Potision control using filtered shaft torsional torque of articulated robots with double encoder motor

Abstract

Performance degradation caused by torsion of the rotation axis is often a problem for articulated robots. A method has been proposed in which the disturbance torque around the motor rotation axis is compensated by the disturbance observer to improve the target value tracking characteristic and the disturbance suppression characteristic. However, if the stiffness of links is low, the control system tends to become unstable. Therefore, in this paper, a frequency shaped axial torsional torque is fed back to a controller to suppress vibration of the end effector. The shaft torsional torque is estimated using the encoder values of the reducer input/output couplings. Validity of the proposed controller is verified by experiments.