Review of sensorless methods for brushless DC

This paper provides a review of the literature addressing sensorless operation of brushless DC machines. Methods explained are state-of-the-art, including those using: (1) measured currents, voltages, fundamental machine equations and algebraic manipulations; (2) observers; (3) the back-EMF method; (4) sensorless starting techniques; and (5) novel techniques not in the previous categories.