Global fast terminal sliding mode control for a Maglev planar motor based enhanced finite-time state observer

Magnetically levitated (maglev) planar motors are widely used in precision manufacturing and micro/nano-processing owing to their vacuum compatibility, non-contact actuation, and compact structure, but nonlinear dynamics, parametric uncertainties, and load disturbances degrade positioning and trajectory tracking accuracy. To address these issues, this paper proposes a global fast terminal sliding mode control (GFTSMC) with an enhanced finite-time state observer (EFTSO). First, an uncertainty-inclusive model is established, and a switching-free continuous sliding control law is devised to suppress high-frequency chattering while guaranteeing global finite-time convergence of the tracking error. Then, the EFTSO performs finite-time estimation of the lumped disturbance, and a Smith predictor is introduced to realize one-step-ahead delay compensation, thereby improving response speed and closed-loop stability. Finally, MATLAB simulations and experiments on a maglev planar motor demonstrate that, for step, sine, and triangular trajectory tracking, the proposed controller reduces the root-mean-square (RMS) error by approximately 35%, 80%, and 73%, respectively, compared with a PID-extended state observer (PID-ESO) and fast terminal sliding-mode control (FTSMC). These results demonstrate that EFTSO-GFTSMC provides superior dynamics, steady-state and robustness, offering an effective solution for high-performance control of maglev systems under complex operating conditions and strong potential for engineering deployment. • EFTSO and Smith predictor enabling finite-time disturbance estimation and one-step-ahead delay compensation. • Robust under uncertainties and impulsive disturbances , yielding small errors and fast recovery. • Simple structure and easy tuning , and convenient for engineering deployment in motor and control systems.