Permanent Magnet Motor Control in Full Speed Range without Mechanical Sensors

This paper presents a control method for permanent magnet (PM) motors based on a combination of a non linear full-order observer and a signal injection scheme. Mechanical-sensorless operating range down to zero speed is obtained using only voltage and current sensors. The signal injection scheme uses the asymmetry of the motor´s d and q axis inductances to estimate rotor position and speed. Such asymmetry is also taken into account in the motor model used to construct the observer. The performance of the proposed scheme is validated through experimental results