Fixed-Time dynamic surface control for permanent magnet linear synchronous motors with modified disturbance observer

This paper presents a novel fixed-time dynamic surface control (DSC) scheme for permanent magnet linear synchronous motors subject to external disturbances. Without employing the fractional power terms or complicated switching strategy to build the control laws, a smooth fixed-time dynamic surface control scheme is proposed, which overcomes the potential singularity problem and explosion of the complexity issue in the fixed-time back-stepping design. To weaken the influence of external disturbances, a modified fixed-time convergence disturbance observer (FTDO) is explored to compensate the normal fixed-time DSC laws, thus largely improving the robustness of the proposed control scheme. The highlights of the proposed design are threefold. First, it is free of the fractional powers terms yet fixed-time convergence property. Second, it increases the robustness of the normal control design by constructing new FTDO. Third, it avoids the explosion of the complexity problem by virtue of modified fixed-time filters. The stability of the proposed control scheme is analyzed using the Lyapunov technique. Simulation results are given to illustrate the effectiveness of the proposed controller.