Motion Control of Robot Arms with Reducers Based on Joint Torque Feedback

Abstract

Since the dynamic equation of robot arms represents a nonlinear and time-varying system, it is difficult to control precisely the manipulator when it moves with high speed and heavy load. In order to solve this problem there have been proposed many control schemes with compensating the dynamic effects involving dynamic interaction between joints. However, it is not easy to compute the inverse dynamics in real time. To reduce the computational burden, many authors have derived various computational schemes of the inverse dynamics.In the present paper, we propose to introduce a torque sensor for each joint, instead of the computation, to measure the torque generated by the dynamic effects. The advantage of this technique is that the computational load is reduced much and the control system becomes robust for unexpecting external disturbance such as gravity acting on objects picked up and put down or other interactions with the environment. Therefore, this control scheme could be useful to the precise and robust control of the robot manipulators. We introduce dynamic modeling and stability analysis of the joint torque feedback control for robot arms with reducers in the drive trains. Furthermore, we will show the experimental results for a two joints arm which prove the validity of the control technique.