A Robust Torque Controller Based on Link-side Damping Assignment for Flexible Joint Robots

Disturbance-observer-based controller has been one of the most widely used robust control methods in force control of flexible joint robots, due to its robustness and simple implementation. However, flexible joint robots will suffer unexpected instability in robust torque control based on disturbance observer (DOB) because of the intrinsic uncertainty of the nominal model. This paper proposes a DOB-based robust torque control method based on link-side damping assignment, which can improve the robust stability of the inner DOB loop without affecting the torque tracking performance. Experiments are implemented on a collaborative robot with flexible joints. The results show that the proposed method can improve robust stability without sacrificing torque tracking performance.