磁悬浮轴承的结构优化设计及其磁路解耦自适应控制

发布时间：2018-05-27 21:51

本文选题：磁轴承 + 电磁场分析　；参考：《湘潭大学》2017年硕士论文

【摘要】：磁悬浮轴承是依靠电磁力悬浮支撑的轴承,较之于一般轴承,具有零摩擦、无需润滑、转子位移精度高、可支撑转速高、寿命长、转动性能可主动控制等优势,因此,磁悬浮轴承的应用已经涉及工业、航天、医疗、计算机等多个国家支柱产业。但由于复杂且昂贵的控制系统,磁悬浮轴承的应用难以得到工业化普及。为了提高综合控制性能,需要从磁场分布的理论角度进行建模分析。通过电磁场仿真发现磁极间存在磁路耦合,耦合程度与几何结构和励磁方式有关,磁路耦合会导致磁力误差从而影响控制性能,因此从磁轴承的几何结构设计入手,分析了不同定子几何参数下的磁场分布,研究了磁场分布对磁力的影响,建立考虑磁路耦合的磁力数学模型,由此提出一种解耦自适应控制策略以实现对磁力的精确控制。文章主要从几何结构、电磁场分布和磁路解耦控制三个方面对主动磁悬浮轴承展开研究。通过对不同的目标优化模型有限元电磁场仿真结果对比分析,发现磁场的分布不仅与励磁方式有关,几何结构对磁场分布的影响也不容小觑,不同几何参数下的磁场分布可能出现不同程度的磁路耦合和漏磁,其中绝大部分的非理想磁场以磁路在磁极间的耦合形式呈现,从而引起了实际电磁力的误差。因此需要进一步研究几何结构参数对磁路耦合影响,以及磁路耦合将如何影响磁力误差。建立了磁路耦合等效模型,并分析了磁路的耦合模式,提出耦合系数?作为磁路耦合程度的评价参数。在磁路耦合等效模型的基础上根据毕奥-萨伐尔定理建立了考虑磁路耦合的磁场分布模型,绘制出了定子磁场分布展开图。得到磁路耦合受几何参数影响的变化趋势。综合考虑电磁轴承的机械耦合和磁路耦合,建立了磁力误差动态数学参考模型,分别分析了耦合系数、转子偏移量和控制电流对磁力误差的影响,由分析结果得出,可以改变控制电流来补偿由于磁路耦合引起的磁力误差,并建立了以消除磁力误差为目的解耦控制策略。为实现自适应控制,设计了参数辨识模块和参数修正控制模块,根据时变的磁场分布和转子位移状态来调整参考模型中的动态参数,从而得到正确、实时的修正控制电流。通过对磁路耦合的理论分析,得到修正控制电流与磁力误差的先验模糊关系,建立模糊控制模型,进一步提高了控制的快速性、容错性和鲁棒性。分别对普通PID控制,解耦自适应控制以及模糊解耦自适应控制进行建模分析,结果证明了磁路解耦的重要性,也说明了自适应解耦容易获得更好的综合控制性能。通过物理实验,验证了理论模型的正确性,通过二自由度的静态悬浮实验和冲击实验证明了解耦自适应控制的优越性。
[Abstract]:Magnetic bearing is a bearing which relies on electromagnetic force suspension support. Compared with ordinary bearing, it has the advantages of zero friction, no lubrication, high displacement accuracy, high supporting speed, long life, active control of rotational performance, etc. Magnetic bearing applications have been involved in industrial, aerospace, medical, computer and other national pillar industries. However, because of the complicated and expensive control system, the application of maglev bearing is difficult to be popularized in industry. In order to improve the comprehensive control performance, it is necessary to model and analyze the magnetic field distribution theory. Through the electromagnetic field simulation, it is found that there is magnetic circuit coupling between magnetic poles, the coupling degree is related to geometry structure and excitation mode. Magnetic circuit coupling will lead to magnetic force error and affect the control performance. Therefore, starting with the geometric structure design of magnetic bearing, The magnetic field distribution under different stator geometry parameters is analyzed, and the influence of magnetic field distribution on magnetic force is studied. A mathematical model of magnetic force considering magnetic circuit coupling is established, and a decoupling adaptive control strategy is proposed to realize the precise control of magnetic force. In this paper, the active magnetic bearing (AMB) is studied from three aspects: geometric structure, electromagnetic field distribution and magnetic circuit decoupling control. By comparing and analyzing the finite element electromagnetic simulation results of different objective optimization models, it is found that the distribution of magnetic field is not only related to the excitation mode, but also the influence of geometric structure on the distribution of magnetic field is not to be underestimated. The magnetic field distribution under different geometric parameters may have different degrees of magnetic circuit coupling and magnetic leakage. Most of the non-ideal magnetic fields are presented in the form of magnetic circuit coupling between the magnetic poles, thus causing the error of the actual electromagnetic force. Therefore, it is necessary to further study the effect of geometric structure parameters on magnetic coupling and how magnetic coupling will affect magnetic force error. The equivalent model of magnetic circuit coupling is established, the coupling mode of magnetic circuit is analyzed, and the coupling coefficient is proposed. As an evaluation parameter of coupling degree of magnetic circuit. Based on the equivalent model of magnetic circuit coupling, the magnetic field distribution model considering magnetic circuit coupling is established according to the Beo-Savart theorem, and the stator magnetic field distribution expansion diagram is drawn. The change trend of magnetic circuit coupling affected by geometric parameters is obtained. Considering the mechanical coupling and magnetic circuit coupling of electromagnetic bearing, the dynamic mathematical reference model of magnetic force error is established. The effects of coupling coefficient, rotor offset and control current on magnetic force error are analyzed respectively. The control current can be changed to compensate the magnetic force error caused by magnetic circuit coupling, and the decoupling control strategy is established to eliminate the magnetic force error. In order to realize the adaptive control, the parameter identification module and the parameter correction control module are designed. According to the time-varying magnetic field distribution and the rotor displacement state, the dynamic parameters in the reference model are adjusted, and the correct and real-time modified control current is obtained. Through the theoretical analysis of magnetic circuit coupling, the priori fuzzy relation between the modified control current and the magnetic force error is obtained, and the fuzzy control model is established, which further improves the speed, fault tolerance and robustness of the control. The modeling and analysis of general PID control decoupling adaptive control and fuzzy decoupling adaptive control are carried out respectively. The results prove the importance of magnetic decoupling and show that adaptive decoupling is easy to obtain better comprehensive control performance. The correctness of the theoretical model is verified by physical experiments. The advantages of decoupling adaptive control are proved by static suspension experiments and shock experiments with two degrees of freedom.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TH133.3;TP273

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