OPTIMIZED AIR-GAP-FLUX ORIENTATED CONTROL OF AN INDUCTION-TYPE BEARINGLESS MOTOR
HE Yi-kang, NIAN Heng, RUAN Bing-tao (College of Electrical Engineering, Zhejiang University, Hangzhou 310027, China)
Due to the coupling between the levitation force and the electromagnetic torque,and between the two orthogonal levitation forces,rotor suspension of an induction-type bearingless motor could become unstable. In connection with the concept that the magnetic levitation force is the active unbalance of the air-gap flux-density between stator and rotor, the air-gap-flux oriented control model of the induction-type bearingless motor was put forward firstly and the stable suspension operation in the dynamic process of starting-up and sudden loading were simulated in this paper. However,the variation of rotor parameters and the non-linear magnetic saturation at loading condition cause the changing in amplitude and phase of the air-gap-flux,which further destroys the decoupling condition between the two perpendicular levitation forces and deteriorates stable suspension of the rotor. To solve these problems,a kind of optimized air-gap-flux orientated control strategy and its implemental system were suggested, in which the amplitude and phase angle of the air-gap-flux were corrected in real-time and the dynamic decoupling control was implemented.These measures effectively enhance the stable suspension capability of the motor with the rotor parameter variation and magnetic saturation considered and offer an implemental scheme for the operation control of a practical bearingless motor system.