JP2008128940A - Tactile sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly-reliable tactile sensor capable of detecting pressure not only in a normal direction but also in a tangential direction with high accuracy. <P>SOLUTION: In the tactile sensor which includes a sheet-shaped pressure sensitive conductive member 7 resistance of which varies with pressing force, an electrode sheet 8 placed at the one lateral face of the above pressure sensitive conductive member 7 where a plurality of electrode cells 14 are arranged in a predetermined direction to detecting impedance of the above pressure sensitive conductive member 7, a plurality of pressure transmitting members 30 placed oppositely to stretch between the neighboring electrode cells 14 pinching the above pressure sensitive conductive member 7 to apply pressure to the above pressure sensitive conductive member 7, and an elastic coating layer 9 for covering the above pressure transmitting member 30, the above pressure transmitting member 30 is supported displaceably in the normal direction and tangential direction of the pressure sensitive conductive member 7 by the above elastic coating layer 9. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a contact sensor that can detect a contact pressure and a contact position with an object as well as slip, and is suitable for industrial robots and hands of next-generation robots, as well as a foot shape and a bed. The present invention relates to a tactile sensor suitable for detecting a distributed pressure such as a posture at a head.

  Conventionally, as a technique that can be applied to a tactile sensor, as shown in Patent Document 1, an elastic electrode portion that is covered on one side of an insulating support body in which through holes are formed in a matrix shape, and each through hole A plurality of second electrode parts provided on the other side corresponding to the part, and the pressure applied to the object is estimated by the current flowing between the elastic body part and the second electrode part by pressing, and pressed. For example, a pressure detection device that detects a pressed position, a pressure sensor sheet that detects a pressed position using a pressure-sensitive conductive member, and the like have been proposed.

  As shown in FIG. 18, a tactile sensor using a pressure-sensitive conductive member has a pair of electrode sheets 20 on which a plurality of parallel electrode patterns 20a and 20b are formed so that the electrode patterns are orthogonal to each other. However, the sheet-like pressure-sensitive conductive member 30 whose electric resistance value is changed by the applied pressure is inserted between the electrode sheets and bonded to each other.

  However, since the sandwich structure that sandwiches and adheres the sheet-like pressure-sensitive conductive member is adopted, the positional relationship between the two electrode sheets with respect to the pressure-sensitive conductive member is strictly determined in order to accurately obtain the detection position of the applied pressure. In addition to manufacturing difficulties, using such a contact sensor for a long time weakens the adhesion between the electrode sheet and the pressure-sensitive conductive member, resulting in peeling or misalignment. There was a problem that the detection accuracy was lowered.

  Therefore, the applicants of the present application are intended to provide a tactile sensor that can be detected with sufficient sensitivity even at high resolution without degrading detection accuracy over a long period of time, and a sensitivity adjustment method for the tactile sensor. An electrode cell comprising a sheet-like pressure-sensitive conductive member whose resistance value changes, and a voltage application electrode and a voltage detection electrode which are arranged on one side surface of the pressure-sensitive conductive member and detect the impedance of the pressure-sensitive conductive member Has been proposed (Japanese Patent Application No. 2005-165374).

On the other hand, in Patent Document 3, as a tactile sensor capable of discriminating an oblique direction or a left / right front / rear pressure direction, a surface forming body on which a pressing surface is formed, and a contact convex portion protruding from the surface forming body, A contact made of a rigid body having pressure, a pressure-sensitive conductive elastomer member to which pressure from the pressing surface of the contact acts, and a surface opposite to the surface facing the pressing surface of the pressure-sensitive conductive elastomer member A printed circuit board disposed along the printed circuit board, and an electrode disposed on the printed circuit board so as to contact the pressure-sensitive conductive elastomer member. The electrode is projected outward from the surface of the conductive elastomer member, the electrode is provided at a position corresponding to the approximate center of the pressing surface, and the periphery of the common electrode corresponding to the peripheral portion of the pressing surface. From multiple arranged outer electrodes Tactile sensor, characterized in Rukoto have been proposed.
JP 2005-10016 A JP 2004-333273 A Japanese Patent No. 2676057

  According to the conventional tactile sensor described in Patent Document 3 described above, the surface of the pressure-sensitive conductive elastomer member is covered with the insulating outer skin, and the surface forming body of the contact is positioned inward from the insulating outer skin. And the contact convex portion of the contact is projected outward from the surface of the insulating skin, and when such a tactile sensor is mounted on a robot hand, the contact is a rigid body. Since the tip of the convex portion is in direct contact with the object to be gripped, there is a risk that the object to be gripped may be damaged or the convex portion for contact may be damaged depending on the hardness. There was a problem that it could not be gripped smoothly. In addition, when detecting the sliding load and direction of the object using such a tactile sensor, the rigid body slips at the contact position with the contact convex portion when the object is a flat rigid body, etc. There was also a problem that a tangential component could not be detected.

  Due to such various problems, there is a problem that an accurate pressure distribution of the object cannot be detected, and further, the shape of the object cannot be detected with high accuracy, and further improvement has been desired.

  In view of the above-described conventional problems, an object of the present invention is to provide a highly reliable tactile sensor that can accurately detect not only the normal direction but also the pressure in the tangential direction.

  In order to achieve the above-mentioned object, the first characteristic configuration of the tactile sensor according to the present invention is a sheet-like pressure-sensitive conductivity whose resistance value is changed by pressing as described in claim 1 of the claims. A member, an electrode sheet disposed on one side surface of the pressure-sensitive conductive member, and a plurality of electrode cells for detecting impedance of the pressure-sensitive conductive member arranged in a predetermined direction, and the pressure-sensitive conductive member sandwiched between And a plurality of pressure transmission members that pressurize the pressure-sensitive conductive member, and an elastic coating layer that covers the pressure transmission member, and the elastic coating layer The pressure transmission member is supported so as to be displaceable in the normal direction and the tangential direction of the pressure-sensitive conductive member.

  According to the above configuration, the pressure-sensitive conductive member is pressurized by the pressure transmission member that is displaced in the normal direction of the pressure-sensitive conductive member or inclined in the tangential direction in response to the pressure from the object. The direction and the magnitude of the applied pressure are detected based on the impedance value detected in each of the electrode cells arranged to face the pressure transmission member. At this time, since the pressure from the object is applied to the pressure transmission member through the elastic coating layer, the normal line of the object is not affected by the frictional force with the elastic coating layer without causing damage to the object. Sliding in the direction is also effectively avoided. Therefore, not only the pressure in the normal direction but also the pressure in the tangential direction can be detected with high accuracy. In addition, the elastic coating layer prevents moisture and dust from entering the electrode sheet even in a wet environment due to oil or moisture, or in a harsh environment where dust is scattered, and avoids deterioration of the tactile sensor. Is also possible.

  In the second characteristic configuration, as described in claim 2, in addition to the first characteristic configuration described above, the Young's modulus of the elastic coating layer is from 50% to 400 of the Young's modulus of the pressure-sensitive conductive member. It is in the point set in the range of%.

  If the Young's modulus of the elastic coating layer is too small, not only is it difficult to transmit the pressure from the object to the pressure transmission member, but even a slight pressure may cause shear fracture between the object and the pressure transmission member. is there. On the other hand, when the Young's modulus is too large, the pressure from the object is distributed and transmitted not only to the pressure transmitting member to be transmitted but also to the surrounding pressure transmitting members, and the pressure detection accuracy and resolution are reduced. May decrease. According to the above-described configuration, since the Young's modulus of the elastic coating layer is set in a range before and after the Young's modulus of the pressure-sensitive conductive member, the material is sheared and fractured at a pressure within an assumed range applied from the object. Therefore, the pressure can be transmitted to the pressure transmission member to which the pressure from the object is to be transmitted, and the influence on the surrounding pressure transmission member is reduced as much as possible, and the pressure detection accuracy and resolution are excellent. Can be realized.

  In the third characteristic configuration, as described in the third aspect, in addition to the first or second characteristic configuration described above, the pressure transmission member includes a contact portion in surface contact with the pressure-sensitive conductive member. A rigid body including a transmission portion that extends from the contact portion in the normal direction and transmits an external force applied through the elastic coating layer to the contact portion, and the contact portion is connected to the electrode cell. The maximum length along the arrangement direction of the electrode cells is set in a range of 40% to 80% of the arrangement direction length of each electrode cell, and the area of the counter region is at least the area of the electrode cell. This is in the range of 15% to 65%.

  When the pressure component in the normal or tangential direction of the pressure-sensitive conductive member received from the object is transmitted to the transmission part, the contact part that forms a rigid body with the transmission part is displaced in the normal direction or inclined in the tangential direction. In this posture, the pressure-sensitive conductive member is pressurized, and the respective impedances are detected by the adjacent electrode cells arranged opposite to the contact portion. In other words, the position of the pressure transmission member is displaced in the normal direction due to the pressure in the normal direction, and the tangential pressure is converted to the normal pressure by being inclined with respect to the normal direction due to the moment generated by the tangential pressure. It is done. In general, when the contact portion and the facing surface of the electrode cell are parallel, the larger the area of the contact region and the facing region of the electrode, the greater the detection sensitivity of the normal direction pressure. Although it was similarly assumed even when not parallel, as a result of analysis by the inventors of the present application, when the facing area of the contact portion to the electrode cell is large, the inclined pressure transmission member and the adjacent pressure transmission member It was found that the detection sensitivity was lowered because the moment was weakened by the stress of the elastic coating layer interposed between them. When the contact area of the contact portion facing the electrode cell is small, the influence of the stress on the elastic coating layer is small, but the pressure on the pressure-sensitive conductive member is reduced and the detection sensitivity is lowered. As a result of intensive research, it has been clarified that the detection sensitivity to the pressure in the tangential direction by the electrode cell can be set satisfactorily by adopting the above-described configuration.

  In the fourth feature configuration, as described in claim 4, in addition to the third feature configuration described above, the pressure transmission member includes the contact portion having a diameter smaller than a maximum diameter of the contact portion. The height in the normal direction of the pressure transmission member is set in the range of 40% to 100% of the maximum diameter of the contact portion. .

Based on FIG. 8, the pressure in the tangential direction applied to the transmission portion of the pressure transmission member is assumed to be Fy, and converted to the normal pressure Fz acting on the end of the contact portion by the moment around the contact portion center G generated by Fy. The yz two-dimensional simple model to be expressed can be expressed by [Equation 1]. Here, z1 is the length of the contact portion in the normal direction, z2 is the length of the transmission portion in the normal direction, y1 is the length of the transmission portion in the tangential direction, and y2 is the tangent of the contact portion. The length of the direction.

  According to [Equation 1], when the height (z1 + z2) of the pressure transmission member is 50% of the width y2 of the contact portion, the pressure conversion efficiency in the normal direction with respect to the pressure in the tangential direction is 100%. Thus, the detection sensitivity increases as the height in the normal direction (z1 + z2) is increased. However, as described above, the moment is weakened by the stress of the elastic coating layer interposed between the inclined pressure transmission member and the adjacent pressure transmission member, and the detection sensitivity is lowered. Further, there is a problem that the thickness of the contact sensor increases as the height in the normal direction (z1 + z2) increases. Therefore, by setting the height in the normal direction of the pressure transmission member in the above-described range, it is possible to obtain a thin tactile sensor while ensuring adequate detection sensitivity of the tangential direction component.

  In the fifth feature configuration, as described in claim 5, in addition to the fourth feature configuration described above, the pressure transmission member has a diameter of the transmission portion from 20% of the maximum diameter of the contact portion. This is in the range of 60%.

  If the diameter of the transmission part is the same as the diameter of the contact part, when the pressure transmission member is inclined by the moment generated by the pressure component in the tangential direction, it is inclined about one end along the inclination direction of the contact part. There is a risk that the other end will be lifted. Further, there is a problem that the detection sensitivity is lowered due to the moment being weakened by the stress of the elastic coating layer interposed between the inclined pressure transmission member and the adjacent pressure transmission member. On the other hand, if the diameter of the transmission part is made smaller than the diameter of the contact part, there is a risk of damage due to insufficient strength. Therefore, by setting the diameter of the transmission portion within the above range, it is possible to obtain a tactile sensor that can eliminate the above-described disadvantages and appropriately detect the tangential direction component.

  In the sixth feature configuration, in addition to the above-described fourth or fifth feature configuration, the pressure transmission member has a height along the normal direction of the transmission portion. Is set in the range of 60% to 90% of the height of the pressure transmission member.

  In order to cope with the problem that the moment is weakened by the stress of the elastic coating layer interposed between the inclined pressure transmission member and the adjacent pressure transmission member and the detection sensitivity is lowered, the thickness of the contact portion is reduced. Although it is preferable to do so, conversely, damage due to insufficient strength is caused. Therefore, by setting the height of the transmission portion along the normal direction in the above-described range, it is possible to obtain a tactile sensor with good detection sensitivity for a pressure component in the tangential direction while ensuring strength.

  The seventh feature configuration is detected by an adjacent electrode cell group disposed opposite to each pressure transmission member in addition to any of the first to sixth feature configurations described above. The normal direction component and the tangential direction component of the applied pressure are calculated based on the impedance to be applied, and based on the pressure distribution pattern of the normal direction component and the tangential direction component calculated for each electrode cell group It is in the point provided with the arithmetic processing part which calculates a shape or a motion.

  The impedance detected by the adjacent electrode cell group disposed opposite to each pressure transmission member includes a normal direction component and a tangential direction component of the external force applied to each pressure transmission member. Therefore, the normal direction component and the tangential direction component of the external force are calculated based on the impedance detected in the electrode cell group by the arithmetic processing unit, and the target is based on the pressure distribution pattern calculated for the plurality of electrode cell groups. The shape or movement of an object is calculated.

  As described above, according to the present invention, it is possible to provide a highly reliable tactile sensor capable of accurately detecting not only the normal direction but also the tangential pressure.

  An embodiment in which the tactile sensor according to the present invention is used for a robot hand will be described below. As shown in FIGS. 1 and 2, the robot hand 20 includes a base body 10 serving as a palm and five finger units (hereinafter referred to as “finger bodies”) 1, 2, and 3 supported by the base body 10. , 4 and 5.

  The finger bodies 1, 2, 3, 4, and 5 are a thumb (first finger), an indicating finger (second finger), a middle finger (third finger), a ring finger (fourth finger), and a little finger (human finger), respectively. Corresponding to the fifth finger), each finger body has four first, second, third, and fourth link members L1, L2, L3, and L4 in the direction perpendicular to the axis P direction. It is composed of joint devices connected via four joint members J1, J2, J3, and J4 that rotate around P1, P2, P3, and P4.

  The fingers 2, 3, 4, and 5 are arranged in parallel to each other, and a first joint member J1 that is rotatable around the first axis P1 in order from the base end side, and a second that is orthogonal to the first axis P1. A second joint member J2 rotatable about the axis P2, a third joint member J3 rotatable about the third axis P3 parallel to the second axis P2, and parallel to the second axis P2. A fourth joint member J4 that is rotatable about the fourth axis P4, and the first joint member J1 is displaced so that the distance between the fingers is widened or narrowed by the rotation of the first joint member J1; The fourth joint member J4 is configured to be displaceable so as to grip or release the object by the rotation of the fourth joint member J4.

  Since each finger 1, 2, 3, 4, 5 has basically the same structure, the finger 2 will be described below as a representative. As shown in FIGS. 2 and 3, each joint member J1, J2, J3, J4 of the finger body 2 incorporates a harmonic drive (registered trademark) reduction mechanism, and the base 10 and the link member L1. , L2 includes a motor with a built-in encoder having a rotation shaft in a direction orthogonal to the axis P, and the joint members J1, J2, J3 are respectively driven by rotating the motor in one direction. The joint members J1, J2, and J3 are driven to swing around the shaft centers P1, P2, and P3 in the gripping direction with respect to the object, and the motor is rotated in the reverse direction. , P2, and P3 are configured to be driven to swing in the opening direction.

  A force sensor (not shown) is provided in the vicinity of each joint member J1, J2, J3, J4, and the abdomen of the link members L2, L3, L4, as shown in FIGS. A tactile sensor A is arranged for each.

  As shown in FIG. 1, the output of each tactile sensor A provided in the above-described universal robot hand 20 is input to the pressure distribution information detection device C1, and the output of each encoder and the output of each force sensor are action controlled. A motor drive signal for driving each joint member J1, J2, J3, J4 is output from the action control device C2 and input to the device C2.

  The pressure distribution information detection device C1 and the behavior control device C2 are connected to an integrated control device C3 via a network N, and the integrated control device C3 is applied to the abdomen of each finger unit analyzed by the pressure distribution information detection device C1. Drive information for each motor is output to the behavior control device C2 based on the pressure information from the target object, the posture information of each joint analyzed by the behavior control device C2, and the force information applied to each link member. It is configured as follows.

  The pressure distribution information detection device C1 performs high-speed calculation processing on the pressure distribution applied to each abdomen of each finger based on output values from the plurality of tactile sensors A, and outputs the pressure distribution to the integrated control device C3.

  The behavior control device C2 calculates and derives the current posture of each link member and the force applied to it based on the output from each force sensor and the encoder output, and outputs it to the integrated control device C3.

  The integrated control device C3 is based on the current posture of each link member input from the behavior control device C2 and the force applied thereto, the pressure distribution applied to each abdomen input from the pressure distribution information detection device C1, and the like. The characteristics of the object to be grasped, such as the shape and hardness, are grasped, and driving information for the motors M1, M2, M3 is output to the behavior control device C2 so that the intended operation is performed.

  As shown in FIGS. 4A and 4B, the tactile sensor A is disposed on a sheet-like pressure-sensitive conductive member 7 whose resistance value is changed by pressing, and one side surface of the pressure-sensitive conductive member 7. The electrode sheet 8 in which a plurality of electrode cells 14 for detecting the impedance of the pressure-sensitive conductive member 7 are arranged in a matrix, and four electrode cells adjacent in the orthogonal direction with the pressure-sensitive conductive member 7 interposed therebetween 14 and a plurality of pressure transmission members 30 that pressurize the pressure-sensitive conductive member 7 and an elastic coating layer 9 that covers the pressure transmission member 30. The pressure transmission member 30 is supported so as to be variably movable in the normal direction and the tangential direction of the pressure-sensitive conductive member 7.

The pressure-sensitive conductive member 7 is formed by uniformly dispersing conductive particles such as metal and carbon in an insulating rubber material such as a silicone resin, and forming the sheet in a non-pressurized state. Although they are not in contact with each other, both the volume resistance and the surface resistance exhibit a high electric resistance value of 10 ⁷ Ω or more, but the conductive particles gradually come into contact with each other during pressurization and the electric resistance value changes smoothly. That is, since the electrical resistance value changes with the distortion of the rubber due to the pressure change by utilizing the elasticity of the rubber, it shows a low electrical resistance value corresponding to the pressure at the time of pressurization. Indicates the resistance value.

  The electrode sheet 8 is composed of a two-layer flexible substrate that detects the impedance of the pressure-sensitive conductive member 7, and is disposed opposite to the pressure-sensitive conductive member 7 as shown in FIG. A plurality of electrode cells 14 including voltage application electrodes 12 and voltage detection electrodes 13 are arranged in a matrix on the substrate 11a, and a plurality of voltage application electrodes 12 arranged in the column direction are connected to each other in each column. A plurality of lead patterns 15a for applying external voltages simultaneously are formed.

  As shown in FIG. 5B, the other second substrate 11b constituting the electrode sheet 8 has a plurality of voltage detection electrodes 13 arranged in the row direction on the first substrate 11a. A through hole 16b to be connected and a plurality of lead patterns 16a for outputting a detection voltage from the voltage detection electrode 13 connected through the through hole 16b are formed.

  As shown in FIG. 6, the electrode cell 14 includes a rectangular voltage application electrode 12 having a pattern width of 0.2 mm and a cell size of 3.4 mm × 1.8 mm, and the voltage application electrode 12 inside the voltage application electrode 12. And a voltage detection electrode 13 arranged so as to be separated by a certain distance. Therefore, the pressure-sensitive conductive member 7 that faces the electrically insulating portion that is the gap between the two electrode patterns is the portion to be measured for electrical resistance. Due to the deformation of the pressurized pressure-sensitive conductive member 7, a conductive path is formed by contact of the conductive particles in a portion facing the gap between the electrodes 12, 13, and the current value flowing between the electrodes along this path The pressure is detected by the resistance value calculated based on the above.

  In the electrode cell 14 described above, in order to increase the detection current and increase the sensitivity by enlarging the area of the electrically insulating portion that is the gap between the electrodes 12 and 13, the pattern in which the electrically insulating portion is arranged in an uneven manner. It is as. That is, the relative distance between the voltage application electrode 12 and the voltage detection electrode 13 of the electrode cell 14 arranged on the electrode sheet 8 or the facing length between the voltage application electrode 12 and the voltage detection electrode 13 is adjusted. By doing so, the sensitivity can be adjusted. Such sensitivity adjustment is appropriately set according to the pressure-electric resistance characteristics of the pressure-sensitive conductive member 7 to be used, the object to be detected, the size of the electrode cell 14, and the application.

  As shown in FIG. 5A, 70 electrode cells 14 are arranged in a matrix on the electrode sheet 8, and the voltage detection electrode is applied when a voltage is applied to an arbitrary column of the voltage application electrodes 12. The pressure in the corresponding electrode cell 14 is calculated from the current detected from the 13 arbitrary rows. In the electrode cells 14 arranged in the column direction, one side of the voltage application electrode 12 is shared, the interval in the row direction is set to 0.2 mm, and the measurement point area with respect to the entire pattern area including the above lead pattern The ratio is about 82 percent and is configured with high density.

  In the electrode cell 14, both electrodes 12, 13 are formed in line with respect to the vertical and horizontal center lines, and are arranged in the same posture as the electrode sheet 8, so that the output characteristics are equal in any electrode cell 14, Therefore, no matter what part is pressed against the pressure-sensitive conductive member 7, a stable output can be obtained with high accuracy.

  As shown in FIGS. 7 and 9A, the pressure transmission member 30 is in contact with the pressure-sensitive conductive member 7 and extends in the normal direction from the center of the contact portion 31. As shown in FIGS. 9 (a) and 9 (b), it is formed of a rigid body made of an acrylic resin having a transmission portion 32 that is formed and transmits an external force applied through the elastic coating layer 9 to the contact portion 31. Further, the center of the contact portion 31 and the center of the four electrode cells 14 adjacent in the orthogonal direction across the pressure-sensitive conductive member 7 are arranged to face each other. FIG. 9 shows a case where the cell size of the electrode cell 14 shown in FIGS. 5 and 6 is 3.2 mm × 1.8 mm and arranged in the column direction at intervals of 0.2 mm.

  The contact portion 31 is a rectangular parallelepiped having a vertical y2 = 5.0 mm, a horizontal x2 = 3.0 mm, and a height z2 = 1.5 mm, and the transmitting portion 32 is a vertical y1 = 1.5 mm, horizontal x1 = 1.5 mm, high They are a rectangular parallelepiped of z1 = 3.0 mm, and they are integrally formed of an insulating material such as an acrylic resin, and the Young's modulus is set to 100 MPa or more.

  The pressure transmission member 30 can be integrally molded by a casting molding method or an optical modeling method.

  The elastic covering layer 9 has a thickness of about 5.5 mm, and is cured and molded by pouring silicone rubber onto the pressure transmitting member 30 positioned on the pressure-sensitive conductive member 7, and its Young's modulus. However, the pressure-sensitive conductive member 7 having a Young's modulus in the range of 50% to 400% is used.

  If the Young's modulus of the material forming the elastic coating layer is too small, not only will it be difficult to transmit the pressure from the object to the pressure transmission member, but even a slight pressure will cause a shear fracture between the object and the pressure transmission member. There is a risk of being. On the other hand, when the Young's modulus is too large, the pressure from the object is distributed and transmitted not only to the pressure transmitting member to be transmitted but also to the surrounding pressure transmitting members, and the pressure detection accuracy and resolution are reduced. May decrease.

  If it is in the above-mentioned range, the consistency with the pressure-sensitive conductive member is good, and the pressure at which the pressure from the object should be transmitted without shear fracture at the pressure within the assumed range given from the object. While being able to transmit a pressure favorably with respect to a transmission member, the influence on a surrounding pressure transmission member is reduced as much as possible, and favorable pressure detection accuracy and resolution can be realized.

  In this embodiment, a silicone rubber having a Young's modulus of the pressure-sensitive conductive member 7 of 0.2 MPa and a Young's modulus of the elastic coating layer 9 of 0.6 MPa (hardness 20 by a type A durometer) is employed. The Young's modulus is measured based on JIS K6254 “Stress / Strain Test Method for Low Deformation of Vulcanized Rubber” in the JIS standard table, and specifically, the load and displacement measured by a testing machine compliant with the JIS standard. It is converted into Young's modulus based on the numerical value. Further, since the Young's modulus of the pressure transmission member 30 is very large compared to the pressure-sensitive conductive member 7 and the elastic coating layer 9, the pressure-sensitive conductive member 7 and the elastic coating layer are used. 9 can be regarded as a rigid body.

  Therefore, the tactile sensor A described above is configured by arranging a plurality of tactile sensor units a including four electrode cells 14 and one pressure transmission member 30 constituting an electrode cell group in a matrix, and detecting the pressure distribution information. The device C1 calculates the normal direction component and the tangential direction component of the applied pressure based on the impedance value detected by the adjacent electrode cell group disposed opposite to the pressure transmission member 30, and each electrode cell group The calculation processing unit calculates the shape or motion of the object based on the pressure distribution pattern of the normal direction component and the tangential direction component calculated for.

  More specifically, the pressure from the object applied to the abdomen of each finger unit in accordance with the gripping operation of the universal robot hand 20 is applied to the transmission unit 32 of the pressure transmission member 30 via the elastic coating layer 9. It is done. The normal direction component of the pressure from the object is transmitted to the entire contact portion 31 by the transmission portion 32, and the pressure-sensitive conductive member 7 is pressed on the entire surface of the contact portion 31. The tangential component of the pressure from the object causes the contact portion 31 to be tilted by the transmitting portion 32 with the center of the contact portion 31 as a fulcrum, and the pressing force corresponding to the tilt is caused by the contact portion 31 to be the pressure sensitive. In addition to the conductive member 7, each electrode cell 14 of the electrode sheet 8 detects pressure based on the impedance of the pressure-sensitive conductive member 7 facing each other.

  For example, as shown in FIG. 10, the pressure distribution D detected in each electrode cell 14 when the object B is applied to the elastic coating layer 9 is illustrated. In FIG. 10, the pressure detected for each section divided corresponding to each electrode cell 14 constituting the tactile sensor A is shown as a density pattern in which the pressure increases as the density increases. In addition, each thick frame d of the pressure distribution D indicates a partition for each electrode cell group constituted by four electrode cells 14, in other words, for each tactile sensor unit a.

  When pressure information from the electrode cell 14 is input to the pressure distribution information detection device C1, the pressure distribution information detection device C1 calculates a normal direction component and a tangential direction component of pressure in each electrode cell group. Calculate the shape or movement of the object. For example, when the characteristics shown in FIGS. 11A, 11B, and 11C are detected, based on the pressure distribution D, at least the contact surface of the object B with the elastic coating layer 9 is a spherical surface. Yes, it can be determined that the elastic coating layer 9 is moved from left to right on the front surface of FIG.

  Further, when a pressure having a tangential component from a very large object with respect to the size of the electrode cell is applied in parallel to the arrangement direction of the electrode cells, all of the pressure transmission members arranged in the arrangement direction are in the tangential direction. A mountain-shaped pressure waveform as shown in FIG. 12 is obtained from the electrode cells inclined in the direction and arranged in that direction. At this time, since the added value of the pressure of the normal direction component and the pressure obtained by converting the tangential direction component into the normal direction is detected in each electrode cell, adjacent electrodes pressed by the same pressure transmission member The normal direction component is calculated by the addition averaging process between the peak side value and the valley side value between the cells, and the tangential direction component is calculated by the subtraction averaging process. Based on such values and the inclination angle changing from the mountain side (valley side) to the valley side (crest side), it is possible to obtain information such as normal direction and tangential pressure and shape from the object.

  Below, the result (from 1st to 5th) which analyzed the distortion which arises when a horizontal direction load is applied to various shapes of a pressure transmission member by the finite element method is explained.

  The suitability of the shape and the like of the pressure transmission member used in the above-described tactile sensor was analyzed using a finite element method. As shown in FIG. 13, a contact sensor A model is constructed in which three pressure transmission members 30 are arranged on a rigid flat plate F on an analysis plane E divided into a predetermined mesh size, and from below the contact sensor A model. A 1.5N equidistributed load is applied, and the rigid flat plate is 2 mm / sec. 14, based on the strain distribution generated in the pressure sensitive conductive member 7 by the pressure applied to the pressure transmitting member 30 through the elastic coating layer 9, as shown in FIG. The strain applied to the member 7 is calculated.

  [First analysis result] y1 = 1.5 mm, y2 = 5.0 mm, z1 = 1.5 mm, z2 = 3.0 mm and the Young's modulus of the elastic coating layer 9 is changed from 0.1 MPa to 0.6 MPa. Then, as shown in FIG. 15, the strain applied to the pressure-sensitive conductive member 7 tends to decrease slightly as the Young's modulus of the elastic coating layer 9 increases. It became clear that it could be detected without problems.

  If the Young's modulus of the elastic coating layer is too small, not only is it difficult to transmit the pressure from the object to the pressure transmission member, but even a slight pressure may cause shear fracture between the object and the pressure transmission member. is there. On the other hand, when the Young's modulus is too large, the pressure from the object is distributed and transmitted not only to the pressure transmitting member to be transmitted but also to the surrounding pressure transmitting members, and the pressure detection accuracy and resolution are reduced. May decrease. Therefore, in order to transmit the pressure to the pressure transmission member to which the pressure from the object is to be transmitted without being sheared and fractured by the pressure within the assumed range applied from the object, the Young of the elastic coating layer is used. The rate is set in the range of 50% to 400% of the Young's modulus of the pressure-sensitive conductive member, but as a result of the above analysis, it has been found that it can be detected without problems.

  [Second Analysis Result] The Young's modulus of the elastic coating layer is set to 0.6 MPa, y1 = 1.5 mm, z1 = 1.5 mm, z2 = 3.0 mm, and analysis is performed by changing y2 from 3 mm to 6 mm. As a result, as shown in FIG. 16 (a), the strain applied to the pressure-sensitive conductive member 7 becomes maximum when y2 is 4 mm, and becomes sharply smaller at 5 mm or more. It is understood that the tangential component of the pressure is attenuated by the elastic coating layer. Although such a tendency is not shown, the same result is obtained even if it is performed for different Young's moduli.

  [Third analysis result] The Young's modulus of the elastic coating layer 9 is set to 0.6 MPa, y1 = 1.5 mm, y2 = 5.5 mm, z2 = 2.0 mm, and z1 is changed from 0 mm to 2.5 mm. As a result of analysis, as shown in FIG. 16B, the strain applied to the pressure-sensitive conductive member 7 has a characteristic that the value becomes higher as z1 increases.

  [Fourth analysis result] The Young's modulus of the elastic coating layer 9 is set to 0.6 MPa, y2 = 4.0 mm, z1 = 3.0 mm, z2 = 1.5 mm, and the analysis is performed by changing y1 from 1 mm to 4 mm. As a result, as shown in FIG. 17A, the strain applied to the pressure-sensitive conductive member 7 tended to decrease as y1 increased. Although such a tendency is not shown, the same result is obtained even if it is performed for different Young's moduli. In this case as well, it is understood that the tangential component of the pressure is attenuated by the elastic coating layer.

  [Fifth Analysis Result] The Young's modulus of the elastic coating layer 9 is set to 0.6 MPa, y1 = 1.5 mm, y2 = 4.0 mm, z1 + z2 = 4.5 mm, and the analysis is performed by changing z1 from 1 mm to 4 mm. As a result, as shown in FIG. 17 (b), it was found that the strain applied to the pressure-sensitive conductive member 7 increases as z1 increases. The simple two-dimensional model described above has been demonstrated. However, when z1 + z2 is limited, it is necessary to adopt an appropriate value in consideration of mechanical strength and the like.

  As a result of comparing and considering the analysis results, various experiments, and the mechanical strength of the member, the pressure transmission member has a maximum in the arrangement direction of the electrode cell in the region where the contact portion is opposed to the electrode cell. It is preferable that the length is set in a range of 40% to 80% of the arrangement direction length of each electrode cell, and the area of the facing region is set in a range of at least 15% to 65% of the area of the electrode cell. . The maximum length along the arrangement direction of the electrode cells is set in a range of 50% to 75% of the arrangement direction length of each electrode cell, and the area of the facing region is at least from 25% of the area of the electrode cells. More preferably, it is set in the range of 57%.

  In addition, the pressure transmission member is formed such that the transmission portion has a diameter smaller than the maximum diameter of the contact portion and extends from the center of the surface of the contact portion in the normal direction, and the height of the pressure transmission member in the normal direction is increased. Is preferably set in the range of 40% to 100% of the maximum diameter of the contact portion, and more preferably in the range of 75% to 95%. The diameter indicates the length of the diagonal line when the cross-sectional shape with respect to the normal line of the contact part or the pressure transmission part formed in a rectangle is rectangular, and the radius when the shape is circular (the same applies hereinafter).

  Further, in the pressure transmission member, the diameter of the transmission part is preferably set in a range of 20% to 60% of the maximum diameter of the contact part, and more preferably in a range of 25% to 50%. preferable.

  Furthermore, the pressure transmission member preferably has a height along the normal direction of the transmission portion set in a range of 60% to 90% of the height of the pressure transmission member, and 65% to 70%. More preferably, it is set within the range.

  Hereinafter, another embodiment will be described. In the above-described embodiment, the elastic coating layer is made of silicone rubber. However, if the Young's modulus of the elastic coating layer is in the range of 50% to 400% of the Young's modulus of the pressure-sensitive conductive member 7. However, the present invention is not limited to this, and urethane, natural rubber, and the like can also be employed, and an elastomer gel material such as urethane gel may be employed. These are appropriately selected according to the use of the contact sensor and the like, and various characteristics such as flexibility and thickness can be appropriately set according to the use.

  In addition, the composition, thickness, electrode cell size, electrode pattern width, voltage application electrode and voltage detection electrode shape, etc. of the sheet-like pressure-sensitive conductive member are appropriately selected within the range where the effects of the present invention are exhibited. It is possible to change and configure. For example, the shape of the electrode cell is not limited to a rectangle, but may be a square, and may further be a circle.

  In the above-described embodiment, the pressure transmitting member is a rectangular parallelepiped having the contact portion 31 with the longitudinal y2 = 5.0 mm, the lateral x2 = 3.0 mm, and the height z2 = 1.5 mm, and the transmitting portion 32 with the longitudinal y1 = 1. Although the description has been made of the rectangular parallelepiped having 5 mm, horizontal x1 = 1.5 mm, and height z1 = 3.0 mm, these numerical values can be appropriately set within the above-described range, and the shape thereof is also described above. As long as it falls within the range, it can be appropriately changed in relation to the shape of the electrode cell. For example, a square may be employed as the shape of the contact portion, and a rectangle may be employed as the cross-sectional shape of the transmission portion. Furthermore, the shape of the transmission portion may be a columnar shape, or may be formed in a truncated cone shape with a diameter reduced toward the upper end side.

  The tactile sensor described above is suitable for humanoid robot hands that can complement human work from extreme work to domestic chores, but with normal and tangential contact pressure and contact position with the object. It can be widely used as a tactile sensor for detecting.

Illustration of robot hand Illustration of robot hand Illustration of the finger Illustration of tactile sensor It is explanatory drawing of the electrode sheet by which the electrode cell is arrange | positioned, (a) is a pattern diagram of the whole electrode sheet, (b) shows the pattern diagram of a 2nd board | substrate. Illustration of electrode cell Explanatory drawing of pressure transmission member Explanatory drawing of pressure transmission member (A) Explanatory drawing of a pressure transmission member, (b) Explanatory drawing of a pressure transmission member Pressure distribution diagram of the tactile sensor when the object is applied Pressure distribution diagram of the tactile sensor when the object is applied Pressure detection characteristic diagram by tactile sensor Diagram used to explain analysis by finite element method of tactile sensor Diagram used to explain analysis by finite element method of tactile sensor Graph used to explain the relationship between the Young's modulus of the elastic coating layer and the strain applied to the pressure-sensitive conductive member (A) A graph showing the relationship between the length of one side of the contact portion of the pressure transmission member and the strain applied to the pressure-sensitive conductive member, (b) the height of the transmission portion of the pressure transmission member and the strain applied to the pressure-sensitive conductive member Graph showing the relationship (A) A graph showing the relationship between the length of one side of the transmission part of the pressure transmission member and the strain applied to the pressure-sensitive conductive member, (b) the height of the transmission part of the pressure transmission member and the strain applied to the pressure-sensitive conductive member Graph showing the relationship (A) Configuration diagram of a tactile sensor showing a conventional example, (b) Configuration diagram of a tactile sensor showing a conventional example.

Explanation of symbols

7: Pressure-sensitive conductive member 8: Electrode sheet 9: Elastic coating layer 14: Electrode cell 30: Pressure transmission member 31: Contact part 32: Transmission part A: Tactile sensor

Claims (7)

  A sheet-like pressure-sensitive conductive member whose resistance value changes when pressed, and a plurality of electrode cells arranged on one side surface of the pressure-sensitive conductive member and detecting the impedance of the pressure-sensitive conductive member are arranged in a predetermined direction. A plurality of pressure transmitting members that are disposed so as to straddle between adjacent electrode cells across the pressure sensitive conductive member, and cover the pressure transmitting member A tactile sensor, wherein the pressure transmission member is supported by the elastic coating layer so as to be displaceable in a normal direction and a tangential direction of the pressure-sensitive conductive member.   The tactile sensor according to claim 1, wherein a Young's modulus of the elastic coating layer is set in a range of 50% to 400% of a Young's modulus of the pressure-sensitive conductive member.   The pressure transmission member transmits a contact portion that is in surface contact with the pressure-sensitive conductive member, and an external force that extends from the contact portion in the normal direction and is applied via the elastic coating layer to the contact portion. The contact portion has a maximum length along the arrangement direction of the electrode cells in a region facing the electrode cells, which is 40% to 80% of the arrangement direction length of each electrode cell. The tactile sensor according to claim 1, wherein an area of the facing region is set to a range of at least 15% to 65% of an area of the electrode cell.   The pressure transmission member is formed such that the transmission portion has a diameter smaller than the maximum diameter of the contact portion and extends in the normal direction from the center of the surface of the contact portion, and the normal direction height of the pressure transmission member is The tactile sensor according to claim 3, wherein the tactile sensor is set in a range of 40% to 100% of a maximum diameter of the contact portion.   The tactile sensor according to claim 4, wherein the pressure transmission member has a diameter of the transmission portion set in a range of 20% to 60% of a maximum diameter of the contact portion.   6. The tactile sensor according to claim 4, wherein the pressure transmission member has a height along the normal direction of the transmission portion set in a range of 60% to 90% of a height of the pressure transmission member.   Based on the impedance value detected in the adjacent electrode cell group arranged opposite to each pressure transmission member, the normal direction component and the tangential direction component of the applied pressure are calculated, and the method calculated for each electrode cell group The tactile sensor according to any one of claims 1 to 6, further comprising an arithmetic processing unit that calculates a shape or a motion of an object based on a pressure distribution pattern of a linear component and a tangential component.