Analytical model and feedback control of the levitation force for an induction-type bearingless motor

A relatively accurate analytical expression of the magnetic levitation force for an induction-type bearingless motor is proposed in this paper with the eccentricity in the location of stator and rotor taking into consideration, and its computation accuracy is verified by ANSOFT, an electro-magnetic field analysis software of electrical machines. Applying this analytical levitation force model, the real-time observation of magnetic levitation force is realized, the closed-loop control of levitation force is then implemented on the basis of air-gap-flux-oriented decoupling control system of the bearingless motor. Simulation study verifies the effectiveness of the approach in improving the static and dynamic performance of an induction-type bearingless motor.