Adaptive Stiffness and Damping Impedance Control for Environmental Interactive Systems with Unknown Uncertainty and Disturbance

This paper presents an impedance controller with adaptive stiffness and damping terms for environmental interactive system with unknown modeling error and external disturbance. The objective is to compensate the uncertainty and disturbance and form a desired close-loop impedance architecture. A disturbance observer for nonlinear system is employed to estimate the lumped uncertainty and disturbance. The stiffness and damping are adjusted by the state-variable-related negative power type parameters. Consequently, the control input is designed with the consideration of the estimation of lumped uncertainty and disturbance as well as the regulated stiffness and damping. The stability is proved and the criterion of parameter selection is pointed out. Although the state-variable-related stiffness and damping parameters will intuitively be singular, the system works without any singularity due to the independence of these parameters in stability analysis. To verify the proposed approach, a one degree of freedom mass system is adopted and numerical simulation is performed accordingly. The simulation results demonstrate the effectiveness and the superiority of the proposed control scheme for environmental interactive system with unknown modeling error and external disturbance.