一种离心式心脏泵磁悬浮系统的耦合特性

为实现一种离心式心脏泵的稳定磁悬浮,需研究该心脏泵的耦合特性。文中分析了径向永磁轴承和开关磁阻电机的耦合特性,导出磁悬浮转子径向运动方程以及干扰力与径向位移的传递函数;并根据永磁轴承磁场分布特性,提出一种基于霍尔传感器的磁悬浮转子位移检测方案;最后,分析了径向和轴向位移在霍尔传感器检测结果中的耦合关系,据此给出解耦方法,实现磁悬浮转子位移检测。研究表明,径向永磁轴承和开关磁阻电机混合磁悬浮控制有利于提高控制系统正刚度并降低电磁能耗,基于霍尔传感器的转子位移检测方案能准确描述磁感应强度检测中径向二自由度位移间的耦合关系。     

径向永磁偏置磁悬浮轴承转子模态分析

分析了某径向永磁偏置磁悬浮轴承刚度阻尼特性,用有限元软件ANSYS对轴承转子进行模态分析,得到PD控制下轴承转子的前五阶固有频率与模态振型,最后分析了支承刚度对轴承转子固有频率的影响。所建立的有限元模型为实际控制系统的运行调试及结构设计提供了理论指导。     

三支承磁悬浮轴承转子系统动态特性分析

在径向两支承磁悬浮轴承转子系统的基础上增加一个辅助径向支承,构成三支承磁悬浮轴承转子系统。对三支承磁悬浮轴承转子系统的动态特性进行理论和实验分析,并与两支承系统进行对比,结果表明,增加磁悬浮辅助支承后,有利于提高系统的各阶模态阻尼,降低转子的振幅,提高系统的稳定性。     

磁悬浮阻尼器参数对系统弯曲模态阻尼的影响

在一般磁悬浮轴承转子系统上安装磁悬浮阻尼器,组成磁悬浮轴承与磁悬浮阻尼器组合支承转子系统.通过理论计算及试验模态分析,研究了磁悬浮阻尼器参数对系统弯曲模态阻尼比的影响.结果表明,随着磁悬浮阻尼器等效支承阻尼的增加,系统第1,2阶弯曲模态的阻尼比显著增加,有利于系统越过前2阶弯曲临界转速.     

同极永磁偏置径向磁悬浮轴承特性分析北大核心

将同极永磁偏置径向磁悬浮轴承应用于轴流式磁悬浮血泵支承系统,利用永磁偏置降低功耗,同极性结构减少转子磁滞损耗引起的发热,以降低轴流式磁悬浮血泵支承系统的体积和功耗,使其便于植入体内。利用等效磁路法建立了轴承承载模型,采用有限元法获得轴承的气隙磁场分布、耦合特性,最后搭建试验平台,进行了试验验证。结果表明,仿真得到的电流刚度、位移刚度和气隙磁场分布与试验测量结果趋势相同,大小误差均在10%以内。     

电磁轴承刚度与阻尼特性的非线性研究

刚度与阻尼特性是电磁轴承重要的性能指标。对电磁轴承刚度与阻尼特性进行了非线性研究,建立了储能飞轮转子系统径向电磁轴承的非线性模型,推导了非线性情况下电磁轴承刚度与阻尼的计算公式,分析了电磁轴承刚度与阻尼的非线性特性,以及控制因数对刚度与阻尼的影响。研究结果表明,增大比例因数,可以使电磁轴承的刚度减小,达到正刚度时的转子位移范围同时减小。通过研究同时确认,电磁轴承阻尼受控制因数的影响较小。     

磁悬浮转子系统耦合特性测试方法及测试台的设计

磁悬浮转子系统中，根据磁力轴承工作原理，径向磁力轴承内存在力耦合、磁耦合；径向磁力轴承之间存在力耦合、力矩耦合。这些耦合现象对磁悬浮转子系统的结构设计、系统建模和控制系统的设计都有影响。在对磁悬浮转子系统耦合特性研究的基础上，提出了磁悬浮转子系统耦合特性测试的实验方法。并且提出了相应测试实验台的设计方案。     

同极永磁偏置径向磁悬浮轴承特性分析

将同极永磁偏置径向磁悬浮轴承应用于轴流式磁悬浮血泵支承系统,利用永磁偏置降低功耗,同极性结构减少转子磁滞损耗引起的发热,以降低轴流式磁悬浮血泵支承系统的体积和功耗,使其便于植入体内。利用等效磁路法建立了轴承承载模型,采用有限元法获得轴承的气隙磁场分布、耦合特性,最后搭建试验平台,进行了试验验证。结果表明,仿真得到的电流刚度、位移刚度和气隙磁场分布与试验测量结果趋势相同,大小误差均在10%以内。     

基于冲击响应的磁悬浮轴承刚度阻尼仿真辨识

轴承的支承特性直接影响着旋转机械的工作效率、可靠性和寿命,磁悬浮轴承的动态特性对整个磁悬浮转子系统起着极其重要的作用。通过辨识冲击载荷引起的瞬态响应可以识别出磁悬浮轴承的刚度和阻尼。介绍基于冲击响应辨识的基本原理,并对五自由度磁悬浮轴承-转子系统进行仿真辨识研究,将识别的系统刚度和阻尼参数与初始赋予的参数值对比,识别效果较好,证明了该识别理论的可行性。     

柔性磁悬浮转子动态特性的研究

主要研究了柔性磁悬浮转子的动态特性,并建立了求解其固有频率和振型的理论与计算模型.分析了支承刚度对磁悬浮转子固有频率的影响,对柔性磁悬浮转子的动态特性的研究和认识有助于改善磁力轴承的结构设计,并对磁力轴承的控制系统研究具有重大意义.     

基于ANSYS的磁悬浮挠性转子模态分析与设计

以一台磁悬浮挠性实验转子为例,结合ANSYS软件,探讨了磁悬浮挠性转子的模态设计方法,研究了支承刚度对转子模态频率和模态振型的影响,在此基础上,分析了过临界转速的磁悬浮挠性转子支承刚度的设定原则,并给出了磁悬浮实验转子的合理支承刚度范围。研究表明：影响转子模态可观性和可控性的一个重要因素是径向磁力轴承转子和位移检测环的长度之和与转子总长度的比值;支承刚度除了影响转子的模态频率外,还影响转子的模态振型,并且当支承刚度高到一定程度后,模态的可控性和可观性严重恶化,甚至可能导致磁悬浮转子过临界转速时失稳。     

Design and parameter estimation of hybrid magnetic bearings for blood pump applications

This paper discusses the design and parameter estimation of the dynamics characteristics of a high-speed hybrid magnetic bearings (HMBs) system for axial flow blood pump applications. The rotor/impeller of the pump is driven by a three-phase permanent magnet (PM) brushless and sensorless DC motor. It is levitated by two HMBs at both ends in five-degree-of-freedom with proportional-integral-derivative (PID) controllers; among which four radial directions are actively controlled and one axial direction is passively controlled. Test results show that the rotor can be stably supported to speeds of 14,000 rpm. The frequency domain parameter estimation technique with statistical analysis is adopted to validate the stiffness and damping coefficients of the HMBs system. A specially designed test rig facilitated the estimation of the bearing's coefficients in air—in both the radial and axial directions. The radial stiffness of the HMBs is compared to the Ansoft's Maxwell 2D/3D finite element magnetostatic results. Experimental estimation showed that the dynamics characteristics of the HMBs system are dominated by the frequency-dependent stiffness coefficients. The actuator gain was also successfully calibrated and may potentially extend the parameter estimation technique developed in the study of identification and monitoring of the pump's dynamics properties under normal operating conditions with fluid.     

高压离心泵滑动轴承稳定性分析

分析了高压离心泵轴承的动力学模型,通过径向滑动轴承的非定常运动雷诺方程计算出油膜的八个刚度系数和阻尼系数,并以此计算出转子的综合刚度和涡动比平方,得到油膜的失稳转速,最后以高压离心泵实际结构参数进行了轴承的稳定性分析,得出转子正常工作时是安全的结论.     

陀螺效应使永磁悬浮心脏泵稳定平衡

为使人工心脏泵可以永久使用，作者研制出一种仅采用永磁轴承实现磁悬浮的离心泵。其保留了电磁悬浮泵的优点，又避免其不足之处。然而，传统理论认为永磁悬浮是不可能稳定平衡的。作者利用陀螺效应解决了此问题。径向驱动的离心泵包括一个转子和一个定子。转子由驱动磁钢和叶轮组成；定子由电机线圈和泵壳构成。两个永磁轴承抵消电机线圈铁心与转子驱动磁钢之间的吸引力。 生理盐水试验表明，当血泵转速超过3250转／分、流量大于1升／分时，转子可以在定子中悬浮起来。高转速是达到陀螺效应的条件，大流量是良好水动力性能的前提。     

A novel negative dislocated seal and influential parameter analyses of static/rotordynamic characteristics

This paper proposes a new type of negative dislocated seal (NDS) based on the dislocated bearing theory to investigate the influential parameters of static rotor eccentricity and dislocated ratio on the static and rotordynamic characteristics of an example seal solved with computational fluid dynamics (CFD) the flow field. The rotordynamic characteristics of the NDS were investigated in respect of the effects of rotor whirling frequency on response force, stiffness coefficients, damping coefficients and rotor system stability, by multifrequency elliptical orbit rotor whirling model. Based on the studies, we reached the following conclusions. The circumferential pressure distribution of NDS and conventional labyrinth seal (LS) presents sine periodic variation approximately, while relative to the LS, the NDS has two divergent wedge gaps and reduces the hydrodynamic pressure effects, then the circumferential pressure difference and tangential force on rotor surface decreases by about 40 %~190 %. The leakage of the NDS linearly increases with the rising eccentricity ratio and dislocation ratio approximately, and is larger (about 0.9 %~1.5 %) than the LS. The direct stiffness coefficients of the two seals increase with the rise of rotor whirling frequency, while the absolute values of both the cross-coupled stiffness coefficients and the damping coefficients decrease with raising rotor whirling frequency. Compared with the LS, the NDS has smaller (about 28.8 %~206.2 %) cross-coupled stiffness coefficient, larger (about 26.15 %~60.39 %) effective damping coefficient, and good stability of rotor system. This study has developed a novel seal structure to improve the seal performance of turbomachinery such as aeroengine.     

流体激振力对高速泵转子振动特性的影响研究

对高速泵三维流场进行了非定常计算,分析了高速泵内的压力分布情况。研究了高速泵叶轮上的稳态径向力和脉动径向力,分析了流体激振力对高速泵叶轮系统的振动及其轴心轨迹的影响。计算结果表明:泵内部流场的压力分布合理,稳态作用力的计算符合实际数据;瞬态作用力与叶轮和隔舌的干涉流动有很大关系;在脉动激振力作用下,泵转子振动响应谱图中出现了脉动激振力的频率及其谐波频率。     

离心式磁悬浮血泵用混合磁悬浮支承设计与仿真

摩擦和磨损会导致离心式血泵机械轴承的寿命短、发热量大,易引起血栓和溶血,针对此,提出了一种离心式血泵用混合磁悬浮支承结构。采用数值计算法对血泵用磁悬浮支承进行了磁场分布数值模拟,设计了基于边缘效应的磁悬浮支承结构实验原型样机,搭建了控制系统,并以实验验证了该结构静态悬浮的可行性。研究结果为离心式磁悬浮血泵的结构设计和溶血问题的改善提供了重要依据。     

Dynamic characteristics of the rotor in a magnetically suspended control moment gyroscope with active magnetic bearing and passive magnetic bearing

For a magnetically suspended control moment gyroscope, stiffness and damping of magnetic bearing will influence modal frequency of a rotor. In this paper the relationship between modal frequency and stiffness and damping has been investigated. The mathematic calculation model of axial passive magnetic bearing (PMB) stiffness is developed. And PID control based on internal model control is introduced into control of radial active magnetic bearing (AMB), considering the radial coupling of axial PMB, a mathematic calculation model of stiffness and damping of radial AMB is established. According to modal analysis, the relationship between modal frequency and modal shapes is achieved. Radial vibration frequency is mainly influenced by stiffness of radial AMB; however, when stiffness increases, radial vibration will disappear and a high frequency bending modal will appear. Stiffness of axial PMB mainly affects the axial vibration mode, which will turn into high-order bending modal. Axial PMB causes bigger influence on torsion modal of the rotor.     

轴向柱塞泵主轴及缸体旋转组件临界转速分析

以斜盘式轴向柱塞泵的主轴及缸体旋转组件组成的转子系统为研究对象,分别利用传递矩阵法及ANSYS有限元分析方法得到了其临界转速,即转子发生共振时的转速,通过两者结果的对比,证明了有限元方法的准确性;进而通过有限元分析,得出增加轴承刚度及减小缸体质量可以有效提高轴向柱塞泵转子系统的一阶临界转速的结论。通过研究,提出了轴向柱塞泵转子系统临界转速的计算方法,为进一步研究轴向柱塞泵转子系统的动力学特性奠定基础。     

转子-机匣系统碰摩的灵敏度研究

针对仅考虑质量偏心的Jeffcott转子碰摩的动力学方程，进行了转子-机理系统碰摩的灵敏度研究，分析了转轴刚度和阻尼、定子刚度和阻尼、偏心距和定子径向刚度对灵敏度的影响，并给出了数值分析解；讨论了参数的变化对碰摩的产生和影响，避免了设计旋转机械的盲目性。