Robust position servo system for industrial robots based on estimated load information

Abstract

This paper proposes a new robust load position servo system for industrial robots based on estimated load information. The compact high-gear reduction without backlash, such as the harmonic gear is frequently used in the driving system for the sake of high load-to-weight performance. Generally, the industrial robots have used the sensors mounted to actuator-side because hardware setting using load-side sensor is very difficult to mount signal lines. Therefore, the end-effector response does not perfectly reach the desired position owing to the effect of external disturbance force, which is called end-effector offset. The proposed robust servo system uses the estimated load information due to repress the effect of external disturbance force and nonlinear inertia variation due to posture change of robot. The proposed position servo system is designed based on the state, disturbance observer and robust speed control system using coprime factorization controller. The effectiveness of the proposed robust system is confirmed by experimental results of prototype mechanical system and simulation results of the tesed 3-link industrial robot.