Robust Position Control System of MDOF Manipulator with Flexible Joints

This paper proposes a disturbance rejection method for a multi-degrees of freedom (MDOF) manipulator with flexible joints. Mechanical transmitters in joints have low stiffness and the arms of the manipulator vibrate during a fast motion. A motor/arm-side encoder that detects motor and arm angles directly is useful for precise position control. In this paper, the MDOF manipulator has motor/arm-side encoders. The system with flexible joints has motor dynamics between the input and torsional reaction torque. It deteriorates disturbance rejection by acceleration control. The proposed method comprises a torque controller compensating for motor dynamics and a filter improving disturbance rejection. The proposed method enables position control that maintains vibration suppression and improves robustness by utilizing both the motor and arm angle. The validity of the proposed method was confirmed by simulations.