Robust Impedance Control for a Five-Bar Parallel Robot Based on Uncertainty Estimation

We proposes a disturbance-observer-based robust impedance control strategy for a five-bar structured robot with a lumped uncertainty composed of the friction force and the system disturbances. Through a constructed reference trajectory, we transform the impedance control design into a impedance trajectory tracking problem. A disturbance observer is designed to approximate the lumped uncertainty without assuming the time derivative of friction forces being bounded prior to control implementation. Then, based on the uncertainty estimation, the robust impedance controller is designed with an interaction control term to enhance transient control performances. We validate the stability of the designed impedance controller and illustrate its effectiveness by simulation results.