Hybrid continuous nonsingular terminal sliding mode control of uncertain flexible manipulators

This paper investigates the robust control of two-link flexible manipulator systems subject to parameter perturbations, and a hybrid control scheme consisting of a continuous nonsingular terminal sliding mode (NTSM) controller and an observer-based LQR controller is proposed. In order to solve the non-minimum phase problem of flexible manipulator, singular perturbation method is utilized to decompose the system into a slow and fast subsystem in two-time scale, and joint angles and corrected flexible modes are modeled as the slow and fast variables, respectively. For the slow subsystem, a novel continuous NTSM control based on the concept of relative degree is proposed for robustness, finite-time convergence and free-chattering. For the fast subsystem, a reduced-order observer is designed to estimate corrected flexible modes and then a LQR controller is proposed for its optimal stability. Simulation results are presented to validate the control scheme.