Grip device and grip device control method

Abstract

To provide a gripping device that can accurately and stably hold objects to be gripped with different hardness.SOLUTION: A gripping device comprises: a motor that rotates in accordance with an operation value; a gripping part that comprises a first finger part and a second finger part, and makes the first finger part and the second finger part grip an object while making the motor change an interval between the first finger part and the second finger part; a force detecting part that detects gripping force for the first finger part and the second finger part to grip the object when the first finger part and the second finger part grip the object; and a control part that outputs the operation value so that the magnitude of the gripping force detected by the force detecting part is equal to a command value. The control part controls the gripping part while setting the command value to a reference command value, and changes the command value from the reference command value to a renewed command value, on the basis of variation of the gripping force detected by the force detecting part after the gripping part grips the object.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a gripping device and a method for controlling a gripping device. [Background technology]

[0002] 2. Description of the Related Art When a product manufacturing line is automated using a robot or the like, a gripping device called a manipulator or a gripper is used to grip an object to be gripped, such as a mechanical part or an electrical part.

[0003] Patent Document 1 discloses a manipulator that includes an article gripping means, a driving means for driving the article gripping means, a force sensor for detecting a force applied to the article gripping means, and a feedback control means for controlling the driving means based on the output of the force sensor. Patent Document 1 also discloses that the control means includes a means for determining the stiffness between the article gripped by the article gripping means and a pressed portion from the force applied to the article gripping means and the displacement of the article gripping means. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 10-264063 Summary of the Invention [Problem to be solved by the invention]

[0005] When a gripping device grips a gripping object, it may grip multiple gripping objects of different hardness individually and successively. Each time the gripping device grips an object, it is required to hold the object accurately and stably, even if the hardness of the object varies.

[0006] The present disclosure provides a gripping device that can accurately and stably hold objects to be gripped that have different hardnesses. [Means for solving the problem]

[0007] In one aspect of the present disclosure, there is provided a gripping device including: a motor that rotates in response to an operation value; a first finger unit; and a second finger unit, the gripping unit changing a distance between the first finger unit and the second finger unit using the motor to grip an object with the first finger unit and the second finger unit; a force detection unit that detects a gripping force with which the first finger unit and the second finger unit grip the object when the object is gripped with the first finger unit and the second finger unit; and a control unit that outputs the operation value so that the magnitude of the gripping force detected by the force detection unit becomes a command value, wherein the control unit controls the gripping unit using the command value as a reference command value, and changes the command value from the reference command value to an updated command value based on a change in the gripping force detected by the force detection unit after the gripping unit grips the object. [Effects of the Invention]

[0008] The gripping device of the present disclosure can accurately and stably hold objects to be gripped that have different hardnesses. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing an example of the configuration of a gripping device according to the first embodiment. [Figure 2] FIG. 2 is a diagram illustrating the functional configuration of the gripping device according to the first embodiment. [Figure 3] FIG. 3 is a diagram illustrating the functional configuration of a processing calculation unit included in the control unit of the gripping device according to the first embodiment. [Figure 4] FIG. 4 is a diagram illustrating the functional configuration of the operation value calculation unit of the processing calculation unit included in the control unit of the gripping device according to the first embodiment. [Figure 5] FIG. 5 is a diagram illustrating the functional configuration of an admittance control calculation unit of the processing calculation unit included in the control unit of the gripping device according to the first embodiment. [Figure 6] FIG. 6 is a diagram illustrating the functional configuration of a position and velocity calculation unit of a processing calculation unit included in a control unit of a gripping device according to the first embodiment. [Figure 7]FIG. 7 is a diagram illustrating the functional configuration of a current calculation unit of a processing calculation unit included in a control unit of a gripping device according to the first embodiment. [Figure 8] FIG. 8 is a flowchart illustrating the processing of the force command generating unit of the processing calculation unit included in the control unit of the gripping device according to the first embodiment. [Figure 9] FIG. 9 is a diagram illustrating the operation of the gripping device according to the first embodiment. [Figure 10] FIG. 10 is a flowchart illustrating the processing of the force command generating unit of the processing calculation unit included in the control unit of the gripping device according to the second embodiment. [Figure 11] FIG. 11 is a diagram illustrating the operation of the gripping device according to the second embodiment. [Figure 12] FIG. 12 is a flowchart illustrating the processing of the force command generating unit of the processing calculation unit included in the control unit of the gripping device according to the third embodiment. [Figure 13] FIG. 13 is a diagram illustrating the operation of the gripping device according to the third embodiment. [Figure 14] FIG. 14 is a diagram illustrating the functional configuration of a gripping device according to the fourth embodiment. [Figure 15] FIG. 15 is a diagram illustrating the functional configuration of a processing calculation unit included in a control unit of a gripping device according to the fourth embodiment. [Figure 16] FIG. 16 is a diagram illustrating the functional configuration of an operation value calculation unit of a processing calculation unit included in a control unit of a gripping device according to the fourth embodiment. [Figure 17] FIG. 17 is a diagram illustrating the functional configuration of a force control unit of a processing calculation unit included in a control unit of a gripping device according to the fourth embodiment. [Figure 18] FIG. 18 is a diagram illustrating the functional configuration of an operation value calculation unit of a processing calculation unit included in a control unit of a gripping device according to the fifth embodiment. [Figure 19] FIG. 19 is a diagram illustrating the functional configuration of a position command value generating unit of a processing calculation unit included in a control unit of a gripping device according to the fifth embodiment. [Figure 20] FIG. 20 is a diagram illustrating the functional configuration of an operation value calculation unit of a processing calculation unit included in a control unit of a gripping device according to the sixth embodiment. [Figure 21] FIG. 21 is a diagram illustrating the functional configuration of an operation value calculation unit of a processing calculation unit included in a control unit of a gripping device according to the seventh embodiment. [Figure 22] FIG. 22 is a diagram illustrating the operation of the gripping device according to the seventh embodiment. [Figure 23] FIG. 23 is a diagram illustrating the operation of a gripping device of a comparative example. [Figure 24] FIG. 24 is a diagram illustrating the operation of the gripping device according to the seventh embodiment and the gripping device of the comparative example. [Figure 25] FIG. 25 is a diagram illustrating the operation of the gripping device according to the seventh embodiment and the gripping device of the comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0010] <<First Embodiment>> <Gripping device 1> The gripping device according to this embodiment will be described in detail below with reference to the drawings. Fig. 1 is a diagram showing an example of the configuration of the gripping device 1 according to this embodiment. Fig. 2 is a diagram explaining the functional configuration of the gripping device 1 according to this embodiment.

[0011] For ease of explanation, a virtual three-dimensional coordinate system (XYZ Cartesian coordinate system) consisting of mutually orthogonal X-axis, Y-axis, and Z-axis (XYZ axes) is set in Fig. 1. However, this coordinate system is defined for the sake of explanation and does not limit the attitude of the gripping device 1.

[0012] 1, the X-axis direction is the direction in which the first finger portion 21a and the second finger portion 21b extend, the Y-axis direction is the direction in which the first finger portion 21a and the second finger portion 21b move, and the Z-axis is the direction perpendicular to the X-axis and the Y-axis.

[0013] The gripping device 1 is attached to, for example, the tip of a robot arm and grips a gripping object TGT. Specifically, the gripping device 1 grips the gripping object TGT between a first finger unit 21a and a second finger unit 21b. The gripping device 1 includes a drive unit 10, a gripping unit 20, a force detection unit 30, a motor drive unit 40, and a control unit 50. Each element of the gripping device 1 will be described in detail.

[0014] The control unit 50 and the motor drive unit 40 are connected by a wire Lm1. The motor drive unit 40 and the drive unit 10, more specifically, the motor drive unit 40 and the power unit 11 (motor 11m) of the drive unit 10, are connected by a wire Lm2. The control unit 50 and the drive unit 10, more specifically, the control unit 50 and the power unit 11 (encoder 11e) of the drive unit 10, are connected by a wire Lm3.

[0015] [Drive unit 10] The driver 10 changes the distance between the first finger portion 21a and the second finger portion 21b. Specifically, the driver 10 moves the first finger portion 21a and the second finger portion 21b in the Y direction in opposite directions.

[0016] The driving unit 10 includes a power unit 11 and a motion conversion unit 12. The power unit 11 and the motion conversion unit 12 will be described in detail below.

[0017] (Power part 11) The power unit 11 rotates the rotary shaft based on the electric power supplied from the motor drive unit 40 via the wiring Lm2. The power unit 11 converts the electric power into rotary motion and transmits it to the motion conversion unit 12.

[0018] The power unit 11 includes a motor 11m and an encoder 11e. The motor 11m is, for example, an alternating current (AC) motor or a stepping motor. The motor 11m rotates a rotating shaft based on power (supplied power Pd) supplied from the motor drive unit 40. As will be described later, the supplied power Pd is determined based on a current manipulation value MVi. Therefore, the motor 11m rotates based on the current manipulation value MVi. Specifically, the motor 11m includes components well known as a motor, such as a rotating shaft, a stator, and a rotor.

[0019] The encoder 11e detects the position and rotation speed of the rotation shaft of the motor 11m, and outputs the detection result to the control unit 50 via a line Lm3.

[0020] (Motion conversion unit 12) The motion conversion unit 12 converts the rotational motion transmitted from the motor 11m into linear motion in the Y-axis direction. The motion conversion unit 12 is composed of mechanical components such as gears, worm gears, and cams. The motion conversion unit 12 includes a moving unit 12a and a moving unit 12b protruding from a housing 12c. The moving unit 12a and the moving unit 12b are each movable relative to the housing 12c. The motion conversion unit 12 converts the rotational motion transmitted from the motor 11m into linear motion that moves the moving unit 12a and the moving unit 12b in the Y-axis direction relative to the housing 12c.

[0021] When motor 11m rotates in one direction, for example, moving unit 12a moves in the +Y direction in the Y-axis direction. When motor 11m rotates in the opposite direction, for example, moving unit 12a moves in the -Y direction in the Y-axis direction. When motor 11m rotates in one direction, for example, moving unit 12b moves in the -Y direction in the Y-axis direction. When motor 11m rotates in the opposite direction, for example, moving unit 12b moves in the +Y direction in the Y-axis direction.

[0022] That is, when motor 11m rotates in one direction, moving unit 12a and moving unit 12b move in opposite directions in the Y-axis direction, specifically, in directions away from each other in the Y-axis direction. Therefore, when motor 11m rotates in one direction, the distance between moving unit 12a and moving unit 12b increases. On the other hand, when motor 11m rotates in the opposite direction, moving unit 12a and moving unit 12b move in opposite directions in the Y-axis direction, specifically, in directions toward each other in the Y-axis direction. Therefore, when motor 11m rotates in the opposite direction, the distance between moving unit 12a and moving unit 12b decreases.

[0023] As described above, the driving unit 10 can change the distance between the moving unit 12a and the moving unit 12b by rotating the motor 11m.

[0024] [Gripping part 20] The gripping unit 20 is controlled by the driving unit 10 to grip the gripping object TGT between the first finger portion 21a and the second finger portion 21b.

[0025] The gripping unit 20 includes a first finger 21a and a first holding unit 22a that holds the first finger 21a, on the +Y side in the Y-axis direction with respect to the central axis Ac. The first finger 21a is fixed to the first holding unit 22a. The first holding unit 22a is fixed to the moving unit 12a via a first force sensor 31a, which will be described later. The gripping device 1 includes a fixing unit 15a for fixing the first force sensor 31a to the moving unit 12a.

[0026] The gripping unit 20 includes a second finger portion 21b and a second holding portion 22b that holds the second finger portion 21b, on the -Y side in the Y-axis direction with respect to the central axis Ac. The second finger portion 21b is fixed to the second holding portion 22b. The second holding portion 22b is fixed to the moving unit 12b via a second force sensor 31b (described later). The gripping device 1 includes a fixing portion 15b to fix the second force sensor 31b to the moving unit 12b.

[0027] When the moving unit 12a moves in the Y-axis direction, the first finger unit 21a moves in the Y-axis direction together with the moving unit 12a. Similarly, when the moving unit 12b moves in the Y-axis direction, the second finger unit 21b moves in the Y-axis direction together with the moving unit 12a. Therefore, when the distance between the moving units 12a and 12b changes, the distance D between the first finger unit 21a and the second finger unit 21b changes. By narrowing the distance D between the first finger unit 21a and the second finger unit 21b, the gripping unit 20 grips the gripping object TGT with the first finger unit 21a and the second finger unit 21b.

[0028] Note that the gripping of the gripping object TGT by the gripping portion 20 is not limited to the case where the gripping object TGT is sandwiched between the first finger portion 21a and the second finger portion 21b. For example, a ring-shaped gripping object may be gripped by inserting the finger portions into the inside of the ring and opening the finger portions from the inside to the outside.

[0029] [Force detection unit 30] The force detection unit 30 detects the force (gripping force) applied between the first finger portion 21a and the second finger portion 21b when the gripping unit 20 grips the gripping target TGT. The force detection unit 30 includes a first force sensor 31a and a second force sensor 31b. Each of the first force sensor 31a and the second force sensor 31b is, for example, a six-axis force sensor.

[0030] The first force sensor 31a is connected to the control unit 50 via a wire La. The second force sensor 31b is connected to the control unit 50 via a wire Lb. The force detection unit 30 uses the detection result related to the force in the Y-axis direction in the output of the six-axis force sensor.

[0031] The first force sensor 31a is fixed to the first holding unit 22a that holds the first finger unit 21a. The first force sensor 31a is also fixed to the moving unit 12a via a fixed unit 15a. The first force sensor 31a detects the force with which the grasp object TGT presses the first finger unit 21a when the grasp unit 20 grasps the grasp object TGT.

[0032] The second force sensor 31b is fixed to the second holding part 22b that holds the second finger part 21b. The second force sensor 31b is also fixed to the moving part 12b via the fixed part 15b. The second force sensor 31b detects the force with which the gripping object TGT presses the second finger part 21b when the gripping part 20 grips the gripping object TGT.

[0033] The gripping device 1 according to this embodiment includes the force detection unit 30 between the drive unit 10 and the gripping unit 20, but the location where the force detection unit 30 is provided is not limited to between the drive unit 10 and the gripping unit 20. For example, the gripping device 1 may include a first force sensor 31a and a second force sensor 31b at the tips of the first finger 21a and the second finger 21b, respectively.

[0034] Furthermore, the type of force sensor is not limited as long as it can detect the gripping force acting between the first finger portion 21a and the second finger portion 21b. As the force sensor, for example, a MEMS (Micro Electro Mechanical Systems) sensor capable of detecting force may be used, or a piezoelectric element or a strain gauge may be used. Note that, for example, when a MEMS sensor or a strain gauge is used, a strain-generating body that generates strain in response to an external force may be used to detect the force, or a part of the grip portion 20 may be used as the strain-generating body.

[0035] Although the force detection unit 30 according to this embodiment includes the first force sensor 31a and the second force sensor 31b, it may include only one of the first force sensor 31a and the second force sensor 31b. In other words, it may include a force sensor in only one of the first finger portion 21a and the second finger portion 21b.

[0036] [Motor drive unit 40] The motor driving unit 40 supplies power (supply power Pd) to the driving unit 10, more specifically to the motor 11m, based on an operation command (current control signal Ip) from the control unit 50. The driving unit 10 is driven by the power supplied from the motor driving unit 40. As the driving unit 10 is driven by the power supplied from the motor driving unit 40, the driving unit 10 operates in accordance with the operation command from the control unit 50.

[0037] The motor driving unit 40 outputs the current value of the power supplied to the driving unit 10 (driving current value Im) to the control unit 50. The control unit 50 controls the driving unit 10 using the current value of the current supplied to the driving unit 10 by the motor driving unit 40.

[0038] [Control unit 50] The control unit 50 controls the drive unit 10 so that the gripping force (first gripping force value Fma and second gripping force value Fmb) detected by the force detection unit 30 becomes a desired gripping force. The control unit 50 also performs control using the position (position information θm) and rotational speed (speed information vm) of the rotation axis detected by the encoder 11e, and a current signal (drive current value Im) from the motor drive unit 40.

[0039] The control unit 50 is configured by, for example, a microprocessing unit including a CPU (Central Processing Unit), RAM (Random Access Memory), and ROM (Read Only Memory). The control unit 50 performs processing by the CPU expanding a program recorded in the ROM into the RAM and executing it.

[0040] The control unit 50 includes an arithmetic processing unit 51, a motor control unit 52, a motor operation data acquisition unit 53, and a force measurement data acquisition unit 54. The arithmetic processing unit 51 outputs a current manipulation value MVi to the motor control unit 52. The motor operation data acquisition unit 53 outputs a current detection value PVi, which is the current value of the drive current supplied from the motor drive unit 40 to the power unit 11 (motor 11m), and a position detection value PVθ and a speed detection value PVv of the rotation shaft of the motor 11m to the arithmetic processing unit 51. The force measurement data acquisition unit 54 outputs a grip force detection value PVf of the grip force F received from the gripping target TGT, detected by the force detection unit 30, to the arithmetic processing unit 51. Details of each element are described below.

[0041] (arithmetic processing unit 51) The calculation processing unit 51 calculates the manipulated variable for operating the drive unit 10 so that the control value becomes the target value. Specifically, the calculation processing unit 51 calculates the current manipulated value MVi so that the grip force detection value PVf, which is the control value, becomes the target grip force value. Details of the calculation processing unit 51 will be described later. Note that, although the calculation processing unit 51 according to this embodiment outputs the current manipulated value MVi as the manipulated value, the manipulated value may not be limited to current but may be power, voltage, or the like, depending on the object to be controlled.

[0042] (Motor control unit 52) The motor control unit 52 outputs an operation value for operating the power unit 11, specifically the motor 11m, to the motor drive unit 40. Specifically, the motor control unit 52 converts the current operation value MVi output by the calculation processing unit 51 into a current control signal Ip that can be input to the motor drive unit 40, based on the current operation value MVi. The motor control unit 52 then outputs the converted current control signal Ip to the motor drive unit 40.

[0043] The motor control unit 52 may output, as the current control signal Ip, an analog signal such as a voltage signal or a current signal, or a digital signal, as long as it can be input to the motor drive unit 40. The motor drive unit 40 supplies power Pd to the motor 11m of the power unit 11 based on the current control signal Ip.

[0044] (Motor operation data acquisition unit 53) The motor operation data acquiring unit 53 acquires motor operation data relating to the operating state of the power unit 11 from the power unit 11 and the motor driving unit 40. Specifically, the motor operation data acquiring unit 53 acquires from the motor driving unit 40 the drive current value Im of the supply power Pd that the motor driving unit 40 supplies to the power unit 11. The motor operation data acquiring unit 53 also acquires from the encoder 11e position information θm and speed information vm of the rotation shaft of the motor 11m.

[0045] The motor operation data acquiring unit 53 may acquire the drive current value Im as, for example, an analog signal or a digital signal from the motor driving unit 40. Similarly, the motor operation data acquiring unit 53 may acquire the position information θm and the speed information vm from the encoder 11e as, for example, an analog signal or a digital signal.

[0046] The motor operation data acquiring unit 53 outputs the detected current value PVi to the calculation processing unit 51 based on the acquired drive current value Im. The motor operation data acquiring unit 53 also outputs the detected position value PVθ to the calculation processing unit 51 based on the acquired position information θm. The motor operation data acquiring unit 53 also outputs the detected speed value PVv to the calculation processing unit 51 based on the acquired speed information vm.

[0047] (Force measurement data acquisition unit 54) The force measurement data acquiring unit 54 acquires measurement data of the gripping force F from the force detecting unit 30. Specifically, the force measurement data acquiring unit 54 acquires the first gripping force value Fma from the first force sensor 31a. The force measurement data acquiring unit 54 also acquires the second gripping force value Fmb from the second force sensor 31b.

[0048] The force measurement data acquiring unit 54 may acquire the first gripping force value Fma from the first force sensor 31a as, for example, an analog signal or a digital signal. Similarly, the force measurement data acquiring unit 54 may acquire the second gripping force value Fmb from the second force sensor 31b as, for example, an analog signal or a digital signal.

[0049] The force measurement data acquisition unit 54 outputs the grip force detection value PVf based on the acquired first grip force value Fma and second grip force value Fmb to the calculation processing unit 51. For example, the force measurement data acquisition unit 54 may output the average grip force value of the first grip force value Fma and the second grip force value Fmb as the grip force detection value PVf.

[0050] <Details of Processing by Arithmetic Processing Unit 51> The processing of the arithmetic processing unit 51, in other words, each step executed in the control method of the gripping device 1, will now be described in detail. Fig. 3 is a diagram illustrating the functional configuration of the arithmetic processing unit 51 included in the control unit 50 of the gripping device 1 according to the first embodiment. Note that in Fig. 3, external components of the arithmetic processing unit 51 are collectively shown as control objects OBJ of the arithmetic processing unit 51. The control objects OBJ include, for example, the drive unit 10, the force detection unit 30, the motor drive unit 40, the motor control unit 52, the motor operation data acquisition unit 53, and the force measurement data acquisition unit 54.

[0051] The calculation processing unit 51 determines a force command value SVf of the gripping force F. Furthermore, the calculation processing unit 51 calculates a current manipulation value MVi so that the gripping force detection value PVf becomes the force command value SVf. Note that the calculation processing unit 51 uses the current detection value PVi, the position detection value PVθ, and the speed detection value PVv to calculate the current manipulation value MVi.

[0052] The calculation processing unit 51 includes an operation value calculation unit 51a and a force command generation unit 51b.

[0053] [Operation value calculation unit 51a] The operation value calculation unit 51a calculates the current operation value MVi so that the gripping force detection value PVf becomes the force command value SVf set by the force command generation unit 51b. Fig. 4 is a diagram illustrating the functional configuration of the operation value calculation unit 51a of the calculation processing unit 51 included in the control unit 50 of the gripping device 1 according to the first embodiment. In the blocks in the block diagram, "1 / s" means integration.

[0054] The operation value calculation unit 51a includes an admittance control calculation unit 51a1, an integral calculation unit 51a2, a position / speed calculation unit 51a3, and a current calculation unit 51a4. Each calculation unit will be described below.

[0055] (Admittance control calculation unit 51a1) The admittance control calculation unit 51a1 converts the force command value SVf into a displacement command value SVd. The admittance control calculation unit 51a1 calculates (generates) the displacement command value SVd so that the gripping force detection value PVf matches the force command value SVf. Figure 5 is a diagram illustrating the functional configuration of the admittance control calculation unit 51a1 of the calculation processing unit 51 included in the control unit 50 of the gripping device 1 according to the first embodiment.

[0056] The admittance control calculation unit 51a1 adjusts the parameters of the virtual spring-mass-damper system by solving the differential equation shown in Equation 1. Note that ΔF is the difference between the force command value SVf and the grip force detection value PVf, M (gain K11) is the mass, C (gain K12) is the damping coefficient of the damper, K (gain K13) is the spring constant of the spring, and x is the displacement.

[0057]

number

[0058] The admittance control calculation unit 51a1 calculates the difference between the force command value SVf and the grip force detection value PVf using the addition / subtraction block A11. The result calculated in the integration block B11 (gain K11) is then calculated in the gain block B13 (gain K12) and fed back to the addition / subtraction block A13. The result calculated in the integration block B11 is then calculated in the integration block B12, and the calculated result is then calculated in the gain block B14 (gain K13) and fed back to the addition / subtraction block A12. The calculation result is then output as the displacement command value SVd. In addition to the admittance control by the admittance control calculation unit 51a1 described above, force control may also be performed in which the displacement command value SVd is calculated from the grip force detection value PVf using only the spring constant K, for example.

[0059] The admittance control calculation unit 51a1 is an example of a force control calculation unit that converts a force command value SVf into a displacement command value SVd. The method of converting the force command value SVf into the displacement command value SVd in the force control calculation unit is not limited to the admittance control calculation unit 51a1, and various other methods can be applied.

[0060] (Integral calculation unit 51a2) The integral calculation unit 51a2 integrates the displacement command value SVd output from the admittance control calculation unit 51a1 and converts it into a position command value SVθ. The admittance control calculation unit 51a1 and the integral calculation unit 51a2 adjust the positions of the first finger 21a and the second finger 21b so that the grip force detection value PVf balances with the force command value SVf.

[0061] (Position speed calculation unit 51a3) The position and velocity calculation unit 51a3 calculates and outputs a current command value SVi such that the first finger 21a and the second finger 21b are positioned at the position of the position command value SVθ output from the integral calculation unit 51a2. The position and velocity calculation unit 51a3 calculates (generates) the current command value SVi such that the position detection value PVθ matches the position command value SVθ. Specifically, the position and velocity calculation unit 51a3 performs P (Proportional) control for position and PI (Proportional-Integral) control for velocity. FIG. 6 is a diagram illustrating the functional configuration of the position and velocity calculation unit 51a3 of the calculation processing unit 51 included in the control unit 50 of the gripping device 1 according to the first embodiment.

[0062] The position and speed calculation unit 51a3 uses an addition / subtraction block A21 to determine the difference between the position command value SVθ and the position detection value PVθ. The position and speed calculation unit 51a3 then performs calculations using a gain block B21 (gain K21) and calculates the difference from the speed detection value PVv using an addition / subtraction block A22. The position and speed calculation unit 51a3 then calculates the determined difference using a gain block B22 (gain K22) and an integration block B23 (gain K23), and adds the calculated results together in an addition / subtraction block A23. The position and speed calculation unit 51a3 then outputs a current command value SVi. Note that gains such as gain K21 are determined appropriately taking into consideration the system response, etc.

[0063] (Current calculation section 51a4) The current calculation unit 51a4 converts the current command value SVi output from the position / speed calculation unit 51a3 into a current manipulation value MVi. The current calculation unit 51a4 calculates (generates) the current manipulation value MVi so that the current detection value PVi matches the current command value SVi. Specifically, the current calculation unit 51a4 performs PI control on the current. FIG. 7 is a diagram illustrating the functional configuration of the current calculation unit 51a4 of the calculation processing unit 51 included in the control unit 50 of the gripping device 1 according to the first embodiment.

[0064] The current calculation unit 51a4 calculates the difference between the current command value SVi and the current detection value PVi using the addition / subtraction block A31. The current calculation unit 51a4 then calculates the calculated difference using the gain block B31 (gain K31) and the integration block B32 (gain K32), and adds the calculated results using the addition / subtraction block A32. The current calculation unit 51a4 then outputs the current manipulation value MVi.

[0065] [Force command generation unit 51b] The force command generating unit 51b generates a force command value SVf based on the grip force detection value PVf. Fig. 8 is a flow diagram illustrating the processing of the force command generating unit 51b of the arithmetic processing unit 51 included in the control unit 50 of the gripping device 1 according to the first embodiment. Fig. 9 is a diagram illustrating the operation of the gripping device 1 according to the first embodiment.

[0066] The vertical axis in Fig. 9 represents the force command value SVf or the grip force detection value PVf, and the horizontal axis in Fig. 9 represents the time from when contact is detected.

[0067] (Step S10) First, the force command generating unit 51b determines whether or not contact with the gripping target TGT of the first finger portion 21a and the second finger portion 21b of the gripping unit 20 has been detected. For example, when the gripping force detection value PVf is greater than a predetermined value, the force command generating unit 51b determines that the first finger portion 21a and the second finger portion 21b of the gripping unit 20 have made contact.

[0068] If the force command generating unit 51b detects that the first finger portion 21a and the second finger portion 21b have contacted the grasp target TGT (Yes in step S10), the force command generating unit 51b proceeds to step S20. If the force command generating unit 51b has not detected that the first finger portion 21a and the second finger portion 21b have contacted the grasp target TGT (No in step S10), the force command generating unit 51b repeats step S10.

[0069] (Step S20) Next, the force command generation unit 51b outputs the reference command value F0 to the operation value calculation unit 51a as the force command value SVf. The operation value calculation unit 51a calculates the current operation value MVi using the reference command value F0 as the force command value SVf.

[0070] (Step S30) Next, the force command generating unit 51b starts measuring time. It is desirable that step S30 be performed simultaneously with step S20 or as soon as possible after step S20 is performed.

[0071] (Step S40) Next, the force command generating unit 51b determines whether the absolute value of the difference between the grip force detection value PVf and the reference response value is less than a threshold value. Here, the reference response value is the grip force detection value PVf with respect to the time from contact when gripping a gripping target TGT of a reference hardness. For example, the reference response value may be an actually measured value or a theoretically calculated value. Note that an arbitrary value may be set as the reference response value.

[0072] Figure 9 shows the reference response value versus time as line Lpn. If the grip force detection value PVf is greater than line Lpn, it is estimated that the gripping object TGT is harder than the reference hardness. If the grip force detection value PVf is smaller than line Lpn, it is estimated that the gripping object TGT is softer than the reference hardness.

[0073] For example, in Fig. 9, the line Lph represents the detected grip force value PVf when gripping a gripping object TGT that is harder than the reference hardness, and the line Lps represents the detected grip force value PVf when gripping a gripping object TGT that is softer than the reference hardness.

[0074] If the absolute value of the difference between the grip force detection value PVf and the reference response value is less than the threshold value (Yes in step S40), the force command generator 51b proceeds to step S50. If the absolute value of the difference between the grip force detection value PVf and the reference response value is equal to or greater than the threshold value (No in step S40), the force command generator 51b proceeds to step S60.

[0075] (Step S50) Next, the force command generation unit 51b determines whether the time elapsed since the contact was detected is equal to or greater than the threshold time ta. If the time elapsed since the contact was detected is equal to or greater than the threshold time ta (Yes in step S50), the force command generation unit 51b ends the process. If the time elapsed since the contact was detected is less than the threshold time ta (No in step S50), the force command generation unit 51b returns to step S40 and repeats the process.

[0076] (Step S60) If the absolute value of the difference between the grip force detection value PVf and the reference response value is equal to or greater than the threshold value (No in step S40), the force command generation unit 51b changes the force command value SVf to an updated command value and outputs it. For example, the force command generation unit 51b increases the updated command value when the gripping object TGT is harder than the reference gripping object TGT. By increasing the updated command value above the reference command value, the gripping device 1 can grip the hard gripping object TGT tightly. Furthermore, the force command generation unit 51b decreases the updated command value when the gripping object TGT is softer than the reference gripping object TGT. By decreasing the updated command value below the reference command value, the gripping device 1 can grip the soft gripping object TGT gently.

[0077] The operation of the gripping device 1 according to the first embodiment will be described with reference to FIG. 9. Line Lpn indicates the time response of the reference response value. Line Lph indicates the detected grip force value PVf when a gripping object TGT that is harder than the standard is gripped, and line Lps indicates the detected grip force value PVf when a gripping object TGT that is softer than the standard is gripped. Line Lsn indicates the reference command value. Line Lsh indicates the force command value SVf when a gripping object TGT that is harder than the standard is gripped, and line Lss indicates the force command value SVf when a gripping object TGT that is softer than the standard is gripped. Note that lines Lsh and Lss are shown shifted up and down to clearly distinguish them from line Lsn at the reference command value F0.

[0078] When the first finger 21a and the second finger 21b come into contact with the grasp target TGT, the grasp force detection value PVf increases over time. Here, in the case of a grasp target TGT that is harder than the reference hardness, the grasp force detection value PVf increases quickly relative to the reference response value (line Lph). In addition, in the case of a grasp target TGT that is softer than the reference hardness, the grasp force detection value PVf decreases relative to the reference response value (line Lps).

[0079] Here, suppose that at time t1, the absolute value of the difference between line Lph and line Lpn, i.e., the absolute value of the difference between the grip force detection value PVf and the reference response value, becomes equal to or greater than the threshold value Δf. Then, in step S60, the force command generator 51b changes the force command value SVf from the reference command value F0 to the updated command value F1, as shown by line Lsh.

[0080] Furthermore, at time t2, if the absolute value of the difference between line Lps and line Lpn, i.e., the absolute value of the difference between the grip force detection value PVf and the reference response value, becomes equal to or greater than the threshold value Δf, then force command generator 51b changes force command value SVf from reference command value F0 to updated command value F2 in step S60, as shown by line Lss.

[0081] Furthermore, the threshold time ta is set to, for example, the time at which the reference response value becomes the reference value Fa (=0.8×F0), which is 0.8 times the reference command value F0. If the absolute value of the difference between the grip force detection value PVf and the reference response value does not become equal to or greater than the threshold value Δf by that time, in step S50, the force command generator 51b ends the processing and holds the force command value SVf at the reference command value F0. The threshold time ta may be determined taking into consideration the processing time, response, etc.

[0082] The update command value may be set to a different value when the object is harder or softer than the reference, or may be changed depending on the time it takes for the difference to exceed the threshold value.

[0083] <Actions and Effects> The gripping device 1 according to the first embodiment can change the gripping force depending on the hardness of the gripping object TGT. Specifically, the gripping device 1 according to the first embodiment can grip a hard gripping object TGT strongly and a soft gripping object TGT gently. Therefore, the gripping device 1 according to the first embodiment can accurately and stably hold gripping objects of different hardness. The gripping device 1 according to the first embodiment is particularly suitable for gripping gripping objects TGT with large differences in hardness.

[0084] Furthermore, according to the gripping device 1 of the first embodiment, the gripping target TGT can be gripped stably with a constant gripping force by controlling using the gripping force detection value PVf detected by the force detection unit 30. Furthermore, according to the gripping device 1 of the first embodiment, the gripping target TGT can be gripped stably with a low gripping force by controlling using the gripping force detection value PVf detected by the force detection unit 30.

[0085] Furthermore, according to the gripping device 1 of the first embodiment, even if the gripping positions of the first finger portion 21a and the second finger portion 21b change significantly and are significantly affected by the cogging torque that depends on the positions of the motor's magnet and iron core, the influence of the motor's cogging torque, which is a position-dependent disturbance, can be compensated for by controlling using the admittance control calculation unit 51a1.

[0086] <<Second embodiment>> The gripping device according to the second embodiment differs from the gripping device 1 according to the first embodiment in the processing in the force command generating unit 51b.

[0087] Fig. 10 is a flow diagram illustrating the processing of the force command generating unit 51b of the arithmetic processing unit 51 included in the control unit 50 of the gripping device according to the second embodiment. Fig. 11 is a diagram illustrating the operation of the gripping device according to the second embodiment.

[0088] The vertical axis in Fig. 11 represents the force command value SVf or the grip force detection value PVf, and the horizontal axis in Fig. 11 represents the time from the detection of contact.

[0089] Steps S10, S20, and S30 are the same as the processes in the force command generating unit 51b of the gripping device 1 according to the first embodiment, and therefore descriptions thereof will be omitted.

[0090] (Step S140) The force command generation unit 51b determines whether the time elapsed since the contact was detected is equal to or greater than the threshold time tb. In other words, the force command generation unit 51b determines whether a predetermined time has elapsed. If the time elapsed since the contact was detected is equal to or greater than the threshold time tb (Yes in step S140), the force command generation unit 51b proceeds to step S150. In other words, the force command generation unit 51b proceeds to step S150 after a predetermined time has elapsed since the contact was detected. If the time elapsed since the contact was detected is less than the threshold time tb (No in step S140), the force command generation unit 51b repeats the processing of step S140. The threshold time tb may be set as appropriate within a range that allows for determination.

[0091] (Step S150) The force command generating unit 51b outputs an update command value based on the grip force detection value PVf at the threshold time. For example, if the grip force detection value PVf at the threshold time is large, it is determined that the gripping object TGT is hard. Then, the force command generating unit 51b sets an update command value higher than the reference command value as the force command value SVf. On the other hand, if the grip force detection value PVf at the threshold time is small, it is determined that the gripping object TGT is softer than the reference hardness. Then, the force command generating unit 51b sets an update command value lower than the standard command value as the force command value SVf. When the processing of step S150 is completed, the force command generating unit 51b ends the processing.

[0092] The operation of the gripping device 1 according to the second embodiment will be described with reference to FIG. 11. Line Lpn1 represents the detected gripping force value PVf when a gripping object TGT of standard hardness is gripped. Line Lph represents the detected gripping force value PVf when a gripping object TGT harder than the standard is gripped, and line Lps represents the detected gripping force value PVf when a gripping object TGT softer than the standard is gripped. Line Lsn represents the reference command value. Line Lsh represents the force command value SVf when a gripping object TGT harder than the standard is gripped, and line Lss represents the force command value SVf when a gripping object TGT softer than the standard is gripped. Note that lines Lsh and Lss are shown shifted up and down to clearly distinguish them from line Lsn at the reference command value F0.

[0093] When the first finger 21a and the second finger 21b come into contact with the grasp target TGT, the grasp force detection value PVf increases over time. Here, in the case of a grasp target TGT that is harder than the reference hardness, the grasp force detection value PVf increases quickly relative to the reference response value (line Lph). In addition, in the case of a grasp target TGT that is softer than the reference hardness, the grasp force detection value PVf decreases relative to the reference response value (line Lps).

[0094] The force command generation unit 51b changes the force command value SVf to an updated command value in accordance with the grip force detected value PVf at the threshold time tb. For example, when a gripping target TGT having a harder hardness than the standard hardness is gripped, the grip force detected value PVf becomes large at the threshold time tb. Therefore, the force command generation unit 51b updates the force command value SVf from the reference command value F0 to an updated command value F11 that is larger than the reference command value F0. For example, when a gripping target TGT having a softer hardness than the standard hardness is gripped, the grip force detected value PVf becomes small at the threshold time tb. Therefore, the force command generation unit 51b updates the force command value SVf from the reference command value F0 to an updated command value F12 that is smaller than the reference command value F0.

[0095] For example, the value of the update command value may be set as a first update command value if the grip force detection value PVf at the threshold time tb is 0.8 times or more the reference command value F0, and as a second update command value if it is 0.4 times or less the reference command value F0. If the value is greater than 0.4 times but less than 0.8 times the reference command value F0, the reference command value F0 may be left unchanged and used as the update command value.

[0096] The value of the update command value may be calculated, for example, according to the grip force detection value PVf at the threshold time tb. For example, the value of the update command value may be calculated using Equation 2. In Equation 2, F0 represents the value of the reference command value, and PVf represents the value of the grip force detection value PVf at the threshold time tb.

[0097] F0 + coefficient × (PVf - 0.5 × F0) (Equation 2)

[0098] <Actions and Effects> According to the gripping device of the second embodiment, the same actions and effects as those of the gripping device 1 of the first embodiment can be obtained.

[0099] <<Third Embodiment>> The gripping device according to the third embodiment differs from the gripping devices according to the first and second embodiments in the processing in the force command generating unit 51b.

[0100] Fig. 12 is a flow diagram illustrating the processing of the force command generating unit 51b of the arithmetic processing unit 51 included in the control unit 50 of the gripping device according to the third embodiment. Fig. 13 is a diagram illustrating the operation of the gripping device according to the third embodiment.

[0101] The vertical axis in Fig. 13 represents the force command value SVf or the grip force detection value PVf, and the horizontal axis in Fig. 13 represents the time from the detection of contact.

[0102] Steps S10, S20, and S30 are the same as the processes in the force command generating unit 51b of the gripping device 1 according to the first embodiment, and therefore descriptions thereof will be omitted.

[0103] In step S20, the reference command value is a reference command value F20, which is the grip force detection value PVf when gripping the gripping object TGT (first gripping object), which is assumed to be the hardest among all possible gripping objects.

[0104] (Step S240) The force command generation unit 51b determines whether the time elapsed since the contact was detected is equal to or greater than the threshold time tc. In other words, the force command generation unit 51b determines whether a predetermined time has elapsed. If the time elapsed since the contact was detected is equal to or greater than the threshold time tc (Yes in step S240), the force command generation unit 51b proceeds to step S250. In other words, the force command generation unit 51b proceeds to step S250 after a predetermined time has elapsed since the contact was detected. If the time elapsed since the contact was detected is less than the threshold time tc (No in step S240), the force command generation unit 51b repeats the processing of step S240. The threshold time tc may be set as appropriate within a range that allows for determination.

[0105] (Step S250) The force command generator 51b outputs the grip force detected value PVf at the threshold time tc as an update command value. When the process of step S250 ends, the force command generator 51b ends the process.

[0106] The operation of the gripping device according to the third embodiment will be described with reference to FIG. 13. Line Lp1 represents the gripping force detection value PVf when gripping a gripping object TGT (first gripping object), which is assumed to be the hardest among all possible gripping objects. Line Lp2 represents the gripping force detection value PVf when gripping a gripping object TGT (second gripping object), which is softer than the first gripping object. Line Lp3 represents the gripping force detection value PVf when gripping a gripping object TGT (third gripping object), which is even softer than the second gripping object. Line Ls1 represents the force command value SVf when gripping the first gripping object, line Ls2 represents the force command value SVf when gripping the second gripping object, and line Ls3 represents the force command value SVf when gripping the third gripping object. Line Ls2 is shown shifted at the reference command value F20 and the threshold time tc to clarify the difference between the lines. The line Ls3 is shifted at the reference command value F20 to clarify the difference between the lines.

[0107] When the first finger 21a and the second finger 21b come into contact with the gripping target TGT, the gripping force detection value PVf increases over time. The force command generator 51b outputs the gripping force detection value PVf at the threshold time tc as an update command value for the force command value SVf.

[0108] For example, when the first object to be grasped is grasped, the grip force detection value PVf is approximately equal to the reference command value F20 at the threshold time tc, and therefore the force command generation unit 51b outputs the reference command value F20 as the update command value. When the second object to be grasped is grasped, the force command generation unit 51b outputs an update command value F21, which is the grip force detection value PVf at the threshold time tc. When the third object to be grasped is grasped, the force command generation unit 51b outputs an update command value F22, which is the grip force detection value PVf at the threshold time tc.

[0109] <Actions and Effects> The gripping device according to the third embodiment can provide the same functions and effects as the gripping device 1 according to the first embodiment. Furthermore, particularly in the third embodiment, the processing in the force command generating unit 51b is simplified.

[0110] <<Fourth Embodiment>> The gripping device according to the fourth embodiment includes a control unit 150 instead of the control unit 50 of the gripping device 1 according to the first embodiment. Moreover, the gripping device according to the fourth embodiment includes an arithmetic processing unit 151 instead of the arithmetic processing unit 51 of the gripping device 1 according to the first embodiment. Furthermore, the gripping device according to the fourth embodiment includes a motor operation data acquisition unit 153 instead of the motor operation data acquisition unit 53 of the gripping device 1 according to the first embodiment. FIG. 14 is a diagram illustrating the functional configuration of the gripping device according to the fourth embodiment.

[0111] The motor operation data acquiring unit 153 acquires, from the motor driving unit 40, the drive current value Im of the supply power Pd that the motor driving unit 40 supplies to the power unit 11 (motor 11m). Then, the motor operation data acquiring unit 153 outputs the current detection value PVi to the calculation processing unit 151.

[0112] The arithmetic processing unit 151 includes an operation value calculation unit 151a and a force command generation unit 51b. It differs from the arithmetic processing unit 51 of the gripping device 1 according to the first embodiment in that it includes an operation value calculation unit 151a instead of the operation value calculation unit 51a. Fig. 15 is a diagram illustrating the functional configuration of the arithmetic processing unit 151 included in the control unit of the gripping device according to the fourth embodiment.

[0113] The calculation processing unit 151 calculates the amount of manipulation for operating the drive unit 10 so that the control value becomes the target value. Specifically, the calculation processing unit 151 calculates the current manipulation value MVi so that the grip force detection value PVf, which is the control value, becomes the grip force value of the target value.

[0114] [Operation value calculation unit 151a] The operation value calculation unit 151a calculates the current operation value MVi so that the gripping force detection value PVf becomes the force command value SVf set by the force command generation unit 51b. Fig. 16 is a diagram illustrating the functional configuration of the operation value calculation unit 151a of the calculation processing unit 151 included in the control unit 150 of the gripping device according to the fourth embodiment.

[0115] The operation value calculation unit 151a includes a force calculation unit 151a1 and a current calculation unit 51a4. Here, the force calculation unit 151a1 will be described.

[0116] (Force calculation section 151a1) The force calculation unit 151a1 converts the force command value SVf into a current command value SVi. The force calculation unit 151a1 calculates (generates) the current command value SVi so that the gripping force detection value PVf matches the force command value SVf. Fig. 17 is a diagram illustrating the functional configuration of the force calculation unit 151a1 of the calculation processing unit 151 included in the control unit 150 of the gripping device according to the fourth embodiment.

[0117] The force calculation unit 151a1 calculates a current command value SVi so as to reduce the difference between the force command value SVf and the grip force detection value PVf. Specifically, the force calculation unit 151a1 performs PI control on the force. The force calculation unit 151a1 calculates the difference between the force command value SVf and the grip force detection value PVf using the addition / subtraction block A41. The force calculation unit 151a1 then performs calculations using the gain block B41 (gain K41) and the integration block B42 (gain K42), and adds the calculation results together in the addition / subtraction block A42. The force calculation unit 151a1 then outputs the current command value SVi.

[0118] <Actions and Effects> The gripping device according to the fourth embodiment can change the gripping force depending on the hardness of the gripping object TGT. Specifically, the gripping device according to the fourth embodiment can grip a hard gripping object TGT strongly and a soft gripping object TGT gently. Therefore, the gripping device according to the fourth embodiment can accurately and stably hold gripping objects of different hardness.

[0119] Furthermore, according to the gripping device of the fourth embodiment, the gripping target TGT can be gripped stably with a constant gripping force by controlling using the gripping force detection value PVf detected by the force detection unit 30. Furthermore, according to the gripping device of the fourth embodiment, the gripping target TGT can be gripped stably with a low gripping force by controlling using the gripping force detection value PVf detected by the force detection unit 30.

[0120] <<Fifth Embodiment>> In order to perform operations up to contacting the object to be grasped TGT at high speed, the grasping device of the fifth embodiment uses position and speed control until it contacts the object to be grasped TGT, and then uses force control after it contacts the object to be grasped TGT.

[0121] The gripping device according to the fifth embodiment includes an operation value calculation unit 251a instead of the operation value calculation unit 51a of the gripping device 1 according to the first embodiment. The operation value calculation unit 251a further includes a position command value generation unit 251a5, a contact determination unit 251a6, and a switching unit 251a7 in addition to the operation value calculation unit 51a. Fig. 18 is a diagram illustrating the functional configuration of the operation value calculation unit 251a of the processing calculation unit included in the control unit of the gripping device according to the fifth embodiment.

[0122] (Position command value generating unit 251a5) The position command value generator 251a5 generates a position command value SVθ2 for performing position control. The position command value generator 251a5 calculates (generates) a position command value SVθ2 that changes at a constant rate up to a constant value. Fig. 19 is a diagram illustrating the functional configuration of the position command value generator 251a5 of the operation value calculator 251a included in the control unit of the gripping device according to the fifth embodiment.

[0123] The position command value generator 251a5 calculates a position command value SVθ2 from the position displacement command value SVdθ. The position displacement command value SVdθ corresponds to the derivative of the position command value SVθ2. The position command value SVθ2 increases in proportion to time. The position command value SVθ2 represents the distance between the first finger portion 21a and the second finger portion 21b. As the position command value SVθ2 increases, the distance between the first finger portion 21a and the second finger portion 21b becomes narrower. The value then changes until the first finger portion 21a and the second finger portion 21b finally come into contact with each other, that is, until the distance between the first finger portion 21a and the second finger portion 21b becomes zero.

[0124] The position command value generator 251a5 integrates the position displacement command value SVdθ in an integration block B51, and then limits the value to a certain value or less by a limiting block B52, specifically, a value at which the first finger portion 21a and the second finger portion 21b come into contact with each other, and outputs a position command value SVθ2.

[0125] The above-described method of generating the position command value SVθ2 in the position command value generating unit 251a5 is one example of a method of generating the position command value SVθ2, and the position command value SVθ2 may be generated using another method.

[0126] (Contact determination unit 251a6) The contact determination unit 251a6 determines whether the gripping target TGT has come into contact with the first finger 21a and the second finger 21b based on the gripping force detection value PVf, and outputs the determination result to the switching unit 251a7 as a switch signal SW.

[0127] (Switching unit 251a7) Switching unit 251a7 outputs either position command value SVθ or position command value SVθ2 as position command value SVθi to position and velocity calculation unit 51a3 based on switch signal SW. One input of switching unit 251a7 is connected to integral calculation unit 51a2, and the other is connected to position command value generation unit 251a5. Switching unit 252a7 has an output connected to position and velocity calculation unit 51a3.

[0128] In the gripping device according to the fifth embodiment, the contact determination unit 251a6 and the switching unit 251a7 switch control before and after the first finger unit 21a and the second finger unit 21b come into contact with the gripping object TGT. Specifically, until the first finger unit 21a and the second finger unit 21b come into contact with the gripping object TGT, the switching unit 251a7 inputs the position command value SVθ2 output by the position command value generation unit 251a5 to the position / velocity calculation unit 51a3 as the position command value SVθi. Therefore, until the first finger unit 21a and the second finger unit 21b come into contact with the gripping object TGT, the gripping device according to the fifth embodiment controls the drive unit 10 by position / velocity control.

[0129] The gripping device of the fifth embodiment can move the first finger portion 21a and the second finger portion 21b at high speed by controlling the drive unit 10 using position and speed control until the first finger portion 21a and the second finger portion 21b come into contact with the gripping object TGT.

[0130] Furthermore, after the first finger portion 21a and the second finger portion 21b come into contact with the grasp target TGT, the switching unit 251a7 inputs the position command value SVθ output by the integral calculation unit 51a2 to the position / velocity calculation unit 51a3 as the position command value SVθi. Therefore, after the first finger portion 21a and the second finger portion 21b come into contact with the grasp target TGT, the grasp device according to the fifth embodiment controls the drive unit 10 by force control.

[0131] The gripping device of the fifth embodiment controls the drive unit 10 by force control after the first finger portion 21a and the second finger portion 21b come into contact with the gripping object TGT, thereby slowly moving the first finger portion 21a and the second finger portion 21b and delicately gripping the gripping object TGT.

[0132] <Actions and Effects> The gripping device according to the fifth embodiment can achieve both high-speed position and speed control and sensitive force control in addition to the effects and advantages of the gripping device 1 according to the first embodiment.

[0133] <<Sixth Embodiment>> In order to perform operations up to contacting the object to be grasped TGT at high speed, the grasping device of the sixth embodiment uses position and speed control until it contacts the object to be grasped TGT, and then uses force control after it contacts the object to be grasped TGT.

[0134] The gripping device according to the sixth embodiment includes an operation value calculation unit 351a instead of the operation value calculation unit 51a of the gripping device 1 according to the first embodiment. The operation value calculation unit 351a further includes a position command value generation unit 251a5, a contact determination unit 251a6, and a switching unit 351a7 compared to the operation value calculation unit 151a of the gripping device according to the fourth embodiment. Furthermore, the gripping device according to the sixth embodiment includes a position velocity calculation unit 51a3 for converting a position command value SVθ2 output from the position command value generation unit 251a5 into a current command value SVi2. FIG. 20 is a diagram illustrating the functional configuration of the operation value calculation unit 351a of the processing calculation unit included in the control unit of the gripping device according to the sixth embodiment.

[0135] (Switching unit 351a7) Based on the switch signal SW, the switching unit 351a7 outputs either the current command value SVi or the current command value SVi2 as the current command value SVii to the current calculation unit 51a4. One input of the switching unit 351a7 is connected to the force calculation unit 151a1, and the other is connected to the position / velocity calculation unit 51a3. The output of the switching unit 352a7 is connected to the current calculation unit 51a4.

[0136] In the gripping device according to the sixth embodiment, the contact determination unit 351a6 and the switching unit 351a7 switch control before and after the first finger unit 21a and the second finger unit 21b come into contact with the gripping object TGT. Specifically, until the first finger unit 21a and the second finger unit 21b come into contact with the gripping object TGT, the switching unit 351a7 inputs the current command value SVi2 output by the position and speed calculation unit 51a3 as the current command value SVii to the current calculation unit 51a4. Therefore, until the first finger unit 21a and the second finger unit 21b come into contact with the gripping object TGT, the gripping device according to the sixth embodiment controls the drive unit 10 by position and speed control.

[0137] The gripping device of the sixth embodiment can move the first finger portion 21a and the second finger portion 21b at high speed by controlling the drive unit 10 using position and speed control until the first finger portion 21a and the second finger portion 21b come into contact with the gripping object TGT.

[0138] Furthermore, after the first finger portion 21a and the second finger portion 21b come into contact with the grasp target TGT, the current command value SVi output by the force calculation unit 151a1 is input as the current command value SVii to the current calculation unit 51a4 by the switching unit 351a7. Therefore, after the first finger portion 21a and the second finger portion 21b come into contact with the grasp target TGT, the grasping device according to the sixth embodiment controls the drive unit 10 by force control.

[0139] The gripping device of the sixth embodiment controls the drive unit 10 by force control after the first finger portion 21a and the second finger portion 21b come into contact with the gripping object TGT, thereby slowly moving the first finger portion 21a and the second finger portion 21b and delicately gripping the gripping object TGT.

[0140] <Actions and Effects> The gripping device according to the sixth embodiment can achieve the functions and effects of the gripping device according to the fourth embodiment, as well as high-speed position and speed control and delicate force control.

[0141] <<Seventh Embodiment>> The gripping device according to the seventh embodiment includes an operation value calculation unit 451a instead of the operation value calculation unit 251a of the gripping device according to the fifth embodiment.

[0142] The operation value calculation unit 451a further includes a value holding unit 451a8 and an addition / subtraction block A61 in addition to the operation value calculation unit 251a of the gripping device according to the fifth embodiment. Fig. 21 is a diagram illustrating the functional configuration of the operation value calculation unit 451a of the processing calculation unit included in the control unit of the gripping device according to the seventh embodiment.

[0143] (value holding unit 451a8) The value holding unit 451a8 outputs, based on the switch signal SW, the position detection value PVθ when the grasp target TGT comes into contact with the first finger portion 21a and the second finger portion 21b, as the position command value SVθ0.

[0144] (Addition / Subtraction Block A61) The addition / subtraction block A61 adds the position command value SVθ output by the integral calculation unit 51a2 and the position command value SVθ0 output by the value holding unit 451a8, and outputs the position command value SVθi to the position / speed calculation unit 51a3.

[0145] The operation of the gripping device according to the seventh embodiment will be described. Fig. 22 is a diagram illustrating the operation of the gripping device according to the seventh embodiment. The vertical axis in Fig. 22 represents position values ​​such as the position command value SVθ and the position detection value PVθ. This also applies to the vertical axes in Figs. 23, 24, and 25. The horizontal axis in Fig. 22 represents the time from the start of the operation. This also applies to the horizontal axes in Figs. 23, 24, and 25.

[0146] 22, line Lsv indicates the position command value SVθi input to position / velocity calculation unit 51a3, and line Lpv indicates the position detection value PVθ. Time td indicates the time when first finger portion 21a and second finger portion 21b come into contact with gripping object TGT.

[0147] The operation value calculation unit 451a changes the position command value SVθ to the position detected value PVθ at time td when the first finger portion 21a and the second finger portion 21b come into contact with the grasp target TGT. That is, as shown by arrow A in FIG. 22, the operation value calculation unit 451a changes the position command value SVθ to the position detected value PVθ at time td. By changing the position command value SVθ to the position detected value PVθ at time td by the operation value calculation unit 451a, it is possible to reduce fluctuations in the position detected value PVθ as shown by Ra. Furthermore, it is possible to hasten the convergence of the position detected value PVθ.

[0148] On the other hand, a case where the position command value SVθ is not changed will be described using a gripping device of a comparative example in Fig. 23. In the gripping device of the comparative example, the position command value SVθ is not changed. In Fig. 23, line Lsvz represents the position command value SVθi input to the position / velocity calculation unit 51a3 of the gripping device of the comparative example, and line Lpvz represents the position detection value PVθ of the gripping device of the comparative example.

[0149] A graph summarizing the position command values ​​SVθ of the gripping device according to the seventh embodiment and the gripping device of the comparative example is shown in Fig. 24. Also, a graph summarizing the position detection values ​​PVθ of the gripping device according to the seventh embodiment and the gripping device of the comparative example is shown in Fig. 25.

[0150] In the gripping device of the comparative example, the position command value SVθ increases at time td, causing the position detection value PVθ to hunt significantly as shown by Rb. In addition, the convergence of the position detection value PVθ also slows.

[0151] The gripping device according to the seventh embodiment can suppress hunting when switching control, compared to the gripping device of the comparative example. By suppressing hunting, the gripping device according to the seventh embodiment can grip the gripping object TGT without significantly crushing the gripping object TGT after gripping it. Furthermore, the gripping device according to the seventh embodiment can converge more quickly after switching control, compared to the gripping device of the comparative example.

[0152] <Actions and Effects> According to the gripping device of the seventh embodiment, in addition to the effects and advantages of the gripping device of the fifth embodiment, it is possible to prevent the gripping object TGT from being crushed when gripping the gripping object TGT.

[0153] Although the gripping device has been described above using an embodiment, the present invention is not limited to the above embodiment. Various modifications and improvements, such as combinations with or substitutions for part or all of other embodiments, are possible within the scope of the present invention. [Explanation of symbols]

[0154] 1 Gripping device 10 Drive unit 11 Power section 11e encoder 11m motor 20 Gripping part 21a 1st finger 21b 2nd finger 30 Force detection unit 31a First force sensor 31b Second force sensor 40 Motor drive unit 50, 150 control section 51, 151 Processing unit 51a, 151a, 251a Operation value calculation unit 51a1 Admittance control calculation unit 51a2 Integral calculation section 51a3 Position speed calculation section 51a4 Current calculation section 51b Force command generation section 52 Motor control unit 53, 153 Motor operation data acquisition unit 54 Force measurement data acquisition unit 151a1 Force calculation section 251a5 Position command value generation unit 251a6 Contact determination part 251a7, 252a7, 351a7, 352a7 Switching section 351a, 451a Operation value calculation unit 451a8 Value storage unit

Claims

1. a motor that rotates in response to an operation value; a gripping unit including a first finger portion and a second finger portion, the gripping unit gripping an object with the first finger portion and the second finger portion by changing the distance between the first finger portion and the second finger portion using the motor; a force detection unit that detects a gripping force with which the first finger unit and the second finger unit grip the object when the object is gripped by the first finger unit and the second finger unit; a control unit that outputs the operation value so that the magnitude of the gripping force detected by the force detection unit becomes a command value; Equipped with The control unit controlling the gripping unit with the command value as a reference command value, and changing the command value from the reference command value to an updated command value based on a change in the gripping force detected by the force detection unit after the gripping unit has gripped the object; changing the command value to the updated command value based on a grip force detection value detected by the force detection unit after a predetermined time has elapsed; updating the update command value to the grip force detection value; gripping device.

2. a motor that rotates in response to an operation value; a gripping unit including a first finger portion and a second finger portion, the gripping unit gripping an object with the first finger portion and the second finger portion by changing the distance between the first finger portion and the second finger portion using the motor; a force detection unit that detects a gripping force with which the first finger unit and the second finger unit grip the object when the object is gripped by the first finger unit and the second finger unit; Equipped with A control method for a gripping device that outputs the operation value so that the magnitude of the gripping force detected by the force detection unit becomes a command value, a step of controlling the gripping unit using the command value as a reference command value, and changing the command value from the reference command value to an updated command value based on a change in the gripping force detected by the force detection unit after the gripping unit has gripped the object; changing the command value to the updated command value based on a grip force detection value detected by the force detection unit after a predetermined time has elapsed; updating the update command value to the grip force detection value; A method for controlling a gripping device.

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