A Novel Robust Adaptive Impedance Control Scheme for Contact Force Tracking With Unknown Environment

Tracking desired force on various environmental surfaces is essential in many modern robotic applications. The constant impedance control (CIPC) has ability to realize this goal with clear environmental information (including stiffness and geometry), but failed when the information is not available. The traditional adaptive impedance control (TAIPC) is capable of tracking desired force even when the stiffness and geometry of environment are unknown, but large force overshoot is caused in contact phase. To cope with drawbacks existed in above two methods, a novel brief and effective robust adaptive impedance control scheme is proposed in this work, which has good ability for desired force tracking with unknown environmental information. A new adaptive compensator is introduced into the impedance framework to deal with lumped uncertainties caused by unknown stiffness and geometry of environment. It can minimize force tracking error and the force overshoot has also been reduced a lot. The stability and convergence analysis is conducted using a spring model, but the method is not applicable to a complex second-order environmental model. Simulation and experimental results sufficiently demonstrate the effectiveness and confirm the theoretical claims of the method.