Adaptive Fixed-Time Speed Control and Position Observation for Sensorless PMSM Control

To enhance the anti-disturbance performance and dynamic response capability of permanent magnet synchronous motors (PMSMs) under sensorless conditions, this article proposes a sensorless robust control scheme that integrates an adaptive fixed-time sliding mode speed controller with an improved back electromotive force (EMF) observer and a variable-gain extended state observer (VGESO). First, an improved back EMF observer is designed based on a high-order sliding mode algorithm, effectively suppressing chattering and enhancing estimation accuracy at lower speeds. On this basis, VGESO is constructed to estimate rotor position and speed information, eliminating the phase-locked loop (PLL) structure and improving the system’s dynamic response. Then, an adaptive fixed-time sliding mode speed controller is proposed, whose convergence time is independent of the system’s initial conditions, thereby enhancing convergence performance. In addition, by incorporating the proposed adaptive law, the assumption of a known upper bound on unknown disturbances is eliminated, reducing the conservatism in controller design. The stability of the system is demonstrated through Lyapunov’s stability theorem. Finally, the experimental results demonstrate that the proposed control scheme significantly enhances the system’s robustness while concurrently improving its dynamic response.