Acceleration feedback control of a harmonic drive parallel robot

This paper presents a new 2-DOF planar parallel robot with high speed and high precision. Harmonic drive is adopted between an AC servomotor and its driven link in each drive joint, and at the same time a rotary encoder feeds the driven link angle into the position controller of each drive joint. Thus, the resolution of the drive joint is improved greatly. However, flexibility of harmonic drive during high-speed motion causes the sharp elastic vibration. Therefore, an acceleration feedback controller is especially designed to increase the damping coefficient and restrain the elastic vibration. Furthermore, the stability of the entire system including the drive joint's position controller and the acceleration feedback controller is proved using a Lyapunov approach. The experiments of trajectory tracking are conducted on the robotic system, and the results validate the proposed control algorithm, contrasted with that obtained by classical PD control without the acceleration feedback loop.