Sensorless control of a BLDC PM motor based on I-f starting and back-EMF zero-crossing detection

The present paper introduces a novel sensorless control of brushless dc permanent magnet (BLDC-PM) motor based on I-f principle for starting (from any initial position) with seamless commutation to BEMF zero crossing detection above a certain speed. The starting method assures a fast response and the criteria for switching to speed sensorless control introduces short transients. This way, for general drives, even with notable load torque at start, the motor will start, although after a short hesitation depending on the initial position of the rotor. Several scenarios were simulated in Matlab/Simulink (with Plecs Library) to confirm the proposed control strategy. Experiments for I-f starting are ongoing.