A study on high frequency signal injection method of aiming at detecting the rotor position of the salient-pole brushless DC motor

The rotor position detection without sensor is very important for permanent magnet brushless DC motor (PM-BLDCM) to fulfil its electric commutation and speed control, a novel rotor position detection method, based on the spatial saliency tracking scheme was presented. The method employed high-frequency voltage-signal injection to make motor form a high-frequency current vector, of which the negative component current contained rotor position information. By rotor position tracking observer, with heterodyning processing adopted, the rotor position signal can be picked up and then the detection of the rotor position can be implemented without any specialized mechanical position sensor. The sensing principle of the spatial saliency tracking scheme, the principal of space voltage PWM (SVPWM) technology to inject the high-frequency signal, the structure of the rotor position tracking observer and the simulation study for the rotor position self-sensing process of a PM-BLDCM at low even zero speed and normal operation were all discussed in detail. Simulation results verified the correctness and availableness of this approach.