Back emf mapping for sensorless control of brushless DC drives

This paper presents a novel sensorless scheme to control Brushless DC motors (BLDCM) using back emf mapping (BEM). A reference back emf (BEMF) point at commutation instant at a given specific speed is used from which all other commutation instances at different operation speeds can be precisely calculated. Thus, torque optimisation commutation point which corresponds to 30 electrical degrees would be achievable. Zero crossing detection point (ZCP), phase shifters, delay managers, integration and third harmonics, hard switching techniques and/or look up table are eliminated. This increases the signal to noise ratio and overcomes some cases where ZCP could be undetected. Simulation is performed validating the proposed approach.