Abstract: The bearingless induction motor which combines magnetic levitation bearings with the drive winding is an extremely complicated nonlinear system. The nonlinear decoupling control of electromagnet torque and radial levitation force is the base of the stable operation of bearingless induction motor. A nonlinear control strategy based on stator flux orientation of motor winding is proposed. An adaptive flux observer is designed by which the needed air-gap flux of motor winding for radial levitation controller is obtained by using the stator flux and current. Using Matlab/Simulink, the sample machine is simulated. The simulation results suggest the good decoupling operation performance of the radial levitation based on stator flux orientation, which verifies the correctness and feasibility of the proposed method.

Key words: Adaptive flux observer, Bearingless induction motor, Magnetic levitation, Stator flux orientation