Robot control method, robot control device, and robot control system
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.
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 of a respective rotary actuator on the joint axis of each link based on at least inertia force, centrifugal force or Coriolis force, and gravity force, each time a link position and orientation allowed by the redundant degree of freedom is changed, by a predetermined value, from an initial link position and orientation to a final link position and orientation, 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 each of the rotary actuators is minimized, while the link position and orientation are being changed from the initial link position and orientation to the final link position and orientation; 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 each of the rotary actuators 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 of a respective rotary actuator on the joint axis of each link based on at least inertia force, centrifugal force or Coriolis force, and gravity force, each time an orientation parameter indicative of link position and orientation allowed by the redundant degree of freedom is sequentially changed, by a predetermined value, from an initial link position and orientation to a final link position and orientation, 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 each of the rotary actuators is minimized, while the orientation parameter is being changed from the initial link position and orientation to the final link position and orientation; 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 each of the rotary actuators 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 of a respective rotary actuator on the joint axis of each link based on at least inertia force, centrifugal force or Coriolis force, and gravity force, each time an orientation parameter indicative of link position and orientation allowed by the redundant degree of freedom is sequentially changed, by a predetermined value, from an initial link position and orientation to a final link position and orientation, 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 each of the rotary actuators is minimized, while the orientation parameter is being changed from the initial link position and orientation to the final link position and orientation; 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 each of the rotary actuators 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 of a respective rotary actuator on the joint axis of each link based on at least inertia force, centrifugal force or Coriolis force, and gravity force, each time an orientation parameter indicative of link position and orientation allowed by the redundant degree of freedom is sequentially changed, by a predetermined value, from an initial link position and orientation to a final link position and orientation, 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 each of the rotary actuators is minimized, while the orientation parameter is being changed from the initial link position and orientation to the final link position and orientation; 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 each of the rotary actuators 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.