Torque-position transformer for task control of position controlled robots
AssigneeThe Board of Trustees of the Leland Stanford Junior University
InventorsOussama Khatib, Peter Thaulad, Jaehoung Park
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Abstract
Torque control capability is provided to a position controlled robot by calculating joint position inputs from transformation of the desired joint torques. This is based on calculating the transfer function 1/E(s), which relates the desired joint torque to joint position. Here E(s) is a servo transfer function D(s) or an effective servo transfer function D*(s). The use of an effective servo transfer function D*s) is helpful in cases where joint nonlinearities are significant. The effective servo transfer function D*(s) is defined with respect to an ideal joint transfer function G*(s)=1/(Ieffs2+beffs), where Ieff is an effective moment of inertia and beff is an effective damping coefficient.
Claims11
A robotic control method for a position controlled robot, the method comprising:
- a) determining a closed loop position transfer function of a selected joint of the robot relating a commanded input joint position to an actual joint position;
- b) selecting a dynamic open loop joint torque to position transfer function relating to the selected joint;
- c) determining a corresponding effective servo transfer function of the selected joint from said closed loop position transfer function and said dynamic open loop torque to position transfer function;
- d) providing a desired dynamic torque of the selected joint;
- and
- e) determining said commanded input joint position of the selected joint corresponding to said desired dynamic torque from said desired dynamic torque, said closed loop position transfer function and said effective servo transfer function.
A robotic control system comprising:
- a) a position controlled robot having a closed loop position transfer function of a selected joint of the robot relating a commanded input joint position to an actual joint position;
- b) a processor including a torque to position converter, wherein said torque to position converter is capable of providing said commanded input joint position corresponding to a desired dynamic torque of the selected joint according to a method comprising:
- selecting a dynamic open loop joint torque to position transfer function relating to the selected joint;
- determining a corresponding effective servo transfer function of the selected joint from said closed loop position transfer function and said dynamic open loop torque to position transfer function;
- and
- determining said commanded input joint position of the selected joint corresponding to said desired dynamic torque from said desired dynamic torque, said closed loop position transfer function and said effective servo transfer function.
Dependencies are inferred from the claim text.