Invariant manifold based nonsingular terminal sliding mode control for systems with multi-source disturbances via output-feedback

This paper proposes an invariant manifold based nonsingular terminal sliding mode control (NTSMC) approach for systems subject to multi-source disturbances to achieve finite-time tracking in the case of only output measurement. By utilizing the invariant manifold, the mismatched disturbances are transferred into the lumped matched disturbance. A universal finite-time observer (UFTO) is designed to estimate the errors between actual states and their desired values, the steady-state of the control input as well as the lumped disturbance. Introducing the estimations, a nonsingular terminal sliding mode controller is constructed. Based on Lyapunov’s theory, the rigorous stability analysis for the closed-loop system is given. Compared with the existing output-feedback sliding mode control (SMC), the proposed approach enables finite-time tracking in the presence of unknown derivatives of the reference signal and multi-source disturbances without requiring additional tracking differentiators. The proposed approach is applied to the DC–DC buck converter system, and simulation results verify the effectiveness of the proposed control strategy.