A new phase-delay free method to detect back EMF zero crossing points for sensorless control of spindle motors

This paper introduces a new phase-delay free rotor position detecting method for the sensorless control of brushless DC spindle motors. It applies a digital filtering procedure to identify the true and false zero-crossing points of the phase back EMFs, the latter of which are caused by the terminal voltage spikes of the commutating freewheeling currents. The suggested method is inherently top speed-limitation free and independent of the motor parameters. It can be applied in all kinds of spindle motors from 1" micro drives to 3.5" high-speed enterprise server drives. The developed prototype of SpinBox based on the invented method has experimentally confirmed its correctness and effectiveness in wide-speed range.