To enhance the speed-control performance of a permanent magnet synchronous motor (PMSM) drive system, an improved sliding-mode anti-interference control strategy is presented. Firstly, to tackle the speed fluctuation issue caused by cogging torque (a periodic disturbance) and time-varying disturbances at low set speeds in PMSM, an improved sliding-mode control (ISMC) is proposed. It consists of a continuous adaptive fast terminal sliding-mode surface (CAFTSMS) and a new reaching law (NRL). The CAFTSMS boosts the system’s immunity to interference, while the NRL, improved via an adaptive function, enhances the fast transient response and notably reduces speed fluctuations. Secondly, a quasi-proportional resonant (QPR) controller is introduced. It suppresses specific-order system harmonics, significantly reducing the harmonic amplitude and strengthening the system’s ability to handle periodic disturbances. Finally, a cascaded extended state observer (CESO) with a special cascade structure is proposed to solve the observation-delay problem in the traditional cascade structure. Experimental results show that the proposed sliding-mode anti-disturbance control strategy performs excellently in overcoming disturbances.

This brief proposes a sensorless control scheme for the permanent magnet synchronous motor (PMSM), which is based on a finite-time adaptive state observer (FTASO) combined with a parallel phase-locked loop (PPLL). In this scheme, an adaptive gain mechanism, a nonlinear compensation term, and the characteristics of the finite-time state observer are integrated to enhance the estimation accuracy and achieve finite-time convergence of the back electromotive force (EMF). Based on the EMF estimated in the initial phase, a parallel PLL is designed to effectively reduce the angle error induced by speed variations during acceleration and deceleration. Finally, the effectiveness of the proposed sensorless control scheme is validated through simulation comparison with the conventional algorithms.

To suppress position estimation errors inherent in speed-sensorless PMSM control, a frequency-domain shaped nonlinear layered observer is proposed in this brief. The proposed method leverages a smooth gating function to naturally establish a layered mechanism: the outer layer exploits high-order nonlinearity to accelerate back electromotive force convergence, while the inner layer transitions into a linear kernel integrated with an internal model term. Through precise frequency-domain shaping, the observer guarantees zero phase lag and unity gain in BEMF estimation, alongside robust DC-bias suppression. Unlike existing linear or nonlinear methods, the FSNLO simultaneously achieves superior dynamic response and uncompromised frequency-domain shaping capabilities. Rigorous stability analyses prove uniform ultimate boundedness. Comparative experiments validate the superiority of the proposed method, demonstrating remarkable enhancements in both steady-state and dynamic estimation precision.