Position estimation in salient PM synchronous motors based on PWM excitation transients

This paper presents a position and speed estimation algorithm based on magnetic saliency of permanent-magnet synchronous motors. The proposed method uses inherent high-frequency content of motor pulsewidth-modulation (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, and for various load torques.