Position sensorless control of BLDC motor based on back EMF difference estimation method

In the proposed scheme the commutation is done at the zero crossing of Back EMF difference. The commutation can be done at the zero crossing point itself hence it does not require any phase delay circuit. Thus the optimal performance is guaranteed by using this signal for commutation. The speed control of this sensorless drive is done in two different ways. The switching sequence and switching frequency of inverter switches can be varied as per the speed requirement. That is speed control by controlling inverter switching. Another method of speed control is by controlling the switching of dc to dc buck converter at the supply side. The performance of the motor is compared in these two cases. The effectiveness of proposed sensorless technique is verified through simulation. The simulation of the proposed sensorless method is done in MATLAB/Simulink. The proposed sensorless control is validated by complete experimental results on a commercial BLDC motor.