Super-twisting impedance control of redundant robots

This paper proposes a robust impedance control method for redundant robots that achieves compliant interaction with unknown environments while rejecting model errors and disturbances. The approach combines a nominal impedance controller with a generalized super-twisting algorithm (GSTA), using a sliding variable that robustly enforces the desired impedance relationship. A geometric formulation based on quaternion kinematics ensures that the stiffness and damping are physically meaningful and geometrically consistent in both position and orientation. Global asymptotic and finite-time stability are proven under bounded disturbances, and the method is experimentally validated on a 7-degree of freedom (DOF) Franka Panda robot. Compared to conventional sliding mode controllers, the proposed method significantly reduces chattering while maintaining robust tracking performance.