Adaptive Synchronous-Frequency Tracking-Mode Observer for the Sensorless Control of a Surface PMSM

This paper proposes a sensorless speed-control method based on an innovative adaptive synchronous-frequency tracking-mode observer (AFTO) for surface permanent-magnet synchronous motor drives. The method uses the AFTO function, based on proportional resonance control, to track stator currents adaptively under variable-frequency scenarios. Then, an orthogonal phase-locked loop supports the estimation of rotor speed. The convergence of stator-current errors guarantees an estimation of the back electromotive force (back EMF) without the influence of harmonic components and the chattering problem. The resulting pure and smooth back EMF provides high-accuracy estimates of the rotor position and speed. Simulations and experimental results are given to provide further validation of the proposed rotor-position and speed estimation schemes under different speed scenarios. The improved control method also maintains high estimation accuracy for rotor speed and position at low speeds.