Force detection device and robotic system

Abstract

The present application provides a force detection device and a robot system with excellent detection accuracy. The force detection device has a first force sensor and a second force sensor, a first inertia sensor, and a second inertia sensor, the first force sensor and the second force sensor are provided with a force detection element with a force detection axis, the first inertia sensor is arranged near the first force sensor, the inertia detection axis of the first inertia sensor is along the force detection axis of the first force sensor, the second inertia sensor is arranged near the second force sensor, and the inertia detection axis of the second inertia sensor is along the force detection axis of the second force sensor.

Description

Technical Field

[0001] This invention relates to force detection devices and robot systems. Background Technology

[0002] The robot described in Patent Document 1 is capable of detecting external forces applied to an actuator mounted on the front end of a robotic arm. In the case where the actuator has a fixed part fixed to the robot and a movable part movable relative to the fixed part, the robot detects the acceleration of the fixed part using an accelerometer, detects the position of the movable part relative to the fixed part using a position detector, outputs a current command value based on the difference between the position detected by the position detector and a reference position using a position control unit, outputs an acceleration compensation value based on the product of the acceleration detected by the accelerometer and the mass on the movable part side using an acceleration compensation unit, adds the acceleration compensation value to the current command value using an adder / subtractor, makes the current value of the drive current match the current command value using a constant current control unit, and detects the external force using an external force detection unit based on the result obtained by subtracting the acceleration compensation value from the current value of the drive current.

[0003] Patent Document 1: Japanese Patent Publication No. 2018-072135

[0004] However, in the robot described in Patent Document 1, there is a problem of low detection accuracy because a force sensor that physically detects the external force on the actuator is not used. Summary of the Invention

[0005] The force detection device of the present invention includes: a first force sensor and a second force sensor, the first force sensor and the second force sensor having a force detection element having a force detection axis; a first inertial sensor disposed near the first force sensor, the inertial detection axis of the first inertial sensor being along the force detection axis of the first force sensor; and a second inertial sensor disposed near the second force sensor, the inertial detection axis of the second inertial sensor being along 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; and a robot control device that controls the drive of the robot based on the detection result of the force detection device. The force detection device comprises: a first force sensor and a second force sensor, the first force sensor and the second force sensor having a force detection element having a force detection axis; a first inertial sensor disposed near the first force sensor, the inertial detection axis of the first inertial sensor being along the force detection axis of the first force sensor; and a second inertial sensor disposed near the second force sensor, the inertial detection axis of the second inertial sensor being along the force detection axis of the second force sensor. Attached Figure Description

[0007] Figure 1 This is an overall configuration diagram of the robot system according to the preferred embodiment.

[0008] Figure 2 A perspective view of the force detection device.

[0009] Figure 3 This is a longitudinal sectional view of the force detection device.

[0010] Figure 4 This is a cross-sectional view showing the force detection device.

[0011] Figure 5 This is a longitudinal sectional view of the force sensor.

[0012] Figure 6 This is a longitudinal sectional view showing the force detection element.

[0013] Figure 7 This is a schematic diagram illustrating the configuration of the force sensor and the inertial sensor.

[0014] Figure 8 An exploded stereoscopic view of the inertial sensor is shown.

[0015] Figure 9 This is a perspective view of the substrate housed inside the inertial sensor.

[0016] Figure 10 This is a block diagram illustrating the circuit configuration of a force detection circuit.

[0017] Figure 11 A longitudinal sectional view showing a modified example of the force detection device.

[0018] Figure 12 A block diagram illustrating a modified example of the force detection device.

[0019] Figure 13 A block diagram illustrating a modified example of the force detection device.

[0020] Explanation of reference numerals in the attached figures

[0021] 1: Robot system; 2: Robot; 20: Robot control device; 21: Base; 22: Robotic arm; 221: Arm; 222: Arm; 223: Arm; 224: Arm; 225: Arm; 226: Arm; 23: End effector; 231: Claw; 232: Claw; 3: Force detection device; 4: Force sensor; 4A: Force sensor; 4B: Force sensor; 4C: Force sensor; 4D: Force sensor; 41: Package; 411: Substrate; 412: Cover; 413: Terminal; 42: Force detection element; 420: Piezoelectric element; 421: First piezoelectric element; 421A: Ground electrode layer; 421B: Piezoelectric layer; 421C: Output electrode layer; 421D: Piezoelectric layer; 421E: Terminal 421F: Ground electrode 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: Housing; 50: Pressurizing bolt; 51: First housing component; 510: Upper surface; 511: Top plate; 511a: Through hole; 512: Pressurizing part; 512a: Through hole; 52: Second housing component; 520: 521: Bottom plate; 521a: Through hole; 522: Pressurizing part; 522a: Internal threaded hole; 53: Side wall component; 6: Inertial sensor; 6A: Inertial sensor; 6B: Inertial sensor; 6C: Inertial sensor; 6D: Inertial sensor; 61: Outer shell; 611: Threaded hole; 62: Sensor module; 621: Inner shell; 621a: Opening; 622: Base plate; 63: Joining component; 64: Connector; 65a: Angular velocity sensor; 65b: Angular velocity sensor; 65c: Angular velocity sensor; 66: Accelerometer; 67: Control IC; 7: Force detection circuit; 71: First processing unit; 72: Second processing unit; 73: Third processing unit; A1: Central shaft; 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; 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; 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;

[0022] 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. Detailed Implementation

[0023] The force detection device and robot system of the present invention will be described in detail below based on the embodiments shown in the accompanying drawings.

[0024] Figure 1 This is an overall configuration diagram of the robot system according to a preferred embodiment. Figure 2 A perspective view of the force detection device. Figure 3 This is a longitudinal sectional view of the force detection device. Figure 4 This is a cross-sectional view showing the force detection device. Figure 5 This is a longitudinal sectional view of the force sensor. Figure 6 This is a longitudinal sectional view showing the force detection element. Figure 7 This is a schematic diagram illustrating the configuration of the force sensor and the inertial sensor. Figure 8 An exploded stereoscopic view of the inertial sensor is shown. Figure 9 This is a perspective view of the substrate housed inside the inertial sensor. Figure 10 This is a block diagram illustrating the circuit configuration of a force detection circuit.

[0025] Robot System 1

[0026] Figure 1 The robot system 1 shown is capable of performing operations such as feeding, unloading, conveying, and assembling precision equipment and components constituting such precision equipment. The robot system 1 includes a robot 2, which is a 6-axis vertical joint robot with a single arm, a robot control device 20 that controls the drive of the robot 2, and a force detection device 3 mounted on the robot 2.

[0027] Additionally, robot 2 includes a base 21, a robotic arm 22 rotatably connected to the base 21, and an end effector 23. The base 21 is fixed to, for example, a floor, wall, ceiling, or a movable trolley. The robotic arm 22 is a robotic arm with multiple arms 221, 222, 223, 224, 225, and 226 rotatably connected, and has six joints J1 to J6. Among them, joints J2, J3, and J5 are bending joints, and joints J1, J4, and J6 are torsional joints. However, there are no particular limitations on the robotic arm 22, and it can be appropriately selected according to the task.

[0028] Motors M and encoders E are respectively installed at joints J1, J2, J3, J4, J5, and J6. During the operation of the robot system 1, the robot control device 20 performs feedback control to ensure that the rotation angles of joints J1 to J6 indicated by the output of each encoder E match the target rotation angles. This ensures that each joint J1 to J6 is at the target rotation angle, allowing the robotic arm 22 to be in the desired position and posture. Therefore, the robot 2 can be driven with the desired motion.

[0029] The robot control device 20 controls the drive of the robot 2. The robot control device 20 is, for example, a computer, and includes a processor (CPU) for processing information, a memory communicatively connected to the processor, and an external interface for connecting to external devices. Various programs executable by the processor are stored in the memory, and the processor can read and execute these programs. It should be noted that some or all of the components of the robot control device 20 may also be located inside the housing of the robot 2. Furthermore, the robot control device 20 may be configured using multiple processors.

[0030] An end effector 23 is mounted on the fore-end of the robotic arm 22, namely the arm 226, via a mechanical interface. The end effector 23 is not particularly limited and can be appropriately selected based on the task at hand. In the illustrated configuration, it is configured to have a pair of claws 231 and 232, which are used to grasp a workpiece (not shown) by opening and closing.

[0031] Force detection device 3 is located between robotic arm 22 and end effector 23. That is, end effector 23 is mounted on the front end of robotic arm 22 via force detection device 3. Force detection device 3 detects the force applied to end effector 23 mounted on force detection device 3. The force detection device 3 will be described in detail below.

[0032] Force detection device 3

[0033] The force detection device 3 is a 6-axis force sensor capable of detecting the 6-axis components of the external force applied to it. It should be noted that the 6-axis components consist of translational force (shear force) components in each direction of the α-axis, β-axis, and γ-axis, which are three mutually orthogonal axes, as well as rotational force (torque) components about each of these three axes.

[0034] like Figure 2 As shown, the force detection device 3 includes four force sensors 4 arranged approximately 90° apart 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 housing 5 that houses all these parts. In the force detection device 3, the output signals from each force sensor 4 are corrected based on the output signals from their corresponding inertial sensors 6, and the external force applied to the force detection device 3 is detected based on the four corrected signals.

[0035] Here, in the force detection device 3, although only the external force F1 applied by the end effector 23 in contact with the object is to be detected, during the operation of the robot 2, the force detection device 3 is also subjected to an external force F2 caused by inertia, i.e., angular velocity and acceleration, generated by the drive of the robotic arm 22, in addition to the external force F1. The signals from the force sensor 4 alone cannot distinguish between the external forces F1 and F2; the force can only be detected as their resultant force F3 (=F1+F2). Therefore, it is not possible to detect the external force F1, which is the object of detection, with high precision. Therefore, in the force detection device 3, an inertial sensor 6 is provided to detect the external force F2 applied to the force sensor 4, so that the external force F1 can be detected by subtracting the external force F2 calculated based on the detection result of the inertial sensor 6 from the resultant force F3 detected by the force sensor 4. Thus, in the force detection device 3, since the external force F1 is detected using both the force physically detected by the force sensor 4 and the force physically detected by the inertial sensor 6, the external force F1 can be detected with excellent precision.

[0036] like Figure 3 As shown, the housing 5 has a first housing component 51, a second housing component 52 spaced apart from the first housing component 51, and sidewall components 53 provided on the outer periphery of the first housing component 51 and the second housing component 52. In this configuration of the housing 5, the upper surface 510 of the first housing component 51 functions as a mounting surface for mounting the end effector 23, and the lower surface 520 of the second housing component 52 functions as a mounting surface for mounting the robotic arm 22. However, this is not a limitation, and the configuration could be reversed.

[0037] like Figure 3 and Figure 4As shown, the first housing component 51 has a top plate 511 and four pressure-applying portions 512. The four pressure-applying portions 512 are disposed on the lower surface of the top plate 511 and are arranged at equal intervals (90° intervals) around the central axis A1. Furthermore, a through hole 511a along the central axis A1 is formed in the center of the top plate 511. Additionally, each pressure-applying portion 512 has multiple through holes 512a for the insertion of the pressure bolt 50, which will be described later.

[0038] Furthermore, the second housing component 52 has a base plate 521 and four pressure-applying portions 522. The four pressure-applying portions 522 are disposed on the upper surface of the base plate 521 and are arranged at equal intervals (90° intervals) around the central axis A1, opposite to the aforementioned four pressure-applying portions 512. Additionally, a through hole 521a along the central axis A1 is formed in the center of the base plate 521. Furthermore, each pressure-applying portion 522 has a plurality of internally threaded holes 522a that engage with the front end of the pressure-applying bolt 50.

[0039] Furthermore, the sidewall component 53 is cylindrical, and its upper and lower ends are respectively fixed to the first housing component 51 and the second housing component 52 by means of threaded fixing or fitting. In addition, four force sensors 4, four inertial sensors 6 and a force detection circuit 7 are housed in the internal space S1 surrounded by the sidewall component 53, the aforementioned top plate 511 and bottom plate 521.

[0040] like Figure 4 As shown, four force sensors 4 are symmetrically arranged relative to a line segment CL passing through the central axis A1 and parallel to the β axis when viewed from above. Each force sensor 4 is located between pairs of pressure-applying parts 512 and 522 and is held by these parts. Pressure bolts 50 connect the pressure-applying parts 512 and 522 and fix the first housing component 51 and the second housing component 52. Furthermore, by tightening the pressure bolts 50, the force sensors 4 located between the pressure-applying parts 512 and 522 are pressurized. A pair of pressure bolts 50 are provided opposite each force sensor 4, with each pair of pressure bolts 50 located on either side of the force sensor 4.

[0041] Next, the force sensor 4 will be explained. Since the four force sensors 4 are identical in configuration, only one force sensor 4 will be described representatively below; the descriptions of the other three will be omitted. For ease of explanation, the force sensor 4 will be defined as three mutually orthogonal axes: A-axis, B-axis, and C-axis. Furthermore, the front end of the arrow representing each axis will be designated as the "positive side," and the base end as the "negative side." The direction along the A-axis will be referred to as the "A-axis direction," the direction along the B-axis as the "B-axis direction," and the direction along the C-axis as the "C-axis direction."

[0042] like Figure 5As shown, the force sensor 4 has a package 41 and a force detection element 42 housed within the package 41. The force sensor 4 is clamped between pressure sections 512 and 522, and the force detection element 42 is pressurized in the direction indicated by arrow P via a pressure bolt 50. The external force applied to the force sensor 4, specifically the shear force in the A-axis direction and the 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. In this way, the external force can be detected with high accuracy by pre-pressurizing the force detection element 42. It should be noted that the pressure applied to the force detection element 42 can be adjusted by appropriately adjusting the tightening force of the pressure bolt 50.

[0043] Additionally, the package 41 has a substrate 411 and a cover 412 that is bonded to the substrate 411. An airtight storage space S is formed inside the package 41, and a force detection element 42 is housed within the storage space S. By housing the force detection element 42 within the package 41, the force detection element 42 can be protected from external influences, i.e., it is dustproof and waterproof. The atmosphere of the storage space S is not particularly limited, but a vacuum state or a near-vacuum depressurization state is preferred.

[0044] The force detection element 42 outputs a charge Qa corresponding to the A-axis component of the external force applied to the force detection element 42 and a charge Qb corresponding to the B-axis component of the external force applied to the force detection element 42. Furthermore, the force detection element 42 includes a piezoelectric element 420 and a pair of intermediate substrates 423 and 424 sandwiched between the piezoelectric element 420 from the C-axis direction. Additionally, the piezoelectric element 420 includes a first piezoelectric element 421 that outputs charge Qa according to the shear force in the A-axis direction and a second piezoelectric element 422 that outputs charge Qb according to the shear force in the B-axis direction.

[0045] like Figure 6 As shown, the first piezoelectric element 421 is configured such that, starting from the negative side in the C-axis direction, a ground electrode layer 421A, a piezoelectric body layer 421B, an output electrode layer 421C, a piezoelectric body layer 421D, a ground electrode layer 421E, a piezoelectric body layer 421F, an output electrode layer 421G, a piezoelectric body layer 421H, and a ground electrode layer 421I are stacked sequentially. Furthermore, the second piezoelectric element 422 is stacked on top of the first piezoelectric element 421, and is configured such that, starting from the negative side in the C-axis direction, a ground electrode layer 422A, a piezoelectric body layer 422B, an output electrode layer 422C, a piezoelectric body layer 422D, a ground electrode layer 422E, a piezoelectric body layer 422F, an output electrode layer 422G, a piezoelectric body layer 422H, and a ground electrode layer 422I are stacked sequentially. It should be noted that, in this embodiment, the ground electrode layers 421I and 422A are integrated.

[0046] Furthermore, piezoelectric layers 421B, 421D, 421F, 421H, 422B, 422D, 422F, and 422H are each composed of Y-cut quartz sheets, i.e., quartz sheets with the Y-axis (mechanical axis), which serves as the crystal axis of the crystal, as the thickness direction. This results in a force sensing element 42 with excellent characteristics such as high sensitivity, wide dynamic range, and high rigidity. In piezoelectric layers 421B and 421F, the X-axis (electric axis), which serves as the crystal axis of the crystal, points towards the positive side of the A-axis direction; in piezoelectric layers 421D and 421H, the X-axis of the crystal points towards the negative side of the A-axis direction. Similarly, in piezoelectric layers 422B and 422F, the X-axis of the crystal points towards the positive side of the B-axis direction; in piezoelectric layers 422D and 422H, the X-axis of the crystal points towards the negative side of the B-axis direction.

[0047] However, the piezoelectric layers 421B, 421D, 421F, 421H, 422B, 422D, 422F, and 422H can also be composed of piezoelectric materials other than crystal. Examples of piezoelectric materials other than crystal include citrine, barium titanate, lead titanate, lead zirconate titanate (PZT: Pb(Zr,Ti)O3), lithium niobate, and lithium tantalate.

[0048] Furthermore, grounding electrode layers 421A, 421E, 421I, 422A, 422E, and 422I are electrically connected to the grounding potential GND. Additionally, output electrode layers 421C and 421G output charges Qa corresponding to the component along the A-axis, and output electrode layers 422C and 422G output charges Qb corresponding to the component along the B-axis. Charges Qa and Qb are respectively sent to the force detection circuit 7 via terminals 413 provided on the substrate 411.

[0049] A pair of intermediate substrates 423 and 424 are configured to sandwich the piezoelectric element 420 from both sides in the C-axis direction. This allows the intermediate substrates 423 and 424 to cover and protect the ground electrode layers 421A and 422I, and to suppress accidental conduction between them and the package 41. Furthermore, pressure applied in the C-axis direction can be uniformly transmitted to the entire area of ​​the piezoelectric element 420.

[0050] Intermediate substrates 423 and 424 are made of crystal. This results in intermediate substrates 423 and 424 with high mechanical strength, enabling accurate transmission of external force to the force sensing element 42. Furthermore, intermediate substrate 423 has the same configuration as the adjacent piezoelectric layer 422H. That is, intermediate substrate 423 is a Y-cut quartz sheet, with the X-axis of the crystal pointing towards the negative side of the B-axis direction. Similarly, intermediate substrate 424 has the same configuration as the adjacent piezoelectric layer 421B. That is, intermediate substrate 424 is a Y-cut quartz sheet, with the X-axis of the crystal pointing towards the positive side of the A-axis direction. Thus, by aligning the crystal axes of intermediate substrates 423 and 424 with the crystal axes of adjacent piezoelectric layers 422H and 421B, their coefficients of thermal expansion can be made consistent, effectively reducing output drift caused by thermal expansion.

[0051] The force sensor 4 has been described above. Here, when the four force sensors 4 are designated as force sensors 4A, 4B, 4C, and 4D, their orientations are as follows: Figure 7 As shown. Force sensor 4A has its A-axis pointing towards the positive γ-axis, and its B-axis tilted at +45° relative to the β-axis. Force sensor 4B has its A-axis pointing towards the negative γ-axis, and its B-axis tilted at -45° relative to the β-axis. Force sensor 4C has its A-axis pointing towards the positive γ-axis, and its B-axis tilted at -135° relative to the β-axis. Force sensor 4D has its A-axis pointing towards the negative γ-axis, and its B-axis tilted at +135° relative to the β-axis.

[0052] In this configuration, the B-axis of the force detection axes of force sensors 4A and 4C intersects with the B-axis of force sensors 4B and 4D when viewed from above the γ-axis. Thus, by having multiple force sensors 4 whose force detection axes intersect rather than be identical, the six-axis components of the external force can be detected. In particular, in this embodiment, since the B-axis of force sensors 4A and 4C is orthogonal to the B-axis of force sensors 4B and 4D, the six-axis components of the external force can be detected with higher accuracy. It should be noted that in this embodiment, force sensors 4A and 4C are "first force sensors," and force sensors 4B and 4D are "second force sensors."

[0053] Next, the inertial sensor 6 will be described. Since the four inertial sensors 6 have the same configuration, only one inertial sensor 6 will be described representatively below. For ease of explanation, the three mutually orthogonal axes, namely the a-axis, b-axis, and c-axis, will be designated as the inertial detection axes of the inertial sensor 6. Furthermore, the front end of the arrow representing each axis will be designated as the "positive side," and the base end as the "negative side." The direction along the a-axis will be called the "a-axis direction," the direction along the b-axis will be called the "b-axis direction," and the direction along the c-axis will be called the "c-axis direction."

[0054] An inertial sensor, also known as an inertial measurement unit (IMU), is a 6-axis sensor capable of independently detecting angular velocities and accelerations along the a, b, and c axes. For example... Figure 8 As shown, the inertial sensor 6 has a housing 61, a sensor module 62 inserted into the housing 61, and a joining member 63 that joins them together. The housing 61 is a rectangular prism with a planar shape that is approximately square, and threaded holes 611 for mounting are formed near two vertices located on the diagonal of the square.

[0055] The sensor module 62 has an inner housing 621 and a substrate 622. The inner housing 621 is a component that supports the substrate 622 and is shaped to be housed inside the outer housing 61. In addition, an opening 621a is formed on the inner housing 621 to expose the connector 64, which will be described later. The inner housing 621 is engaged with the outer housing 61 via a coupling member 63.

[0056] like Figure 9 As shown, a connector 64, an angular velocity sensor 65c for detecting the angular velocity about the c-axis, and an accelerometer 66 for detecting the acceleration along the a-axis, b-axis, and c-axis are mounted on the upper surface of the substrate 622. Additionally, an angular velocity sensor 65a for detecting the angular velocity about the a-axis and an angular velocity sensor 65b for detecting the angular velocity about the b-axis are mounted on the side of the substrate 622.

[0057] Additionally, a control IC 67 is mounted on the lower surface of the substrate 622. The control IC 67 is a Micro Controller Unit (MCU) that controls the various components of the inertial sensor 6. The control IC 67 has a processor (CPU) for processing information, a memory communicatively connected to the processor, and an external interface. Furthermore, the memory stores programs executable by the processor, which reads and executes these programs. This control IC 67 independently detects the angular velocities around the a-axis, b-axis, and c-axis, and the accelerations along each axis, based on the output signals from the angular velocity sensors 65a, 65b, and 65c and the accelerometer 66.

[0058] The above describes the inertial sensor 6. Here, when the four inertial sensors 6 are designated as inertial sensors 6A, 6B, 6C, and 6D, their configuration is as follows: Figure 7 As shown.

[0059] Inertial sensor 6A is paired with force sensor 4A and fixed to the same pressure part 522 as force sensor 4A, positioned near force sensor 4A. Similarly, inertial sensor 6B is paired with force sensor 4B and fixed to the same pressure part 522 as force sensor 4B, positioned near force sensor 4B. Inertial sensor 6C is paired with force sensor 4C and fixed to the same pressure part 522 as force sensor 4C, positioned near force sensor 4C. Inertial sensor 6D corresponds to force sensor 4D and is fixed to the same pressure part 522 as force sensor 4D, positioned near force sensor 4D. By arranging the paired sensors close to each other, the acceleration and angular velocity applied to the detection axis of force sensor 4 can be detected with high precision using the paired inertial sensors 6. It should be noted that in this embodiment, the inertial sensors 6A and 6C paired with force sensors 4A and 4C are "first inertial sensors", and the inertial sensors 6B and 6D paired with force sensors 4B and 4D are "second force sensors".

[0060] Here, the placement of inertial sensor 6A near force sensor 4A means, as Figure 7 As shown, the separation distance DA between inertial sensor 6A and force sensor 4A is smaller than the separation distances DB, DC, and DD between unpaired inertial sensor 6A and force sensor 4B, and between inertial sensor 6A and force sensor 4C, and between inertial sensor 6A and force sensor 4D, respectively. The same applies to inertial sensors 6B, 6C, and 6D. Therefore, it is possible to detect the acceleration and angular velocity applied to the paired force sensors 4 with high precision using each inertial sensor 6.

[0061] In addition, the orientations of inertial sensors 6A, 6B, 6C, and 6D are as follows: Figure 7 As shown. The a-axis and b-axis of inertial sensor 6A are along the A-axis and B-axis of the paired force sensor 4A, respectively. Similarly, the a-axis and b-axis of inertial sensor 6B are along the A-axis and B-axis of the paired force sensor 4B, respectively. Furthermore, the a-axis and b-axis of inertial sensor 6C are along the A-axis and B-axis of the paired force sensor 4C, respectively. Finally, the a-axis and b-axis of inertial sensor 6D are along the A-axis and B-axis of the paired force sensor 4D, respectively.

[0062] In this way, by aligning the inertial detection axis with the force detection axis between the paired inertial sensors 6 and force sensors 4, the acceleration and angular velocity components contained in the signals (charges Qa and Qb) output from the paired force sensors 4 can be detected with high precision by each inertial sensor 6. It should be noted that the aforementioned "a-axis along A-axis" includes not only the case where a-axis and A-axis are parallel or on the same straight line, but also cases with technically permissible errors or manufacturing errors. Similarly, the aforementioned "b-axis along B-axis" includes not only the case where b-axis and B-axis are parallel or on the same straight line, but also cases with technically permissible errors or manufacturing errors.

[0063] Here, although a 6-axis sensor capable of independently detecting angular velocities and accelerations in each of the a, b, and c axes is used as the inertial sensor 6, the acceleration in the c-axis direction and the angular velocity around the c-axis are not used in the force detection device 3. Therefore, the element for detecting the acceleration in the c-axis direction and the angular velocity around the c-axis can also be omitted from the inertial sensor 6. In other words, the inertial sensor 6 only needs to be able to detect the angular velocities around the a and b axes and the accelerations in the a and b axis directions.

[0064] Next, the force detection circuit 7 will be described. The force detection circuit 7 detects the external force F1 received by the end effector 23 based on signals from each force sensor 4 and each inertial sensor 6. For example... Figure 10 As shown, the force detection circuit 7 has a first processing unit 71 that calculates the force based on the signal from the force sensor 4, a second processing unit 72 that removes the 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.

[0065] The first processing unit 71 calculates the forces applied to the 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 the force sensor 4A, calculates the forces applied to the 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 the force sensor 4B, calculates the forces applied to the 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 the force sensor 4C, and calculates the forces applied to the 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 the force sensor 4D.

[0066] Here, as mentioned earlier, the shear forces FAa to FDa detected in the A-axis direction calculated by the first processing unit 71 include the acceleration component and the angular velocity component around the A-axis applied to the end effector 23 due to the driving of the robotic arm 22. The shear forces FAb to FDb in the B-axis direction include the acceleration component and the angular velocity component around the B-axis applied to the end effector 23 due to the driving of the robotic arm 22. Therefore, in the second processing unit 72, the acceleration component and the angular velocity component around the A-axis are removed from the shear forces FAa to FDa in the A-axis direction calculated by the first processing unit 71, and the acceleration component and the angular velocity component around the B-axis are removed from the shear forces FAb to FDb in the B-axis direction.

[0067] The second processing unit 72 calculates the shear force FAAa caused by the acceleration in the a-axis direction detected by the inertial sensor 6A, the shear force FAAb caused by the acceleration in the B-axis direction based on the acceleration AAa in the a-axis direction detected by the inertial sensor 6A, the shear force FωAa caused by the angular velocity ωAa around the a-axis detected by the inertial sensor 6A, and the shear force FωAb caused by the angular velocity ωAb around the b-axis detected by the inertial sensor 6A.

[0068] Here, as mentioned earlier, since the inertial sensor 6A is arranged near the pair of force sensors 4A, the inertia experienced by the inertial sensor 6A can be made approximately equal to the inertia experienced by the force sensor 4A. Therefore, shear forces FAAa, FAAb, FωAa, and FωAb can be detected with high precision.

[0069] The shear forces FAAa and FAAb can be calculated, for example, by multiplying the accelerations AAa and AAB by coefficients calculated based on the mass of the end effector 23. Similarly, the shear forces FωAa and FωAb can be calculated, for example, by multiplying the angular velocities ωAa and ωAb by coefficients calculated based on the mass of the end effector 23. However, there are no particular limitations on the methods for calculating the shear forces FAAa, FAAb, FωAa, and FωAb.

[0070] Similarly, the second processing unit 72 calculates the shear forces FABa, FABb, FACa, FACb, FADa, and FADb of force sensors 4B, 4C, and 4D caused by the accelerations ABa, ABb, ACa, ACb, ADa, and ADb detected by inertial sensors 6B, 6C, and 6D in the a-axis and b-axis directions, based on the accelerations ABa, ABb, ACa, ACb, ADa, and ADb detected by inertial sensors 6B, 6C, and 6D. It also calculates the shear forces FωBa, FωBb, FωCa, FωCb, FωDa, and FωDb of force sensors 4B, 4C, and 4D caused by the angular velocities ωBa, ωBb, ωCa, ωCb, ωDa, and FωDb detected by inertial sensors 6B, 6C, and 6D in the a-axis and b-axis directions, based on the accelerations ABa, ABb, ACa, ACb, ADa, and ADb detected by inertial sensors 6B, 6C, and 6D.

[0071] Next, the second processing unit 72 calculates the corrected shear force FAa0 by subtracting shear forces FAAa and FωAa from the shear force FAa, and calculates the corrected shear force FAb0 by subtracting shear forces FAAb and FωAb from the shear force FAb. That is, FAa0 = FAa - (FAAa + FωAa), FAb0 = FAb - (FAAb + FωAb). Thus, the corrected shear forces FAa0 and FAb0 obtained by removing the angular velocity received by the force sensor 4A and the force component caused by the angular velocity from the shear forces FAa and FAb are obtained.

[0072] Similarly, the second processing unit 72 calculates the corrected shear force FBa0 by subtracting shear forces FABa and FωBa from the shear force FBa, and calculates the corrected shear force FBb0 by subtracting shear forces FABb and FωBb from the shear force FBb. Additionally, it calculates the corrected shear force FCa0 by subtracting shear forces FACa and FωCa from the shear force FCa, and calculates the corrected shear force FCb0 by subtracting shear forces FACb and FωCb from the shear force FCb. Furthermore, it calculates the corrected shear force FDa0 by subtracting shear forces FADa and FωDa from the shear force FDa, and calculates the corrected shear force FDb0 by subtracting shear forces FADb and FωDb from the shear force FDb.

[0073] 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) on 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 way is sent to the robot control unit 20. Then, the robot control unit 20 controls the drive of the robot 2 based on the external force F1. This enables more precise control of the robot 2.

[0074] The robot system 1 and the force detection device 3 have been described above. As previously mentioned, such a force detection device 3 includes a force sensor 4A as a first force sensor, a force sensor 4B as a second force sensor, an inertial sensor 6A as a first inertial sensor, and an inertial sensor 6B as a second inertial sensor. The force sensors 4A and 4B each have a force detection element 42 with a force detection axis. The inertial sensor 6A is positioned near the force sensor 4A, and its inertial detection axis is along the force detection axis of the force sensor 4A. The inertial sensor 6B is positioned near the force sensor 4B, and its inertial detection axis is along the force detection axis of the force sensor 4B. With this configuration, external forces can be detected based on the forces physically detected by the force sensors 4A and 4B, and the inertial forces physically detected by the inertial sensors 6A and 6B. Therefore, external forces can be detected with excellent accuracy.

[0075] Furthermore, as mentioned earlier, 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. Therefore, by positioning inertial sensor 6A and force sensor 4A closer together, the detection accuracy of external forces is further improved.

[0076] Furthermore, as mentioned above, inertial sensors 6A and 6B are sensors that detect acceleration along the directions of the a-axis and b-axis, which serve as inertial detection axes; sensors that detect angular velocities about the a-axis and b-axis; or sensors that detect both acceleration along the a-axis and b-axis and angular velocities about the a-axis and b-axis. This allows for high-precision detection of the force caused by inertia applied to force sensors 4A and 4B. In particular, the inertial sensors 6A and 6B of this embodiment detect both acceleration along the a-axis and b-axis and angular velocities about the a-axis and b-axis. Therefore, the aforementioned effects become even more pronounced.

[0077] Furthermore, as mentioned earlier, the force detection axes of force sensors 4A and 4B intersect each other. In this embodiment, the B-axis of force sensors 4A and 4B intersect each other. Therefore, the force detection device 3 can detect force components in more directions, thus improving the accuracy of force detection.

[0078] Furthermore, as mentioned above, the force sensing element 42 has piezoelectric layers 421B, 421D, 421F, 421H, 422B, 422D, 422F, and 422H, which serve as a quartz sheet. Thus, it becomes a force sensing element 42 with excellent characteristics such as high sensitivity, wide dynamic range, and high rigidity.

[0079] Furthermore, as mentioned above, the force detection device 3 includes a force detection circuit 7. This circuit calculates corrected shear forces FAa0 and FAb0 as a first force based on the detection results of the inertial sensor 6A, and calculates corrected shear forces FBa0 and FBb0 as a second force based on the detection results of the inertial sensor 6B. It also calculates the applied external force F1 based on these corrected shear forces FAa0 and FAb0 and the corrected shear forces FBa0 and FBb0. The corrected shear forces FAa0 and FAb0 are obtained by removing the inertial component from the shear forces FAa and FAb received by the force sensor 4A, and the corrected shear forces FBa0 and FBb0 are obtained by removing the inertial component from the shear forces FBa and FBb received by the force sensor 4B. This allows for high-precision detection of external forces.

[0080] Furthermore, as previously described, the robot system 1 includes a robot 2, a force detection device 3 mounted on the robot 2, and a robot control device 20 that controls the drive of the robot 2 based on the detection results from the force detection device 3. The force detection device 3 includes a force sensor 4A as a first force sensor, a force sensor 4B as a second force sensor, an inertial sensor 6A as a first inertial sensor, and an inertial sensor 6B as a second inertial sensor. The force sensors 4A and 4B each have a force detection element 42 with a force detection axis. The inertial sensor 6A is positioned near the force sensor 4A, and its inertial detection axis is along the force detection axis of the force sensor 4A. The inertial sensor 6B is positioned near the force sensor 4B, and its inertial detection axis is along the force detection axis of the force sensor 4B. With this configuration, external forces can be detected based on the forces physically detected by the force sensors 4A and 4B, and the inertial forces physically detected by the inertial sensors 6A and 6B. Therefore, external forces can be detected with excellent accuracy.

[0081] 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 thereto, and the configuration of each part can be replaced with any configuration having the same function. Furthermore, other arbitrary components can be added to the present invention. Additionally, the force detection device of the present invention can also be embedded in devices other than robot systems, for example, it can be mounted on a mobile body such as a car.

[0082] For example, in the aforementioned embodiment, the inertial sensor 6 and the force sensor 4A are disposed opposite each other on the side of the pressurizing part 522, but it is not limited to this as long as it can be disposed near the paired force sensors 4. For example, as Figure 11 As shown, the inertial sensor 6 can be disposed on the upper surface of the pressurizing part 522, or on the bottom plate 521 of the second housing part 52, or disposed on the side of the pressurizing part 512 opposite to the force sensor 4.

[0083] For example, in the aforementioned embodiment, the inertial sensor 6 detects both acceleration and angular velocity, but it is not limited to this; it can also detect either acceleration or angular velocity. That is, it can also be... Figure 12 or Figure 13 The structure shown. In Figure 12 In the case of FAa0 = FAa - FAAa and FAb0 = FAb - FAAb, the calculation is as follows: Figure 13 In the case of FBa0, the calculation is FAa0 = FAa - FωAa, FAb0 = FAb - FωAb. The same applies to FBa0, FBb0, FCa0, FCb0, FDa0, and FDb0. With this configuration, the same effect as the aforementioned implementation method can be achieved.

Claims

1. A force detection device, characterized in that, have: A first force sensor and a second force sensor, wherein the first force sensor and the second force sensor have a force detection element having a force detection axis; A first inertial sensor is disposed near the first force sensor, and the inertial detection axis of the first inertial sensor is along the force detection axis of the first force sensor; as well as A second inertial sensor is disposed near the second force sensor, and the inertial detection axis of the second inertial sensor is along the force detection axis of the second force sensor. The force detection axes of the first force sensor and the second force sensor intersect each other. The inertial detection axes of the first inertial sensor and the second inertial sensor intersect each other. The first force sensor and the second force sensor are located between and held by pairs of pressure-applying parts. The first inertial sensor and the second inertial sensor are respectively sensors that detect acceleration along the direction of the inertial detection axis, sensors that detect angular velocity about the inertial detection axis, or sensors that detect both acceleration and angular velocity. The force detection device has a force detection circuit. The force detection circuit calculates a first force based on the detection result of the first inertial sensor, calculates a second force based on the detection result of the second inertial sensor, and calculates the external force received based on the first force and the second force. The first force is obtained by removing the inertial component from the force received by the first force sensor, and the second force is obtained by removing the inertial component from the force received by the second force sensor.

2. The force detection device according to claim 1, characterized in that, The separation distance between the first inertial sensor and the first force sensor is smaller than the separation distance between the first inertial sensor and the second force sensor. The separation distance between the second inertial sensor and the second force sensor is smaller than the separation distance between the second inertial sensor and the first force sensor.

3. The force detection device according to claim 1, characterized in that, The force sensing element has a quartz plate.

4. A robot system, characterized in that, have: robot; Force detection device, mounted on the robot; as well as The robot control device controls the robot's drive based on the detection results from the force detection device. The force detection device has: A first force sensor and a second force sensor, wherein the first force sensor and the second force sensor have a force detection element having a force detection axis; A first inertial sensor is disposed near the first force sensor, and the inertial detection axis of the first inertial sensor is along the force detection axis of the first force sensor; as well as A second inertial sensor is disposed near the second force sensor, and the inertial detection axis of the second inertial sensor is along the force detection axis of the second force sensor. The force detection axes of the first force sensor and the second force sensor intersect each other. The inertial detection axes of the first inertial sensor and the second inertial sensor intersect each other. The first force sensor and the second force sensor are located between and held by pairs of pressure-applying parts. The first inertial sensor and the second inertial sensor are respectively sensors that detect acceleration along the direction of the inertial detection axis, sensors that detect angular velocity about the inertial detection axis, or sensors that detect both acceleration and angular velocity. The force detection device has a force detection circuit. The force detection circuit calculates a first force based on the detection result of the first inertial sensor, calculates a second force based on the detection result of the second inertial sensor, and calculates the external force received based on the first force and the second force. The first force is obtained by removing the inertial component from the force received by the first force sensor, and the second force is obtained by removing the inertial component from the force received by the second force sensor.

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