This research is concerned with the development and analysis of sensorless control strategies for Permanent Magnet Synchronous Motors (PMSMs), with a particular emphasis on the critical zero- and low-speed operating regions. Specific focus is given to the challenges encountered at low speeds, where the back electromotive force (Back-EMF) is minimal, necessitating the utilisation of alternative methods for rotor position estimation. The three high-frequency injection (HFI) techniques, namely pulsating injection with a sinusoidal wave, rotating injection with a triangular wave and pulsating injection with a square wave, are subjected to a comprehensive analysis. The research methodology is based on a combination of simulation and experimental validation. A comprehensive simulation of the proposed algorithms was conducted to study their behaviour and robustness under a variety of operating conditions. The simulations yielded valuable insights that informed the subsequent implementation of the techniques on a physical PMSM test bench. The experimental measurements corroborated the efficacy of the pulsating and rotating HFI approaches for estimating rotor position and speed in the low-speed region, while also identifying areas that warrant further examination. The results demonstrate that the proposed sensorless control methods are capable of achieving reliable performance under challenging conditions, thereby providing a foundation for further advancements in the field. This work makes a contribution to the understanding and practical implementation of sensorless PMSM control, particularly in applications that require precise operation at low speeds.
Franko et al. (Thu,) studied this question.