On the use of spectral analysis of air-gap flux density in permanent magnet bearingless motors

In this paper, the authors propose an overall analysis of the flux density harmonics in the air-gap of bearingless machines in order to control two functions: levitation and rotation. This harmonic analysis allows the determination of the contributions of different interactions of the field components and therefore determines a control strategy. It also allows to evaluate the parasitic forces which can disturb the system. The harmonic model is semi-analytical and allows to obtain good results by means of very low CPU time.