Disturbance-Observer-Based Terminal Sliding Mode Control for Linear Traction System With Prescribed Performance

In this article, a terminal sliding mode control (SMC) strategy based on the nonlinear disturbance observer (NDO) and prescribed performance method is proposed to deal with the speed tracking problem for permanent-magnet linear synchronous traction systems in urban rail transit. First, to improve the dynamic and static performances, a prescribed performance control characterizing the tracking performance employed for error transformation. This limits the tracking error of the original system to a prescribed bound if the transformed system is stable. Then, a terminal SMC is designed with backstepping, which guarantees the states converge to equilibrium point in finite time, realizing fast transient response of the system. Considering the existence of the uncertain disturbance, an NDO is utilized to estimate perturbations, and then, the estimation is used for the feedforward compensation, further improving system stability. Finally, the effectiveness and advantages of the proposed scheme are illustrated by computer simulations and experiments in dSPACE.