Accurate Impedance Control for Robot Joints with 3K Gear Reducers Based on Transmission Efficiency

Compliant motion control of the collaborative robot is crucial for human-robot interaction. However, due to the nonlinear nature of the friction coefficient and damping factor, it is very difficult to model them accurately, which poses a challenge to improve the compliant motion control performance. In this paper, an accurate efficiency-based dynamic modelling approach is proposed for a robot joint, as the energy loss resulting from the friction and damping can be accounted into its efficiency. With the efficiency-based dynamic model, an impedance control method is investigated. Furthermore, a torque observer (TOB) is designed to compensate for friction and damping at the motor side, and the time-varying efficiency in the joint dynamic model is handled by feedback linearization. Both simulations and experimental results demonstrate that the proposed method significantly enhances the impedance control performance of the robot joint.