Fractional-order Sliding Mode Based Variable Stiffness and Damping Impedance Control with Disturbance Observer

摘要

This paper proposes a fractional-order sliding mode based variable stiffness and damping impedance controller. A new closed-loop impedance architecture containing the negative power type stiffness and damping parameters is built, and an integral fractional-order sliding surface synthesizes constant and variable impedance parameters to construct a reduced order system, which indicates an impedance behavior. The external disturbance easily propagates to the preset impedance architecture to degenerate the stable performance of reduced order system, and it is well estimated by a fractional-order disturbance observer to reduce the adverse effect by partially eliminating the disturbance. The proposed impedance architecture owns better transient performance compared with the trivial spring-damper impedance architecture, which is well illustrated by the verified numerical results.