Fuzzy impedance control based on a built-in torque sensor in harmonic drive gear

To meet the intrinsically safe demands for joint torque measuring and joint compliance in collaborative manipulator (co-manipulator), a torque measuring method by using a built-in torque sensor in harmonic drive gear (HDG) has been improved. Based on that novel torque sensor, fuzzy impedance control strategy is proposed and tested in a physical experiment prototype as well. In this paper, aiming for period-varying ripple interference, which is caused by the intrinsic properties of HDG's flexspline, a highly real-time and precise online Kalman filter algorithm is designed to mitigate this problem. Besides, an impedance control strategy, whose parameters are modified by fuzzy controller online, is proposed, and the rapidity and stability of the proposed impedance control in the interaction with unstructured environment are improved and proved by observing simulation data. The experiments' results on physical prototype show the feasibility and effectiveness of the joint torque measuring method in this novel torque sensor and parameter-varying impedance control strategy.