Methodology for Sensorless Displacement Control on a Homopolar Bearingless Motor

Bearingless slice motors (BELMs) integrate a motor and a radial magnetic bearing within a shared stator core, allowing for rotor tilt and axial stabilization through passive magnetic coupling. However, incorporating mechanical sensors for both rotation and displacement control within a limited space increases system complexity and cost. To address this, we propose a robust sensorless displacement control method for BELMs with separated windings. The approach utilizes the voltage difference between centrally symmetrical armature coils, where coil terminal voltage (CTV) contains high-SNR radial displacement information, unlike the low-SNR phase terminal voltage (PTV). High-frequency signals are injected to enhance SNR and enable accurate, fast displacement estimation without interfering with suspension current control.