Robust Link Position Tracking Control for Robot Manipulators with Series Elastic Actuators Using Time-delay Estimation

Abstract

This paper aims to develop a controller for a robot manipulator equipped with series elastic actuators (SEAs) to precisely track the desired link position coping with deflections from the intrinsic compliance. The well-known time-delay estimation (TDE) technique is modified for devising the new controller. In this paper, we first report that the conventional use of a constant gain matrix for the TDE framework is insufficient for high accuracy tracking because the tracking accuracy is significantly deteriorated and the closed-loop stability may be threatened. Accordingly, the new controller employs link inertia information with dynamic coupling terms to define the gain for TDE and then employs terminal sliding mode (TSM) control to enhance robustness and convergence speed. Particularly, the modified TDE is applied in the two-staged manner which enables to compensate the complicated nonlinear dynamics terms in SEA dynamics. The TSM synergistically amalgamates the accuracy, robustness, and convergence in tracking. The proposed controller is numerically validated by comparative experiments with a SEA-driven manipulator.