Sensorless brushless DC motor drive based on commutation instants derived from the line voltages and line voltage differences

Determination of commutation instant is essential for the control of brushless DC motor (BLDC) drive. Conventionally hall sensors have been used to derive commutation instants. Use of position sensors has its own merits and demerits. In order to overcome the limitations of position sensor based drives, sensorless techniques are used for control of BLDC motor. The detection of the zero-crossing of the back-EMF is a widely used method for sensorless control. The commutation instants are derived from the information of zero crossing point of the back EMF. Several algorithms have been proposed in literature for the detection of back EMF zero crossing. In this paper a novel method for determining the commutation instants directly from the comparison of the line-to-line voltages and their difference voltages is presented. The performance of the BLDC drive with the proposed algorithm is studied and verified through simulation done in MATLAB/SIMULINK environment.