JP2663144B2 - Robot gripper - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gripper for a robot, and more particularly to a gripper for a robot having a tactile sensor for detecting a gripping state of a workpiece.

[Conventional technology]

Industrial robots are currently used in various fields, but a portion of a gripper that actually holds a work in the robot requires operation control suitable for the work. For example, a gripper using a glass product as a work requires more precise control than a gripper using a bolt and a nut as a work.

In order to perform such precise control, it is effective to attach a tactile sensor to the gripper and adjust the gripping force, detect the presence or absence of a work, and detect the position of the work. Such touches are generally classified into touch, pressure, force, slip, and the like. Microswitches and touch sensors are used as contact sensors, and strain gauges and conductive rubber are used as pressure sensors and force sensors. Further, as the slip sensor, no effective sensor has been developed at present because the surface slip has no directionality.

[Problems to be solved by the invention]

However, as described above, some tactile sensors are used in the conventional robot gripper, but all have a problem. That is, a touch sensor such as a microswitch or a touch sensor can only detect the presence or absence of a touch, and cannot detect a pressure sense. In addition, pressure sensors and force sensors such as strain gauges and conductive rubber have low sensitivity and cannot provide a linear output. In the slip sensor, there is no effective sensor.

Therefore, an object of the present invention is to provide a robot gripper provided with a highly accurate tactile sensor capable of sufficiently grasping a gripping state of a work.

[Means for solving the problem]

The present invention includes a finger member for gripping a work, and a hand member movably supporting the finger member, and has a function of gripping the work by moving the finger member with respect to the hand member. The member comprises a first joint, a second joint,
In a robot gripper having an indirect connection between them, a supporting portion connected to the first joint portion, an operating portion connected to the second joint portion, and a movable portion formed between the supporting portion and the operating portion. A flexible portion is disposed around the acting portion, a support portion is disposed around the flexible portion, and the thickness of the flexible portion is smaller than the thickness of the supporting portion and the acting portion. By setting, the flexible portion forms a structure showing flexibility, and is joined to a strain generating body that generates mechanical deformation by displacement of the acting portion with respect to the support portion, and to the strain generating body so that the mechanical deformation is transmitted. A single crystal substrate, and a piezoresistive effect in which the electrical resistance changes due to mechanical deformation, and a resistance element formed on the single crystal substrate. The grip state between the finger and the finger member is defined as the change in the electrical resistance of the resistance element. This makes it possible to detect.

(Operation)

The tactile sensor used in the present invention is a sensor using a single crystal substrate such as a semiconductor, and a very accurate linear output is obtained as an electric resistance value of a resistance element with respect to a force applied to the substrate. In addition, by devising the arrangement of the resistance elements on the single crystal substrate, it is possible to detect forces in all axial directions and moments around all axes in the three-dimensional coordinate system. Therefore, sufficient information on the grip state of the work can be obtained. In addition, the finger member is not directly connected to the single crystal substrate but is connected via a strain body. Therefore, even if a large force necessary for the function as the robot gripper is applied, the single crystal substrate is not damaged.

〔Example〕

The structure of the embodiment will be described below based on an embodiment illustrating the present invention.
FIG. 1 is a view showing a gripper for a robot according to one embodiment of the present invention, and FIG. 1 (a) is a side view of a gripper tip,
FIG. 1B is a partially enlarged cross-sectional view thereof. The gripper includes two finger members 100 for gripping a work, and a hand member 200 for movably supporting the two finger members. The finger member 100 is the hand member 2 as shown by the broken line in the figure.
It slides with respect to 00 and works to clamp the work between them. A link mechanism, a hydraulic mechanism, and the like for driving the finger member 100 are provided inside the hand member 200, but the description of these mechanisms is omitted here.

The finger member 100 is, as shown in FIG.
10, the joint 120, and the second joint 130. The first joint 110 and the second joint 130 are formed of a rigid body such as a metal. The indirect 120 is a tactile sensor having the single crystal substrate 10 and the strain body 20 as main components, and a portion (supporting portion) around the strain body 20 is fixed to the first joint portion by a screw 30.
It is attached to 110, and the center part (action part)
The second joint 130 is attached by 31. Flexure element 20
A thin flexible portion is formed between the support portion around the peripheral portion and the central acting portion, and when a force is applied between the first node portion 110 and the second node portion 130, this flexible portion is formed. The part bends, and displacement occurs between the support part and the working part. Due to this displacement, the single crystal substrate 10 is distorted. A resistance element is formed on the single crystal substrate 10, and the electric resistance of the resistance element changes due to strain. As a result, the force applied between the first node 110 and the second node 130 can be detected as a change in the electric resistance of the resistance element on the single crystal substrate 10. An electric signal is extracted from the single crystal substrate 10 to the outside via an electrode 13 for external wiring.

Structure of Tactile Sensor Next, the structure and details of the tactile sensor used as the joint 120 in the above-described embodiment will be described. Fig. 2 (a)
Is a side sectional view of the tactile sensor, and FIG. Here, it is assumed that the X axis, the Y axis, and the Z axis are defined in the direction of the drawing. FIG. 2A corresponds to a cross-sectional view of the sensor shown in FIG. 2B cut along the X-axis.

In this sensor, a total of 12 resistive elements R are formed on a single crystal silicon substrate 10. Resistance element
Rx1 to Rx4 are arranged on the X axis and used for force detection in the X axis direction, resistance elements Ry1 to Ry4 are arranged on the Y axis and used for force detection in the Y axis direction, and resistance elements Rz1 to Rz4 are arranged on the X axis. Are arranged on an axis in the vicinity of this axis and used for force detection in the Z-axis direction.
The specific structure of each resistance element R and its manufacturing method will be described later in detail, but these resistance elements R are elements having a piezoresistance effect in which the electric resistance changes due to mechanical deformation.

The single crystal substrate 10 is bonded to a strain body 20. Second
In the example shown in the figure, the flexure element 20 is composed of a peripheral support portion 21, a flexible portion 22 having a reduced thickness for providing flexibility, and an action portion 23 projecting to the center. . Kovar (an alloy of iron, cobalt, and nickel) is used as the material of the flexure element 20. Since Kovar has a coefficient of thermal expansion substantially equal to that of the silicon single crystal substrate 10, it has an advantage that even when adhered to the single crystal substrate 10, the thermal stress generated by a temperature change is extremely small. The material and shape of the flexure element 20 are not limited to those described above, and the embodiment shown here is merely an optimal embodiment. The strain body 20 is provided with a mounting hole 24 through which screws are fixed.

Wiring as shown in FIG. 3 is provided for each resistance element.
That is, the resistance elements Rx1 to Rx4 are assembled in a bridge circuit as shown in FIG. 3A, the resistance elements Ry1 to Ry4 are assembled in a bridge circuit as shown in FIG.
1 to Rz4 are assembled in a bridge as shown in FIG. A predetermined voltage or current is supplied to each bridge circuit from a power supply 50, and each bridge voltage is measured by voltmeters 51 to 53. In order to perform such wiring for each resistance element R, as shown in FIG. 2, a bonding pad 11 electrically connected to each resistance element R and an electrode 13 for external wiring are formed on a single crystal substrate 10. Are connected by a bonding wire 12. The electrode 13 is led out through a wiring hole 25.

Principle of Tactile Sensor In FIG. 2 (a), when a force is applied to the action point S at the tip of the action portion 23, a stress strain corresponding to the applied force is generated in the flexure element 20. As described above, since the flexible portion 22 has a small thickness and has a flexible portion, displacement occurs between the operating portion 23 and the support portion 21, and each resistance element R is mechanically deformed. Due to this deformation, the electric resistance of each resistance element R changes, and eventually, the applied force is detected as a change in each bridge voltage shown in FIG.

FIG. 4 shows the relationship between the stress strain and the change in the electric resistance of the resistance element R. Here, for convenience of explanation, the single crystal substrate 10
Only the action part 23 of the strain body 20 of FIG.
Consider a case where two resistance elements R1 to R4 are formed. First, as shown in FIG. 4 (a), when no force is applied to the point of action S, no stress strain is applied to the single crystal substrate 10, and the resistance change of all the resistance elements is zero. However, when a downward force F1 is applied, the single crystal substrate 10 is mechanically deformed as shown in the figure. Now, assuming that the conductivity type of the resistive element is P-type, this deformation causes the resistive elements R1 and R4 to expand and increase the resistance (indicated by a + sign), and the resistive elements R2 and R3 to contract and reduce the resistance. (I will show it with a minus sign)
Will be. When a rightward force F2 is applied, the single crystal substrate 10 is mechanically deformed as shown in the figure. (Actually, the force F2 acts as a moment force on the single crystal substrate 10). Due to this deformation, the resistance elements R1 and R3 expand and increase the resistance, and the resistance elements R2 and R4 contract and reduce the resistance. Since each resistance element R is a resistance element whose longitudinal direction is in the horizontal direction of the drawing, when a force is applied in a direction perpendicular to the plane of the drawing, the change in the resistance value of each resistance element can be ignored. As described above, in the present sensor, the force in each direction is independently detected by utilizing the fact that the resistance change characteristic of the resistance element differs depending on the direction of the applied force.

Operation of Tactile Sensor Hereinafter, an operation of the above-described tactile sensor will be described with reference to FIGS. FIG. 5 shows a case where a force is applied in the X-axis direction, FIG. 6 shows a case where a force is applied in the Y-axis direction, and FIG.
The graph shows the stress applied to each resistance element when a force is applied in the axial direction (+ indicates the direction of expansion, − indicates the direction of contraction, and 0 indicates no change). In each figure, the cross section of the sensor shown in FIG. 2 cut along the X axis is (a), the cross section cut along the Y axis is (b), and the element Rz is parallel to the X axis.
A cross section taken along 1 to Rz4 is shown as (c).

First, an arrow Fx (fifth in FIGS. 5 (a), 5 (b) and 5 (c)) is used.
Considering the case where a force in the X-axis direction is applied as shown by a direction (perpendicular to the paper surface in FIG. 2B), stresses of the illustrated polarities are generated. The polarity of this stress can be easily understood from the description of FIG. A resistance change corresponding to this stress occurs in each resistance element R. For example, the resistance of the resistance element Rx1 decreases (-), the resistance of the resistance element Rx2 increases (+), and the resistance of the resistance element Ry1 does not change (0). Further, when forces are applied in the Y-axis and Z-axis directions as indicated by arrows Fy and Fz in FIGS. 6 and 7, respectively, a stress as shown is generated.

After all, the relation between the applied force and the change of each resistance element is summarized in a table as shown in Table 1.

Here, taking into consideration that the resistance element R forms a bridge as shown in FIG. 3, the applied force and the presence or absence of a change in each of the voltmeters 51 to 53 have a relationship as shown in Table 2.

Although the resistance elements Rz1 to Rz4 undergo substantially the same stress change as the resistance elements Rz1 to Rz4, the voltmeter 51 and the voltmeter 53 respond differently because the bridge configurations are different as shown in FIG. Please be careful. Eventually, the voltmeters 51, 52, 53 will respond to forces in the X, Y, and Z directions, respectively. Although only the presence or absence of a change is shown in Table 2, the polarity of the change is governed by the direction of the applied force, and the amount of change is governed by the magnitude of the applied force.

Structure of tactile sensor capable of detecting 6-axis components In the above-described tactile sensor, force and moment in each axial direction are not clearly distinguished. However, the tactile sensor described here uses force acting in each axial direction. And the moment acting around each axis can be separately detected. That is, detection of six-axis components is possible. Hereinafter, this sensor is referred to as a six-axis component sensor.

FIG. 8 is a top view of the six-axis component sensor, and FIG.
It is sectional drawing which cut | disconnected the apparatus shown in a figure along cutting line AA. In this embodiment, 16 resistive element groups R1 to R16 are formed on the surface of the flexure element 210. The strain body 210 is formed of a silicon single crystal substrate, and each of the resistance element groups R1 to R16 is a set of a plurality of resistance elements, and each resistance element is formed by diffusing impurities on the single crystal substrate. You. The resistance element thus formed exhibits a piezoresistive effect, and has a property that electric resistance changes due to mechanical deformation.

The flexure element 210 has a fixed portion 211 formed in an annular shape around its periphery.
And four bridges 212 to 215 and the four bridges 21
And an action part 216 to which 2 to 215 are connected.
The fixing portion 211 is fixed to the outside, and a force or moment to be detected is applied to an action point P at the center of the action portion 216. Since the fixing portion 211 is fixed to the outside, when a force or a moment is applied to the point of action P, a stress strain corresponding to the force or the moment is generated in the bridge portions 212 to 215, and an electric resistance is applied to the resistance element groups R1 to R16. Changes occur. This device is
The force and moment are detected based on the change in the electric resistance. In this embodiment, the resistance elements have the same size, shape, and material, and all have the same resistance value. Further, the resistance change rates based on the stress strain are all equal.

Now, as shown in FIG. 8 and FIG.
The action point P at the center of is defined as the origin of the XYZ three-dimensional coordinate system,
It is assumed that three axes of X, Y, and Z are defined as shown in the figure. That is, in FIG. 8, the right side of the figure is defined as the positive direction of the X axis, the lower side is defined as the positive direction of the Y axis, and the lower side perpendicular to the plane of the drawing is defined as the positive direction of the Z axis. Acting bodies 221 and 222 are mounted above and below the acting section 216, and all the forces and moments acting on the acting point P are given via the acting bodies 221 and 222. Here, regarding the action point P,
The force applied in the X-axis direction is FX, the force applied in the Y-axis direction is FY,
Assuming that the force applied in the Z-axis direction is FZ, the moment applied around the X-axis is MX, the moment applied around the Y-axis is MY, and the moment applied around the Z-axis is MZ, each force and moment is represented by each arrow in FIG. Is defined in the direction indicated by. That is, the force FX applied in the X-axis direction is a force that moves both the operating bodies 221 and 222 to the right in the figure, and the force FY applied in the Y-axis direction moves the operating bodies 221 and 222 together in a direction perpendicular to the plane of the drawing. And the force FZ applied in the Z-axis direction.
Is a force that moves both the action bodies 221 and 222 downward in the figure. Further, the moment MX about the X axis is equal to the acting body 221.
Is moved upward in the direction perpendicular to the plane of the drawing, and the moment MY about the Y axis is moved to the left in the figure, and the moment MY about the Y axis is moved to the left in the figure. In addition, the moment MZ about the Z-axis is a moment that moves both the action bodies 221 and 222 clockwise as viewed from above the apparatus.

The 16 resistance element groups R1 to R16 are arranged at symmetrical positions as shown in FIG. That is, the bridge 212
R1 to R4, R5 to R8 in the bridge portion 213, and R5 to R8 in the bridge portion 214.
R9 to R12 are provided, and R13 to R16 are provided in the bridge portion 215, respectively. Looking at each bridging portion, a pair of resistance element groups are provided near the fixed portion 211, and a pair of resistance element groups are provided near the action portion 216. Each pair of resistance element groups is provided on both sides with the X axis or the Y axis narrowed. I have.

FIG. 10 (a) to FIG.
Six types of bridges are formed as shown in FIG. A power supply 230 is connected to each bridge, and a voltage VFX, VFY, VFZ, VM proportional to FX, FY, FZ, MX, MY, MZ.
Voltmeters 241 to 24 that output X, VMY, VMZ as bridge voltage
6 is connected.

Note that the symbol of each resistance element shown in this bridge circuit diagram means one resistance element in the resistance element group, and even if the resistance elements are given the same symbol, they are not. It means different resistance elements belonging to the same resistance element group. For example, although R1 is used in the two bridges shown in FIGS. 10 (b) and (d), actually, two resistance elements are arranged at the position of R1 in FIG. Is used.

Hereinafter, for convenience of description, the same symbol Rx will be used to indicate one resistance element belonging to the resistance element group Rx (x = 1 to 16).

Operation of Six-Axis Component Sensor Hereinafter, the operation of the above-described device will be described. When the resistive elements are arranged as shown in FIG. 8, when the force or moment FX, FY, FZ, MX, MY, MZ is applied to the point of action P, each of the resistive elements R1 to R16 becomes as shown in FIG. An electric resistance change occurs as shown in the table (each resistance element is made of a P-type semiconductor). Here, “0” indicates no change, “+” indicates an increase in electric resistance, and “−” indicates a decrease in electric resistance.

Here, the reason why the result as shown in FIG. 11 is obtained will be briefly described with reference to FIGS. 12 to 17 show the force or moment FX, FY, FZ, MX, MY, MZ at the point of action P.
FIG. 4 is a diagram showing changes in stress strain and electric resistance generated in a bridge portion when is applied, and each diagram (a) is a top view of the bridge portion;
Each figure (b) is a front sectional view, and each figure (c) is a side sectional view.
For example, FIG. 12 shows a state in which a force FX in the X-axis direction acts on the point of action P. The force FX causes the bridge 214 to expand and the bridge 215 to contract. Therefore, the resistance elements (R9 to R12) in the bridge 214 expand and the electric resistance increases (in the case of a P-type semiconductor), and the resistance elements (R13 to R16) in the bridge 215 shrink and the electric resistance decreases. . The resistance elements in the bridge portions 212 and 213 expand and contract depending on the arrangement position. After all, it can be easily understood that the result as shown in the first column of the table in FIG. 11 is obtained. Below,
Referring to FIGS. 13 to 17, it can also be understood that the results in columns 2 to 6 in the table of FIG. 11 are obtained.

Now, considering that a bridge as shown in FIG. 10 is configured by each of the resistance elements R1 to R16,
FX, FY, FZ, MX, MY, MZ added to the action point P, and voltmeters 241-2
The relationship between the detection voltages VFX, VFY, VFZ, VMX, VMY, and VMZ appearing in 46 is as shown in the table of FIG. Here, “0” indicates that no voltage change occurs, and “V” indicates that a voltage change depending on the applied force or moment occurs. The polarity of the voltage change depends on the direction of the applied force or moment, and the magnitude of the voltage change will depend on the magnitude of the applied force or moment.

It is easy to obtain a table as shown in FIG. 18 when considering that there is no voltage change when the products of the resistance values of the resistance elements on the opposite sides of the bridge in the circuit diagram of FIG. 10 are equal to each other. I can understand. For example, when a force FX is applied, each resistance element changes in electric resistance as shown in the first column of the table of FIG. Referring now to FIG. 10 (a), R
9, R10, R11, R12 all increase in resistance, R13, R14, R15, R
In both cases, the resistance value decreases. Therefore, a large difference occurs in the product of the resistance values of the resistive elements on the opposite side, and the voltage change “V”
Will be detected. On the other hand, FIGS. 10 (b) to (f)
No change occurs in the bridge voltage. For example, in the circuit of FIG. 10 (b), R1 is "-"
In this case, R2 becomes “+”, and the resistance change is canceled for each branch. As described above, the effect of the force FX affects only the VFX, and the force FX can be independently detected by measuring the VFX.

As a result, only the diagonal component in the table of FIG.
The fact that all other values are "0" indicates that each detected value can be obtained directly as a voltmeter reading without performing any operation.

By configuring the bridge as described above, it is possible to cancel the influence of the resistance change based on factors other than the stress. For example, although the electric resistance of each resistance element changes depending on the temperature, all the resistance elements forming the bridge change almost equally, so that the influence of this temperature change is canceled out. Therefore, more accurate measurement can be performed by this bridge configuration.

If the 6-axis component sensor described here is used instead of the tactile sensor shown in FIG. 2 to obtain detection data for the 6-axis component, more detailed information on the grip state of the workpiece can be obtained. it can. In this case, in FIG. 1 (b), the fixing part 210 of the six-axis component sensor
May be connected, and the action part 216 of the six-axis component sensor may be connected to the node 130, or the connection may be completely reversed.

Production of Resistive Element Having Piezoresistive Effect Next, an example of a method for producing a resistive element used in the above-described sensor will be briefly described. This resistive element has a piezoresistive effect and is formed on a semiconductor substrate by a semiconductor planar process. First, as shown in FIG. 19A, an N-type silicon substrate 401 is thermally oxidized to form a silicon oxide layer 402 on the surface. Subsequently, as shown in FIG. 1B, the silicon oxide layer 402 is etched by photolithography to form an opening 403. Next, FIG.
As shown in the figure, boron is thermally diffused from this opening 403,
A P-type diffusion region 404 is formed. Note that a silicon oxide layer 405 is formed in the opening 403 in this heat diffusion step. Next, as shown in FIG. 3D, silicon nitride is deposited by a CVD method, and silicon nitride 406 is formed as a protective layer. Then, as shown in FIG. 4E, a contact hole is opened in the silicon nitride 406 and the silicon oxide layer 405 by photolithography, and then, as shown in FIG. 4F, an aluminum wiring layer 407 is formed by vapor deposition. . Finally, the aluminum wiring layer 407 is patterned by photolithography to obtain a structure as shown in FIG.

The above-described manufacturing process is shown as an example, and the sensor used in the present invention can be realized by using any resistance element having a piezoresistance effect.

Operation as Robot Gripper The structure and operation of the tactile sensor used in the robot gripper according to the present invention have been described above in detail. Next, the operation of the robot gripper provided with this tactile sensor will be described. FIG. 20 is a diagram showing a state where the workpiece 500 is gripped by the robot gripper. As described above, the two finger members 100 are movably supported by the hand member 200, and the work 500 is sandwiched between the two finger members 100 so as to hold the work 500 from both sides as illustrated. Can be. In this example, the work 500 comes into contact with the two finger members 100 at the contact points P1 and P2. Work 500
Is maintained, force exists at the contact points P1 and P2. That is, a force is applied to the action point S1 by the force generated at the contact point P1, and a force is applied to the action point S2 by the force generated at the action point P2. Indirect as described above
120 constitutes a tactile sensor, and has a flexure element 20. When a force is applied to the point of action, the flexible flexure element 20 bends, and the direction and magnitude of the applied force are extracted as an electric signal. The tactile sensor using the single crystal substrate 10 can obtain a very high-precision linear output, and an accurate value of the contact pressure on the workpiece 500 can be obtained based on the output signal. As mentioned above, the tactile sensor
Since it has a function of detecting the force acting on the contact point for each component in the three-dimensional direction, it is also possible to obtain information on the surface direction of the workpiece at the contact point.

Here, the physical quantity detected by the tactile sensor is actually a moment force. Now, in a schematic diagram as shown in FIG. 21, consider a case where the work 500 is at the position of 500a and a case where it is at 500b (actually, the work 500 is sandwiched between two finger members. For the sake of explanation, only one of them will be considered.) In each case, section 2
Assuming that 130 always holds down the work 500 with a constant force F, the moment force detected by the indirect (tactile sensor) 120 is M (a) = K · F · l for the work 500a. For the work 500b, M (b) = K · F · (l−Δl). Here, K is a constant. Therefore, the work 500, which should have been held at the position of the distance l with the force F, is moved to the distance Δl
Even if only sliding, based on the above two equations,
The slip distance Δl can be obtained by calculation. This function is nothing more than a function for measuring slipperiness that could not be measured with a conventional sensor.

Further, if the above-described six-axis component sensor is used indirectly, even if the force pressing down on the work 500 changes, it is possible to measure the slip sense. That is, when the force F1 is pressed against the work 500a and the force F2 is pressed against the work 500b, M (a) = K · F1 · l M (b) = K · F2 · (l −Δl), but with the six-axis component sensor, M (a), M (b), F1, F2
Can be detected separately, so that the slip distance Δl can be calculated also based on the above two equations.

FIG. 22 is a diagram showing an embodiment in which the finger member 100 is composed of a large number of nodes. As in the previous embodiment, two finger members
100 is supported by the hand member 200. A first joint 110 is rotatably attached to the hand member 200, and an indirect 120 is connected to the first joint 110.
The second joint 130 is connected to “0”. The second joint 130 is further rotatably connected to the drive joint 140. A first joint 110 is further rotatably attached to the drive joint 140. Hereinafter, a finger member will be described by repeating the above-described members.
100 are configured. The drive joint 140 is provided with, for example, a link mechanism, a hydraulic mechanism, or the like, and can adjust an angle between the first joint 110 and the second joint 130 connected to both sides thereof. With the gripper having such a structure, a gripping operation closer to that of a human finger is possible, and a plurality of joints 120 can detect a force applied to each joint.

Another Embodiment FIG. 23 (a) is a diagram showing a gripper for a robot according to another embodiment of the present invention, wherein FIG. 23 (a) is a side view of a gripper tip and FIG. It is a partial expanded sectional view. In this gripper, the point that two finger members 150 are supported by the hand member 200 is the same as in the above-described embodiment, but the tactile sensor 160 is formed on the work supporting surface of the finger member 150. The configuration of the tactile sensor 160 is the same as that of the tactile sensor used as the indirect part 120 in the above-described embodiment, and the periphery of the flexure element 20 is fixed to the finger member 150 by the screw 30. The wiring between the outside of the single crystal substrate 10 is performed by the flexible printed board 60. A contact plate 170 is fixed to the center end of the tactile sensor 160 by a screw portion 171.

As shown in FIG. 24, the finger member 150 is
c and a drive indirect unit 180 connecting them, so as to approximate the movement of a human finger. By arranging the tactile sensors in this way, the contact pressure of each part can be detected as an electric signal. Further, similarly to the above-described embodiment, slip detection can be detected. That is, as shown in FIG. 25 (a), if the work 500 is at the position of 500a, the contact point P
Since the contact with the contact plate 170 is made at 1, the single crystal substrate 10 of the tactile sensor 160 has a moment force M2 as shown in the figure.
Will be detected. On the other hand, as shown in FIG. 25 (b), if the workpiece 500 is at the position of 500b, the contact point P
Since the contact with the contact plate 170 is made in 2, the single crystal substrate 10 of the tactile sensor 160 has a moment force M2 as shown in the figure.
Will be detected. Therefore, the work 500 is 500a
When it slips from 500b to 500b, this can be recognized from the change in the detected value.

Slip detection when acceleration is applied When acceleration is applied, slip detection can be detected by using a three-dimensional acceleration sensor together. This principle will be described with reference to FIG. Now, consider a case where a work 500 having a mass m is gripped as shown in the figure. Here, it is assumed that both the center of gravity G of the workpiece 500 and the contact point P are on the center axis of the tactile sensor 160 in order to simplify the model. It is assumed that the contact plate 170 presses the work 500 with the force F. In this case, the vertical force Fv acting on the contact point P is Fv = mg / 2, and the horizontal force Fh is Fh = F. Here, g is the gravitational acceleration.

Now, let us consider a case where the vertical acceleration α is further acting, for example, when the entire system is mounted on a vehicle. In this case, if the force acting on the contact point P is indicated by adding a dash, Fv ′ = m (g + α) / 2 Fh ′ = F. Here, when slippage occurs further in the vertical direction, two dashes are applied to the force acting on the contact point P by F
Expressing v ″, Fh ″, Fh ″ = Fh ′ = F, but Fv ″ ≠ Fv ′. Since the force acting on the contact point P can be detected by the tactile sensor 160, if it is recognized that Fv "≠ Fv ', it is possible to judge the presence or absence of slip even under the condition of acceleration action.

To detect the acting acceleration α, any three-dimensional acceleration sensor may be used. In the example shown in FIG. 26,
The acceleration sensor 600 is used. This acceleration sensor 600
Has almost the same configuration as the tactile sensor described above.
That is, the single crystal substrate 10 is formed on the strain generating body 20, and the strain generated in the strain generating body 20 can be detected as a change in the electric resistance on the single crystal substrate 10. However, a weight body 70 is connected to the distal end of the center of the flexure element 20, and the support around the flexure element 20 is fixed to the gripper body 700 by the support base 80. Further, a cover 90 for protection is covered on the upper part. When the acceleration acts, a force acts on the weight 70, and this can be detected as a change in the electric resistance of the resistance element on the single crystal substrate 10.

〔The invention's effect〕

As described above, according to the present invention, in the robot gripper, a tactile sensor including a resistive element provided on a single crystal substrate and a strain element that causes mechanical deformation of the resistive element is attached. It is possible to perform high-precision control that can sufficiently grasp the gripping state of the work.

[Brief description of the drawings]

1 is a view showing the structure of a gripper for a robot according to one embodiment of the present invention, FIG. 2 is a view showing a tactile sensor used for the gripper shown in FIG. 1, and FIG. 3 is a tactile sensor shown in FIG. 4 to 7 are diagrams showing the operation principle of the tactile sensor shown in FIG. 2, FIG. 8 is a top view of a six-axis component sensor,
FIG. 9 is a cross-sectional view of the device of FIG. 8 taken along section line AA,
FIG. 10 is a circuit diagram of six bridges formed by using the respective resistive elements of the device shown in FIG. 8, FIG. 11 is a table showing changes of the respective resistive elements of the device shown in FIG. 8, and FIG. FIG. 8 is a diagram showing a state when a force in the X-axis direction acts on the device shown in FIG. 8;
FIG. 13 is a diagram showing a state when a force in the Y-axis direction is applied to the device shown in FIG. 8, and FIG. 14 is a diagram showing a state when a force in the Z-axis direction is applied to the device shown in FIG. FIG. 15 shows a state when a moment about the X axis acts on the device shown in FIG. 8, and FIG. 16 shows a state when a moment about the Y axis acts on the device shown in FIG. FIG. 17 is a diagram showing a state when a moment about the Z axis acts on the device shown in FIG. 8, and FIG. 18 is a relationship between a force to be detected and a detected voltage in the device shown in FIG. FIG. 19 is a diagram showing an example of a method for manufacturing a single crystal substrate constituting the tactile sensor shown in FIG. 2, FIG. 20 and FIG. 21 are diagrams for explaining the operation of the gripper shown in FIG. FIG. 22 is a view showing a modification of the gripper shown in FIG. 1, and FIG. 23 is a view showing the structure of a gripper for a robot according to another embodiment of the present invention. FIG. 24 is a diagram showing a modification of the gripper shown in FIG. 23, FIG. 25 is an explanatory diagram of the operation of the gripper shown in FIG. 23, and FIG. It is operation | movement explanatory drawing at the time of acting. 10 ... single crystal substrate, 11 ... bonding pad, 12 ...
Bonding wires, 13 ... Electrodes for external wiring, 20 ...
Flexure element, 21 support section, 22 flexible section, 23 action section,
24 mounting holes, 25 wiring holes, 30 screws, 50 power supplies, 60 flexible printed circuit boards, 70 weight bodies,
80 ... support base, 90 ... lid, 100 ... finger member, 110 ... first
Joint, 120 indirect, 130, second joint, 131, screw, 140, drive joint, 160, tactile sensor, 170
Contact plate, 180: Drive indirect part, 200: Hand member, 201
…… Strain body, 211 …… Fixed part, 212-215 …… Bridged part, 216
… Working part, 221 and 222… Working body, 230… Power supply, 241-2
46 voltmeter, 401 silicon substrate, 402 silicon oxide layer, 403 opening, 404 p-type diffusion region, 405
... silicon oxide layer, 406 ... silicon nitride layer, 407 ... aluminum wiring layer, 500 ... work, 600 ... acceleration sensor, 700 ... gripper body, S ... working point, R ... resistance element.

Claims (2)

(57) [Claims] A finger member for gripping a work, and a hand member for movably supporting the finger member, a function of gripping the work by moving the finger member with respect to the hand member. The finger member has a first joint,
In a robot gripper having a second joint and an indirect connecting them, a support unit connected to the first joint, an action unit connected to the second joint, the support unit, A flexible part formed between the flexible part and the action part, wherein the flexible part is arranged around the action part, the support part is arranged around the flexible part, and a thickness of the support part. And by setting the thickness of the flexible portion smaller than the thickness of the working portion, the flexible portion has a structure showing flexibility, and mechanical deformation is caused by displacement of the working portion with respect to the support portion. A flexure element, a single crystal substrate bonded to the flexure element so that the mechanical deformation is transmitted, and a piezoresistive effect in which electric resistance changes due to the mechanical deformation. A finger element is formed by a tactile sensor comprising: Configure the indirect of the member,
A gripper for a robot, wherein a grip state between a work and the finger member can be detected as a change in an electric resistance value of the resistance element. 2. The gripper for a robot according to claim 1, wherein in the XYZ three-dimensional coordinate system, each force acting on the single crystal substrate in each coordinate axis direction and a moment around each coordinate axis can be detected. A gripper for a robot, wherein at least four resistance elements are provided for an axis, and a bridge is formed by each of the four resistance elements.