JP2009045687A - Grip control device of gripping device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a grip control device of a gripping device which can simplify the structure and can reduce the production cost without any need for exclusive sensor for detecting external force. <P>SOLUTION: The external force applied to a movable section is estimated by the change in the rotating angle of a motor and current detection value. When the estimated external force falls within a specified range, position control is stopped and the current is controlled to a gripping force application setting current value 19 by a current controlling means 14. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a gripping control device for a gripping device that is widely used from an industrial field to a general field, for example, a gripping control device for a gripping device that can flexibly grip a hard object from a relatively soft object.

In a conventional gripping device, the gripping means is composed of a robot hand having a mechanism for gripping a gripping object and a force sensor for detecting an external force acting on the gripping movable part, and a change in sensor signal from the force sensor is detected. Some have been proposed for controlling the receiving and gripping output (Patent Documents 1 and 2).
Japanese Patent Laid-Open No. 2004-167654 JP 2004-160594 A

  In the conventional gripping device, a dedicated sensor is required to detect an external force acting on the movable part, and a complicated structure, control circuit, control algorithm, and the like are required. Therefore, the manufacturing cost of the gripping device increases.

  An object of the present invention is to provide a grip control device for a grip device that does not require a dedicated sensor for detecting an external force, can simplify the structure, and can reduce the manufacturing cost.

  The gripping control device 2 of the gripping device 1 of the present invention has one or a plurality of movable parts 3 to 8 and a motor M for operating the movable parts 3 to 8, and grips by the operation of the movable parts 3 to 8. The gripping device 1 that grips the object W is a gripping control device 2 that controls the operation of the movable parts 3 to 8, and includes a position detector 11 that detects the rotation angle of the motor M, and driving of the motor M. A current detector 12 for detecting a current, a position control means 13 for controlling the position of the motor M, and a current control for controlling the driving current of the motor M to a set current value in a closed loop according to a detection value of the current detector 12 And an external force estimating means for monitoring the detected value of the position detector 11 and the detected value of the current detector 12 and estimating the external force acting on the movable portion from the change in the motor rotation angle and the detected current value. 15 and the movable Position control by the position control means 13 is performed until the command position at which 3 to 8 is in the gripping state of the gripping object W, and the position control by the position control means 13 is performed when the estimated external force by the external force estimation means 15 falls within a set range. And a control method switching means 16 for causing the current control means 14 to perform current control with a set current value for applying a gripping force.

According to this configuration, the gripping device 1 grips the gripping target object W by operating the movable parts 3 to 8 by the motor M. The position detector 11 detects the rotation angle of the motor M, and the current detector 12 detects the drive current of the motor M. The position control means 13 controls the position of the motor M, and the current control means 14 performs a closed loop control of the drive current of the motor M to a set current value according to the detection value of the current detector 12.
Here, the gripping force for gripping the gripping object W is proportional to the motor torque, and the motor torque is proportional to the drive current of the motor M. Therefore, the external force acting on the movable portion 8 and the like is estimated by detecting and calculating the change in the motor rotation angle and the drive current of the motor M. That is, the external force estimating means 15 monitors the detection value of the position detector 11 and the detection value of the current detection value 12. Thereby, the external force acting on the movable part 8 and the like is estimated from the change in the motor rotation angle and the detected current value 12. Further, the control method switching means 16 determines whether or not the estimated external force is within the set range. The set range is, for example, a range that exceeds a threshold value. If it is determined that the estimated external force by the external force estimating means 15 is not within the set range, the position control by the position control means 13 is continued.

When the gripping target object W is gripped, the motor speed is lowered by the reaction force, and as a result, the induced voltage is lowered and the current value is increased. Accordingly, when it is determined that the estimated external force is within the set range, the control method switching unit 16 stops the position control and causes the current control unit 14 to perform current control with the gripping force applying set current value.
Thus, the current detector 12 necessary for torque control is used as a sensor for detecting external force without using a force sensor or the like, so that the structure of the grip control device 2 is simplified and the manufacturing cost is reduced. Can do. In addition, since the number of sensors can be reduced, the configuration of the gripping device 1 can be simplified.

  While the position control means 13 performs position control, the control method switching means 16 causes the current control means 14 to perform current control with the approaching action setting current value lower than the gripping force application setting current value. It is desirable to make it. In this case, damage to the gripping object W and the gripping device itself can be prevented.

  The gripping device 1 has a plurality of the movable parts, the motor M for each rotating part, and all or any one of the movable part individual control parts 9 that respectively control the plurality of motors M The movable unit individual control unit 9 may include the position control unit 13, the current control unit 14, the external force estimation unit 15, and the control method switching unit 16, respectively. In this case, a multi-axis gripping device 1 having a plurality of movable parts 3 to 8 can be realized, and versatility to which the gripping device 1 can be applied can be enhanced.

  In the invention in which the plurality of movable unit individual control units 9 include the position control unit 13, the current control unit 14, the external force estimation unit 15, and the control method switching unit 16, respectively, the positions in the plurality of movable unit individual control units 9 By providing the control means 13 with the operation pattern setting unit 10 that stores the position command values of the movable units 3 to 8 that are set according to the shape of the gripping target W, the plurality of movable units 3 to 8 are provided. Position control can be easily performed while the holding device 1 having the control device is a control target.

  The control method switching means 16 may maintain current control at the gripping force applying set current value until a grip release command is issued. In this case, it is possible to reliably hold the gripping target object W, and it is possible to move the gripping target object W by moving the movable parts 3 to 8 to arbitrary positions.

  The gripping device 1 is an articulated robot, and among the plurality of movable parts 3 to 8, individual movable parts that are control parts of a motor M that drives a finger part 8 that is a movable part that directly contacts at least the grasped object W. The control unit 9 may include the position control means 13, current control means 14, external force estimation means 15, and control method switching means 16. In this case, when the external force acting on the finger portion 8 is estimated by the external force estimating means 15 and it is determined that the estimated external force is within the set range, the control method switching means 16 in the movable part individual control part 9 Switch from control to appropriate current control, that is, torque control. Therefore, the finger portion 8 can be gripped flexibly from a relatively soft gripping object W to a hard gripping object W.

  A gripping control device for a gripping device according to the present invention includes: one or a plurality of movable parts; and a motor that operates each of the movable parts. The gripping apparatus grips an object to be gripped by the operation of the movable part. A position control unit that detects a rotation angle of the motor, a current detector that detects a drive current of the motor, a position control unit that controls the position of the motor, A current control means for controlling the motor driving current to a set current value according to a detection value of the current detector in a closed loop; a detection value of the position detector; and a detection value of the current detector; The external force estimating means for estimating the external force acting on the movable part from the change of the current and the detected current value, and the position control means performs position control to the command position where the movable part is in the gripping state of the gripping object. Control means switching means for stopping the position control by the position control means when the estimated external force by the external force estimation means is within a set range and causing the current control means to perform current control with a set current value for applying a gripping force. . For this reason, a dedicated sensor for detecting external force is not required, the structure can be simplified, and the manufacturing cost can be reduced.

  An embodiment of the present invention will be described with reference to FIGS. The gripping device according to this embodiment is an example applied to an articulated robot. In this embodiment, the present invention is applied to an articulated robot having six axes of freedom, but the present invention is not limited to six axes. It is also possible to apply this gripping device to a loading device for machine tools other than the articulated robot, an industrial machine, or the like. In addition, the following description also includes the description about the holding | grip control method of a holding | grip apparatus.

  As shown in FIG. 1, the gripping device 1 includes a plurality of movable parts, a motor M that operates each movable part, and a gripping control apparatus 2 that controls the operation of the movable part. The plurality of movable parts are a base part 3, a connecting part 4, an arm body part 5, an arm part 6, an arm tip part 7, and a finger part 8. Among these, the base part 3 is provided so as to be able to turn around the vertical axis with respect to the base BD installed on the installation surface. The connecting portion 4 is provided such that one end of the connecting portion 4 is rotatable about the horizontal axis with respect to the base portion 3, and the arm body portion 5 is rotated about the horizontal axis with respect to the other end of the connecting portion 4. Provided possible. The arm portion 6 is a rod-like member protruding from the connecting portion 4, and is provided so as to be rotatable about the longitudinal axis with respect to the connecting portion 4. The arm tip 7 is provided at one end of the arm 6 so as to be rotatable. The finger portion 8 is a movable portion that is in direct contact with the grasped object W and is provided so as to be operable with respect to the arm tip portion 7.

  As shown in FIG. 2B, the finger portion 8 includes, for example, a finger portion main body 23 and a pair of linear motion bearings 25 and 25 that are linearly guided by rails 24 attached to the finger portion main body 23. The flanges 23a and 23a are spaced apart from the finger body 23 and protrude a predetermined small distance in a direction perpendicular to the longitudinal direction of the rail 24. The flanges 23a and 23a are rotatably supported by the flanges 23a and 23a. The screw shaft 26 is provided in parallel to the direction, and the motor M is fixed to one flange 23a and rotates the screw shaft 26. Further, the finger portion 8 has a pair of ball nuts 27, 27. Each ball nut 27 is fixed to the linear motion bearing 25 and screwed to the screw shaft 26.

  The screw shaft 26 is integrally formed with the reverse screw at the left half in the longitudinal direction with respect to the right half in the longitudinal direction in FIG. One ball nut 27 is screwed to the right half of the screw shaft 26 in the longitudinal direction, and the other ball nut 27 is screwed to the left half of the screw shaft 26 in the longitudinal direction. The ball nuts 27, 27 are integrally provided with gripping portions 8a, 8a for gripping the gripping target object W. When the screw shaft 26 is rotated by driving the motor M, both ball nuts 27, 27 move so as to be separated from each other. Thereby, the gripping portions 8a and 8a grip or release the gripping object W. The finger portion 8 is not limited to the one using the ball screw mechanism, and may be one using a rack and pinion mechanism, for example.

A motor M is provided for each of the individual movable parts, and as shown in FIG. 3, the grip control device 2 includes a movable part individual control unit 9 that controls each of the plurality of motors M. That is, the grip control device 2 includes a plurality of individual movable part control units 9 and an operation pattern setting unit 10 to be described later. The grip control device 2 is configured by an electronic circuit such as a logic circuit or a computer, for example.
Each movable part individual control unit 9 includes a position detector 11, a current detector 12, a position control unit 13, a current control unit 14, an external force estimation unit 15, and a control method switching unit 16. The operation pattern setting unit 10 stores position command values 17 of the respective movable parts that are set in accordance with the shape of the grasped object W with respect to the position control means 13 in the plurality of individual movable part control units 9. . The operation pattern setting unit 10 is realized by, for example, a readable / writable memory or the like.

In each movable part individual control unit 9, the position control unit 13, the current control unit 14, the motor M, the position detector 11, the external force estimation unit 15, and the control method switching unit 16 are electrically connected. Yes. Among these, the position detector 11 detects the rotation angle of the motor M, and is constituted by, for example, a position detection means attached to the motor M, or an encoder separate from the motor M. . The position detector 11 may detect the position of the movable part.
The current detector 12 is electrically connected to the motor M so that the drive current of the motor M can be detected. Position control means 13 electrically connected to the operation pattern setting unit 10 controls the position of the motor M.

  The position control means 13 is a means for controlling the rotation angle (including the case of exceeding 360 °) of the motor M so that the position command value 17 given from the operation pattern setting unit 10 is obtained. Closed loop control is performed using the detected value. In addition, the position control means 13 may perform the open loop control by feedforward control.

The current control means 14 performs a closed loop control of the drive current of the motor M to a set current value according to the detection value of the current detector 12. That is, the set current value and the detected value of the current detector 12 are compared by the comparison unit 22 and controlled so that the set current value is obtained. This closed-loop controlled current value is amplified as a data drive current via the amplifier 18 and transmitted to the motor M. The external force estimation means 15 monitors the detection value of the position detector 11 and the detection value of the current detector 12, and from the change of the motor rotation angle and the current detection value according to a setting rule determined by an arithmetic expression or a table. The external force acting on this movable part is estimated.
The control method switching means 16 causes the position control means 13 to perform position control up to the gripping position where the movable part is gripping the gripping object W and the solid line position P1 of the finger part 8 in FIG. Furthermore, when the estimated external force by the external force estimating means 15 falls within the set range, that is, when the current value detected by the current detector 12 exceeds the threshold value, the control method switching means 16 stops the position control and performs current control.
That is, the finger portion 8 grips the gripping object W, and the motor speed is decreased by the reaction force F1 from the gripping object W. As a result, the induced voltage is decreased and the detection value of the current detector 12 is increased. When the value exceeds a predetermined threshold value, the position control means 13 stops the position control. Then, the control method switching unit 16 causes the current control unit 14 to perform current control with the gripping force applying set current value 19. Further, the control method switching means 16 has a function of maintaining current control at this gripping force applying set current value 19 until a grip release command is issued.

  While the position control means 13 performs the position control, the control method switching means 16 has a normal operation set current value 21 having a higher current value than an approach operation set current value 20 described later in the initial operation stage of the movable part. Thus, current control is executed by the current control means 14, and in the approaching operation stage of the movable part to the gripping object W, the approaching operation setting current value 20 that is lower than the gripping force applying setting current value 19 is Current control is performed by the current control means 14. The approaching operation setting current value 20 is a current value such that the gripping target object W is not crushed when the gripping target object W is gripped by the finger portion 8.

  FIG. 4 is a flowchart showing the grip control of the grip control device step by step. When the grip control device 2 receives a grip operation command based on an operator's switch operation or a setting program of the host control device (step S1), the process proceeds to step S2. In step S2, the position of the motor M is controlled by the position control means 13, and each movable part is moved to the gripping posture. During this position control, current control by the current control means 14 is performed with the approaching operation setting current value 20 lower than the gripping force application setting current value 19.

  Thereafter, the process proceeds to step S3, and the control method switching means 16 determines whether or not the estimated external force by the external force estimating means 15 is within the set range. If the determination is NO, the process of returning to step S2 is repeated. If it is determined that the estimated external force is within the set range, that is, the detected value of the current detector 12 has increased and the current value has exceeded a predetermined threshold value, the process proceeds to step S4. In step S4, the control method switching means 16 stops the position control by the position control means 13 and causes the current control means 14 to perform current control with the gripping force setting current value 19. In step S5, the object to be grasped W is grasped with an appropriate torque by this current control. Thereafter, the control method switching means 16 determines whether or not there is a grip release command, for example. If NO, the current control is maintained at the gripping force applying set current value 19 and the process returns to step S5. When it is determined that there is a grip release command, the current control at the gripping force applying set current value 19 is canceled, and for example, the position of the motor M of the movable part is controlled at the normal operation set current value 21 to release the grip. Thereafter, the process returns to step S1.

According to the grip control device 2 of the grip device 1 described above, the position detector 11 detects the rotation angle of the motor M, and the current detector 12 detects the drive current of the motor M. The position control means 13 controls the position of the motor M, and the current control means 14 performs a closed loop control of the drive current of the motor M to a set current value according to the detection value of the current detector 12.
Here, the gripping force for gripping the gripping object W is proportional to the motor torque, and the motor torque is proportional to the drive current of the motor M. Therefore, the external force acting on the movable portion is estimated by detecting and calculating the change in the rotation angle of the motor M and the drive current of the motor M. That is, the external force estimating means 15 monitors the detection value of the position detector 11 and the detection value of the current detector 12. Thus, the external force acting on the movable part is estimated from the change in the motor rotation angle and the detected current value. Further, the control method switching means 16 determines whether or not the estimated external force is within the set range. If it is determined that the estimated external force by the external force estimating means 15 is not within the set range, the position control by the position control means 13 is continued.

When the gripping object W is gripped by the finger portion 8, the motor speed is lowered by the reaction force, and as a result, the induced voltage is lowered and the current value is increased. Thus, when it is determined that the estimated external force is within the set range, the control method switching unit 16 stops the position control and causes the current control unit 14 to perform current control with the gripping force applying set current value 19.
Thus, the current detector 12 necessary for torque control is used as a sensor for detecting external force without using a force sensor or the like, so that the structure of the grip control device 2 is simplified and the manufacturing cost is reduced. Can do. Further, since the number of sensors can be reduced, the structure of the gripping device 1 can be simplified and the manufacturing cost can be reduced.

  In the present embodiment, the control method switching means 16 controls the current control by the current control means 14 at the approach operation setting current value 20 lower than the gripping force setting current value 19 while the position control means 13 performs the position control. To do. In this case, damage to the gripping object W and the gripping device itself can be prevented.

  In the present embodiment, the gripping device 1 has a plurality of movable parts, the motor M is provided for each movable part, and all or any of the movable part individual control units 9 that respectively control the plurality of motors M. Each of the plurality of movable unit individual control units 9 includes the position control unit 13, the current control unit 14, the external force estimation unit 15, and the control method switching unit 16. In this case, a multi-axis gripping device having a plurality of movable parts, such as an articulated robot, can be realized, and versatility to which this gripping device can be applied can be enhanced. Further, for example, it is possible to hold the gripping target object W with another movable part while pressing the gripping target object W with one movable part. In this case, the movable unit individual control unit 9 for the movable unit that presses the grasped object W is configured to include the position control unit 13, the current control unit 14, and the external force estimation unit 15. In this way, it is possible to easily grip the gripping object W of various sizes and shapes by interlocking a plurality of movable parts. In addition, it is also possible to grip a movable gripping object W by interlocking a plurality of movable parts.

  The grip control device 2 stores an operation pattern in which position command values 17 of the movable parts set according to the shape of the gripping object W are stored in the position control means 13 of the plurality of individual movable part control units 9. The setting unit 10 is provided. Therefore, position control can be easily performed while the gripping device 1 having a plurality of movable parts is a control target.

In the present embodiment, all of the movable part individual control units 9 among the movable part individual control units 9 that respectively control the plurality of motors M include the position control unit 13, the current control unit 14, the external force estimation unit 15, and the control unit. The method switching unit 16 and the like are provided, but the present invention is not necessarily limited to this mode. For example, any one of the plurality of movable unit individual control units 9 among all the movable unit individual control units 9 includes a position control unit 13, a current control unit 14, an external force estimation unit 15, a control method switching unit 16, and the like. It may be configured. However, the plurality of movable unit individual control units 9 include at least a movable unit individual control unit of the motor M that operates the finger unit 8 that is in direct contact with the grasped object W.
In addition, a single-axis gripping device may be provided, and the movable unit individual control unit 9 may be provided only in the motor M that operates the movable unit that is in direct contact with the gripping target W. Even in this case, the same effects as in the present embodiment can be obtained.

  In the present embodiment, the approach operation set current value 20 is set, but this setting may be omitted. In this case, the control system can be simplified and the manufacturing cost of the gripping device can be further reduced. The current detector 12 may be attached to the motor M and directly detect the drive current of the motor M. In this case, the number of parts can be reduced and the structure can be simplified.

(A) is a side view of a gripping device according to an embodiment of the present invention, and (B) is a side view showing a stage before the gripping device grips a gripping object. (A) is an enlarged view showing the main part of the gripping device and the object to be gripped, and (B) is an enlarged view of the finger portion of the gripping device. It is a block diagram showing the electric constitution of the grip control device of the gripping device. It is a flowchart showing grip control of the grip control device in steps.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Gripping device 2 ... Gripping control device 3 ... Base part 4 ... Connection part 5 ... Arm main body part 6 ... Arm part 7 ... Arm tip part 8 ... Finger part 9 ... Movable part individual control part 10 ... Operation pattern setting part 11 ... Position detector 12 ... Current detector 13 ... Position control means 14 ... Current control means 15 ... External force estimation means 16 ... Control method switching means M ... Motor W ... Holding object

Claims (6)

A gripping control device that has one or a plurality of movable parts and a motor that operates each of the movable parts, and that controls the operation of the movable part in a gripping device that grips a gripping object by the operation of the movable part. ,
A position detector for detecting a rotation angle of the motor; a current detector for detecting a drive current of the motor; a position control means for controlling the position of the motor; and a detection value of the motor according to a detection value of the current detector. Current control means for controlling the drive current to a set current value in a closed loop, and the detected value of the position detector and the detected value of the current detector are monitored, and the change in the motor rotation angle and the detected current value are sent to the movable part. An external force estimating means for estimating an acting external force, and a position control by the position control means until the command position where the movable part is in a gripping state of the gripping object, and when the estimated external force by the external force estimating means is within a set range A gripping device comprising: a control method switching means for stopping the position control by the position control means and causing the current control means to perform a current control with a set current value for applying a gripping force. The control device.   2. The control method switching means according to claim 1, wherein the control method switching means performs current control by the current control means at an approach operation setting current value lower than the gripping force setting current value while the position control means performs position control. A gripping control device for a gripping device to be performed.   The gripping device according to claim 1 or 2, wherein the gripping device includes a plurality of the movable portions, the motor is provided for each of the rotating portions, and each of the movable portion individual control portions that respectively control the plurality of motors. A gripping control device for a gripping device, wherein all or any of the plurality of movable unit individual control units respectively include the position control means, current control means, external force estimation means, and control method switching means.   4. A gripping apparatus according to claim 3, wherein an operation pattern setting unit storing position command values of the respective movable parts set in accordance with the shape of the gripping object is provided for the position control means in the plurality of movable part individual control parts. Device gripping control device.   5. The gripping control device for a gripping device according to claim 1, wherein the control method switching means maintains current control at the gripping force applying set current value until a grip release command is issued.   6. The motor according to claim 1, wherein the gripping device is an articulated robot, and a motor that drives a finger portion that is at least a movable portion that is in direct contact with a grasped object among the plurality of movable portions. A gripping control device for a gripping device, wherein a movable part individual control unit as a control unit includes the position control means, current control means, external force estimation means, and control method switching means.

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