A high-frequency signal injection based sensorless drive method for brushless DC motor

Inductance saliency-based position sensing method is a common complement to the ineffectiveness of the traditional back-emf-based methods in low-speed applications, which effect originates from zigzag saturation on core teeth. In this paper, an impedance-tracking based self-sensing method is proposed, which is capable of quickly estimating rotor position by tracking variations on attenuated response of an injected high-frequency signal. Compared to other inductance tracking-based self-sensing methods, this solution removes specific nonlinearities such as semiconductor voltage drop characteristics and coil resistive effect while having minimal impact on the control distortion. Measurements and experiment results demonstrate the versatility of the method on different brushless motor constructions.