一种考虑被动轴向力的5自由度磁悬浮PMSM轴向悬浮控制前馈补偿策略

In the five-degrees of freedom (5-DoF) magnetic levitation system, passive axial forces (PAFs) usually occur when stator and rotor are not aligned axially during levitation, which tends to pull the rotor back to the balanced position and is benefit for the reduction of axial displacement ripple further. However, they are generally ignored in conventional axial levitation control of 5-DoF magnetic levitation permanent magnet synchronous motors (PMSMs). This paper analyzes the influence of PAFs on axial displacement, and improves the conventional control. Besides, coil-current fluctuation of radial magnetic bearings (RMBs) and motor can also result in PAF ripples, which increases the axial displacement ripple further. On the basis of it, the influence of RMB coil-current fluctuation on axial displacement is analyzed, and a feedforward compensation strategy is also proposed to reduce the axial displacement ripple. Experimental results show that the axial displacement ripples are reduced by 38.6% and 37.3% at 0 r/min and 20000 r/min with improved control, respectively. Further, the axial displacement ripples are also reduced by 37.8% and 27.7% at 0 r/min and 20000 r/min with the proposed strategy, respectively.