Study of Harmonic Drive and Design of Controllers Reducing Torque Oscillation

Abstract

Harmonic drive gear, together with permanent magnet DC servo motor, is used in high precision applicatlons, for Its high gear reduction ratio, compact size, and high energy transfer efficiency. However, it has been observed that the output torque from the harmonic drive flexspline oscillates. This paper examines the cause of the torque oscillation by studying three models of harmonic drive, and then demonstrates a torque feedback controller which could reduce torque oscillation in our experimental setup. This controller incorporates an inner loop torque P controller and an outer loop position PI controller.