一种锥形定转子交直流磁轴承建模与耦合特性研究

为简化三自由度轴向-径向磁轴承结构,减小轴向长度和提高系统临界转速,设计了一种新型三自由度交直流轴向-径向混合磁轴承。该磁轴承定子采用两片式六极结构,分隔式锥形磁极与圆锥形转子均有30°锥角,磁场对圆锥形转子产生的磁吸力在轴向和径向方向上均有分量,实现了利用同一工作气隙同时控制圆锥形转子在轴向和径向3个自由度的悬浮。论文介绍了三自由度锥形定转子交直流混合磁轴承基本结构及悬浮力产生的工作原理,用等效磁路法对永磁和励磁混合磁轴承的磁路进行了分析,推导出了悬浮力数学模型。利用Matlab工具对磁轴承各变量之间的非线性关系和各自由度之间运动、磁路之间的耦合特性进行了计算和分析,并对各自由度之间的电磁耦合特性及各变量之间的非线性关系用ANSOFT软件进行了有限元分析验证。理论分析和仿真结果表明:该磁轴承各自由度在平衡位置附近时运动和磁路之间没有耦合,各变量之间具有良好的线性关系,对各自由度可采用分散独立的PID控制实现磁轴承的稳定悬浮。

Modeling of an AC-DC Magnetic Bearing with Cone-shaped Stator and Rotor and its Coupling Characteristics

To simplify the mechanical structure,decrease the axial length and raise the critical speed of the 3 degrees of freedom axial-radial magnetic bearing,an innovated AC-DC 3 degrees of freedom hybrid magnetic bearing(AC-DC-3DOF-HMB) is proposed with the structure of both pieces and six poles.Both the spit poles and the rotor have the 30° cone-angle face,and the suspension force produced by the magnetic field can be divided into axial-force and radial-force.The structure of cone-shaped faces achieves 3 degrees of freedom controlling using the same common air gap.In the paper,the structure and principle for producing magnetic suspension forces are introduced.The flux path is calculated by using equivalent magnetic circuits,the mathematics models of the magnetic suspension forces are deduced.The nonlinearity relations among variables and the coupling characteristics of movement and magnetic circuit between radial-and axial-direction round the balance position are calculated and analyzed by Matlab software.The electromagnetic coupling characteristics among 3 degrees of freedom and the nonlinearity relations among variables are analyzed using ANSOFT finite element analysis software.The theoretical analysis and simulation results have shown that the movement and magnetic circuits among 3 degrees of freedom round the balance position have no coupling,and using independent PID control among 3 degrees of freedom can achieve stable suspension for this magnetic bearing.