Nonsingular terminal sliding-mode control for nonlinear robot manipulators with uncertain parameters

This paper proposes an effective nonsingular terminal sliding-mode controller (TSMC) for nonlinear robot manipulators to obtain higher precision as well as stronger robustness. In general SMC systems, there exists a paradox of balancing steady-state precision and robustness. First, the terminal sliding mode surface is designed to guarantee any initial states to converge to the original point along the sliding mode surface in finite time. Then, a chattering-free sliding-mode controller has been developed and applied to the trajectory tracking of a nonlinear four-joint SCARA robot manipulator with parameter uncertainties. Robot performances using traditional PD+FF controller and this nonsingular TSMC were compared. Simulation results are presented to verify the effectiveness of the proposed control approach. The proposed nonsingular TSMC can not only provide excellent tracking performance but also eliminate chattering.