Time-varying disturbance-observer-based tracking control of uncertain flexible-joint manipulator

Abstract

This paper presents a time-varying disturbance-observer- (TVDO-) based improved sliding-mode control (ISMC) method to achieve tracking control of uncertain flexible-joint manipulator (UFJM). Based on the UFJM dynamic model and its ideal dynamic model regardless of uncertainties, an error system in the form of an integral chain with disturbances is established. The tracking control objective of the UFJM is achieved by designing the TVDO-based ISMC law to guarantee the ultimate boundedness of link angle errors for the error system. Specifically, by employing the TVDO, the disturbances in the error system are estimated. By using the TVDO-based ISMC method, the uncertainties are overcome, and the chattering problem is reduced. The contradiction between high tracking accuracy and suitable torque without peaking phenomenon is alleviated. Finally, the stability analysis of the closed-loop control system is presented, and the validity of the proposed method is illustrated by simulation and experiment.