Saliency-based position estimation in PM synchronous motors

This paper presents a position and speed estimation algorithm based on magnetic saliency of PM synchronous motors. The proposed method uses inherent high frequency content of motor PWM excitation to measure position dependent inductance parameters, which are then processed using a simple nonlinear observer to produce the position and speed estimates. To ensure persistent excitation at all operating voltages (speeds), a novel PWM algorithm with full voltage output is developed and presented. The efficiency of the modified excitation was evaluated and compared to the efficiency of the standard position-sensorless motor drive excitation. Experimental results are presented as well, showing good algorithm performance in a wide speed range, including zero.