but are not limited thereto. The capacitors 40xa and 40xb may be arranged so as not to be parallel to the X axis with the contact portion 23 of the contact surface 21 interposed therebetween. The capacitors 40ya and 40yb are arranged point-symmetrically with respect to the contact portion 23, but are not limited thereto. Capacitors 40ya and 40yb may be arranged so as not to be parallel to the Y axis with contact portion 23 of contact surface 21 interposed therebetween.

(Modification 1)
FIG. 14A and FIG. 14B are diagrams for explaining the first modification. As illustrated in FIG. 14A, an elastic body 22 is provided on the contact surface 21 of the tactile sensor element 20, but the shape of the elastic body 22 is not limited thereto. For example, as illustrated in FIG. 14B, an elastic convex portion 22 a may be provided at a location corresponding to the contact portion 23. For example, the convex portion 22a has a hemispherical shape. By providing the convex portion 22a, the center of rotation at the time of contact between the object and the tactile sensor element 20 can be easily matched. Thereby, a stable output value of each force detection element can be obtained.

(Modification 2)
FIG. 15 is a diagram illustrating a robot system according to the second modification. In each example described above, the control unit 40 detects each shear force from the tactile sensor element 20. On the other hand, the server 202 having the function of the control unit 40 may acquire each shear force from the tactile sensor element 20 through the telecommunication line 201 such as the Internet.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

DESCRIPTION OF SYMBOLS 10 Robot hand 20 Tactile sensor element 21 Contact surface 22 Elastic body 23 Contact part 30 Detection circuit 30xa, 30xb, 30ya, 30yb, 30za, 30zb, 30ra, 30rb Piezoresistive element 40 Control part 40xa, 40xb, 40ya, 40yb, 40za, 40zb, 40ra, 40rb Capacitor 100 Robot system

Claims (15)

A pair of force detection elements arranged at different positions in the circumferential direction of the predetermined area around the predetermined area of the predetermined plane;
A detection circuit that detects a change in state of the pair of force detection elements as an electrical signal;
The detection circuit is configured to change the intensity of the electric signal according to the shearing force when a shearing force is applied in a rotation direction of a vertical axis with respect to the predetermined plane in the predetermined region. A featured tactile sensor. The pair of force detection elements are a first pair of piezoresistive elements,
When a shearing force in the rotational direction is applied, the piezoresistive layer of one piezoresistive element of the first pair of piezoresistive elements receives a tensile force and the piezoresistive layer of the other piezoresistive element is compressed. The tactile sensor according to claim 1, wherein the tactile sensor is configured to receive a force. The first pair of piezoresistive elements has a structure in which the piezoresistive layer and an elastic body are joined to each other.
The tactile sensor according to claim 2, wherein the arrangement side of the elastic body and the piezoresistive layer of the first pair of piezoresistive elements is reversed with respect to the same circumferential direction. A second pair of piezoresistive elements comprising an elastic body and a piezoresistive layer joined together;
The second pair of piezoresistive elements are arranged across the predetermined region on the predetermined plane, and the arrangement side of the elastic body and the piezoresistive layer is the same in the same circumferential direction. The tactile sensor according to any one of claims 1 to 3, wherein the tactile sensor is disposed on the touch sensor. A third pair of piezoresistive elements comprising an elastic body and a piezoresistive layer joined together,
The third pair of piezoresistive elements are arranged such that arrangement sides of the elastic body and the piezoresistive layer are reversed in the vertical axis direction. The tactile sensor according to claim 1.   The tactile sensor according to claim 1, wherein the detection circuit is a bridge circuit. The pair of force detection elements is a first pair of capacitors;
2. The tactile sensor according to claim 1, wherein the first pair of capacitors are configured such that an increase or decrease in capacitance is the same direction when a shearing force in the rotational direction is applied. The first pair of capacitors includes a first electrode fixed at both ends, and a second electrode opposite to the first electrode and fixed at one end and not fixed at the other end,
The tactile sensor according to claim 7, wherein the first electrode and the second electrode of the first pair of capacitors are disposed on the same circumferential direction in the same circumferential direction. A second pair of capacitors comprising a first electrode having both ends fixed, and a second electrode facing the first electrode and having one end fixed and the other end not fixed;
The second pair of capacitors are arranged on the predetermined plane with the predetermined region interposed therebetween, and the arrangement side of the first electrode and the second electrode is reversed with respect to the same circumferential direction. The tactile sensor according to claim 1, wherein the tactile sensor is arranged. A third pair of capacitors comprising a first electrode having both ends fixed, and a second electrode facing the first electrode and having one end fixed and the other end not fixed;
10. The third pair of capacitors are arranged such that arrangement sides of the first electrode and the second electrode are the same with respect to the vertical axis. The tactile sensor according to any one of the above.   The tactile sensor according to claim 1, wherein the detection circuit is an LC circuit. A pair of piezoresistive elements arranged at different positions in the circumferential direction of the predetermined area around the predetermined area of the predetermined plane;
The pair of piezoresistive elements includes an elastic body and a piezoresistive layer bonded to each other,
A tactile sensor, wherein the arrangement side of the elastic body and the piezoresistive layer of the pair of piezoresistive elements is reversed with respect to the same circumferential direction. A pair of capacitors arranged at different positions in the circumferential direction of the predetermined region around the predetermined region of the predetermined plane;
The pair of capacitors includes a first electrode fixed at both ends, and a second electrode opposite to the first electrode and fixed at one end and not fixed at the other end,
The tactile sensor according to claim 1, wherein the first electrode and the second electrode of the pair of capacitors are arranged in the same circumferential direction. An elastic body on the predetermined plane;
The tactile sensor according to claim 12 or 13, wherein the elastic body includes a convex portion on the predetermined region. In a tactile sensor in which a pair of force detection elements are arranged at different positions in the circumferential direction of the predetermined area around the predetermined area of the predetermined plane, a shear force is applied in the rotation direction of the vertical axis with respect to the predetermined plane in the predetermined area When it is, the intensity of the electrical signal detected as a state change of the pair of force detection elements is changed according to the shear force,
A method of detecting a shear force, comprising: detecting an intensity of the electrical signal after being changed.

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