Low cost sensorless control of permanent magnet motors - an overview and evaluation

This paper provides a review of the literature addressing sensorless operation of PM brushless machines. The methods explained are state-of-the-art of open and closed loop control strategies. The closed loop review includes those methods based on voltage and current measurements, and algebraic manipulations of machine equations, those methods based on back emf measurements, and those methods based on novel techniques not included in the previous categories. A review of machine model equations is also treated. The paper concludes with a comparison table including all main features for all control strategies