A fuzzy-based impedance control for force tracking in unknown environment

Industrial manufacturing operations, such as grinding and polishing, are characterized by relatively constant contact force. In this article, a fuzzy-based adaptive impedance is proposed, which can grind or polish workpieces of different materials with constant contact force. The environmental parameters are estimated by iterative calculation with recursive least squares (RLS). The impedance parameters, such as damping and stiffness, are taken as the outputs of the fuzzy controller. The proposed force controller can track the desired force without the prior knowledge of the environment information. Experiments are conducted in finishing tasks using the self-developed industrial robot to verify the adaptive impedance control. The environmental parameters are instantly estimated for the following adjustment of the impedance parameters, and the real time contact force shows that the adaptive fuzzy logic impedance controller can achieve better performance with the oscillation below 2 N as the machining surface of the workpiece is not predefined.