Finite-time extended state observer enhanced nonsingular terminal sliding mode control for buck converters in the presence of disturbances: design, analysis and experiments

A sliding mode control (SMC) method is designed to attenuate the disturbances in the DC-DC buck converter system based on the estimated values of extended state observer (ESO). A conventional ESO is unable to accurately estimate system states and disturbances in finite time limited by its linear nature. This weakness cannot ensure that the system reaches the nominal sliding mode surface within finite time, thus the sliding mode trajectory will be affected. Therefore, a novel finite-time extended state observer (FTESO) is presented, utilizing a homogeneous theorem for finite-time convergence. Subsequently, a FTESO-based nonsingular terminal sliding mode control (NTSMC) method is devised for achieving globally finite-time stable of the closed-loop system. The Lyapunov stability theorem and homogeneous theorem are used to prove the finite-time stability, and the upper bound of settling time is estimated explicitly. Finally, both numerical simulations and experiments demonstrate the superiority of the designed control scheme with modeling errors and load disturbances.