Rotor displacement sensorless control strategy for PM type bearingless motor based on the parameter identification

A rotor radial displacement estimation scheme using high frequency signal injection in the torque winding was suggested, which will meet the need of displacement sensorless operation for an inset PM type bearingless motor. And the inductance parameters in the torque winding and suspension winding used for the position estimation are online identified using the recursive least-squares method to improve the self-sensing accuracy with the consideration of the saturation condition. The rotor radial displacement detecting principle, such as the injection of high-frequency carrier signal, the differential voltage extraction in the suspension winding, the design of the tracking observations for rotor radial displacement estimation, and the parameter identification technique were all discussed. Simulation study demonstrates that the proposed method is capable of effectively estimating the rotor radial displacement for an inset PM type bearingless motor and is able to achieve stable sensorless suspension operation.