磁悬浮飞轮用轴向力偏转永磁偏置轴向磁轴承磁路耦合特性

摘要

为使磁悬浮飞轮具有高精度、大力矩、多自由度动量交换能力,提出并设计了一种永磁偏置轴向磁轴承(AGMB),主动控制飞轮转子沿轴向平动和绕径向偏转这3个自由度的运动.提出偏置磁通耦合度、控制磁通耦合度的概念,并给出了定义.通过磁路分析得到了AGMB和应用于微动框架的传统永磁偏置径向磁轴承(即径向力偏转磁轴承,RGMB)的耦合度的解析表达式.建立了磁路模型与磁路耦合程度之间的数值公式联系,进而定量分析了磁路耦合度对决定飞轮微动框架性能的偏置力变化率、电流刚度变化率以及最大承载力等磁轴承性能指标的影响,为解析分析和评价磁轴承的磁路耦合特性及其对磁轴承性能的影响提供了一条理论途径.经解析计算和有限元(FE)仿真验证表明,AG.MB具有更好的磁路弱耦合特性和偏转性能:微动框架时磁路耦合度的变化范围较RGMB小近一个数量级,从而偏置力变化率、电流刚度变化率的变化范围小近一个数量级,飞轮最大偏转力矩指标是RGMB的2.7倍以上.基于AGMB所设计的50 N·m·s磁悬浮飞轮,可实现最大偏转角0.5°、最大偏转力矩8.1 N·m,偏置力与电流刚度的变化率全工况下不超过15%的大容量、高精度的微动框架功能.%To satisfy the requirements of the high precision vernier-gimballing function of a magnetically suspended flywheel,an axial magnetic bearing biased with a permanent magnet, i.e., the axial gimballing magnetic bearing (AGMB) is presented, with the capacity of controlling the 3 degrees of freedom rotor motion including axial translation and radial tilt. The concepts of bias-flux coupling degree and control-flux coupling degree are introduced and defined. Based on the coupling degree analytical expression of AGMB and the traditional radial magnetic bearing biased with a permanent magnet (called radial gimballing magnetic bearing applied for vernier-gimbailing, RGMB for short) from an equivalent magnetic circuit, the quantirive relationship between the magnetic circuit model and the coupling degree is constructed, and the coupling degree influence on the magnetic bearing performance, such as its bias-force change rate, current stiffness change rate, and maximal loading ability, is obtained to further decide flywheel vernier-gimballing performance. This opens a theoretical path for the analysis and evaluation of magnetic flux coupling and magnetic bearing performance. It is verified by magnetic-circuit analysis and finite element (FE) simulation that the coupling degree and bias-force change rate, current stiffness change rate of AGMB are nearly one order less than those of RGMB, and the maximal gimballing moment of flywheel is 2.7 times larger. As a result, a 50 N·m·s flywheel based on AGMB has the large and high precision gimballing capacity of 0.5* maximal gimbailing angle, 8.1 N · m maximal gimballing moment, and less than 15％ of bias-force change rate and current stiffness change rate over all the statues.