Friction compensation of harmonic gear based on location relationship

In the harmonic gear servo system, friction is associated with not only the velocity of the input shaft but also its angle position. Traditional friction compensation based on the velocity cannot guarantee the high motion accuracy. To address this problem, this article proposed a new friction model of harmonic gear servo system, which is related to both its velocity and position. The new model includes two parts: in the presliding region, the static friction is determined by the maximum elastic deformation recovery angle of the input shaft, and in the sliding region, the friction not only has Stribeck effect from velocity but also has harmonic series relative to the input shaft’s position. In this article, the parameters of friction model were obtained by preliminary experiments. A control diagram based on this model was established for friction compensation and the proposed control algorithm showed its superiority in the experiments.