ROBOT CONTROL METHOD, ROBOT CONTROL DEVICE, AND ROBOT CONTROL SYSTEM

• US 20130245829A1
• Filed: 03/12/2013
• Published: 09/19/2013
• Est. Priority Date: 03/15/2012
• Status: Active Grant

• Current Assignee: Jtekt Corporation (Toyota Motor Corporation)
• Original Assignee: Jtekt Corporation (Toyota Motor Corporation)
• Inventors: Ohta, Hiromichi, Mukai, Yasuharu, Numazaki, Kazuya
• Granted Patent: US 9,002,519 B2
• Time in Patent Office: Days
• US Class Current: 700/261
• CPC Class Codes: B25J 9/1628 characterised by the control loop
• 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: B25J 9/1641 compensation for backlash, friction, compliance, elasticity in the joints
• CPC Class Codes: B25J 9/1643 redundant control
• CPC Class Codes: G05B 2219/40367 Redundant manipulator
• CPC Class Codes: G05B 2219/40461 Plan for even distribution of motor load of joints
• CPC Class Codes: Y10S 901/09 Closed loop, sensor feedback controls arm movement

Abstract

A CPU of a robot control device calculates load torque based on the inertia force, centrifugal force or Coriolis force, gravity force, friction torque, and actuator inertia torque applied to a joint axis of each link, each time an orientation parameter indicative of the link position and orientation allowed by a redundant degree of freedom is sequentially changed, under a constraint of end-effector position and orientation as target values. The CPU obtains the link position and orientation at which the ratio of the load torque to the rated torque of a rotary actuator provided for each joint is minimized, while the orientation parameter is being changed, and provides a feed-forward value that gives rise to each load torque obtained when the ratio of the load torque to the rated torque of the rotary actuator is minimized, to a control command generated to the rotary actuator of each joint axis for achieving the end-effector position and orientation as target values.

Claims

1. A method of controlling a robot having a manipulator formed by coupling a plurality of links at respective joint axes and having at least one redundant degree of freedom that is redundant with respect to task degrees of freedom, each of the joint axes being driven by a rotary actuator provided for each joint of the manipulator, comprising:

calculating load torque based on at least inertia force, centrifugal force or Coriolis force, and gravity force of the joint axis of each link, when link position and orientation allowed by the redundant degree of freedom is changed, under a constraint of end-effector position and orientation set as target values;

obtaining the link position and orientation at which the ratio of the load torque to rated torque of the rotary actuator is minimized, while the link position and orientation are being changed; and

providing a feed-forward value that gives rise to each load torque obtained when the ratio of the load torque to the rated torque of the rotary actuator is minimized, to a control command generated to the rotary actuator of each joint axis for achieving the end-effector position and orientation as target values.

2. The method according to claim 1, wherein the load torque includes friction torque.

3. A method of controlling a robot having a manipulator formed by coupling a plurality of links at respective joint axes and having at least one redundant degree of freedom that is redundant with respect to task degrees of freedom, each of the joint axes being driven by a rotary actuator provided for each joint of the manipulator, comprising:

calculating load torque based on at least inertia force, centrifugal force or Coriolis force, and gravity force of the joint axis of each link, each time an orientation parameter indicative of link position and orientation allowed by the redundant degree of freedom is sequentially changed, under a constraint of end-effector position and orientation set as target values;

obtaining the link position and orientation at which the ratio of the load torque to rated torque of the rotary actuator is minimized, while the orientation parameter is being changed; and

providing a feed-forward value that gives rise to each load torque obtained when the ratio of the load torque to the rated torque of the rotary actuator is minimized, to a control command generated to the rotary actuator of each joint axis for achieving the end-effector position and orientation as target values.

4. The method according to claim 3, wherein the load torque includes friction torque.

5. A robot control device that controls a robot having a manipulator formed by coupling a plurality of links at respective joint axes and having at least one redundant degree of freedom that is redundant with respect to task degrees of freedom, each of the joint axes being driven by a rotary actuator provided for each joint of the manipulator, comprising:

a load torque calculating unit that calculates load torque based on at least inertia force, centrifugal force or Coriolis force, and gravity force of the joint axis of each link, each time an orientation parameter indicative of link position and orientation allowed by the redundant degree of freedom is sequentially changed, under a constraint of end-effector position and orientation set as target values;

a link orientation calculating unit that obtains the link position and orientation at which the ratio of the load torque to rated torque of the rotary actuator is minimized, while the orientation parameter is being changed; and

a providing unit that provides a feed-forward value that gives rise to each load torque obtained when the ratio of the load torque to the rated torque of the rotary actuator is minimized, to a control command generated to the rotary actuator of each joint axis for achieving the end-effector position and orientation as target values.

6. The robot control device according to claim 5, wherein the load torque calculating unit calculates the load torque including friction torque in addition to the inertia force, centrifugal force or Coriolis force, and gravity force of the joint axis of each link.

7. A robot control system that controls a robot having a manipulator formed by coupling a plurality of links at respective joint axes and having at least one redundant degree of freedom that is redundant with respect to task degrees of freedom, each of the joint axes being driven by a rotary actuator provided for each joint of the manipulator, comprising:

a load torque calculating unit that calculates load torque based on at least inertia force, centrifugal force or Coriolis force, and gravity force of the joint axis of each link, each time an orientation parameter indicative of link position and orientation allowed by the redundant degree of freedom is sequentially changed, under a constraint of end-effector position and orientation set as target values;

a link orientation calculating unit that obtains the link position and orientation at which the ratio of the load torque to rated torque of the rotary actuator is minimized, while the orientation parameter is being changed; and

a providing unit that provides a feed-forward value that gives rise to each load torque obtained when the ratio of the load torque to the rated torque of the rotary actuator is minimized, to a control command generated to the rotary actuator of each joint axis for achieving the end-effector position and orientation as target values.

8. The robot control system according to claim 7, wherein the load torque calculating unit calculates the load torque including friction torque in addition to the inertia force, centrifugal force or Coriolis force, and gravity force of the joint axis of each link.