Piezoelectric sensor and hand

Abstract

To provide a piezoelectric sensor that can detect sliding of an object with respect to an elastic body based on a frictional force generated between the object and the elastic body, and a hand including such a piezoelectric sensor.SOLUTION: A piezoelectric sensor comprises: an elastic body; a piezoelectric element that is arranged at a position in contact with the elastic body and outputs a voltage signal when deformed along with deformation of the elastic body; and a detection unit that detects the voltage signal output from the piezoelectric element. After the elastic body is brought into contact with an object, when the elastic body moves relative to the object, the detection unit detects a kinetic frictional force generated between the object and the elastic body based on a change in the voltage signal due to the relative movement of the object.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present invention relates to a piezoelectric sensor and a hand.

Background Art

[0002] Patent Document 1 discloses a robot having a gripping device provided with a pressure-sensitive sensor as an industrial robot used in a production line or the like. The pressure-sensitive sensor is a sensor that outputs pressure as an electrical signal.

[0003] This gripping device includes a pair of grippers that can be opened and closed, and a pressure-sensitive sensor provided on the gripper. When the object to be gripped is gripped by the gripper, the pressure-sensitive sensor comes into contact with the object to be gripped and is deformed, and a voltage signal is output from the pressure-sensitive sensor. Based on this voltage signal, the control device of the robot controls the gripping force of the gripping device.

[0004] This pressure-sensitive sensor has a first electrode and a second electrode, and an intermediate layer provided therebetween as a piezoelectric body that generates electricity by deformation. Between each electrode and the intermediate layer, a change in capacitance occurs and electricity is generated. By detecting the amount of this power generation and the presence or absence of power generation, the pressure-sensitive sensor functions.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the pressure-sensitive sensor described in Patent Document 1, electricity is generated when the intermediate layer is deformed, but in order to generate electricity, it is necessary to apply pressure along the direction connecting the first electrode and the second electrode. For this reason, with this pressure-sensitive sensor, for example, it is possible to detect the gripping force received when the gripper grips the object to be gripped.

[0007] However, even if the object being gripped slips from the gripping part, the gripping force hardly changes. For this reason, it is difficult for the pressure sensor described in Patent Document 1 to detect that the object being gripped has slipped from the gripping part. [Means for solving the problem]

[0008] A piezoelectric sensor according to an application example of the present invention is An elastic body and A piezoelectric element is positioned in contact with the elastic body and outputs a voltage signal when it deforms in accordance with the deformation of the elastic body. A detection unit for detecting the voltage signal output from the piezoelectric element, Equipped with, The detection unit is characterized in that, after the elastic body has come into contact with the object, when the elastic body moves relative to the object, it detects the dynamic friction force generated between the object and the elastic body based on the change in the voltage signal due to the relative movement of the object.

[0009] The hand according to an application example of the present invention is The present invention is characterized by comprising a piezoelectric sensor according to an application example of the present invention. [Brief explanation of the drawing]

[0010] [Figure 1] This is a diagram showing a hand according to an embodiment. [Figure 2] Figure 1 is a perspective view showing an enlarged view of the tip of the finger portion, and is a perspective view showing the piezoelectric sensor according to the first embodiment in an exploded state. [Figure 3] Figure 2 is a plan view of the piezoelectric sensor as seen from a position on the X-axis. [Figure 4] This is an example of an output circuit that amplifies the voltage generated in a piezoelectric element. [Figure 5] Figure 3 illustrates the deformation modes of an elastic body when forces are applied to the piezoelectric sensor shown in Figure 3 from various directions. [Figure 6]It is a diagram showing an example of the waveform (output waveform) of the voltage signal output from the piezoelectric element shown in Fig. 3 when the elastic body is deformed in the deformation mode shown in Fig. 5. [Figure 7] It is a diagram showing an example of the output waveform from the piezoelectric element when slipping occurs between the object and the elastic body. [Figure 8] It is a diagram showing one of the three output waveforms shown in Fig. 7. [Figure 9] It is a diagram showing an example of the output waveform from the piezoelectric element when the piezoelectric sensor is moved along a floor surface having irregularities. [Figure 10] It is a side view showing the piezoelectric sensor according to the second embodiment. [Figure 11] It is a diagram for explaining the deformation mode of the elastic body when forces are applied to the piezoelectric sensor shown in Fig. 10 from various directions. [Figure 12] It is a plan view when the piezoelectric sensor according to the third embodiment is viewed from a position on the X-axis. [Figure 13] It is a diagram showing an example of the waveform (output waveform) of the voltage signal output from the piezoelectric element shown in Fig. 12 when the elastic body is deformed in the deformation mode shown in Fig. 5. [Figure 14] It is a plan view when the piezoelectric sensor according to the fourth embodiment is viewed from a position on the X-axis. [Figure 15] It is a diagram for explaining the deformation mode of the elastic body when forces are applied to the piezoelectric sensor shown in Fig. 14 from various directions. [Figure 16] It is a plan view when the piezoelectric sensor according to the fifth embodiment is viewed from a position on the X-axis. [Figure 17] It is a plan view when the piezoelectric sensor according to the sixth embodiment is viewed from a position on the X-axis. [Figure 18] It is a plan view when the piezoelectric sensor according to the seventh embodiment is viewed from a position on the X-axis. [Figure 19] It is a diagram for explaining the deformation mode of the elastic body when forces are applied to the piezoelectric sensor shown in Fig. 18 from various directions. [Figure 20]It is a diagram showing an example of the waveform (output waveform) of the voltage signal output from the piezoelectric element shown in FIG. 18 when the elastic body is deformed in the deformation mode shown in FIG. 19. [Figure 21] It is a plan view when the piezoelectric sensor according to the eighth embodiment is viewed from a position on the X-axis. [Figure 22] It is a diagram showing an example of the waveform (output waveform) of the voltage signal output from the piezoelectric element shown in FIG. 21 when the elastic body is deformed in the deformation mode shown in FIG. 19. [Figure 23] It is a plan view when the piezoelectric sensor according to the ninth embodiment is viewed from a position on the X-axis. [Figure 24] It is a plan view when the piezoelectric sensor according to the tenth embodiment is viewed from a position on the X-axis.

Modes for Carrying Out the Invention

[0011] Hereinafter, preferred embodiments of the piezoelectric sensor and the hand of the present invention will be described in detail based on the accompanying drawings. 1. Hand First, the hand according to the embodiment will be described.

[0012] FIG. 1 is a diagram showing a hand according to the embodiment. In FIG. 1, an X-axis, a Y-axis, and a Z-axis are set as three axes orthogonal to each other. Each axis is represented by an arrow, with the tip side being "plus" and the base end side being "minus". In the following description, for example, the "X-axis direction" includes both the plus direction and the minus direction of the X-axis. Also, in the following description, the Z-axis plus side may be described as "up" and the Z-axis minus side may be described as "down".

[0013] The hand 10 shown in FIG. 1 includes a pair of finger portions 14 and 15. By changing the distance between the finger portion 14 and the finger portion 15, the object W can be sandwiched and gripped from both sides, or the gripped object W can be released.

[0014] The hand 10 comprises a base 11, a pair of sliders 12 and 13 that slide relative to the base 11, finger portions 14 and 15 fixed to the sliders 12 and 13, motors 16 and 17 that slide the sliders 12 and 13, and a piezoelectric sensor 1. The configuration of the hand is not limited to this.

[0015] Sliders 12 and 13 are each slidable in the X-axis direction relative to the base 11. A motor 16 is connected to slider 12, and slider 12 slides when driven by motor 16. Similarly, a motor 17 is connected to slider 13, and slider 13 slides when driven by motor 17.

[0016] By selecting the rotation direction of motors 16 and 17, sliders 12 and 13 can be moved in opposite directions, thereby bringing the finger portions 14 and 15 closer together or further apart. This allows the finger portions 14 and 15 to grasp an object W or release the grasped object W. The hand 10 may also be configured such that one of the finger portions 14 and 15 is movable while the other is fixed.

[0017] Each of the finger portions 14 and 15 is provided with a piezoelectric sensor 1. The piezoelectric sensors 1 are provided on the faces of the finger portions 14 and 15 that face each other, i.e., the gripping surfaces 141 and 151. When an object W is held between the gripping surfaces 141 and 151, the piezoelectric sensors 1 are interposed between the gripping surfaces 141 and 151 and the object W. Therefore, each piezoelectric sensor 1 receives a reaction force from the object W and outputs a voltage corresponding to that reaction force. As a result, the hand 10 has the function of detecting the gripping state of the object W based on the output voltage from the piezoelectric sensors 1. Note that the piezoelectric sensors 1 may be provided on only one of the finger portions 14 and 15.

[0018] The hand 10 has been described above, but the piezoelectric sensor 1 may also be used in various other devices besides the hand 10, such as tactile sensors, game controllers, remote control controllers, MR (mixed reality) controllers, flexible user interfaces, various ON / OFF sensors, etc.

[0019] 2. Piezoelectric sensor according to the first embodiment Next, the piezoelectric sensor according to the first embodiment will be described.

[0020] Figure 2 is a perspective view showing an enlarged view of the tip of the finger portion 14 in Figure 1, and is an exploded perspective view of the piezoelectric sensor 1 according to the first embodiment. Figure 3 is a plan view of the piezoelectric sensor 1 shown in Figure 2 as seen from a position on the X axis.

[0021] The piezoelectric sensor 1 shown in Figures 2 and 3 is attached to the gripping surface 141 of the finger portion 14. The piezoelectric sensor 1 comprises an elastic body 2, a regulating portion 3, a piezoelectric element 41, and an output circuit 49 having a detection portion 494.

[0022] The elastic body 2 is elastic and is positioned to be in contact with the gripping surface 141. An arbitrary object may be interposed between the elastic body 2 and the gripping surface 141. Elasticity refers to the property of deforming in accordance with an applied force and returning to its original shape when the force is removed. Therefore, when a force is applied to the elastic body 2, it deforms, and the force propagates to various parts of the elastic body 2.

[0023] The elastic body 2 shown in Figures 2 and 3 is plate-shaped and extends in the YZ plane, having six faces. Of the six faces, the two faces intersecting the Y axis are designated as the first face 201 and the second face 202, the two faces intersecting the X axis are designated as the third face 203 and the fourth face 204, and the two faces intersecting the Z axis are designated as the fifth face 205 and the sixth face 206.

[0024] The third surface 203 and the fourth surface 204 are two main surfaces of the elastic body 2 that are in a front-and-back relationship with each other. The third surface 203 is the surface facing the object W, and the fourth surface 204 is fixed to the gripping surface 141. The third surface 203 and the fourth surface 204 shown in Figure 3 are rectangular in shape. In addition, in the elastic body 2 shown in Figure 2, the central part of the third surface 203 is a convex curved surface 207. As a result, when the third surface 203 contacts the object W, the convex curved surface 207 can preferentially make contact. Consequently, when a force is applied to the elastic body 2, the force can be transmitted from the central part of the third surface 203 towards the periphery.

[0025] Examples of constituent materials for the elastic body 2 include rubber, elastomers, and foamed resins. Among these, examples of rubber include polyisobutylene, polyisoprene, chloroprene rubber, butyl rubber, silicone rubber, fluororubber, acrylic rubber, urethane rubber, ethylene propylene rubber, butadiene rubber, acrylonitrile butadiene rubber, and styrene butadiene rubber.

[0026] The restricting portion 3 shown in Figures 2 and 3 is provided on the gripping surface 141 and forms a frame-like structure surrounding the elastic body 2. The inner surface of the restricting portion 3 is in contact with the outer surface of the elastic body 2. In other words, when the third surface 203 of the elastic body 2 is viewed from above, the elastic body 2 is contained within the restricting portion 3. There may be a small gap between the restricting portion 3 and the elastic body 2. Furthermore, any object may be interposed between the restricting portion 3 and the gripping surface 141.

[0027] The restricting section 3 has two first wall sections 31 and 32 extending along the Z-axis, and two second wall sections 33 and 34 extending along the Y-axis.

[0028] The first walls 31 and 32 each have a thickness t1 greater than the thickness t2 of the second walls 33 and 34. As a result, the first walls 31 and 32 have higher bending rigidity than the second walls 33 and 34. Consequently, the first walls 31 and 32 are less likely to deform even when pressed by the elastic body 2. In other words, the first walls 31 and 32 face the first surface 201 and the second surface 202 of the elastic body 2 in its natural state. Specifically, the first walls 31 and 32 are either in contact with the first surface 201 and the second surface 202 of the elastic body 2, or are adjacent to each other with only a small gap between them. Therefore, when the elastic body 2 is subjected to force and attempts to deform in the Y-axis direction, the first walls restrict that deformation. Note that the thickness of the first walls 31 and 32 refers to their length in the Y-axis direction.

[0029] The second wall sections 33 and 34 are thinner than the first wall sections 31 and 32. As a result, the second wall sections 33 and 34 have lower bending rigidity compared to the first wall sections 31 and 32. Consequently, the second wall sections 33 and 34 are more easily deformed when pressed by the elastic body 2. In other words, the second wall sections 33 and 34 are either in contact with the elastic body 2 in its natural state or adjacent to it with only a small gap between them. Therefore, when the elastic body 2 is subjected to a force and attempts to deform in the Z-axis direction, the second wall sections 33 and 34 also displace along the Z-axis in accordance with the deformation of the elastic body 2. In other words, bending deformation occurs in the Z-axis direction of the second wall sections 33 and 34. At this time, the ends of the second wall sections 33 and 34 in the Y-axis direction are connected to the first wall sections 31 and 32 and therefore hardly displace. Note that the thickness of the second wall sections 33 and 34 refers to their length in the Z-axis direction.

[0030] The constituent materials of the regulating section 3 are not particularly limited, but examples include resin materials, ceramic materials, metal materials, and the like.

[0031] The thickness of the first wall portions 31 and 32 is set appropriately according to the constituent materials, but as an example, it is preferably 0.5 mm to 20 mm, and more preferably 1 mm to 10 mm. As a result, the first wall portions 31 and 32 have sufficient bending rigidity and are particularly resistant to deformation even when force is applied to the elastic body 2.

[0032] The thickness of the second walls 33 and 34 is also set appropriately according to the constituent materials, but as an example, it is preferably 60% or less of the thickness of the first walls 31 and 32, and more preferably 5% to 40%. As a result, the second walls 33 and 34 have sufficient flexibility and deform easily when force is applied to the elastic body 2. Therefore, deformation is more easily transmitted to the piezoelectric element 41, and the sensitivity of the piezoelectric sensor 1 can be increased.

[0033] The piezoelectric element 41, although not shown, comprises a piezoelectric body and a pair of electrodes provided via the piezoelectric body. When the piezoelectric body is deformed, for example by bending, it generates a voltage between the electrodes due to the piezoelectric effect. By detecting the voltage output from the piezoelectric element 41, the direction and magnitude of the applied force can be determined.

[0034] The piezoelectric element 41 shown in Figure 2 is provided between the fifth surface 205 of the elastic body 2 and the second wall portion 33. When bending deformation occurs in the second wall portion 33 due to the deformation of the elastic body 2, bending deformation also occurs in the piezoelectric element 41. By fixing a part of the piezoelectric element 41 to the second wall portion 33 in this way, damage to the piezoelectric element 41 due to bending deformation can be suppressed. In other words, by reinforcing the piezoelectric element 41 with the second wall portion 33, the piezoelectric properties of the piezoelectric element 41 are less likely to deteriorate even if bending deformation occurs repeatedly in the piezoelectric element 41 at short intervals. Furthermore, when the load is removed, the piezoelectric element 41 is more likely to return to its original shape. That is, the ability of the piezoelectric element 41 to follow the deformation of the elastic body 2 is improved. This can suppress a decrease in the accuracy of force detection.

[0035] Examples of piezoelectric materials that constitute a piezoelectric body include piezoelectric ceramics such as lead zirconate titanate (PZT), barium titanate, and lead titanate, as well as piezoelectric plastics such as polyvinylidene fluoride and polylactic acid.

[0036] Furthermore, piezoelectric materials exhibit anisotropy in their piezoelectric effect depending on the piezoelectric constant of the piezoelectric material. In this embodiment, the piezoelectric material is selected such that a voltage is generated between the electrodes in response to bending deformation occurring in the Z-axis direction. This makes it possible to determine the direction and magnitude of the force acting on the elastic body 2 according to the output from the piezoelectric element 41. An example of a piezoelectric constant exhibiting such piezoelectricity is d 31 These are some examples.

[0037] Examples of materials used to construct electrodes include elements or alloys of Al, Cu, Ni, Ag, Au, etc.

[0038] Figure 4 shows an example of an output circuit that amplifies the voltage generated in the piezoelectric element 41. The output circuit 49 shown in Figure 4 comprises an amplifier 491, a power supply 492, a power supply 493, and a detection unit 494. The piezoelectric element 41 is connected between the inverting input terminal and the non-inverting input terminal of the amplifier 491. The power supply 492 is connected to the non-inverting input terminal. The power supply 493 is connected to the power supply terminal of the amplifier 491. The detection unit 494 is connected to the output terminal of the amplifier 491.

[0039] In this output circuit 49, the voltage generated by the piezoelectric element 41 is amplified and output as a voltage signal with a large amplitude. As shown in Figure 4, when the power supply 492 is connected to the input terminal of the amplifier 491, the input signal is offset by the power supply 492. Therefore, the detection unit 494 outputs an offset voltage, that is, a voltage signal that increases or decreases from the reference voltage. The power supply 492 may be provided as needed and may be omitted.

[0040] The detection unit 494 has functions such as detecting the time change of a voltage signal that increases or decreases from a reference voltage, and determining whether or not there is slippage between the object W and the piezoelectric sensor 1 based on the voltage value. The detection unit 494 shown in Figures 2 and 4 includes, as an example, a measurement unit 495, a calculation unit 496, and a judgment unit 497. The measurement unit 495 measures the amplitude of the voltage signal output from the amplifier 491. The calculation unit 496 calculates the increase or decrease in the amplitude of the voltage signal relative to the reference voltage. The judgment unit 497 compares the calculation result of the calculation unit 496, for example, a preset tolerance range, with the calculation result and outputs the result.

[0041] At least a portion of the detection unit 494 is composed of hardware including a processor, memory, and external interfaces. An example of a processor is a CPU (Central Processing Unit). The processor reads and executes a program stored in memory, thereby realizing the functions of the detection unit 494. However, the hardware configuration is not limited to this, and may include configurations such as LSI (Large Scale Integration), ASIC (Application Specific Integrated Circuit), FPGA (Field-Programmable Gate Array), etc.

[0042] Furthermore, the circuit configuration of the output circuit of the piezoelectric sensor 1 is not limited to the circuit configuration shown in Figure 4, and may include, for example, a charge amplifier.

[0043] Figure 5 illustrates the deformation modes of the elastic body 2 when forces are applied from various directions to the piezoelectric sensor 1 shown in Figure 3. Figure 6 shows an example of the waveform of the voltage signal output from the piezoelectric element 41 shown in Figure 3 when the elastic body 2 is deformed in the deformation modes shown in Figure 5. Note that in the example shown in Figure 6, the waveform of the potential relative to the reference voltage is shown.

[0044] When no force is applied to the piezoelectric sensor 1, the elastic body 2 maintains its natural state, and as shown in the upper left of Figure 5, the piezoelectric element 41 does not deform. Therefore, theoretically, no voltage is generated in the piezoelectric element 41.

[0045] When a downward force is applied to the piezoelectric sensor 1, a downward pulling force is applied to the third surface 203 of the elastic body 2, as shown by the arrow in the upper right diagram of Figure 5. As a result, the elastic body 2 deforms as if being dragged downwards, and consequently, the piezoelectric element 41 undergoes downward bending deformation. At this time, the piezoelectric element 41 outputs a negative voltage signal relative to the reference voltage, as shown in Figure 6. In other words, a voltage signal decreasing from the reference voltage is output. This makes it possible to identify that a downward force is being applied to the piezoelectric sensor 1. Note that the output direction of the voltage signal relative to the reference potential is determined by the polarization direction of the piezoelectric element and the circuit configuration, so the output direction of the voltage signal may be the opposite of the above. In that case, subsequent outputs will also be the opposite result.

[0046] Furthermore, if the hand 10 is moved while gripping the object W, the weight of the object W will cause a downward force to be applied to the piezoelectric sensor 1. Therefore, it is possible to determine the state in which the hand 10 is lifting the object W based on the output waveform from the piezoelectric element 41.

[0047] When an upward force is applied to the piezoelectric sensor 1, an upward pulling force is applied to the third surface 203 of the elastic body 2, as shown by the arrow in the lower left diagram of Figure 5. As a result, the elastic body 2 deforms as if being dragged upward, and consequently, the piezoelectric element 41 undergoes upward bending deformation. At this time, the piezoelectric element 41 outputs a voltage signal, for example, a positive voltage signal relative to the reference voltage, as shown in Figure 6. In other words, a voltage signal increasing from the reference voltage is output. This makes it possible to determine that an upward force is being applied to the piezoelectric sensor 1.

[0048] Furthermore, when the hand 10 is moved while gripping the object W, pressing the underside of the object W against another object, an upward force is applied to the piezoelectric sensor 1. Therefore, based on the output waveform from the piezoelectric element 41, it is possible to determine that the hand 10 is pressing the object W against another object.

[0049] When a pressing force is applied to the piezoelectric sensor 1, that is, a force pushing the elastic body 2 shown in Figure 5 from the positive X-axis side to the negative X-axis side, the third surface 203 of the elastic body 2 undergoes deformation that extends vertically, as shown by the arrow in the lower right diagram of Figure 5. As a result, the elastic body 2 stretches vertically, and consequently, the piezoelectric element 41 undergoes bending deformation in the upward direction. However, the amount of bending deformation is smaller than that when the upward force described above is applied. Therefore, the piezoelectric element 41 outputs a positive voltage signal, for example, a voltage value that is relatively small compared to the reference voltage, as shown in Figure 6. This makes it possible to identify that a pressing force is being applied to the piezoelectric sensor 1.

[0050] When the hand 10 grasps the object W, the reaction force from the object W presses the piezoelectric sensor 1 against the gripping surface 141. Therefore, it is possible to determine that the hand 10 is grasping the object W based on the output waveform from the piezoelectric element 41.

[0051] The above describes examples of deformation modes, but the deformation direction may be other than upward or downward.

[0052] Here, let's consider the case where the object W being held by the hand 10 is pressed firmly against the floor surface, for example. In this case, the upward arrow shown in Figure 5 corresponds to the direction of the reaction force applied from the floor surface to the object W when the hand 10 presses the object W against the floor surface. This reaction force becomes the deformation force that deforms the elastic body 2. As the elastic body 2 deforms, bending deformation occurs in the piezoelectric element 41, making it possible to detect the direction and magnitude (bending radius) of the bending deformation.

[0053] On the other hand, frictional force is generated between the object W and the elastic body 2. When the deformation force and the frictional force are balanced, the positional relationship between the object W and the hand 10 is maintained. In this case, no slippage occurs between the object W and the piezoelectric sensor 1.

[0054] Subsequently, when the entire hand 10 is moved downward, the force pressing the object W against the floor gradually increases. When the deformation force exceeds the frictional force, slippage occurs between the object W and the elastic body 2. The frictional force immediately before slippage occurs is called the "static friction force." Since the frictional force immediately before slippage occurs is equal to the deformation force, the static friction force can be detected by the piezoelectric element 41. When slippage occurs, the frictional force decreases below the static friction force. The frictional force when slippage occurs is called the "dynamic friction force." Since the dynamic friction force is smaller than the static friction force, it is possible to distinguish between the occurrence of static friction force and the occurrence of dynamic friction force based on the voltage signal output from the piezoelectric element 41. Furthermore, since the frictional force when slippage occurs is also balanced with the deformation force, the dynamic friction force can be detected by the piezoelectric element 41. Also, since the dynamic friction force continues to be detected while slippage is occurring, the output waveform from the piezoelectric element 41 will include a peak corresponding to the static friction force and a voltage value corresponding to the dynamic friction force observed afterward.

[0055] Figure 7 shows an example of the output waveform from the piezoelectric element 41 when slip occurs between the object W and the elastic body 2. In Figure 7, the horizontal axis represents time, and the vertical axis represents the output voltage from the piezoelectric element 41. Figure 7 also shows the output waveforms superimposed when the gripping force of the object W, i.e., the distance between the piezoelectric sensor 1 and the object W, is changed in three stages.

[0056] The output waveform shown in Figure 7 includes a peak P that appears immediately after a significant voltage value is observed, and a region B in which voltage values ​​lower than peak P are observed afterward.

[0057] Peak P corresponds to the bending deformation that occurs in the piezoelectric element 41 when static friction force is present. Region B corresponds to the bending deformation that occurs in the piezoelectric element 41 when kinetic friction force is present. As mentioned above, since kinetic friction force is smaller than static friction force, region B is lower than peak P. Therefore, if region B is detected after peak P is detected, it can be determined that slip has occurred between the object W and the elastic body 2. In other words, based on the presence of peak P and region B, the piezoelectric sensor 1 can detect the kinetic friction force corresponding to region B and, based on that, determine whether or not slip has occurred.

[0058] Figure 8 shows one of the three output waveforms shown in Figure 7. When the determination unit 497 of the detection unit 494 determines whether or not slip occurs, it first detects a peak P. Since the peak P takes a maximum value, it can be identified, for example, by the presence or absence of a maximum value. Next, the determination unit 497 sets an acceptable range TL based on the height of the peak P. The acceptable range TL is preferably in the range of 20% or more and less than 100% of the height of the peak P, and more preferably in the range of 40% or more and less than 100%. Next, the determination unit 497 can determine whether or not slip occurs based on the time TM during which region B is continuously contained within this acceptable range TL. The time TM is set appropriately depending on the type of object W, the size of the elastic body 2, the degree of noise, etc., but as an example, it is preferably 0.1 seconds or more, and more preferably 0.5 seconds or more. Note that the determination process is not limited to this.

[0059] As described above, the presence or absence of slippage can be detected. This allows the piezoelectric sensor 1 to detect, via the current sensor, any signs that the object W is about to fall from the hand 10 when the hand 10 is pressing the object W against the floor, for example. As a result, the operation of the hand 10 can be changed before the object W falls. In other words, the hand 10 can be made to take an avoidance action to prevent the object W from falling.

[0060] Furthermore, the detection of slippage as described above does not depend on the gripping force of the object W. As mentioned earlier, Figure 7 shows the output waveforms when the magnitude of the gripping force is changed in three stages, but even when the gripping force is changed, a peak P and region B can be observed in each output waveform.

[0061] Furthermore, the detection of slippage as described above does not depend on the relative velocity when the object W and the elastic body 2 slip. Although not shown in the figures, even if the relative velocity changes, a peak P and region B can be observed in the output waveform from the piezoelectric element 41.

[0062] Furthermore, the object W is not limited to the grippable object shown in Figure 1. For example, when the piezoelectric sensor 1 is brought into direct contact with the floor surface as the object and moved along the floor surface, an output waveform like the one shown in Figure 7 can be obtained. In this case, static friction and kinetic friction generated between the floor surface and the elastic body 2 can be detected, and based on this, the presence or absence of slippage can be detected. Moreover, if there are irregularities on the floor surface, the output waveform will change in accordance with the irregularities.

[0063] Figure 9 shows an example of the output waveform from the piezoelectric element 41 when the piezoelectric sensor 1 is moved along an uneven floor surface. In Figure 9, the horizontal axis represents time, and the vertical axis represents the output voltage from the piezoelectric element 41. In addition, Figure 9 shows superimposed output waveforms when the distance between the floor surface and the piezoelectric sensor 1, i.e., the force that the piezoelectric sensor 1 receives from the floor surface, is changed in two stages.

[0064] The output waveform shown in Figure 9 also includes a peak P and a region B where the voltage value is lower than the peak P. Therefore, based on the output waveform shown in Figure 9, it is possible to detect whether or not there is slippage between the piezoelectric sensor 1 and objects such as floor surfaces that are not being gripped.

[0065] Furthermore, the output waveform shown in Figure 9 reflects the unevenness of the floor surface. The change points C1, C2, and C3 shown in Figure 9 are common to both output waveforms. The times when these change points C1, C2, and C3 are observed correspond to the times when the piezoelectric sensor 1 passed over the unevenness of the floor surface. Therefore, the piezoelectric sensor 1 can detect not only the presence or absence of slippage, but also shape changes such as the unevenness present on the surface of the object W. In other words, the piezoelectric sensor 1 makes it possible to indirectly detect the unevenness based on the change in kinetic friction force when passing over the unevenness.

[0066] As described above, the piezoelectric sensor 1 according to this embodiment comprises an elastic body 2, a piezoelectric element 41, and a detection unit 494. The piezoelectric element 41 is positioned in contact with the elastic body 2 and outputs a voltage signal when it deforms in accordance with the deformation of the elastic body 2. Deformation of the piezoelectric element 41 means a change in the shape of the piezoelectric element 41 from when the elastic body 2 is not deformed. After the elastic body 2 comes into contact with the object W, when the elastic body 2 moves relative to the object W, the detection unit 494 detects the dynamic friction force generated between the object W and the elastic body 2 based on the change in the voltage signal due to the relative movement of the object W.

[0067] Such a piezoelectric sensor 1 can detect the dynamic friction force generated between the object W and the elastic body 2. Specifically, when the elastic body 2 deforms in accordance with the object W, the piezoelectric element 41 can capture the change in the amount of deformation, so that static friction and dynamic friction can be detected separately. This makes it possible to detect dynamic friction and, based on a comparison with static friction, to detect whether or not slippage is occurring between the object W and the elastic body 2. As a result, for example, a hand 10 can be realized that can easily determine whether or not the object W is being held stably.

[0068] Furthermore, since the force is transmitted to the piezoelectric element 41 via the elastic body 2, it is possible to suppress the direct application of shock to the piezoelectric element 41. This makes the piezoelectric element 41 less susceptible to damage.

[0069] Furthermore, the hand 10 according to the aforementioned embodiment includes the piezoelectric sensor 1 as described above.

[0070] When the piezoelectric sensor 1 is used in a hand 10 as shown in Figure 1, for example, it is possible to realize a hand 10 that can detect not only whether an object W is being gripped, but also whether or not slippage occurs between the gripped object W and the elastic body 2. Furthermore, in a hand 10 equipped with the piezoelectric sensor 1 described above, in addition to gripping the object W, it becomes possible to identify, for example, whether the object W is being lifted or whether the object W is being pressed against an object. Moreover, the piezoelectric sensor 1 has a structure in which the elastic body 2 is in contact with the object W. As a result, even if the piezoelectric sensor 1 comes into contact with the object W, a large impact is unlikely to occur, so even if the rigidity of the object W is low, the object W can be gripped by the hand 10 without damaging the object W. In addition, damage to the piezoelectric element 41 due to impact can be suppressed. The hand 10 may be equipped with piezoelectric sensors according to the embodiments described later.

[0071] Furthermore, in the piezoelectric sensor 1 according to this embodiment, when the elastic body 2 comes into contact with the object W, the detection unit 494 detects the static friction force generated between the object W and the elastic body 2 based on the voltage signal output from the piezoelectric element 41.

[0072] With such a piezoelectric sensor 1, the elasticity of the elastic body 2 can be used to effectively generate a stable static friction force between the object W and the elastic body 2. Therefore, regardless of the surface condition of the object W, the static friction force can be stably detected based on the voltage signal output from the piezoelectric element 41.

[0073] Furthermore, in the piezoelectric sensor 1 according to this embodiment, the elastic body 2 has a first surface 201 as described above. The piezoelectric sensor 1 also includes a restricting part 3 positioned facing the first surface 201 of the elastic body 2, which restricts the deformation of the elastic body 2. A portion of the piezoelectric element 41 is fixed to the restricting part 3.

[0074] With this configuration, when force is applied to the elastic body 2 from multiple different directions, such as upward, downward, and downward, the direction of the applied force can be detected. As a result, the hand 10 equipped with this piezoelectric sensor 1 can identify not only that it is gripping the object W, but also, for example, that the object W is being lifted or that the object W is being pressed against an object. Therefore, the hand 10 can be operated appropriately according to these different states, thereby increasing convenience.

[0075] Furthermore, in the piezoelectric sensor 1 according to this embodiment, the elastic body 2 has a second surface 202 facing the first surface 201. The regulating section 3 comprises two first wall sections 31 and 32 and two second wall sections 33 and 34. The two first wall sections 31 and 32 are positioned facing the first surface 201 and the second surface 202, respectively. The two second wall sections 33 and 34 connect the first wall section 31 and the first wall section 32 and are thinner than the first wall sections 31 and 32. The piezoelectric element 41 is fixed to the second wall section 33.

[0076] With this configuration, since the piezoelectric element 41 is fixed to the second wall portion 33, the durability of the piezoelectric element 41 is increased, and the ability of the piezoelectric element 41 to follow the deformation of the elastic body 2 is improved.

[0077] Furthermore, the elastic body 2 has a rectangular third surface 203. The elastic body 2 is plate-shaped with this third surface 203 as its main surface.

[0078] With this configuration, the relatively wide third surface 203 faces the object W, thus ensuring a large contact area between the object W and the elastic body 2. This allows a large force to be applied to the elastic body 2, increasing the displacement of the fifth surface 205 facing the piezoelectric element 41. As a result, the sensitivity of the piezoelectric sensor 1 can be further increased.

[0079] Furthermore, the shape of the third surface 203 is not limited to a rectangle, but may be other shapes, such as a square or a polygon. It may also be a shape with rounded or chamfered corners.

[0080] Furthermore, as shown in Figure 2, the elastic body 2 has a convex curved surface 207 as a contact surface that contacts the object W. The convex curved surface 207 is located at a distance from the piezoelectric element 41.

[0081] With this configuration, even if the convex curved surface 207 comes into contact with the object W, contact between the piezoelectric element 41 and the object W can be avoided. This prevents damage to the piezoelectric element 41. Furthermore, because the elastic body 2 is elastic, even if the piezoelectric element 41 is positioned away from the convex curved surface 207, the frictional force generated between the elastic body 2 and the object W is efficiently converted into deformation of the piezoelectric element 41. As a result, the piezoelectric element 41 can efficiently detect the frictional force. Consequently, a piezoelectric sensor 1 with good sensitivity is realized.

[0082] The elastic body 2 may have a convex surface of any shape instead of the convex curved surface 207, but if it has a convex curved surface 207, a piezoelectric sensor 1 that can reliably detect forces applied from various directions can be easily realized.

[0083] 3. Piezoelectric sensor according to the second embodiment Next, a piezoelectric sensor according to the second embodiment will be described.

[0084] Figure 10 is a side view showing a piezoelectric sensor according to the second embodiment. In Figure 10, the x-axis, y-axis, and z-axis are defined as three mutually orthogonal axes. Each axis is represented by an arrow, with the tip side being "positive" and the base side being "negative". In the following explanation, for example, "x-axis direction" includes both the positive and negative directions of the x-axis. Also, in the following explanation, the positive side of the z-axis may be referred to as "up", the negative side of the z-axis as "down", the positive side of the y-axis as "right", and the negative side of the y-axis as "left".

[0085] The second embodiment will be described below, focusing on the differences from the first embodiment, and similar matters will be omitted from the description. In each figure, components similar to those in the first embodiment are denoted by the same reference numerals.

[0086] The piezoelectric sensor 1a according to the second embodiment is the same as the piezoelectric sensor 1 according to the first embodiment, except that the shape of the elastic body 2 and the arrangement of the piezoelectric elements 41 are different, and the holding part 6 is provided instead of the regulating part 3.

[0087] The piezoelectric sensor 1a shown in Figure 10 comprises an elastic body 2, a piezoelectric element 41, and a holding part 6. Although not shown in Figure 10, the piezoelectric sensor 1a also includes an output circuit 49 having the aforementioned detection unit 494.

[0088] The elastic body 2 shown in Figure 10 is cylindrical in shape with an axis parallel to the x-axis. The elastic body 2 possesses elasticity inherent to its material as well as elasticity due to its cylindrical shape. Therefore, the elastic body 2 has good elasticity in the yz plane.

[0089] Furthermore, in Figure 10, the elastic body 2 has a contact surface 21 on the negative z-axis side of its outer cylindrical surface that contacts the object W. The piezoelectric sensor 1a functions properly when this contact surface 21 is in contact with the object W.

[0090] The holding part 6 shown in Figure 10 holds the upper part of the elastic body 2 at its lower end. The upper part of the holding part 6 is fixed to, for example, the fingers 14 and 15 of the hand 10. This allows the distance between the elastic body 2 and the object W to be adjusted according to the purpose.

[0091] The piezoelectric element 41 shown in Figure 10 is positioned on the outer surface of the elastic body 2, away from the contact surface 21. Specifically, the piezoelectric element 41 is positioned on the outer surface of the elastic body 2 between the holding portion 6 and the position furthest towards the positive y-axis.

[0092] With this configuration, even if the contact surface 21 of the elastic body 2 comes into contact with the object W, contact between the piezoelectric element 41 and the object W can be avoided. This prevents damage to the piezoelectric element 41. Furthermore, because the elastic body 2 is cylindrical, even if the piezoelectric element 41 is positioned away from the contact surface 21, the frictional force generated between the elastic body 2 and the object W is efficiently converted into deformation of the piezoelectric element 41. As a result, the piezoelectric element 41 can efficiently detect the frictional force. Consequently, a piezoelectric sensor 1a with good sensitivity is realized.

[0093] Figure 11 is a diagram illustrating the deformation modes of the elastic body 2 when forces are applied from various directions to the piezoelectric sensor 1a shown in Figure 10.

[0094] When no force is applied to the piezoelectric sensor 1a, the elastic body 2 maintains its natural state. Therefore, the piezoelectric element 41 maintains its initial shape, as shown in the upper diagram of Figure 11. The output voltage from the piezoelectric element 41 in this state is defined as the initial state.

[0095] When an upward force is applied to the piezoelectric sensor 1a, the elastic body 2 deforms in a way that it collapses vertically, as shown in the middle diagram of Figure 11. This reduces the bending radius of the piezoelectric element 41, and the output voltage from the piezoelectric element 41 changes from its initial state. Based on this, it becomes possible to identify the state in which an upward force is being applied. This state in which only an upward force is being applied corresponds, for example, to a state in which static friction force is generated between the object W and the elastic body 2.

[0096] When a force is applied to the piezoelectric sensor 1a from a state where the elastic body 2 is compressed in the vertical direction, as shown in the lower diagram of Figure 11, the elastic body 2 deforms so that the holding part 6 and the contact surface 21 are shifted in the left-right direction (Y-axis direction). As a result, the bending radius of the piezoelectric element 41 becomes larger than when an upward force is applied to the piezoelectric sensor 1a. Consequently, it becomes possible to identify the state in which a force is applied to the piezoelectric sensor 1a in the left direction. This state in which a force is applied to the left corresponds, for example, to a state in which kinetic friction force is generated between the object W and the elastic body 2.

[0097] As described above, the piezoelectric sensor 1a according to this embodiment can also detect static friction and kinetic friction in the same manner as in the first embodiment. Therefore, the piezoelectric sensor 1a can also obtain output waveforms similar to those in Figures 7 to 9, corresponding to static friction and kinetic friction. Thus, the same effects as in the first embodiment can be obtained in this embodiment as well.

[0098] The outer diameter d of the elastic body 2 in its natural state is not particularly limited, but is preferably 10 mm or more and 100 mm or less, and more preferably 20 mm or more and 80 mm or less.

[0099] Furthermore, the thickness t3 of the elastic body 2 is not particularly limited, but is preferably 1 mm or more and 10 mm or less, and more preferably 2 mm or more and 8 mm or less.

[0100] 4. Piezoelectric sensor according to the third embodiment Next, a piezoelectric sensor according to the third embodiment will be described.

[0101] Figure 12 is a plan view of the piezoelectric sensor according to the third embodiment, as seen from a position on the X-axis.

[0102] The third embodiment will be described below, focusing on the differences from the first embodiment, and similar matters will be omitted from the explanation. In each figure, components similar to those in the first embodiment are denoted by the same reference numerals.

[0103] The piezoelectric sensor 1A according to the third embodiment is the same as the piezoelectric sensor 1 according to the first embodiment, except that it includes a piezoelectric element 42 in addition to the piezoelectric element 41.

[0104] As shown in Figure 12, the piezoelectric element 42 is provided between the elastic body 2 and the second wall portion 34. When bending deformation occurs in the second wall portion 34 due to the deformation of the elastic body 2, bending deformation also occurs in the piezoelectric element 42. The configuration of the piezoelectric element 42 is the same as that of the piezoelectric element 41.

[0105] Furthermore, the relationship between the bending deformation direction of the piezoelectric element 42 and the output waveform from the piezoelectric element 42 may be the same as the relationship between the bending deformation direction of the piezoelectric element 41 and the output waveform from the piezoelectric element 41, but it is preferable that they be reversed. In other words, when the piezoelectric element 42 is bent in the same direction as the piezoelectric element 41, it is preferable that the sign of the output voltage signal is different. This makes it possible to more accurately determine the direction of the force applied to the elastic body 2 based on the output waveforms from the two piezoelectric elements 41 and 42. As a result, when slippage occurs between the object W and the elastic body 2, it is possible to more accurately determine whether the object W is sliding upward or downward relative to the elastic body 2.

[0106] Figure 13 shows an example of the waveform of the voltage signal (output waveform) output from the piezoelectric elements 41 and 42 shown in Figure 12 when the elastic body 2 is deformed in the deformation mode shown in Figure 5. Note that the output waveform shown in Figure 13 is the waveform when the piezoelectric elements 41 and 42 are bent in the same direction and are set to output voltage signals with different signs. Furthermore, the example shown in Figure 13 shows the waveform of the potential relative to the reference voltage.

[0107] When a downward force is applied to the piezoelectric sensor 1A, the piezoelectric elements 41 and 42 undergo downward bending deformation. As a result, the piezoelectric elements 41 and 42 output voltage signals with different signs. For example, in the example shown in Figure 13, it can be determined that a downward force is being applied to the piezoelectric sensor 1A based on the fact that the sign of the voltage signal output from piezoelectric element 41 is negative relative to the reference voltage, and the sign of the voltage signal output from piezoelectric element 42 is positive relative to the reference voltage. Based on this state of downward force application, the static friction force and kinetic friction force generated between the object W and the elastic body 2 can be detected. Note that the direction of the voltage signal relative to the reference potential is determined by the polarization direction of the piezoelectric element and the circuit configuration, so the output direction may be the opposite of the above. In that case, subsequent outputs will also be the opposite result.

[0108] When an upward force is applied to the piezoelectric sensor 1A, the piezoelectric elements 41 and 42 undergo upward bending deformation. As a result, the piezoelectric elements 41 and 42 output voltage signals with different signs. For example, in the example shown in Figure 13, it can be determined that an upward force is being applied to the piezoelectric sensor 1A based on the fact that the sign of the voltage signal output from piezoelectric element 41 is positive relative to the reference voltage, and the sign of the voltage signal output from piezoelectric element 42 is negative relative to the reference voltage. Based on this state of upward force application, the static friction force and kinetic friction force generated between the object W and the elastic body 2 can be detected.

[0109] When a pressing force is applied to the piezoelectric sensor 1A, that is, a force pushing the elastic body 2 shown in Figure 12 from the positive X-axis side to the negative X-axis side, the piezoelectric element 41 undergoes an upward bending deformation, and the piezoelectric element 42 undergoes a downward bending deformation. As a result, piezoelectric elements 41 and 42 output voltage signals with the same sign. This makes it possible to determine that a pressing force is being applied to the piezoelectric sensor 1A. In this third embodiment, the same effects as in the first embodiment can be obtained.

[0110] As described above, the elastic body 2 of the piezoelectric sensor 1A has a fifth surface 205 and a sixth surface 206 as two opposing surfaces corresponding to two sides facing each other when the third surface 203 is viewed from above. The piezoelectric elements 41 and 42 are positioned facing the fifth surface 205 and the sixth surface 206.

[0111] With this configuration, for example, by making the signs of the voltage signals output when bent in the same direction different for the piezoelectric elements 41 and 42, the voltage signals output from the piezoelectric elements 41 and 42 can be made such that one is a signal increasing from a reference voltage and the other is a signal decreasing from a reference voltage. This makes the difference in the waveforms of the voltage signals output from the piezoelectric elements 41 and 42 clearer. As a result, even if noise is introduced into the voltage signal, for example, the direction of the force applied to the elastic body 2 can be easily determined.

[0112] 5. Piezoelectric sensor according to the fourth embodiment Next, a piezoelectric sensor according to the fourth embodiment will be described.

[0113] Figure 14 is a plan view of the piezoelectric sensor according to the fourth embodiment, as seen from a position on the X-axis.

[0114] The fourth embodiment will be described below, focusing on the differences from the first embodiment, and similar aspects will be omitted. Note that components identical to those in the first embodiment are denoted by the same reference numerals in each figure.

[0115] In the piezoelectric sensor 1B according to this embodiment, the elastic body 2 has a second surface 202 facing the first surface 201. The regulating portion 3 also includes two first wall portions 31 and 32. The first wall portion 31 is positioned facing the first surface 201 of the elastic body 2, and the first wall portion 32 is positioned facing the second surface 202 of the elastic body 2.

[0116] In other words, in the first embodiment described above, the regulating section 3 has two first wall sections 31 and 32 and two second wall sections 33 and 34. In contrast, in this embodiment, the second wall sections 33 and 34 are omitted. As a result, in this embodiment, as shown in Figure 14, the regulating section 3 is composed only of the two first wall sections 31 and 32.

[0117] Furthermore, in the first embodiment described above, the piezoelectric element 41 is fixed to the second wall portion 33, whereas in this embodiment, the piezoelectric element 41 is fixed so as to connect the first wall portions 31 and 32. Specifically, the piezoelectric element 41 is positioned facing the fifth surface 205 of the elastic body 2, and the Y-axis positive end of the piezoelectric element 41 is fixed to the first wall portion 31, while the Y-axis negative end of the piezoelectric element 41 is fixed to the first wall portion 32.

[0118] With this configuration, similar to the first embodiment, the deformation of the elastic body 2 is restricted by the two first wall portions 31 and 32 extending along the Z-axis. In this embodiment, the second wall portions 33 and 34 present in the first embodiment are omitted. Therefore, the fifth surface 205 of the elastic body 2 is no longer restricted in deformation by the second wall portions 33 and 34. As a result, the amount of deformation of the piezoelectric element 41 tends to be larger than in the first embodiment.

[0119] Therefore, by positioning the piezoelectric element 41 facing the fifth surface 205, the sensitivity of the piezoelectric sensor 1B can be further increased.

[0120] Figure 15 is a diagram illustrating the deformation modes of the elastic body 2 when forces are applied from various directions to the piezoelectric sensor 1B shown in Figure 14.

[0121] When a downward force is applied to the piezoelectric sensor 1B, the piezoelectric element 41 undergoes a downward bending deformation, as shown in the upper right diagram of Figure 15. At this time, the piezoelectric element 41 outputs a negative voltage signal relative to the reference voltage, as shown in Figure 10. This makes it possible to identify that a downward force is being applied to the piezoelectric sensor 1B.

[0122] When an upward force is applied to the piezoelectric sensor 1B, the piezoelectric element 41 undergoes an upward bending deformation, as shown in the lower left diagram of Figure 15. As a result, the piezoelectric element 41 outputs a positive voltage signal relative to the reference voltage, as shown in Figure 10. This makes it possible to determine that an upward force is being applied to the piezoelectric sensor 1B.

[0123] When a pressing force is applied to the piezoelectric sensor 1B, that is, a force pushing the elastic body 2 shown in Figure 15 from the positive X-axis side to the negative X-axis side, the piezoelectric element 41 undergoes an upward bending deformation, as shown in the lower right of Figure 15. However, the amount of deformation is smaller than when an upward force is applied as described above. Therefore, the piezoelectric element 41 outputs a positive voltage signal, for example, one with a voltage value relatively small compared to the reference voltage, as shown in Figure 10. This makes it possible to determine that a pressing force is being applied to the piezoelectric sensor 1B. In the fourth embodiment described above, the same effects as in the first embodiment can be obtained.

[0124] 6. Piezoelectric sensor according to the fifth embodiment Next, a piezoelectric sensor according to the fifth embodiment will be described.

[0125] Figure 16 is a plan view of the piezoelectric sensor according to the fifth embodiment, as seen from a position on the X-axis.

[0126] The fifth embodiment will be described below, focusing on the differences from the third and fourth embodiments, and omitting explanations of similar aspects. Note that in each figure, components similar to those in the third and fourth embodiments are denoted by the same reference numerals.

[0127] The piezoelectric sensor 1C according to the fifth embodiment is the same as the piezoelectric sensor 1B according to the fourth embodiment, except that it includes a piezoelectric element 42 in addition to the piezoelectric element 41.

[0128] As shown in Figure 16, the piezoelectric element 42 is fixed so as to connect the first wall portions 31 and 32. Specifically, the piezoelectric element 42 is positioned facing the sixth surface 206 of the elastic body 2, and the Y-axis positive end of the piezoelectric element 42 is fixed to the first wall portion 31, while the Y-axis negative end of the piezoelectric element 42 is fixed to the first wall portion 32.

[0129] With this configuration, similar to the third embodiment, for example, by making the signs of the voltage signals output when bent in the same direction different for the piezoelectric elements 41 and 42, the voltage signals output from the piezoelectric elements 41 and 42 can be made such that one signal increases from a reference voltage and the other signal decreases from a reference voltage. As a result, the difference between the two becomes clear, and even if noise is introduced into the output signal, the direction of the force applied to the elastic body 2 can be easily determined. In the fifth embodiment described above, the same effects as those of the first to fourth embodiments can be obtained.

[0130] 7. Piezoelectric sensor according to the sixth embodiment Next, a piezoelectric sensor according to the sixth embodiment will be described.

[0131] Figure 17 is a plan view of the piezoelectric sensor according to the sixth embodiment, as seen from a position on the X-axis.

[0132] The sixth embodiment will now be described, focusing on the differences from the fourth embodiment, and similar aspects will be omitted. Note that in each figure, components identical to those in the fourth embodiment are denoted by the same reference numerals.

[0133] The piezoelectric sensor 1D according to the sixth embodiment is the same as the piezoelectric sensor 1B according to the fourth embodiment, except that the shape of the regulating portion 3 is different.

[0134] The regulating section 3 shown in Figure 17 comprises four columnar sections 351 to 354. The four columnar sections 351 to 354 are positioned at the four corners of the elastic body 2.

[0135] With this configuration, the volume of the regulating section 3 can be reduced to the minimum necessary. Therefore, the weight of the piezoelectric sensor 1D can be reduced.

[0136] The columnar portion 351 is positioned at the corners of the elastic body 2 that are on the positive Y-axis and positive Z-axis sides, the columnar portion 352 is positioned at the corners that are on the positive Y-axis and negative Z-axis sides, the columnar portion 353 is positioned at the corners of the elastic body 2 that are on the negative Y-axis and positive Z-axis sides, and the columnar portion 354 is positioned at the corners that are on the negative Y-axis and negative Z-axis sides.

[0137] As shown in Figure 17, the piezoelectric element 41 is fixed so as to connect the columnar portions 351 and 353. In the sixth embodiment described above, the same effects as in the fourth embodiment can be obtained.

[0138] 8. Piezoelectric sensor according to the seventh embodiment Next, a piezoelectric sensor according to the seventh embodiment will be described.

[0139] Figure 18 is a plan view of the piezoelectric sensor according to the seventh embodiment, as seen from a position on the X-axis.

[0140] The following description will focus on the differences between the seventh embodiment and the fifth and sixth embodiments, omitting explanations of similar aspects. Note that components identical to those in the fifth and sixth embodiments are denoted by the same reference numerals in each figure.

[0141] The piezoelectric sensor 1E according to the seventh embodiment is the same as the piezoelectric sensor 1D according to the sixth embodiment, except that it includes a piezoelectric element 43 in addition to the piezoelectric element 41. The piezoelectric element 43 is fixed so as to connect the columnar parts 353 and 354.

[0142] In other words, the piezoelectric sensor 1E comprises multiple piezoelectric elements 41 and 43. Since the piezoelectric elements 41 and 43 are mounted in different directions, they deform in different directions as the elastic body 2 deforms.

[0143] Specifically, the fifth embodiment described above also includes a plurality of piezoelectric elements 41 and 42, but these piezoelectric elements 41 and 42 deform in the same direction as the elastic body 2 deforms. For example, since the piezoelectric elements 41 and 42 have detection axes parallel to the Z-axis, when a downward force is applied to the elastic body 2, both the piezoelectric elements 41 and 42 undergo downward bending deformation.

[0144] In contrast, in the piezoelectric sensor 1E according to this embodiment, the piezoelectric element 41 is positioned facing the fifth surface 205 of the elastic body 2, while the piezoelectric element 43 is positioned facing the second surface 202 of the elastic body 2. That is, the piezoelectric element 41 has a detection axis parallel to the Z axis, while the piezoelectric element 43 has a detection axis parallel to the Y axis. Therefore, the piezoelectric sensor 1E can detect not only deformation in the Z axis direction of the elastic body 2, but also deformation in the Y axis direction. In the seventh embodiment described above, the same effects as those of the fifth and sixth embodiments can be obtained.

[0145] Figure 19 is a diagram illustrating the deformation modes of the elastic body 2 when forces are applied from various directions to the piezoelectric sensor 1E shown in Figure 18. Figure 20 is a diagram showing an example of the waveform of the voltage signal (output waveform) output from the piezoelectric elements 41 and 43 shown in Figure 18 when the elastic body 2 is deformed in the deformation modes shown in Figure 19. Note that in the example shown in Figure 20, the waveform of the potential relative to the reference voltage is shown.

[0146] When a downward force is applied to the piezoelectric sensor 1E, a downward pulling force is applied to the third surface 203 of the elastic body 2, as shown by the arrow in the upper right diagram of Figure 19. This causes a downward bending deformation in the piezoelectric element 41. At this time, the piezoelectric element 41 outputs a negative voltage signal relative to the reference voltage, as shown in Figure 20. This allows us to identify that a downward force is being applied to the piezoelectric sensor 1E. Based on this downward force, the static friction force and kinetic friction force between the object W and the elastic body 2 can be detected. On the other hand, the piezoelectric element 43 undergoes almost no deformation. Therefore, the piezoelectric element 43 outputs almost no voltage signal that increases or decreases from the reference voltage.

[0147] When an upward force is applied to the piezoelectric sensor 1E, an upward pulling force is applied to the third surface 203 of the elastic body 2, as shown by the arrow in the left middle diagram of Figure 19. This causes an upward bending deformation in the piezoelectric element 41. At this time, the piezoelectric element 41 outputs a positive voltage signal relative to the reference voltage, as shown in Figure 20. This allows us to identify that an upward force is being applied to the piezoelectric sensor 1E. Based on this state of upward force, the static friction force and kinetic friction force generated between the object W and the elastic body 2 can be detected. On the other hand, the piezoelectric element 43 undergoes almost no deformation. Therefore, the piezoelectric element 43 outputs almost no voltage signal that increases or decreases from the reference voltage.

[0148] When a pressing force is applied to the piezoelectric sensor 1E, that is, a force pushing the elastic body 2 shown in Figure 19 from the positive X-axis side to the negative X-axis side, deformation occurs on the third surface 203 of the elastic body 2, spreading out in all directions as shown by the arrows in the right middle diagram of Figure 19. As a result, a bending deformation occurs in the piezoelectric element 41 in the upward direction. At this time, the piezoelectric element 41 outputs a positive voltage signal with a voltage value that is relatively small compared to the reference voltage, as shown in Figure 20. Also, a bending deformation occurs in the leftward direction (negative Y-axis direction) to the piezoelectric element 43. At this time, the piezoelectric element 43 outputs a positive voltage signal with a voltage value that is relatively small compared to the reference voltage, as shown in Figure 20. These voltage waveforms allow us to determine that a pressing force is being applied to the piezoelectric sensor 1E.

[0149] When a force is applied to the piezoelectric sensor 1E in the leftward direction (negative Y-axis direction), a pulling force is applied to the third surface 203 of the elastic body 2 in the leftward direction, as shown by the arrow in the lower left diagram of Figure 19. This causes bending deformation to the leftward direction in the piezoelectric element 43. At this time, the piezoelectric element 43 outputs a positive voltage signal relative to the reference voltage, as shown in Figure 20. This allows us to identify that a force is being applied to the piezoelectric sensor 1E in the leftward direction. Based on this state of a force being applied in the leftward direction, the static friction force and kinetic friction force generated between the object W and the elastic body 2 can be detected. On the other hand, the piezoelectric element 41 undergoes almost no deformation. Therefore, the piezoelectric element 41 outputs almost no voltage signal that increases or decreases from the reference voltage.

[0150] When a force is applied to the piezoelectric sensor 1E in the rightward direction (positive Y-axis direction), a pulling force is applied to the third surface 203 of the elastic body 2 in the rightward direction, as shown by the arrow in the lower right diagram of Figure 19. This causes bending deformation to the rightward direction in the piezoelectric element 43. At this time, the piezoelectric element 43 outputs a negative voltage signal relative to the reference voltage, as shown in Figure 20. This allows us to identify that a force is being applied to the piezoelectric sensor 1E in the rightward direction. Based on this state of a force being applied in the rightward direction, the static friction force and kinetic friction force generated between the object W and the elastic body 2 can be detected. On the other hand, the piezoelectric element 41 undergoes almost no deformation. Therefore, the piezoelectric element 41 outputs almost no voltage signal that increases or decreases from the reference voltage.

[0151] The above describes examples of deformation modes, but the deformation directions are not limited to upward, downward, leftward, and rightward; other directions are also acceptable.

[0152] As described above, when the third surface 203 of the piezoelectric sensor 1E is viewed from above, the elastic body 2 has a fifth surface 205 and a second surface 202 as two adjacent surfaces corresponding to two adjacent edges. The piezoelectric elements 41 and 43 are positioned facing the fifth surface 205 and the second surface 202.

[0153] With this configuration, a piezoelectric sensor 1E capable of detecting the direction of force application can be realized even when forces are applied from more directions than in the fourth embodiment. Specifically, for example, forces applied not only upward and downward, but also to the left and right can be distinguished and detected. As a result, various movements of the hand 10 can be captured more precisely based on the output results of the piezoelectric sensor 1E. Consequently, the hand 10 can be operated more appropriately, and convenience can be further enhanced.

[0154] 9. Piezoelectric sensor according to the 8th embodiment Next, a piezoelectric sensor according to the eighth embodiment will be described.

[0155] Figure 21 is a plan view of the piezoelectric sensor according to the eighth embodiment, as seen from a position on the X-axis.

[0156] The following describes the eighth embodiment, focusing on the differences from the sixth and seventh embodiments, and omitting explanations of similar aspects. Note that in each figure, components similar to those in the sixth and seventh embodiments are denoted by the same reference numerals.

[0157] The piezoelectric sensor 1F according to the eighth embodiment is the same as the piezoelectric sensor 1E according to the seventh embodiment, except that it includes piezoelectric elements 42 and 44 in addition to piezoelectric elements 41 and 43.

[0158] The piezoelectric element 42 is fixed so as to connect the columnar parts 352 and 354. The piezoelectric element 44 is fixed so as to connect the columnar parts 351 and 352.

[0159] In other words, the piezoelectric sensor 1F comprises a plurality of piezoelectric elements 41 to 44. Specifically, when the elastic body 2 of the piezoelectric sensor 1F is viewed from above, the third surface 203 has four outer surfaces corresponding to the four edges that make up the outer edge: the first surface 201, the second surface 202, the fifth surface 205, and the sixth surface 206. As shown in Figure 21, piezoelectric element 41 is positioned facing the fifth surface 205, piezoelectric element 42 is positioned facing the sixth surface 206, piezoelectric element 43 is positioned facing the second surface 202, and piezoelectric element 44 is positioned facing the first surface 201.

[0160] With this configuration, since the four piezoelectric elements 41-44 are arranged to surround the elastic body 2, voltage signals will be output from at least two piezoelectric elements regardless of the direction of the force applied to the elastic body 2. Therefore, the piezoelectric sensor 1F according to this embodiment combines the effects of the fifth embodiment and the effects of the seventh embodiment. Specifically, for example, it can distinguish and detect forces applied in the upward, downward, leftward, and rightward directions, and the voltage signals output from the two piezoelectric elements can be configured such that one signal increases from a reference voltage and the other signal decreases from a reference voltage. Therefore, forces applied in various directions can be detected with greater accuracy.

[0161] Figure 22 shows an example of the waveform of the voltage signal (output waveform) output from the piezoelectric elements 41-44 shown in Figure 21 when the elastic body 2 is deformed in the deformation mode shown in Figure 19. Note that in the example shown in Figure 22, the waveform of the potential relative to the reference voltage is shown.

[0162] When a downward force is applied to the piezoelectric sensor 1F, the piezoelectric element 41 undergoes downward bending deformation, and as shown in Figure 22, for example, a negative voltage signal is output. Similarly, the piezoelectric element 42 also undergoes downward bending deformation, and as shown in Figure 22, for example, a positive voltage signal relative to the reference voltage is output.

[0163] When an upward force is applied to the piezoelectric sensor 1F, the piezoelectric element 41 undergoes upward bending deformation, and as shown in Figure 22, for example, a positive voltage signal is output. Similarly, the piezoelectric element 42 also undergoes upward bending deformation, and as shown in Figure 22, for example, a negative voltage signal relative to the reference voltage is output.

[0164] When a pressing force is applied to the piezoelectric sensor 1F, that is, a force pushing the elastic body 2 shown in Figure 21 from the positive X-axis side to the negative X-axis side, bending deformation occurs in the piezoelectric element 41 in the upward direction, in the piezoelectric element 42 in the downward direction, in the piezoelectric element 43 in the leftward direction, and in the piezoelectric element 44 in the rightward direction. As shown in Figure 22, each of these outputs a positive voltage signal with a voltage value that is relatively small with respect to, for example, a reference voltage.

[0165] When a force is applied to the piezoelectric sensor 1F in the leftward direction, the piezoelectric element 43 undergoes bending deformation in the leftward direction, and as shown in Figure 22, for example, a positive voltage signal is output. Similarly, the piezoelectric element 44 also undergoes bending deformation in the leftward direction, and as shown in Figure 22, for example, a negative voltage signal relative to the reference voltage is output.

[0166] When a force is applied to the piezoelectric sensor 1F in the rightward direction, the piezoelectric element 43 undergoes bending deformation in the rightward direction, and as shown in Figure 22, for example, a negative voltage signal is output. Similarly, the piezoelectric element 44 also undergoes bending deformation in the rightward direction, and as shown in Figure 22, for example, a positive voltage signal relative to the reference voltage is output. In the eighth embodiment described above, the same effects as those of the sixth and seventh embodiments can be obtained.

[0167] 10. Piezoelectric sensor according to the ninth embodiment Next, a piezoelectric sensor according to the ninth embodiment will be described.

[0168] Figure 23 is a plan view of the piezoelectric sensor according to the ninth embodiment, as seen from a position on the X-axis.

[0169] The ninth embodiment will now be described, focusing on the differences from the third embodiment, and similar aspects will be omitted. Note that components identical to those in the third embodiment are denoted by the same reference numerals in each figure.

[0170] The piezoelectric sensor 1G according to the ninth embodiment is the same as the piezoelectric sensor 1A according to the third embodiment, except that the regulating portion 3 is annular in shape.

[0171] Because the regulating portion 3 is annular, when the third surface 203 of the elastic body 2 is viewed from above, the elastic body 2 is circular, as shown in Figure 23. In other words, the third surface 203 of the elastic body 2 is circular. The circle includes perfect circles, ovals, ellipses, etc.

[0172] Because the plan view shape of the elastic body 2 is circular, the anisotropy of the shape of the elastic body 2 is reduced compared to when the plan view shape of the elastic body 2 is rectangular. As a result, it is possible to detect the direction and magnitude of the force while suppressing the variation in sensitivity due to the direction of the force applied to the piezoelectric sensor 1G.

[0173] Of the ring-shaped regulating portion 3, the portion on the positive Y-axis side is the first wall portion 31, and the portion on the negative Y-axis side is the first wall portion 32. Also, the portion on the positive Z-axis side is the second wall portion 33, and the portion on the negative Z-axis side is the second wall portion 34.

[0174] Furthermore, of the sides of the elastic body 2, that is, the surfaces other than the third surface 203 and the fourth surface 204, the part on the positive Y-axis side is the first surface 201, the part on the negative Y-axis side is the second surface 202, the part on the positive Z-axis side is the fifth surface 205, and the part on the negative Z-axis side is the sixth surface 206. The first wall portion 31 is positioned facing the first surface 201, the first wall portion 32 is positioned facing the second surface 202, the second wall portion 33 is positioned facing the fifth surface 205, and the second wall portion 34 is positioned facing the sixth surface 206.

[0175] In the second embodiment described above, a piezoelectric element 41 is provided between the elastic body 2 and the second wall portion 33, and a piezoelectric element 42 is provided between the elastic body 2 and the second wall portion 34. In contrast, in this embodiment, the piezoelectric element 41 is fixed to the side of the second wall portion 33 opposite to the elastic body 2, and the piezoelectric element 42 is provided to the side of the second wall portion 34 opposite to the elastic body 2. In the ninth embodiment described above, the same effects as in the second embodiment can be obtained.

[0176] 11. Piezoelectric sensor according to the 10th embodiment Next, a piezoelectric sensor according to the tenth embodiment will be described.

[0177] Figure 24 is a plan view of the piezoelectric sensor according to the 10th embodiment, as seen from a position on the X-axis.

[0178] The following describes the tenth embodiment, focusing on the differences from the seventh and ninth embodiments, and omitting explanations of similar matters. In each figure, components similar to those in the seventh and ninth embodiments are denoted by the same reference numerals.

[0179] The piezoelectric sensor 1H according to the 10th embodiment is the same as the piezoelectric sensor 1E according to the 7th embodiment, except that the regulating portion 3 is annular in shape.

[0180] As the regulating portion 3 is annular in shape, when the third surface 203 of the elastic body 2 is viewed from above, the elastic body 2 is circular, as shown in Figure 24.

[0181] Because the elastic body 2 has a circular shape in plan view, the anisotropy of the shape of the elastic body 2 is reduced compared to when the elastic body 2 has a rectangular shape in plan view. As a result, it is possible to detect the direction and magnitude of a force while suppressing variations in sensitivity due to the direction of the force applied to the piezoelectric sensor 1H.

[0182] The regulating section 3 shown in Figure 24 comprises four columnar sections 351 to 354. Columnar section 351 is located on the positive Y-axis and positive Z-axis side, relative to the center of the elastic body 2. Columnar section 352 is located on the positive Y-axis and negative Z-axis side. Columnar section 353 is located on the negative Y-axis and positive Z-axis side. Columnar section 354 is located on the negative Y-axis and negative Z-axis side. Columnar sections 351 and 352 are positioned facing the first surface 201, while columnar sections 353 and 354 are positioned facing the second surface 202. A piezoelectric element 41 is fixed connecting columnar sections 351 and 353, and a piezoelectric element 43 is fixed connecting columnar sections 353 and 354.

[0183] In the tenth embodiment described above, the same effects as those of the seventh and ninth embodiments can be obtained.

[0184] Although the piezoelectric sensor and hand of the present invention have been described above based on the illustrated embodiments, the piezoelectric sensor and hand of the present invention are not limited to the embodiments described above. For example, each part of the embodiments may be replaced with any configuration having a similar function, any configuration may be added to the embodiments, or a combination of multiple embodiments may be used. [Explanation of Symbols]

[0185] 1...Piezoelectric sensor, 1A...Piezoelectric sensor, 1B...Piezoelectric sensor, 1C...Piezoelectric sensor, 1D...Piezoelectric sensor, 1E...Piezoelectric sensor, 1F...Piezoelectric sensor, 1G...Piezoelectric sensor, 1H...Piezoelectric sensor, 1a...Piezoelectric sensor, 2...Elastic body, 3...Restricting part, 6...Holding part, 10...Hand, 11...Base, 12...Slider, 13...Slider, 14...Finger part, 15...Finger part, 16...Motor, 17...Motor, 21...Contact surface, 31...First wall part, 32...First wall part, 33...Second wall part, 34...Second wall part, 41...Piezoelectric element, 42...Piezoelectric element, 43...Piezoelectric element, 44...Pressure Electrical element, 49…Output circuit, 141…Gripping surface, 151…Gripping surface, 201…First surface, 202…Second surface, 203…Third surface, 204…Fourth surface, 205…Fifth surface, 206…Sixth surface, 207…Convex curved surface, 351…Columnar part, 352…Columnar part, 353…Columnar part, 354…Columnar part, 491…Amplifier, 492…Power supply, 493…Power supply, 494…Detection unit, 495…Measurement unit, 496…Calculation unit, 497…Decision unit, B…Area, C1…Change point, C2…Change point, C3…Change point, P…Peak, TM…Time, TL…Tolerance range, W…Object, d…Outer diameter, t1…Thickness, t2…Thickness, t3…Thickness

Claims

1. An elastic body and A piezoelectric element is positioned in contact with the elastic body and outputs a voltage signal when it deforms in accordance with the deformation of the elastic body. A detection unit for detecting the voltage signal output from the piezoelectric element, Equipped with, The elastic body is cylindrical in shape. The elastic body is provided on its outer surface and has a contact surface that comes into contact with the object, The elastic body is provided with a holding portion, The piezoelectric element is arranged on the outer surface away from the contact surface, A piezoelectric sensor characterized in that, after the elastic body comes into contact with the object, when the elastic body moves relative to the object, the detection unit detects the dynamic friction force generated between the object and the elastic body based on the change in the voltage signal due to the relative movement of the object.

2. A hand characterized by comprising the piezoelectric sensor described in Claim 1.

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