Research of modeling axial magnetic bearing based on system identification

Magnetic bearings can effectively increase the critical speed of high-speed motors,but axial magnetic bearings have a significant eddy current effect at high rotor speeds and solid materials. For the modeling of solid axial magnetic bearings, the eddy current effect is often ignored when using the equivalent magnetic circuit method to establish the axial magnetic bearing model, resulting in a large error between the theoretical model and the actual model. In order to obtain an accurate model of axial magnetic bearings closer to the reality, the axial part of a hybrid 3-degree-of-freedom magnetic bearing was identified, and the determination process and error criteria of the fractional order model were studied. The mathematical model of axial magnetic levitation bearing was derived. The results show that the fractional-order system model can compensate for the phase characteristic error of the integer-order model in the high frequency band, and has higher accuracy in the entire frequency domain. © 2024 Editorial Department of Electric Machines and Control. All rights reserved.