Force detection device and robot system

Abstract

To provide a force detection device and a robot system that have excellent detection accuracy.SOLUTION: A force detection device includes: a first force sensor and a second force sensor each including a force detection element having a force detection axis; a first inertial sensor disposed in the vicinity of the first force sensor and having an inertia detection axis along the force detection axis of the first force sensor; and a second inertial sensor disposed in the vicinity of the second force sensor and having an inertia detection axis along the force detection axis of the second force sensor.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a force detection device and a robot system. [Background technology]

[0002] The robot described in Patent Document 1 can detect external forces acting on an actuator attached to the tip of a robot arm. When the actuator has a fixed part fixed to the robot and a movable part movable relative to the fixed part, the robot has an acceleration detector that detects the acceleration of the fixed part, a position detector that detects the position of the movable part relative to the fixed part, a position control unit that outputs a current command value based on the difference between the position detected by the position detector and a reference position, an acceleration compensation unit that outputs an acceleration compensation value based on the result of multiplying the acceleration detected by the acceleration detector by the mass of the movable part, an adder-subtractor that adds the acceleration compensation value to the current command value, a constant current control unit that matches the current value of the drive current with the current command value, and an external force detection unit that detects external force based on the result of subtracting the acceleration compensation value from the current value of the drive current. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-072135 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the robot described in Patent Document 1 does not use a force sensor that physically detects the external force that the actuator receives, and therefore has the problem of low detection accuracy. [Means for solving the problem]

[0005] The force detection device of the present invention includes a first force sensor and a second force sensor each having a force detection element having a force detection axis; a first inertial sensor disposed near the first force sensor, the first inertial sensor having an inertial detection axis aligned with the force detection axis of the first force sensor; a second inertial sensor disposed near the second force sensor, the inertial detection axis of the second force sensor being aligned with the force detection axis of the second force sensor;

[0006] The robot system of the present invention comprises: a robot; a force detection device mounted on the robot; a robot control device that controls driving of the robot based on the detection result of the force detection device, The force detection device is a first force sensor and a second force sensor each having a force sensing element with a force sensing axis; a first inertial sensor disposed near the first force sensor, the inertial detection axis of the first force sensor being aligned with the force detection axis of the first force sensor; a second inertial sensor disposed near the second force sensor, the inertial detection axis of the second force sensor being aligned with the force detection axis of the second force sensor; [Brief explanation of the drawings]

[0007] [Figure 1] 1 is an overall configuration diagram of a robot system according to a preferred embodiment. [Figure 2] FIG. 2 is a perspective view showing a force detection device. [Figure 3] FIG. 2 is a longitudinal sectional view showing the force detection device. [Figure 4] FIG. 2 is a cross-sectional view showing the force detection device. [Figure 5] FIG. 2 is a longitudinal cross-sectional view showing a force sensor. [Figure 6] FIG. 2 is a longitudinal cross-sectional view showing a force detection element. [Figure 7] FIG. 2 is a schematic diagram showing the arrangement of a force sensor and an inertial sensor. [Figure 8] FIG. 2 is an exploded perspective view showing the inertial sensor. [Figure 9] FIG. 2 is a perspective view showing a substrate housed inside the inertial sensor. [Figure 10]FIG. 2 is a block diagram showing the circuit configuration of a force detection circuit. [Figure 11] FIG. 10 is a longitudinal sectional view showing a modified example of the force detection device. [Figure 12] FIG. 10 is a block diagram showing a modified example of the force detection device. [Figure 13] FIG. 10 is a block diagram showing a modified example of the force detection device. DETAILED DESCRIPTION OF THE INVENTION

[0008] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A force detection device and a robot system according to the present invention will be described in detail below with reference to the embodiments shown in the accompanying drawings.

[0009] FIG. 1 is an overall configuration diagram of a robot system according to a preferred embodiment. FIG. 2 is a perspective view showing a force detection device. FIG. 3 is a longitudinal sectional view showing the force detection device. FIG. 4 is a transverse sectional view showing the force detection device. FIG. 5 is a longitudinal sectional view showing a force sensor. FIG. 6 is a longitudinal sectional view showing a force detection element. FIG. 7 is a schematic diagram showing the arrangement of a force sensor and an inertial sensor. FIG. 8 is an exploded perspective view showing the inertial sensor. FIG. 9 is a perspective view showing a substrate housed inside the inertial sensor. FIG. 10 is a block diagram showing the circuit configuration of a force detection circuit.

[0010] <Robot System 1> 1 can perform tasks such as supplying, removing, transporting, and assembling objects such as precision instruments and components that constitute them. The robot system 1 includes a robot 2, which is a single-arm, six-axis vertical articulated robot, a robot control device 20 that controls the driving of the robot 2, and a force detection device 3 attached to the robot 2.

[0011] The robot 2 also has a base 21, a robot arm 22 rotatably connected to the base 21, and an end effector 23. The base 21 is fixed to, for example, the floor, a wall, a ceiling, or the top of a movable cart. The robot arm 22 is a robotic arm in which multiple arms 221, 222, 223, 224, 225, and 226 are rotatably connected, and has six joints J1 to J6. Of these, joints J2, J3, and J5 are bending joints, and joints J1, J4, and J6 are torsion joints. However, the robot arm 22 is not particularly limited and can be selected appropriately depending on the work content.

[0012] Each of the joints J1, J2, J3, J4, J5, and J6 is provided with a motor M and an encoder E. During operation of the robot system 1, the robot control device 20 executes feedback control to match the rotation angles of the joints J1 to J6 indicated by the output of each encoder E with the target rotation angles that are control targets. This allows each of the joints J1 to J6 to be maintained at the target rotation angle, and the robot arm 22 to be positioned and oriented as desired. As a result, the robot 2 can be driven to perform the desired operation.

[0013] The robot control device 20 controls the driving of the robot 2. The robot control device 20 is configured, for example, by a computer, and has a processor (CPU) that processes information, a memory communicatively connected to the processor, and an external interface that connects to external devices. Various programs that can be executed by the processor are stored in the memory, and the processor can read and execute the various programs stored in the memory. Some or all of the components of the robot control device 20 may be located inside the housing of the robot 2. The robot control device 20 may also be configured with multiple processors.

[0014] An end effector 23 is attached to the tip of the robot arm 22, i.e., the arm 226, via a mechanical interface. The end effector 23 is not particularly limited and can be selected appropriately depending on the work content. In the configuration shown, it has a pair of claws 231, 232, and is configured to grip a workpiece (not shown) by opening and closing these pair of claws 231, 232.

[0015] A force detection device 3 is interposed between the robot arm 22 and the end effector 23. In other words, the end effector 23 is attached to the tip of the robot arm 22 via the force detection device 3. The force detection device 3 detects the force applied to the end effector 23 attached to the force detection device 3. The force detection device 3 will be described in detail below.

[0016] <Force detection device 3> The force detection device 3 is a six-axis force sensor capable of detecting six-axis components of an external force applied to the force detection device 3. The six-axis components consist of translational force (shear force) components in the directions of three mutually orthogonal axes, the α-axis, the β-axis, and the γ-axis, and rotational force (moment) components around each of these three axes.

[0017] 2, the force detection device 3 has four force sensors 4 arranged at approximately 90° intervals around its central axis A1, four inertial sensors 6 arranged corresponding to the four force sensors 4, a force detection circuit 7 that detects external forces based on signals from each force sensor 4 and each inertial sensor 6, and a case 5 that houses these components. The force detection device 3 corrects the output signal from each force sensor 4 based on the output signal from the corresponding inertial sensor 6, and detects the external force applied to the force detection device 3 based on the four corrected signals.

[0018] Here, the force detection device 3 is intended to detect only the external force F1 applied when the end effector 23 contacts an object. However, during operation of the robot 2, the force detection device 3 receives not only the external force F1 but also an external force F2 resulting from inertia, i.e., angular velocity and acceleration, generated by the movement of the robot arm 22. The external forces F1 and F2 cannot be distinguished from each other based on the signal from the force sensor 4 alone, and only a resultant force F3 (= F1 + F2) can be detected. Therefore, the external force F1, which is the target of detection, cannot be detected accurately. Therefore, the force detection device 3 is provided with an inertial sensor 6 to detect the external force F2 applied to the force sensor 4. The external force F2 calculated based on the detection result of the inertial sensor 6 is subtracted from the resultant force F3 detected by the force sensor 4 to detect the external force F1. In this way, the force detection device 3 detects the external force F1 using the force physically detected by the force sensor 4 and the force physically detected by the inertial sensor 6, thereby enabling detection of the external force F1 with high accuracy.

[0019] 3, the case 5 has a first case member 51, a second case member 52 arranged at an interval from the first case member 51, and sidewall members 53 provided on the outer peripheries of the first case member 51 and the second case member 52. In the case 5 configured as above, the upper surface 510 of the first case member 51 functions as an end effector mounting surface for mounting the end effector 23, and the lower surface 520 of the second case member 52 functions as an arm mounting surface for mounting the robot arm 22. However, this is not limiting and the reverse may also be possible.

[0020] 3 and 4, the first case member 51 has a top plate 511 and four pressurizing portions 512 provided on the underside of the top plate 511 and arranged at equal intervals (90° intervals) around the central axis A1. A through hole 511a is formed in the center of the top plate 511 along the central axis A1. Each of the pressurizing portions 512 is formed with a plurality of through holes 512a through which pressurizing bolts 50 (described later) are inserted.

[0021] The second case member 52 also has a bottom plate 521 and four pressurizing portions 522 provided on the upper surface of the bottom plate 521 and arranged at equal intervals (90° intervals) around the central axis A1 so as to face the four pressurizing portions 512. The bottom plate 521 also has a through hole 521a formed in its center along the central axis A1. Each pressurizing portion 522 also has a plurality of female screw holes 522a formed therein into which the tip end of the pressurizing bolt 50 is threadedly fitted.

[0022] The side wall member 53 is cylindrical, and its upper and lower ends are fixed to the first case member 51 and the second case member 52, respectively, by, for example, screws, fitting, etc. The four force sensors 4, four inertia sensors 6, and a force detection circuit 7 are housed in the internal space S1 surrounded by the side wall member 53 and the above-mentioned top plate 511 and bottom plate 521.

[0023] As shown in FIG. 4 , the four force sensors 4 are arranged symmetrically with respect to a line segment CL that passes through the central axis A1 and is parallel to the β-axis in a plan view. Each force sensor 4 is located between a pair of pressurizing parts 512, 522 and is sandwiched between these pressurizing parts 512, 522. A pressurizing bolt 50 connects the pressurizing parts 512, 522 and fixes the first case member 51 and the second case member 52. By tightening the pressurizing bolt 50, the force sensor 4 located between the pressurizing parts 512, 522 is pressurized. A pair of pressurizing bolts 50 is provided for each force sensor 4, and the pair of pressurizing bolts 50 are located on both sides of the force sensor 4.

[0024] Next, the force sensor 4 will be described. Because the four force sensors 4 have the same configuration, one force sensor 4 will be described below as a representative, and the description of the other three will be omitted. For ease of explanation, three mutually orthogonal axes, the A-axis, the B-axis, and the C-axis, are set for the force sensor 4. Furthermore, the tip side of the arrow indicating each axis will be referred to as the "plus side," and the base side will be referred to as the "minus side." The direction along the A-axis will be referred to as the "A-axis direction," the direction along the B-axis will be referred to as the "B-axis direction," and the direction along the C-axis will be referred to as the "C-axis direction."

[0025] As shown in FIG. 5 , the force sensor 4 includes a package 41 and a force detection element 42 housed in the package 41. The force sensor 4 is sandwiched between pressure applying portions 512 and 522, and the force detection element 42 is pressurized in the direction indicated by arrow P by a pressure applying bolt 50. An external force applied to the force sensor 4, specifically, a shear force in the A-axis direction and a shear force in the B-axis direction, is transmitted to the force detection element 42 via the package 41, and a signal based on the received external force is output from the force detection element 42. By pressurizing the force detection element 42 in this way, the external force can be detected with high accuracy. The pressure applied to the force detection element 42 can be adjusted by appropriately adjusting the fastening force of the pressure applying bolt 50.

[0026] The package 41 also has a base 411 and a lid 412 joined to the base 411. An airtight storage space S is formed inside the package 41, and the force detection element 42 is stored in the storage space S. By storing the force detection element 42 in the package 41, the force detection element 42 can be protected from the outside world, i.e., dustproof and waterproof. The atmosphere in the storage space S is not particularly limited, but is preferably a vacuum state or a reduced pressure state close to that.

[0027] Force detection element 42 outputs an electric charge Qa corresponding to the A-axis component of an external force applied to force detection element 42, and an electric charge Qb corresponding to the B-axis component. Force detection element 42 also has a piezoelectric element 420 and a pair of intermediate substrates 423 and 424 that sandwich piezoelectric element 420 from the C-axis direction. Piezoelectric element 420 also has a first piezoelectric element 421 that outputs an electric charge Qa in response to a shear force in the A-axis direction, and a second piezoelectric element 422 that outputs an electric charge Qb in response to a shear force in the B-axis direction.

[0028] 6, the first piezoelectric element 421 has a configuration in which, from the negative C-axis direction, a ground electrode layer 421A, a piezoelectric layer 421B, an output electrode layer 421C, a piezoelectric layer 421D, a ground electrode layer 421E, a piezoelectric layer 421F, an output electrode layer 421G, a piezoelectric layer 421H, and a ground electrode layer 421I are laminated in this order. The second piezoelectric element 422 is laminated on the first piezoelectric element 421, and has a configuration in which, from the negative C-axis direction, a ground electrode layer 422A, a piezoelectric layer 422B, an output electrode layer 422C, a piezoelectric layer 422D, a ground electrode layer 422E, a piezoelectric layer 422F, an output electrode layer 422G, a piezoelectric layer 422H, and a ground electrode layer 422I are laminated in this order. In this embodiment, the ground electrode layers 421I and 422A are integrated.

[0029] Furthermore, piezoelectric layers 421B, 421D, 421F, 421H, 422B, 422D, 422F, and 422H are each composed of a Y-cut quartz crystal plate, i.e., a quartz crystal plate with the Y-axis (mechanical axis) of the quartz crystal aligned along its thickness direction. This results in force detection element 42 with excellent characteristics, such as high sensitivity, a wide dynamic range, and high rigidity. In piezoelectric layers 421B and 421F, the X-axis (electrical axis) of the quartz crystal is aligned along the positive side of the A-axis, while in piezoelectric layers 421D and 421H, the X-axis of the quartz crystal is aligned along the negative side of the A-axis. In piezoelectric layers 422B and 422F, the X-axis of the quartz crystal is aligned along the positive side of the B-axis, while in piezoelectric layers 422D and 422H, the X-axis of the quartz crystal is aligned along the negative side of the B-axis.

[0030] However, the piezoelectric layers 421B, 421D, 421F, 421H, 422B, 422D, 422F, and 422H may be made of a piezoelectric material other than quartz, such as topaz, barium titanate, lead titanate, lead zirconate titanate (PZT: Pb(Zr,Ti)O), lithium niobate, and lithium tantalate.

[0031] Furthermore, ground electrode layers 421A, 421E, 421I, 422A, 422E, and 422I are each electrically connected to ground potential GND. Furthermore, output electrode layers 421C and 421G output charge Qa corresponding to the component in the A-axis direction, and output electrode layers 422C and 422G output charge Qb corresponding to the component in the B-axis direction. Charges Qa and Qb are each sent to force detection circuit 7 via terminals 413 provided on base 411.

[0032] The pair of intermediate substrates 423, 424 are arranged to sandwich the piezoelectric element 420 from both sides in the C-axis direction. This allows the ground electrode layers 421A, 422I to be covered by the intermediate substrates 423, 424, thereby protecting them and preventing unintended electrical connection between them and the package 41. Furthermore, the pressure in the C-axis direction can be uniformly transmitted to the entire area of the piezoelectric element 420.

[0033] Intermediate substrates 423 and 424 are made of quartz crystal. This provides intermediate substrates 423 and 424 with high mechanical strength, allowing them to accurately transmit external forces to force detection element 42. Furthermore, intermediate substrate 423 has the same configuration as adjacent piezoelectric layer 422H. That is, intermediate substrate 423 is a Y-cut quartz crystal plate, with the X-axis of the quartz crystal facing the negative side of the B-axis direction. Similarly, intermediate substrate 424 has the same configuration as adjacent piezoelectric layer 421B. That is, intermediate substrate 424 is a Y-cut quartz crystal plate, with the X-axis of the quartz crystal facing the positive side of the A-axis direction. In this way, by aligning the crystal axes of intermediate substrates 423 and 424 with the crystal axes of adjacent piezoelectric layers 422H and 421B, their thermal expansion coefficients can be aligned, effectively reducing output drift caused by thermal expansion.

[0034] The force sensor 4 has been described above. Here, let us assume that the four force sensors 4 are force sensors 4A, 4B, 4C, and 4D. The orientations of these four force sensors 4A, 4B, 4C, and 4D are as shown in FIG. 7. Force sensor 4A has its A-axis pointing toward the positive side of the γ-axis, and its B-axis inclined at +45° with respect to the β-axis. Force sensor 4B has its A-axis pointing toward the negative side of the γ-axis, and its B-axis inclined at -45° with respect to the β-axis. Force sensor 4C has its A-axis pointing toward the positive side of the γ-axis, and its B-axis inclined at -135° with respect to the β-axis. Force sensor 4D has its A-axis pointing toward the negative side of the γ-axis, and its B-axis inclined at +135° with respect to the β-axis.

[0035] In this arrangement, the B-axis, which is the force detection axis of the force sensors 4A and 4C, and the B-axis, which is the force detection axis of the force sensors 4B and 4D, intersect with each other in a plan view from the γ-axis. In this manner, the force detection axes of the multiple force sensors 4 are not identical to each other but intersect with each other, making it possible to detect six-axis components of an external force. In particular, in this embodiment, the B-axis of the force sensors 4A and 4C and the B-axis of the force sensors 4B and 4D are perpendicular to each other, making it possible to detect six-axis components of an external force with greater accuracy. In this embodiment, the force sensors 4A and 4C are "first force sensors," and the force sensors 4B and 4D are "second force sensors."

[0036] Next, the inertial sensors 6 will be described. However, since the four inertial sensors 6 have the same configuration, the following description will focus on one inertial sensor 6. For ease of explanation, the inertial detection axes of the inertial sensor 6 will be defined as three mutually perpendicular axes, the a-axis, the b-axis, and the c-axis. Furthermore, the tip end of the arrow indicating each axis will be referred to as the "plus side," and the base end will be referred to as the "minus side." The direction along the a-axis will be referred to as the "a-axis direction," the direction along the b-axis will be referred to as the "b-axis direction," and the direction along the c-axis will be referred to as the "c-axis direction."

[0037] The inertial sensor 6, also known as an inertial measurement unit (IMU), is a six-axis sensor that can independently detect angular velocity around the a-axis, b-axis, and c-axis, and acceleration in each axial direction. As shown in Fig. 8, the inertial sensor 6 has an outer case 61, a sensor module 62 inserted into the outer case 61, and a joining member 63 that joins them together. The outer shape of the outer case 61 is a rectangular parallelepiped with a substantially square planar shape, and screw holes 611 for mounting are formed near each of two vertices located diagonally across the square.

[0038] The sensor module 62 has an inner case 621 and a substrate 622. The inner case 621 is a member that supports the substrate 622, and is shaped to fit inside the outer case 61. The inner case 621 is also formed with an opening 621a for exposing a connector 64, which will be described later. The inner case 621 is joined to the outer case 61 via a joining member 63.

[0039] 9, connector 64, angular velocity sensor 65c that detects angular velocity around the c-axis, and acceleration sensor 66 that detects acceleration in the directions of the a-axis, b-axis, and c-axis are mounted on the top surface of substrate 622. In addition, angular velocity sensor 65a that detects angular velocity around the a-axis and angular velocity sensor 65b that detects angular velocity around the b-axis are mounted on the side surface of substrate 622.

[0040] A control IC 67 is mounted on the underside of the substrate 622. The control IC 67 is an MCU (Micro Controller Unit) that controls each part of the inertial sensor 6. The control IC 67 has a processor (CPU) that processes information, a memory communicatively connected to the processor, and an external interface. The memory also stores programs executable by the processor, and the processor reads and executes the programs stored in the memory. The control IC 67 independently detects angular velocities around the a-axis, b-axis, and c-axis and accelerations along each axis based on output signals from the angular velocity sensors 65a, 65b, and 65c and the acceleration sensor 66.

[0041] The above has described the inertial sensor 6. Here, when the four inertial sensors 6 are inertial sensors 6A, 6B, 6C, and 6D, the arrangement of these four inertial sensors 6A, 6B, 6C, and 6D is as shown in FIG.

[0042] Inertial sensor 6A is paired with force sensor 4A, is fixed to the same pressurized portion 522 as force sensor 4A, and is located near force sensor 4A. Inertial sensor 6B is paired with force sensor 4B, is fixed to the same pressurized portion 522 as force sensor 4B, and is located near force sensor 4B. Inertial sensor 6C is paired with force sensor 4C, is fixed to the same pressurized portion 522 as force sensor 4C, and is located near force sensor 4C. Inertial sensor 6D corresponds to force sensor 4D, is fixed to the same pressurized portion 522 as force sensor 4D, and is located near force sensor 4D. By arranging paired sensors closely in this manner, the acceleration and angular velocity applied to the detection axis of force sensor 4 can be accurately detected by the paired inertial sensors 6. In this embodiment, the inertial sensors 6A and 6C paired with the force sensors 4A and 4C are "first inertial sensors," and the inertial sensors 6B and 6D paired with the force sensors 4B and 4D are "second force sensors."

[0043] Here, placing the inertial sensor 6A near the force sensor 4A means that the separation distance DA between the inertial sensor 6A and the force sensor 4A is smaller than the separation distance DB between the unpaired inertial sensor 6A and the force sensor 4B, the separation distance DC between the inertial sensor 6A and the force sensor 4C, and the separation distance DD between the inertial sensor 6A and the force sensor 4D, as shown in Figure 7. The same applies to the inertial sensors 6B, 6C, and 6D. This allows each inertial sensor 6A to accurately detect the acceleration and angular velocity applied to its paired force sensor 4.

[0044] The orientations of inertial sensors 6A, 6B, 6C, and 6D are as shown in Figure 7. The a-axis and b-axis of inertial sensor 6A are aligned with the A-axis and B-axis of its paired force sensor 4A, respectively. The a-axis and b-axis of inertial sensor 6B are aligned with the A-axis and B-axis of its paired force sensor 4B, respectively. The a-axis and b-axis of inertial sensor 6C are aligned with the A-axis and B-axis of its paired force sensor 4C, respectively. The a-axis and b-axis of inertial sensor 6D are aligned with the A-axis and B-axis of its paired force sensor 4D, respectively.

[0045] In this way, by aligning the inertial detection axis and the force detection axis of the paired inertial sensor 6 and force sensor 4, each inertial sensor 6 can accurately detect the acceleration component and the angular velocity component contained in the signal (charges Qa, Qb) output from the paired force sensor 4. Note that the phrase "the a-axis is aligned with the A-axis" does not only mean that the a-axis and the A-axis are parallel or collinear, but also means that they have, for example, technically acceptable errors, errors that may occur during manufacturing, etc. The same applies to the phrase "the b-axis is aligned with the B-axis," which does not only mean that the b-axis and the B-axis are parallel or collinear, but also means that they have, for example, technically acceptable errors, errors that may occur during manufacturing, etc.

[0046] Here, a six-axis sensor capable of independently detecting angular velocities around the a-axis, b-axis, and c-axis and acceleration in each axial direction is used as the inertial sensor 6, but the force detection device 3 does not use acceleration in the c-axis direction or angular velocity around the c-axis. Therefore, the elements detecting acceleration in the c-axis direction and angular velocity around the c-axis may be omitted from the inertial sensor 6. In other words, it is sufficient for the inertial sensor 6 to be able to detect angular velocities around the a-axis and b-axis, and acceleration in the a-axis and b-axis directions.

[0047] Next, we will explain the force detection circuit 7. The force detection circuit 7 detects an external force F1 received by the end effector 23 based on signals from each force sensor 4 and each inertial sensor 6. As shown in Figure 10, the force detection circuit 7 has a first processing unit 71 that calculates a force based on signals from the force sensors 4, a second processing unit 72 that removes an inertial component from the force calculated by the first processing unit 71, and a third processing unit 73 that calculates the external force F1 based on the force calculated by the second processing unit 72.

[0048] The first processing unit 71 calculates the force applied to force sensor 4A (shear force FAa in the A-axis direction and shear force FAb in the B-axis direction) based on the charges Qa and Qb from force sensor 4A, calculates the force applied to force sensor 4B (shear force FBa in the A-axis direction and shear force FBb in the B-axis direction) based on the charges Qa and Qb from force sensor 4B, calculates the force applied to force sensor 4C (shear force FCa in the A-axis direction and shear force FCb in the B-axis direction) based on the charges Qa and Qb from force sensor 4C, and calculates the force applied to force sensor 4D (shear force FDa in the A-axis direction and shear force FDb in the B-axis direction) based on the charges Qa and Qb from force sensor 4D.

[0049] As described above, the detected shear forces FAa to FDa in the A-axis direction calculated by the first processing unit 71 include an acceleration component in the A-axis direction and an angular velocity component about the A-axis that are applied to the end effector 23 due to the driving of the robot arm 22, and the shear forces FAb to FDb in the B-axis direction include an acceleration component in the B-axis direction and an angular velocity component about the B-axis that are applied to the end effector 23 due to the driving of the robot arm 22. Therefore, the second processing unit 72 removes the acceleration component in the A-axis direction and the angular velocity component about the A-axis from the shear forces FAa to FDa in the A-axis direction calculated by the first processing unit 71, and removes the acceleration component in the B-axis direction and the angular velocity component about the B-axis from the shear forces FAb to FDb in the B-axis direction.

[0050] The second processing unit 72 calculates the shear force FAAa received by the force sensor 4A due to acceleration in the A-axis direction based on the acceleration AAa in the a-axis direction detected by the inertial sensor 6A, calculates the shear force FAAb received by the force sensor 4A due to acceleration in the B-axis direction based on the acceleration AAb in the b-axis direction detected by the inertial sensor 6A, calculates the shear force FωAa received by the force sensor 4A due to angular velocity around the A-axis based on the angular velocity ωAa about the a-axis detected by the inertial sensor 6A, and calculates the shear force FωAb received by the force sensor 4A due to angular velocity around the B-axis based on the angular velocity ωAb about the b-axis detected by the inertial sensor 6A.

[0051] Here, as described above, since the inertial sensor 6A is disposed near its paired force sensor 4A, the inertia received by the inertia sensor 6A can be made substantially equal to the inertia received by the force sensor 4A, and therefore the shear forces FAAa, FAAb, FωAa, and FωAb can be detected with high accuracy.

[0052] The shear forces FAAa and FAAb can be calculated, for example, by multiplying the accelerations AAa and AAb by a coefficient calculated from the mass and other factors of the end effector 23. Furthermore, the shear forces FωAa and FωAb can be calculated, for example, by multiplying the angular velocities ωAa and ωAb by a coefficient calculated from the mass and other factors of the end effector 23. However, there are no particular limitations on the method of calculating the shear forces FAAa, FAAb, FωAa, and FωAb.

[0053] Similarly, the second processing unit 72 determines the shear forces FABa, FABb, FACa, FACb, FADA, and FADb received by the force sensors 4B, 4C, and 4D due to the accelerations in the A-axis and B-axis directions based on the accelerations ABa, ABb, ACa, ACb, ADa, and ADb in the a-axis and b-axis directions detected by the inertial sensors 6B, 6C, and 6D, and determines the shear forces FωBa, FωBb, FωCa, FωCb, FωDa, and FωDb received by the force sensors 4B, 4C, and 4D due to the angular velocities around the A-axis and the B-axis based on the angular velocities ωBa, ωBb, ωCa, ωCb, ωDa, and ωDb around the a-axis and the b-axis detected by the inertial sensors 6B, 6C, and 6D.

[0054] Next, the second processing unit 72 calculates a corrected shear force FAa0 by subtracting the shear forces FAAa and FωAa from the shear force FAa, and calculates a corrected shear force FAb0 by subtracting the shear forces FAAb and FωAb from the shear force FAb. That is, FAa0 = FAa - (FAAa + FωAa) and FAb0 = FAb - (FAAb + FωAb). This allows the corrected shear forces FAa0 and FAb0 to be obtained by removing the angular velocity received by the force sensor 4A and the force components resulting from the angular velocity from the shear forces FAa and FAb.

[0055] Similarly, the second processing unit 72 calculates a corrected shear force FBa0 by subtracting the shear forces FABa and FωBa from the shear force FBa, and calculates a corrected shear force FBb0 by subtracting the shear forces FABb and FωBb from the shear force FBb. It also calculates a corrected shear force FCa0 by subtracting the shear forces FACa and FωCa from the shear force FCa, and calculates a corrected shear force FCb0 by subtracting the shear forces FACb and FωCb from the shear force FCb. It also calculates a corrected shear force FDa0 by subtracting the shear forces FADA and FωDa from the shear force FDa, and calculates a corrected shear force FDb0 by subtracting the shear forces FADb and FωDb from the shear force FDb.

[0056] The third processing unit 73 calculates the external force F1 (translational force component Fα in the α-axis direction, translational force component Fβ in the β-axis direction, translational force component Fγ in the γ-axis direction, rotational force component Mα about the α-axis, rotational force component Mβ about the β-axis, and rotational force component Mγ about the γ-axis) applied to the end effector 23 based on the eight corrected shear forces FAa0, FAb0, FBa0, FBb0, FCa0, FCb0, FDa0, and FDb0 calculated by the second processing unit 72. The external force F1 calculated in this manner is transmitted to the robot control device 20. The robot control device 20 then controls the driving of the robot 2 based on the external force F1. This enables the robot 2 to be controlled with greater precision.

[0057] The robot system 1 and the force detection device 3 have been described above. As described above, the force detection device 3 includes a force sensor 4A as a first force sensor and a force sensor 4B as a second force sensor, each of which includes a force detection element 42 having a force detection axis; an inertial sensor 6A as a first inertial sensor disposed near the force sensor 4A and having an inertial detection axis aligned with the force detection axis of the force sensor 4A; and an inertial sensor 6B as a second inertial sensor disposed near the force sensor 4B and having an inertial detection axis aligned with the force detection axis of the force sensor 4B. This configuration allows an external force to be detected based on the force physically detected by the force sensors 4A and 4B and the inertia physically detected by the inertial sensors 6A and 6B. This allows for detection of an external force with high accuracy.

[0058] Furthermore, as described above, the separation distance DA between inertial sensor 6A and force sensor 4A is smaller than the separation distance DB between inertial sensor 6A and force sensor 4B, and the separation distance between inertial sensor 6B and force sensor 4B is smaller than the separation distance between inertial sensor 6B and force sensor 4A. This allows inertial sensor 6A and force sensor 4A to be positioned closer to each other, further improving the accuracy of external force detection.

[0059] As described above, the inertial sensors 6A and 6B are sensors that detect acceleration along the a-axis and b-axis as inertial detection axes, sensors that detect angular velocity around the a-axis and b-axis, or sensors that detect both acceleration along the a-axis and b-axis and angular velocity around the a-axis and b-axis, respectively. This allows for accurate detection of forces due to inertia acting on the force sensors 4A and 4B. In particular, the inertial sensors 6A and 6B of this embodiment are sensors that detect both acceleration along the a-axis and b-axis and angular velocity around the a-axis and b-axis. This makes the above-mentioned effects more pronounced.

[0060] As described above, the force detection axes of force sensor 4A and force sensor 4B intersect with each other. In this embodiment, the B axes of force sensor 4A and force sensor 4B intersect with each other. This allows the force detection device 3 to detect force components in more directions, improving the force detection accuracy of the force detection device 3.

[0061] As described above, force detection element 42 has piezoelectric layers 421B, 421D, 421F, 421H, 422B, 422D, 422F, and 422H, which are quartz crystal plates, resulting in force detection element 42 with excellent characteristics such as high sensitivity, a wide dynamic range, and high rigidity.

[0062] As described above, the force detection device 3 has a force detection circuit 7 that calculates corrected shear forces FAa0, FAb0, which are first forces obtained by removing the inertial components from the shear forces FAa, FAb received by the force sensor 4A based on the detection results of the inertial sensor 6A, calculates corrected shear forces FBa0, FBb0, which are second forces obtained by removing the inertial components from the shear forces FBa, FBb received by the force sensor 4B based on the detection results of the inertial sensor 6B, and calculates the received external force F1 based on the corrected shear forces FAa0, FAb0 and the corrected shear forces FBa0, FBb0. This enables the external force to be detected with high accuracy.

[0063] As described above, the robot system 1 includes the robot 2, the force detection device 3 mounted on the robot 2, and the robot control device 20 that controls the operation of the robot 2 based on the detection results of the force detection device 3. The force detection device 3 includes a force sensor 4A (first force sensor) and a force sensor 4B (second force sensor) each equipped with a force detection element 42 having a force detection axis, an inertial sensor 6A (first inertial sensor) arranged near the force sensor 4A and having an inertial detection axis aligned with the force detection axis of the force sensor 4A, and an inertial sensor 6B (second inertial sensor) arranged near the force sensor 4B and having an inertial detection axis aligned with the force detection axis of the force sensor 4B. This configuration allows an external force to be detected based on the force physically detected by the force sensors 4A and 4B and the inertia physically detected by the inertial sensors 6A and 6B. This allows for highly accurate detection of external forces.

[0064] The force detection device and robot system of the present invention have been described above based on the illustrated embodiments, but the present invention is not limited to this, and the configuration of each part can be replaced with any configuration having a similar function. Furthermore, any other components may be added to the present invention. Furthermore, the force detection device of the present invention can be incorporated into equipment other than a robot system, and may be mounted on a moving object such as an automobile.

[0065] For example, in the embodiment described above, the inertial sensor 6 is disposed on the side surface of the pressurized part 522 opposite the force sensor 4A, but this is not limiting as long as it can be disposed near the paired force sensor 4. For example, as shown in Fig. 11, the inertial sensor 6 may be disposed on the upper surface of the pressurized part 522, or on the bottom plate 521 of the second case member 52, or may be disposed on the side surface of the pressurized part 512 opposite the force sensor 4.

[0066] For example, in the above-described embodiment, the inertial sensor 6 detects both acceleration and angular velocity, but this is not limited thereto and may detect either acceleration or angular velocity alone. That is, the configuration shown in FIG. 12 or FIG. 13 may be used. In the case of FIG. 12, the calculations are made as FAa0 = FAa - FAAa and FAb0 = FAb - FAAb, and in the case of FIG. 13, the calculations are made as FAa0 = FAa - FωAa and FAb0 = FAb - FωAb. The same applies to FBa0, FBb0, FCa0, FCb0, FDa0, and FDb0. Even with such a configuration, it is possible to achieve the same effects as the above-described embodiment. [Explanation of symbols]

[0067] 1...robot system, 2...robot, 20...robot control device, 21...base, 22...robot arm, 221...arm, 222...arm, 223...arm, 224...arm, 225...arm, 226...arm, 23...end effector, 231...claw portion, 232...claw portion, 3...force detection device, 4...force sensor, 4A...force sensor, 4B...force sensor, 4C...force sensor, 4D...force sensor, 41...package, 411...base, 412...lid, 413...terminal, 42...force detection element, 420...piezoelectric element, 421...first piezoelectric element, 421A...ground electrode layer, 42 1B...piezoelectric layer, 421C...output electrode layer, 421D...piezoelectric layer, 421E...ground electrode layer, 421F...piezoelectric layer, 421G...output electrode layer, 421H...piezoelectric layer, 421I...ground electrode layer, 422...second piezoelectric element, 422A...ground electrode layer, 422B...piezoelectric layer, 422C...output electrode layer, 422D...piezoelectric layer, 422E...ground electrode layer, 422F...piezoelectric layer, 422G...output electrode layer, 422H...piezoelectric layer, 422I...ground electrode layer, 423...intermediate substrate, 424...intermediate substrate, 5...case, 50...pressurizing bolt, 51...first case member, 510...top surface, 511...top plate, 511a...through hole, 512...pressurized portion, 512a...through hole, 52...second case member, 520...underside, 521...bottom plate, 521a...through hole, 522...pressurized portion, 522a...female screw hole, 53...side wall member, 6...inertial sensor, 6A...inertial sensor, 6B...inertial sensor, 6C...inertial sensor, 6D...inertial sensor, 61...outer case, 611...screw hole, 62...sensor module, 621...inner case, 621a...opening, 622...board, 63...joint member, 64...connector, 65a...angular velocity sensor, 65b...angular velocity sensor, 65c...angular velocity Sensor, 66...acceleration sensor, 67...control IC, 7...force detection circuit, 71...first processing unit, 72...second processing unit, 73...third processing unit, A1...central axis, AAa...acceleration, AAb...acceleration, ABa...acceleration, ABb...acceleration, ACa...acceleration, ACb...acceleration, ADa...acceleration, ADb...acceleration, CL...line segment, DA...separation distance, DB...separation distance, DC...separation distance, DD...separation distance, E...encoder, F1...external force, F2...external force, F3...resultant force, FAa...shear force, FAb...shear force, FBa...shear force, FBb...shear force, FCa...shear force, FCb...shear force,FDa...shear force, FDb...shear force, FAAa...shear force, FAAb...shear force, FABa...shear force, FABb...shear force, FACa...shear force, FACb...shear force, FADa...shear force, FADb...shear force, FAa0...corrected shear force, FAb0...corrected shear force, FBa0...corrected shear force, FBb0...corrected shear force, FCa0...corrected shear force, FCb0...corrected shear force, FDa0...corrected shear force, FDb0...corrected shear force, Fα...translational force component, Fβ...translational force component, Fγ...translational force component, FωAa...shear force, FωAb...shear force Force, FωBa...shear force, FωBb...shear force, FωCa...shear force, FωCb...shear force, FωDa...shear force, FωDb...shear force, GND...ground potential, J1...joint, J2...joint, J3...joint, J4...joint, J5...joint, J6...joint, M...motor, Mα...rotational force component, Mβ...rotational force component, Mγ...rotational force component, P...arrow, Qa...charge, Qb...charge, S...storage space, S1...internal space, ωAa...angular velocity, ωAb...angular velocity, ωBa...angular velocity, ωBb...angular velocity, ωCa...angular velocity, ωCb...angular velocity, ωDa...angular velocity, ωDb...angular velocity,

Claims

1. a first force sensor and a second force sensor each having a force sensing element with a force sensing axis; a first inertial sensor disposed near the first force sensor, the first inertial sensor having an inertial detection axis aligned with the force detection axis of the first force sensor; a second inertial sensor disposed near the second force sensor, the second inertial sensor having an inertial detection axis aligned with the force detection axis of the second force sensor; A force detection device characterized in that the force detection element has a quartz plate.

2. a first force sensor and a second force sensor each having a force sensing element with a force sensing axis; a first inertial sensor disposed near the first force sensor, the first inertial sensor having an inertial detection axis aligned with the force detection axis of the first force sensor; a second inertial sensor disposed near the second force sensor, the second inertial sensor having an inertial detection axis aligned with the force detection axis of the second force sensor; a force detection circuit that calculates a first force by removing an inertial component from the force received by the first force sensor based on the detection result of the first inertial sensor, calculates a second force by removing an inertial component from the force received by the second force sensor based on the detection result of the second inertial sensor, and calculates an external force received based on the first force and the second force.

3. a separation distance between the first inertial sensor and the first force sensor is smaller than a separation distance between the first inertial sensor and the second force sensor; 3. The force detection device according to claim 1, wherein a distance between the second inertial sensor and the second force sensor is smaller than a distance between the second inertial sensor and the first force sensor.

4. 4. The force detection device according to claim 1, wherein the first inertial sensor and the second inertial sensor are sensors that detect acceleration in a direction along the inertial detection axis, sensors that detect angular velocity around the inertial detection axis, or sensors that detect both the acceleration and the angular velocity, respectively.

5. The force detection device according to claim 1 , wherein the force detection axes of the first force sensor and the second force sensor intersect with each other.

6. Robots and a force detection device mounted on the robot; a robot control device that controls driving of the robot based on the detection result of the force detection device, The force detection device is a first force sensor and a second force sensor each having a force sensing element with a force sensing axis; a first inertial sensor disposed near the first force sensor, the first inertial sensor having an inertial detection axis aligned with the force detection axis of the first force sensor; a second inertial sensor disposed near the second force sensor, the second inertial sensor having an inertial detection axis aligned with the force detection axis of the second force sensor; A robot system characterized in that the force detection element has a quartz plate.

7. Robots and a force detection device mounted on the robot; a robot control device that controls driving of the robot based on the detection result of the force detection device, The force detection device is a first force sensor and a second force sensor each having a force sensing element with a force sensing axis; a first inertial sensor disposed near the first force sensor, the first inertial sensor having an inertial detection axis aligned with the force detection axis of the first force sensor; a second inertial sensor disposed near the second force sensor, the second inertial sensor having an inertial detection axis aligned with the force detection axis of the second force sensor; a force detection circuit that calculates a first force by removing an inertial component from the force received by the first force sensor based on the detection result of the first inertial sensor, calculates a second force by removing an inertial component from the force received by the second force sensor based on the detection result of the second inertial sensor, and calculates an external force received based on the first force and the second force.

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