Evaluation of velocity servo performance of IMPSM drive under high-performance sensorless operation

This paper examines the accuracy and suitability of sensorless velocity estimation for application in a velocity servo system. Because of the magnetic saliency, the interior permanent magnet (IPM) motors have advantages of acting as their own position and velocity sensors, of course via estimators, over other more conventional AC machines with uniform airgap. The elimination of the position/speed sensor is also desirable as it reduces the overall cost while increasing its reliability. Instead, the rotor speed and position are estimated from the measured stator currents and voltages. Existing solutions can be broadly classified into open and closed-loop estimators and signal injection methods, exploiting the saliency property of the IPM motor. This paper provides an overview of these methods and highlights their strengths and weaknesses. Simulation and experimental results are included to supplement the discussion of this topic.