轴-径向混合磁轴承动态特性及控制研究

为了减小三自由度轴-径向混合磁轴承（ARHMB）的涡流损耗并增加轴向磁力，提出轴向采用软磁复合材料（SMCs）制备的推力轴承，在推力盘与转子的气隙处引入Halbach阵列以增强轴向气隙磁密，径向采用叠片结构. 首先，基于动态磁通分布及等效磁路法，建立综合考虑涡流、漏磁及交叉耦合效应的等效磁阻模型；其次，对比分析了材料类型及交叉耦合效应对等效磁阻频率响应、动态刚度的影响；最后，采用计及涡流、漏磁及交叉耦合效应不完全微分PID控制对ARHMB进行研究. 研究结果表明:SMCs制备的ARHMB相比碳钢材料可以提供更大、更稳定的磁力以及更大的工作带宽，在高频条件下具有更好的动态特性；考虑交叉耦合效应时，SMCs制备的ARHMB动态特性在高频时变化率较大，不可忽略；对于低带宽工作的碳钢轴承，交叉耦合效应不明显；电磁轴承系统响应速度很快、超调量小、稳态误差近似为0，具有良好的控制特性. 

Research on Dynamic Characteristics and Control of Axial-Radial Hybrid Magnetic Bearing

In order to reduce the eddy current loss and increase the axial magnetic force for three degrees of freedom axial-radial hybrid magnetic bearings (ARHMB), a thrust bearing made of soft magnetic composite materials (SMCs) in the axial direction was proposed. The Halbach array was introduced at the air gap between the thrust plate and the rotor to enhance the magnetic density of the axial air gap. In the radial direction, the laminated structure was used for the radial bearing. Firstly, based on the dynamic magnetic flux distribution and the equivalent magnetic circuit method, the equivalent reluctance model considering eddy current, magnetic leakage and cross-coupling effects was established. Then, the influence of material types and cross-coupling effect on the equivalent reluctance frequency response and dynamic stiffness was analyzed. Finally, ARHMB was studied by incomplete derivative PID control considering the effect of eddy current, magnetic leakage and cross-coupling. The results show that ARHMB prepared by SMCs can provide greater and more stable magnetic force and larger bandwidth than that made of carbon steel, and has better dynamic characteristics under high-frequency conditions. When considering the cross-coupling effect, the dynamic characteristics of ARHMB made of SMCs have a large change rate at high frequency and cannot be ignored. For low-bandwidth carbon steel bearings, the cross-coupling effect is not obvious. The system of magnetic bearing has a fast response speed, small overshoot, and approximately zero steady-state error, which has good control characteristics.