Grip device and grip device control method

Abstract

To provide a holding device capable of stably holding objects to held (holding objects) having different hardness levels.SOLUTION: A holding device includes: a motor which rotates in response to an operation value; a holding part which holds an object with a first finger part and a second finger part; a force detection part which detects a holding force of the first finger part and the second finger part holding the object when the object is held by the first finger part and the second finger part; and a control unit which outputs the operation value so that the force detection value of the holding force detected by the force detection part becomes a force command value. The control unit performs a step in which the operation value is calculated by a first gain setting for changing a clearance between the first finger part and the second finger part at high speed to be output; a step in which the operation value is calculated by a second gain setting for preventing the clearance from causing hunting to be output; and a step in which the operation value is calculated by a third gain setting for shortening a time for reducing the clearance to be output.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 robot hand that reliably detects contact of a fingertip with an object, estimates the physical properties of the object, and realizes danger avoidance control that is suited to the physical properties. Patent Document 1 also discloses adjusting a control gain so that the fingers of the hand do not damage the object they are in contact with. Patent Document 2 discloses a robot hand that adjusts a grip force control gain according to the rigidity of the object. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2019 / 244710 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-086313 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 capable of stably holding objects to be gripped that have different hardnesses. [Means for solving the problem]

[0007] In one aspect of the present disclosure, a gripping unit includes 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 by 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 force detection value of the gripping force detected by the force detection unit becomes a force command value, and the control unit controls the first finger unit and The gripping device performs the following steps: before detecting that the second finger portion has come into contact with the object, calculating and outputting the operation value using a first gain setting that changes the gap at high speed; after detecting that the first finger portion and the second finger portion have come into contact with the object, calculating and outputting the operation value using a second gain setting that prevents hunting of the gap; and when it is determined that the contacted object is soft, calculating and outputting the operation value using a third gain setting that shortens the time it takes for the gap to converge. [Effects of the Invention]

[0008] The gripping device of the present disclosure can 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 this embodiment. [Figure 2] FIG. 2 is a diagram illustrating the functional configuration of the gripping device according to this embodiment. [Figure 3] FIG. 3 is a diagram illustrating the functional configuration of the processing calculation unit included in the control unit of the gripping device according to this 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 this embodiment. [Figure 5]FIG. 5 is a diagram illustrating the functional configuration of the admittance control calculation unit of the processing calculation unit included in the control unit of the gripping device according to this embodiment. [Figure 6] FIG. 6 is a diagram illustrating the functional configuration of the position and velocity calculation unit of the processing calculation unit included in the control unit of the gripping device according to this embodiment. [Figure 7] FIG. 7 is a diagram illustrating the functional configuration of the current calculation unit of the processing calculation unit included in the control unit of the gripping device according to this embodiment. [Figure 8] FIG. 8 is a flowchart illustrating the processing of the processing calculation unit included in the control unit of the gripping device according to this embodiment. [Figure 9] FIG. 9 is a diagram illustrating the operation of the gripping device according to this embodiment. [Figure 10] FIG. 10 is a diagram illustrating the operation of the gripping device according to this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] <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-, Y-, and Z-axes (XYZ axes) is set in Fig. 1. For example, for a coordinate axis perpendicular to the paper surface of the drawing, a black circle within a circle of the coordinate axis indicates that the front side of the paper surface is the positive region of the coordinate axis. However, this coordinate system is defined for the purpose 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 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. 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 grips the object to be gripped TGT between the first finger portion 21a and the second finger portion 21b by the drive unit 10 changing the distance between the moving portion 12a and the moving portion 12b.

[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 the supply 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 the 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 this embodiment. Note that in Fig. 3, external components of the arithmetic processing unit 51 are collectively shown as control object OBJ of the arithmetic processing unit 51. The control object OBJ includes, 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, a force command generation unit 51b, and a determination unit 51c.

[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 this embodiment. Note that 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 this embodiment.

[0056] The admittance control calculation unit 51a1 adjusts the parameters of the virtual spring-mass-damper system model 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 is the mass, C is the damping coefficient of the damper, K is the spring constant of the spring, and x is the displacement.

[0057]

number

[0058] The admittance control calculation unit 51a1 includes an addition / subtraction block A11, an addition / subtraction block A12, an addition / subtraction block A13, an integration block B11, an integration block B12, a gain block B13, and a gain block B14. The addition / subtraction block outputs the result of adding or subtracting a plurality of inputs. The integration block outputs the result of integrating the inputs. The gain block outputs the result of multiplying the inputs by a gain. The same applies below.

[0059] The addition / subtraction block A11 calculates the difference between the force command value SVf and the grip force detection value PVf. The addition / subtraction block A11 outputs the calculation result to the addition / subtraction block A12. The addition / subtraction block A12 adds the output of the addition / subtraction block A11 and the output of the gain block B14. The addition / subtraction block A12 outputs the calculation result to the addition / subtraction block A13. The addition / subtraction block A13 adds the output of the addition / subtraction block A12 and the output of the gain block B13. The addition / subtraction block A13 outputs the calculation result to the integration block B11.

[0060] The integration block B11 integrates the output from the addition / subtraction block A13 and multiplies the integration result by a gain K11, and outputs the calculation result to the integration block B12 and the gain block B13.

[0061] The integration block B12 integrates the output from the integration block B11 and outputs the result. The integration block B12 outputs the calculation result, a displacement command value SVd, as the output of the admittance control calculation unit 51a1. The integration block B12 also outputs the calculation result to a gain block B14.

[0062] Gain block B13 multiplies the output of integration block B11 by gain K12 and outputs the result to addition / subtraction block A13. Gain block B14 multiplies the output of integration block B12 by gain K13 and outputs the result to addition / subtraction block A12.

[0063] The gain K11 corresponds to the mass M in Equation 1. The gain K12 corresponds to the damping coefficient C in Equation 1. The gain K13 corresponds to the spring constant K in Equation 1.

[0064] The determination unit 51c outputs a gain adjustment signal Sig to the integration block B11, the gain block B13, and the gain block B14. The integration block B11 sets a gain K11 based on the gain adjustment signal Sig. The gain block B13 sets a gain K12 based on the gain adjustment signal Sig. The gain block B14 adjusts the gain K13 based on the gain adjustment signal Sig.

[0065] The admittance control by the admittance control calculation unit 51a1 described above is an example of processing, and in addition to the above control, for example, force control may be performed to calculate a displacement command value SVd from the grip force detection value PVf using only the spring constant K.

[0066] 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.

[0067] (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.

[0068] (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 this embodiment.

[0069] The position / speed calculation unit 51a3 includes an addition / subtraction block A21, an addition / subtraction block A22, an addition / subtraction block A23, a gain block B21, a gain block B22, and an integration block B23.

[0070] The addition / subtraction block A21 calculates the difference between the position command value SVθ and the position detection value PVθ. The addition / subtraction block A21 outputs the calculation result to the gain block B21. The gain block B21 multiplies the output of the addition / subtraction block A21 by a gain K21 and outputs the result to the addition / subtraction block A22. The addition / subtraction block A22 calculates the difference between the output of the gain block B21 and the speed detection value PVv. The addition / subtraction block A22 outputs the calculation result to the gain block B22 and the integration block B23.

[0071] The gain block B22 multiplies the output of the addition / subtraction block A22 by a gain K22 and outputs the result to the addition / subtraction block A23. The integration block B23 integrates the output from the addition / subtraction block A22 and multiplies the integrated result by a gain K23. The integration block B23 outputs the calculation result to the addition / subtraction block A23.

[0072] The addition / subtraction block A23 calculates the sum of the output of the gain block B22 and the output of the integration block B23. The addition / subtraction block A23 then outputs the current command value SVi as the output of the position / speed calculation unit 51a3. Note that gains such as the gain K21 are determined appropriately taking into consideration the system response, etc.

[0073] (Current calculation unit 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 this embodiment.

[0074] The current calculation section 51a4 includes an addition / subtraction block A31, an addition / subtraction block A32, a gain block B31, and an integration block B32.

[0075] The addition / subtraction block A31 calculates the difference between the current command value SVi and the current detection value PVi, and outputs the calculation result to the gain block B31 and the integration block B32.

[0076] Gain block B31 multiplies the output of addition / subtraction block A31 by gain K31 and outputs the result to addition / subtraction block A32. Integration block B32 integrates the output from addition / subtraction block A31 and multiplies the integrated result by gain K32. Integration block B32 outputs the calculation result to addition / subtraction block A32.

[0077] The adder / subtractor block A32 calculates the sum of the output of the gain block B31 and the output of the integrator block B32. The adder / subtractor block A32 then outputs the current manipulation value MVi as the output of the current calculator 51a4. Note that gains such as the gain K31 are determined appropriately taking into consideration the system response, etc.

[0078] [Force command generation unit 51b] The force command generating unit 51b generates a force command value SVf and outputs the force command value SVf according to the expected hardness of the object to be grasped.

[0079] [Determination unit 51c] The determination unit 51c detects whether the grasp target TGT has come into contact with either the first finger portion 21a or the second finger portion 21b. The determination unit 51c also determines the hardness of the grasp target TGT. Furthermore, the determination unit 51c outputs a gain adjustment signal Sig to the admittance control calculation unit 51a1 based on the detection result and the determination result.

[0080] 8 is a flow diagram illustrating the processing of the arithmetic processing unit 51 included in the control unit 50 of the gripping device 1 according to this embodiment. At the stage when the gripping device 1 starts the processing, the first finger portion 21a and the second finger portion 21b are not in contact with the gripping target TGT.

[0081] (Step S10) When the calculation processing unit 51 starts processing, it sets the setting that determines the operation of the gripping device 1 to a high-speed opening / closing parameter setting that causes the first finger portion 21a and the second finger portion 21b to move at high speed. Specifically, the determination unit 51c included in the calculation processing unit 51 determines that the first finger portion 21a and the second finger portion 21b are not in contact with the gripping target TGT and outputs a gain adjustment signal Sig to reduce the spring constant K. That is, the determination unit 51c outputs the gain adjustment signal Sig to the gain block B14 to reduce the gain K13.

[0082] The gain block B14 receives the gain adjustment signal Sig and reduces the gain K13. The setting of the gain K13 set by the gain block B14 in step S10 is referred to as the first gain setting. The setting value of the gain K13 set by the gain block B14 in step S10 is referred to as the first gain setting value. When the gain K13 is reduced, the first finger 21a and the second finger 21b are controlled by the admittance control calculation unit 51a1 to move at high speed.

[0083] Note that the setting of the gain K13 when holding a gripping object TGT of standard hardness, for example, a gripping object TGT whose hardness is the median of the expected range, among the gripping objects TGT expected to be gripped by the gripping device 1, is referred to as the standard gain setting. The set value of the gain K13 when the standard gain setting is used is referred to as the standard gain setting value. The first gain setting is a setting for control prior to gripping the gripping object TGT, which places emphasis on moving the first finger portion 21a and the second finger portion 21b at high speed. Therefore, the first gain setting value is smaller than the standard gain setting value.

[0084] (Step S20) Next, the calculation processing unit 51 detects whether the first finger portion 21a and the second finger portion 21b have come into contact with the grasp target TGT. Specifically, the determination unit 51c included in the calculation processing unit 51 detects whether the first finger portion 21a and the second finger portion 21b have come into contact with the grasp target TGT based on the grip force detection value PVf.

[0085] For example, the determination unit 51c may detect that the first finger portion 21a and the second finger portion 21b have come into contact with the grasp target TGT when the grip force detection value PVf becomes larger than a predetermined threshold value.

[0086] In the above description, whether the first finger portion 21a and the second finger portion 21b have come into contact with the object to be grasped TGT is detected based on the gripping force detection value PVf, but it may also be detected based on, for example, at least one of the first gripping force value Fma and the second gripping force value Fmb.

[0087] If the arithmetic processing unit 51 detects that the first finger portion 21a and the second finger portion 21b have contacted the grasp object TGT (Yes in step S20), the process proceeds to step S30. If the arithmetic processing unit 51 does not detect that the first finger portion 21a and the second finger portion 21b have contacted the grasp object TGT (No in step S20), the process returns to step S20 and repeats the process.

[0088] (Step S30) Next, the calculation processing unit 51 changes the setting that determines the operation of the gripping device 1 to a hunting prevention parameter setting that prevents hunting when the first finger unit 21a and the second finger unit 21b operate. Specifically, the determination unit 51c included in the calculation processing unit 51 outputs a gain adjustment signal Sig to increase the spring constant K. That is, the determination unit 51c outputs the gain adjustment signal Sig to the gain block B14 to increase the gain K13.

[0089] The gain block B14 receives the gain adjustment signal Sig and increases the gain K13. The setting of the gain K13 set by the gain block B14 in step S30 is referred to as the second gain setting. The setting value of the gain K13 set by the gain block B14 in step S30 is referred to as the second gain setting value. When the gain K13 is increased, the first finger portion 21a and the second finger portion 21b are controlled by the admittance control calculation unit 51a1 to suppress hunting.

[0090] The operation according to the hunting prevention parameter setting will be described. FIG. 9 is a diagram illustrating the operation of the gripping device 1 according to this embodiment. The horizontal axis indicates the elapsed time since the gripping device 1 started to operate. The vertical axis indicates the gripping force detection value PVf. Time t1 indicates the time when the gripping device 1 comes into contact with the gripping object TGT. The gripping object TGT is a hard gripping object TGT within the assumed range.

[0091] Line L1 in the graph of Figure 9 represents the grip force detection value PVf when the robot is operated with the hunting prevention parameter settings after contact is detected at time t1. Note that F1 represents the force command value. On the other hand, line L1z represents the grip force detection value PVf when the robot is operated with the standard settings, for example.

[0092] As shown by line L1 in Fig. 9, by operating the gripping device 1 with the hunting prevention parameter settings, the amount of hunting from the force command value F1 after time t1 can be reduced. On the other hand, when the gripping device 1 is operated with the conventionally known standard settings, the amount of hunting from the force command value F1 after time t1 becomes large, as shown by line L1z in Fig. 9.

[0093] (Step S40) Next, the calculation processing unit 51 determines whether the grasp target TGT is soft. Specifically, the determination unit 51c included in the calculation processing unit 51 detects whether the grasp target TGT is soft based on the grip force detection value PVf.

[0094] For example, the determination unit 51c may determine that the grasp target TGT is soft when the grip force detection value PVf after a certain time has elapsed since the first finger portion 21a and the second finger portion 21b came into contact is smaller than a predetermined threshold. Alternatively, the determination unit 51c may determine that the grasp target TGT is hard, i.e., the grasp target is not soft, when the grip force detection value PVf after a certain time has elapsed since the first finger portion 21a and the second finger portion 21b came into contact is equal to or greater than a predetermined threshold.

[0095] If the calculation processing unit 51 determines that the grasp object TGT is soft (Yes in step S40), the process proceeds to step S50. If the calculation processing unit 51 determines that the grasp object TGT is not soft (No in step S40), the process proceeds to step S70.

[0096] (Step S50) Next, if the calculation processing unit 51 determines that the grasp target TGT is soft, the calculation processing unit 51 changes the setting that determines the operation of the grasp device 1 to a convergence time shortening parameter setting that quickly converges the operations of the first finger portion 21a and the second finger portion 21b. Specifically, the determination unit 51c included in the calculation processing unit 51 outputs a gain adjustment signal Sig to reduce the spring constant K. That is, the determination unit 51c outputs the gain adjustment signal Sig to the gain block B14 to reduce the gain K13.

[0097] The gain block B14 receives the gain adjustment signal Sig and reduces the gain K13. The setting of the gain K13 set by the gain block B14 in step S50 is referred to as a third gain setting. The setting value of the gain K13 set by the gain block B14 in step S50 is referred to as a third gain setting value. When the gain K13 is reduced, the first finger 21a and the second finger 21b are controlled by the admittance control calculation unit 51a1 so that the movements of the first finger 21a and the second finger 21b converge quickly.

[0098] The operation according to the convergence time shortening parameter setting will be described. FIG. 10 is a diagram illustrating the operation of the gripping device 1 according to this embodiment. The horizontal axis indicates the time elapsed since the gripping device 1 started operation. The vertical axis indicates the gripping force detection value PVf. Time t1 indicates the time when the gripping device 1 comes into contact with the gripping target TGT. Time t2 is the time after a predetermined time has elapsed since time t1. The gripping target TGT is a soft gripping target TGT within the assumed range.

[0099] When the gripping device 1 grips a hard gripping object TGT, the gripping force detection value PVf increases rapidly after the first finger portion 21a and the second finger portion 21b come into contact with the gripping object TGT. That is, when the gripping device 1 grips a hard gripping object TGT, the gripping force detection value PVf increases rapidly after time t1. Therefore, the gripping force command value is reached relatively quickly after time t1.

[0100] On the other hand, when the gripping device 1 grips a soft gripping object TGT, the gripping force detection value PVf increases slowly after the first finger portion 21a and the second finger portion 21b come into contact with the gripping object TGT. That is, when the gripping device 1 grips a soft gripping object TGT, the gripping force detection value PVf increases slowly after time t1. Therefore, it takes time after time t1 until the gripping force command value is reached.

[0101] Therefore, when the gripping device 1 according to this embodiment determines that the gripping target TGT is soft, it changes the operation setting to a convergence time shortening parameter setting so as to shorten the convergence time.

[0102] Line L2 in the graph of Figure 10 represents the detected grip force value PVf when the robot is operated at time t2 with the convergence time shortening parameter setting. Note that F1 represents the force command value. On the other hand, line L2z represents the detected grip force value PVf when the robot is operated at time t2 without changing the operation setting.

[0103] 10, by operating the gripping device 1 with the convergence time shortening parameter set, the gripping force detection value PVf converges to the force command value F1 at time Tb after time t2. On the other hand, when the gripping device 1 is operated without the convergence time shortening parameter set, the gripping force detection value PVf converges to the force command value F1 at time Tz after time t1.

[0104] (Step S60) Next, the calculation processing unit 51 determines whether the grip force detection value PVf has reached the force command value SVf. Specifically, the determination unit 51c included in the calculation processing unit 51 determines whether the grip force detection value PVf has reached the force command value SVf.

[0105] If the grip force detection value PVf reaches the force command value SVf (Yes in step S60), the calculation processing unit 51 proceeds to step S70. If the calculation processing unit 51 determines that the grip force detection value PVf has not reached the force command value SVf (No in step S60), the calculation processing unit 51 returns to step S60 and repeats the process.

[0106] (Step S70) Next, the calculation processing unit 51 changes the setting that determines the operation of the gripping device 1 to a stable gripping parameter setting that stably grips the gripping object TGT with the first finger unit 21a and the second finger unit 21b in accordance with the hardness of the gripping object TGT. Specifically, the determination unit 51c included in the calculation processing unit 51 outputs a gain adjustment signal Sig that changes the spring constant K to a gain K13 in accordance with the hardness of the gripping object TGT. That is, the determination unit 51c outputs the gain adjustment signal Sig to a gain block B14 in accordance with the hardness of the gripping object TGT.

[0107] The gain block B14 receives the gain adjustment signal Sig and sets the gain K13 to a value corresponding to the grasped object TGT. The setting of the gain K13 set by the gain block B14 in step S70 is referred to as a fourth gain setting. The setting value of the gain K13 set by the gain block B14 in step S70 is referred to as a fourth gain setting value.

[0108] For example, when the determination unit 51c determines that the grasp object TGT is soft, it increases the set value of the gain K13. On the other hand, when the determination unit 51c determines that the grasp object TGT is hard, it decreases the set value of the gain K13.

[0109] <Actions and Effects> The gripping device 1 according to this embodiment can stably hold gripping objects TGT having different hardnesses. Specifically, the gripping device 1 according to this embodiment can stably and quickly grip gripping objects TGT having different hardnesses by switching the operation settings of the gripping device 1.

[0110] 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 or substitutions with part or all of other embodiments, are possible within the scope of the present invention. For example, the technology disclosed herein can also be applied to robot hands with three or more fingers. [Explanation of symbols]

[0111] 1 Gripping device 10 Drive unit 11 Power section 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 control section 51 Processing unit 51a 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 51c Judgment section PVf Gripping force detection value PVi current detection value PVv Speed ​​detection value PVθ Position detection value SVf Force command value SVi current command value SVθ Position command value TGT Grasped object

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 force detection value of the gripping force detected by the force detection unit becomes a force command value; Equipped with The control unit calculating and outputting the operation value using a first gain setting that changes the gap at a high speed before detecting that the first finger portion and the second finger portion have come into contact with the object; calculating and outputting the operation value using a second gain setting that prevents hunting of the gap after detecting that the first finger portion and the second finger portion have come into contact with the object; If it is determined that the contacted object is soft, calculating and outputting the operation value using a third gain setting that shortens the time it takes for the distance to converge, the control unit calculates a displacement command value from the force detection value and the force command value using a model including a spring constant, and calculates the operation value based on the displacement command value; the spring constant at the second gain setting is greater than the spring constant at each of the first gain setting and the third gain setting; gripping device.

2. The control unit and further performing a step of calculating and outputting the operation value using a fourth gain setting that stably holds the object in accordance with the hardness of the contacted object. The gripping device according to claim 1 .

3. the spring constant in the fourth gain setting is determined according to the hardness of the object; The gripping device according to claim 2 .

4. 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 a force detection value of the gripping force detected by the force detection unit becomes a force command value, calculating and outputting the operation value using a first gain setting that changes the gap at a high speed before detecting that the first finger portion and the second finger portion have come into contact with the object; calculating and outputting the operation value using a second gain setting that prevents hunting of the gap after detecting that the first finger portion and the second finger portion have come into contact with the object; and when it is determined that the contacted object is soft, calculating and outputting the operation value using a third gain setting that shortens the time it takes for the distance to converge, calculating a displacement command value from the force detection value and the force command value using a model including a spring constant, and calculating the operation value based on the displacement command value; the spring constant at the second gain setting is greater than the spring constant at each of the first gain setting and the third gain setting; A method for controlling a gripping device.

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