Nonsingular terminal sliding mode control of nonlinear second-order systems with input saturation

This paper considers the nonsingular terminal sliding mode (TSM) controller design for a nonlinear second-order system subject to input saturation. A new nonsingular TSM manifold is constructed by integrating the conventional nonsingular TSM manifold with a saturation function. When the bound of the uncertainty is known, based on the designed TSM manifold, a saturated controller can be designed directly for the nonlinear system. When the bound of the uncertainty is unknown, a disturbance observer is first employed to estimate the uncertainty, followed by constructing a composite controller consisting of a bounded feedback controller and a forward compensator. Theoretical analysis shows that under the proposed two control methods, the states of the closed-loop system will both converge to zero in finite time. Simulation results demonstrate the effectiveness of the proposed methods.