Disturbance Observer Structure Applied to Sensorless Brushless DC Motors Drive

Abstract—In a permanent magnet (PM) brushless dc motor (BLDC), the performance of Hall effect sensors are not reliable in some applications. The back electromotive force (back-EMF) signal is used instead since the zero-crossing points of back-EMF can be used to provide the rotor position information. In this paper, a new back-EMF difference detection method based on disturbance observer is proposed. The proposed structure can detect the back-EMF as well as back-EMF difference signal. The zero-crossing points of the back-EMF difference can be used directly for commutation, requiring no phase shift. Simulation and experiment results are provided to show the feasibility of the proposed method.