A new position detecting method for brushless DC motor

A new rotor position detecting method for sensorless brushless DC motor (BLDCM), speed-independent position function, is proposed in this paper. The principle of this method is discussed in detail. Depending on the powerful operation function of digital signal processing (DSP), the speed-independent position function G(thetas) is determined by analyzing the phase current and phase voltage of BLDCM. In order to verify the validity of the proposed control method, the experimental system including hardware and software segments has been developed and the experiments have been conducted. The experimental results demonstrate that this new rotor position detecting method can detect the rotor position from near zero speed to high speeds directly without position sensor. Furthermore, the experiments also indicate that the method can simplify the hardware circuit, generate reliable and precise commutation operation and promote the estimation accuracy of rotor position, which proves that this new method has favorable performance of speed adjustment.