Radial Displacement Sensorless Control in Full Speed Range of Single-Winding Bearingless Flux-Switching Permanent Magnet Motor

Abstract

It is a key to realizing stable suspension operation of bearingless motor that the rotor radial displacement information is acquired accurately. Sensor applications are sensitive to environments, limiting to scenarios, and increasing costs. Herein, a radial displacement sensorless control method in the full speed range for single-winding bearingless flux-switching permanent magnet motor is proposed. First, an eccentric modulation function is presented, and the flux linkage equation of each winding with rotor eccentricity is derived based on the air-gap magnetic field modulation theory. Therein, the phase inductance and flux are functions of the rotor displacement. Second, the bias-flux equations of the symmetric windings are deduced, and the rotor displacement observer of the medium-high speed is established based on the bias-flux amplitude. Due to flux information being difficult to extract at low speed, the high-frequency current signal is injected into the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d_T</i> -axis of the torque plane. The rotor displacement observer of the zero-low speed is established based on the high-frequency bias-induced EMF amplitude. Besides, a novel smooth switching process is designed. Finally, the observers are analyzed, and the radial displacement sensorless control strategy is built. The experimental results verified the validity of the proposed method.