New Approach to Rotor Position Detection and Precision Speed Control of the BLDC Motor

This paper presents particular methods for deployment of the sensorless permanent magnet brushless DC (PM BLDC) motor drive system. The waveform of the motor internal voltages (or back emf) contains fundamental and higher order frequency harmonics. Therefore the third harmonic component is extracted from the stator phase voltage. The resulting third harmonic signal maintains a constant phase relationship with the rotor flux at any motor speed and load condition. In addition, in this paper, a simple starting method and speed estimation approach are also proposed. Experimental results are provided, to demonstrate the validity of the proposed control method