Direct Levitation Force Control for a Bearingless Induction Motor Based on Model Prediction

Aiming at the high-performance operation requirements of a bearingless induction motor (BIM), a direct levitation force control strategy based on model prediction for the BIM is proposed. Based on mathematical models of the BIM, the flux linkage at the next moment is predicted according to the current observation value of the flux linkage of levitation force winding, and the objective function of the flux linkage is constructed to output the optimal flux linkage. Inverter drive control signals are generated from the SVPWM module to control the BIM levitation. In addition, to deal with the problem of the initial error caused by reverse electromotive force integration in the traditional observation of flux linkage during the process of motor control, an improved flux observer is introduced and applied to the control system. The simulation and experimental results show that the proposed control strategy cannot only effectively improve the suspension stability of the rotor, but also enhance the anti-disturbance ability of the system in comparison to the traditional levitation force control. In the meantime, it has a good dynamic and static performance which verifies the effectiveness and reliability of the proposed control strategy.