A Comparative Study of State Observers for Position Sensorless Control of Permanent Magnet Synchronous Machines

High performance control strategies for permanent magnet synchronous machines (PMSMs) drives rely on sensors to obtain accurate information of rotor position and speed. However, mechanical sensors are expensive and susceptible to harsh environment. Therefore, various sensorless control strategies have been proposed and intensively investigated for decades. Among them, observer based sensorless techniques are becoming more and more popular and universal. This paper presents a comparative study of three mainstream state observers for PMSM sensorless control drives: Luenberger observer, sliding mode observer, and Kalman filter. Theoretical principles of these three state observers are illustrated and a series of simulation results are presented to evaluate and compare the performances of three observers. Comprehensive analyses and fair comparisons are given considering practical implementation issues including machine parameter variations, measurement noises and low sampling frequency ratio.