ROBOT CONTROL APPARATUS FOR FORCE CONTROL

• US 20080140257A1
• Filed: 12/06/2007
• Published: 06/12/2008
• Est. Priority Date: 12/07/2006
• Status: Abandoned Application

• Current Assignee: Fanuc Ltd (Fanuc Corporation)
• Original Assignee: Fanuc Ltd (Fanuc Corporation)
• Inventors: SATO, Takashi, IWATAKE, Takahiro
• Application Number:
  US11/951,457
• Publication Number:
  US 20080140257A1
• Time in Patent Office: Days
• US Class Current: 700/258
• CPC Class Codes: B25J 9/1633 compliant, force, torque control, e.g. combined with position control
• CPC Class Codes: B25J 9/1638 compensation for arm bending/inertia, pay load weight/inertia
• CPC Class Codes: G05B 2219/39178 Compensation inertia arms
• CPC Class Codes: G05B 2219/39194 Compensation gravity
• CPC Class Codes: G05B 2219/39319 Force control, force as reference, active compliance
• CPC Class Codes: G05B 2219/39341 Sliding mode based impedance control
• CPC Class Codes: G05B 2219/39343 Force based impedance control

Abstract

A robot control apparatus for controlling force exerted between a working tool mounted at the forward end of a robot arm and a workpiece is disclosed. The apparatus includes a force measuring unit for acquiring the force data required for the control operation, a calculating unit for calculating the force exerted by gravity on the force measuring unit and the dynamic terms generated by the motion of the robot arm, of all the forces exerted on the force measuring unit from the working tool, a compensation unit for compensating the force measured by the force measuring unit using the force exerted by gravity and the dynamic terms calculated by the calculating unit, and a command adjusting unit for adjusting the operation command for the robot arm in accordance with the force exerted on the force measuring unit by the dynamic terms and gravity in the case where each of the dynamic terms is larger than a predetermined threshold value. As a result, the workpiece can be accurately machined even in the case where the forward end portion of the robot arm is changed a comparatively great degree in the direction of movement thereof.

Claims

1. A robot control apparatus for controlling force exerted between a working tool mounted at the forward end of a robot arm and a workpiece, comprising:

a force measuring unit for acquiring the force data required for the control operation;

a calculating unit for calculating the force exerted by gravity on the force measuring unit and the dynamic terms generated by the motion of the robot arm, of all the forces applied from the working tool to the force measuring unit;

a compensating unit for compensating the force measured by the force measuring unit, using the force exerted by gravity on the force measuring unit and the dynamic terms calculated by the calculating unit; and

a command adjusting unit for adjusting the operation command for the robot arm in accordance with the dynamic terms and the force exerted by gravity on the force measuring unit in the case where each of the dynamic terms is larger than a predetermined threshold value.

2. A robot control apparatus for controlling the force exerted between a workpiece held by a hand mounted at the forward end of a robot arm and a fixed working tool, comprising:

a force measuring unit for acquiring the force data required for the control operation;

a calculating unit for calculating the force exerted by gravity on the force measuring unit and the dynamic terms generated by the motion of the robot arm, of all the forces applied from the hand holding the workpiece to the force measuring unit;

a compensating unit for compensating the force measured by the force measuring unit, using the force exerted by gravity on the force measuring unit and the dynamic terms calculated by the calculating unit; and

a command adjusting unit for adjusting the operation command for the robot arm in accordance with the dynamic terms and the force exerted by gravity on the force measuring unit in the case where each of the dynamic terms is larger than a predetermined threshold value.

3. The robot control apparatus according to claim 1, wherein the operation command for the robot arm adjusted by the command adjusting unit includes a command on the force to be exerted between the working tool and the workpiece.

4. The robot control apparatus according to claim 1, wherein the operation command for the robot arm adjusted by the command adjusting unit includes the speed of the robot arm in the proceeding direction.

5. The robot control apparatus according to claim 1, wherein the operation command for the robot arm adjusted by the command adjusting unit includes the target trajectory of the robot arm.

6. The robot control apparatus according to claim 1, wherein the operation command for the robot arm adjusted by the command adjusting unit includes the gain of the force control operation.

7. The robot control apparatus according to claim 1, wherein the calculating unit calculates the dynamic terms and gravity from the posture, the operating speed and the operating acceleration of the robot arm and the mass and the center of gravity of the end effector mounted at the forward end of the robot arm.

8. The robot control apparatus according to claim 1, wherein the force measuring unit is a force sensor.

9. The robot control apparatus according to claim 1, wherein the force measuring unit estimates the force based on the current value of the actuator for driving the robot arm.

10. The robot control apparatus according to claim 1, wherein the force control operation performed by the robot control apparatus is the impedance control operation.

11. The robot control apparatus according to claim 1, wherein the force control operation performed by the robot control apparatus is the damping control operation.

12. The robot control apparatus according to claim 2, wherein the operation command for the robot arm adjusted by the command adjusting unit includes a command on the force to be exerted between the working tool and the workpiece.

13. The robot control apparatus according to claim 2, wherein the operation command for the robot arm adjusted by the command adjusting unit includes the speed of the robot arm in the proceeding direction.

14. The robot control apparatus according to claim 2, wherein the operation command for the robot arm adjusted by the command adjusting unit includes the target trajectory of the robot arm.

15. The robot control apparatus according to claim 2, wherein the operation command for the robot arm adjusted by the command adjusting unit includes the gain of the force control operation.

16. The robot control apparatus according to claim 2, wherein the calculating unit calculates the dynamic terms and gravity from the posture, the operating speed and the operating acceleration of the robot arm and the mass and the center of gravity of the end effector mounted at the forward end of the robot arm.

17. The robot control apparatus according to claim 2, wherein the force measuring unit is a force sensor.

18. The robot control apparatus according to claim 2, wherein the force measuring unit estimates the force based on the current value of the actuator for driving the robot arm.

19. The robot control apparatus according to claim 2, wherein the force control operation performed by the robot control apparatus is the impedance control operation.

20. The robot control apparatus according to claim 2, wherein the force control operation performed by the robot control apparatus is the damping control operation.