Experiments on the destabilizing factors in tilting pad bearings

Rotor systems with tilting pad bearings, may be unstable under normal working conditions due to destabilizing factors in the bearings. Theoretical and experimental results on the instability of tilting pad bearings are presented.     

电磁轴承的主动控制研究

鉴于磁力轴承本质上是不稳定的，因而引入闭环主动控制后的主动型电磁轴承（简称电磁轴承），就成为人们关注和研究的重点．本文在介绍电磁轴承工作原理的基础上分析和给出了单自由度磁悬浮系统的数学模型及相应的闭环控制方块图．结合一个设计实例，给出了确定控制器参数的稳定范围的方法，并讨论了控制器参数对电磁轴承系统动态参数的影响等．     

磁悬浮飞轮陀螺力学与控制原理

通过对磁悬浮飞轮陀螺力学进行研究,并分析电磁力对转子章动、进动特性的影响,将磁轴承电磁力对飞轮转子的作用分成四种基本支承成分,分别讨论它们对转子章动与进动稳定性的不同影响.控制器可通过调整四种基本成分在总的电磁力中的比重,改变转子章动、进动的阻尼特性,实现转子的高速稳定运行.基于这些分析,总结出磁悬浮飞轮控制器设计的基本原则.该原则为高速下磁悬浮飞轮转子系统控制器的设计指明方向.     

气体静压轴承相位致振气锤失稳机理与试验

针对气体静压轴承在结构不合理或者工作参数选择不恰当时容易产生气锤失稳的问题,开展基于相位致振的气体静压轴承气锤失稳机理研究。从气体静压轴承的工作气压与气膜间隙随时间变化的相位关系出发,建立基于相位致振的气体静压止推轴承自激失稳理论模型,分析气体静压止推轴承在发生气锤失稳过程中,工作气压与气膜厚度的相位变化对应情况。理论分析和实验研究结果表明,在气体静压止推轴承发生气锤失稳过程中,工作气压与气膜厚度的相位不断变化,并在相位差为180°时发生气锤失稳,进而说明可以从相位角度解释气体静压轴承发生气锤失稳的原因。该研究进一步完善了气体静压止推轴承的自激失稳作用机理分析,为气体静压轴承的气锤失稳的机理分析及其抑制提供了一种新的方法。     

Nonlinear Control of Magnetic Bearings

In this paper, recent results controling nonlinear systems with output tracking error constraints are applied to the design of new tracking controllers for magnetic bearings. The proposed controllers can force the rotor to track a bounded and sufficiently smooth refer-ence trajectory asymptotically and guarantee non-contactedness be-tween the rotor and the stator of the magnetic bearings. Simulation results are included to illustrate the effectiveness of the proposed con-trollers.     

Influence of the electromagnetic gap in gas–magnetic bearings on the output characteristics of high-speed rotor systems

The electromagnetic gap in gas–magnetic bearings has a considerable influence on the output load and rigidity characteristics of high-speed rotor systems, as shown by experiments and simulation.     

从天然气到核能:主动磁悬浮轴承系统的多种应用（英文）

Active magnetic bearings present unique capabilities compared to other bearing systems, allowing their use in a range of challenging environments and applications. This paper reviews these unique capabilities, which can be broadly categorized as: elimination of wear; elimination of sealing and lubrication systems; reduction or elimination of transmitted noise and force; use as instrumentation systems; and thermal capabilities. When combined, these capabilities can provide high reliability and availability in challenging applications. The paper goes on to consider how a challenging application or environment may affect the design of a magnetic bearing system and the use of these capabilities. Examples of such applications within the author's own company are presented together with a brief review of some of the available literature.     

High-speed stability of a rigid rotor supported by aerostatic journal bearings with compound restrictors

Demands for higher rotational speed and accuracy for effective manufacture of small holes on printed circuit boards and very small precise parts have been increasing remarkably. Aerostatic journal bearings with compound restrictors have greater stiffness than those with conventional inherently compensated restrictors and are one of the most effective candidates to satisfy these demands. In this work, the instability of a rigid rotor supported by aerostatic journal bearings with compound restrictors was investigated numerically and experimentally. It was found that this type of aerostatic bearings showed a much higher threshold speed for instability compared with bearings with inherently compensated restrictors.     

Influence of bearing damping on instability of asymmetric shafts-Part I. Stabilizing and destabilizing effects

This paper investigates the influence of bearing damping on the instability of rotating asymmetric shafts supported by isotropic bearings. In the rotating frame of reference, an analytical method based on modal expansion is developed to determine transition curves for stable and unstable regions. The effects of damping coefficients of bearings on the dynamic instability are evaluated for various bearing stiffness.     

超导磁液推力轴承的结构设计及性能分析

为提高大型飞轮储能系统的效率和稳定性,设计了一种超导磁力与静压流体力相复合、由16块超导瓦和8块带小孔节流器的静压瓦组成的推力轴承。首先基于超导体局域模型和静压流体方程建立分析模型,然后采用解耦的方法分析复合轴承的刚度等性能指标,对复合轴承进行优化。结果表明复合轴承既可以保证稳定悬浮,又能保持较大的刚度,其功率损耗也在可接受范围内。     

电磁轴承动刚度的自动测量

针对电磁轴承动刚度难以测量的问题,构建了一套简单的刚度测量系统用来自动测量电磁轴承的动刚度。该系统采用电磁轴承的数字控制器、功放、电磁铁作为激振器,电磁轴承的电涡流传感器作为拾振器,自行研制的测量分析系统作为测量分析工具。给出电磁轴承动刚度的测量结果。测量结果表明,该系统能较准确测量电磁轴承的动刚度。此测量系统还可以用于其他轴承刚度的测量,也可用于系统辨识。     

磁轴承不平衡控制技术的研究进展

通过大量文献调研,重点阐述了磁轴承不平衡控制这一重要技术在磁轴承高速旋转机械中的研究发展情况。简要分析了各种算法的优缺点及其在原理上的相通之处,最后讨论了磁轴承不平衡控制技术进一步发展的方向。     

磁轴承激励下转子系统动力学特性

为分析磁轴承激励下转子系统的振动机理,应用一维有限元方法建立了双盘转子系统动力学特性计算模型,研究了不同类型磁轴承激励下转子系统的动力学行为.研究结果表明:同向旋转的扫频激励力激发了转子系统的正进动模态,而反向旋转的扫频激励力激发了转子系统的反进动模态,两种情况下转子系统均以圆轨迹进动;由于单向简谐激励力可以分解为同向...     

Dynamic behaviour of geared systems with backlash due to stick-slip vibratory motion

Stick-slip phenomena occur with low speed rotors in fluid bearings. A typical case is the turning gear mechanism of large turbomachinery which becomes vulnerable to damage. In other cases such as rolling mills or textile machinery the stick-slip phenomenon influences product quality.An analytical investigation of a linear rotor with a complex turning gear system of many degrees of freedom is presented. Gearing backlash was included in the model. The mechanism of backlash was found to be of considerable importance for the appearance of instability. Velocity and damping were the most influential factors on the amplitude of stick-slip motion and instability.In highly unstable areas of system operation, stick-slip is not present owing to the violent nature of the unstable motion. At the onset of instability and during the transients of stable systems, stick-slip is present. Fatigue damage may result from gear backlash, even in stable systems.     

Research on the Relationship Between Dynamic Behavior of Active Magnetic Bearing System And the Performance of the Auxiliary Bearing

Auxiliary bearings (ABs) are important backup and safety components in active magnetic bearing (AMB) systems. The performance of ABs significantly affects the r...     

五自由度磁悬浮电主轴结构与有限元分析

提出一种五自由度稳定悬浮的电主轴,由二自由度磁悬浮异步电机与三自由度轴向混合磁轴承实现五个自由度的稳定悬浮。其中,三自由度混合磁轴承采用四个定子磁极来控制轴向悬浮力与径向扭转力,可有效减少轴向长度。文中介绍了五自由度磁悬浮电主轴工作原理,建立磁悬浮异步电机和混合磁轴承的数学模型,并用电磁场分析软件welll5．0分析其磁场和悬浮力,验证电主轴的可行性,最后运用biatlab软件建立基于转子磁场定向的无轴承异步电机控制系统,仿真结果表明该控制方法可有效稳定控制电机。     

径向永磁轴承承载能力数值分析与设计

研究了一类径向水磁轴承在轴向、径向偏移时承载能力的两种计算方法，着重分析了径向永磁轴承的结构尺寸的优化问题，从理论上阐述了在设计过程中如何确定径向永磁轴承的高度及载面尺寸，对永磁轴承结构尺寸的合理设计有关实际的指导意义。     

Magnetoelastic Stability of Magnetic Axial Bearings

Permanent magnet bearings offer no wear and no mechanical friction. Recently, Rare Earth (RE) permanent magnets have been used, which give rise to force fields 20 times greater than those of common magnets. RE also allows to build magnets suitable for bearings of every shape. RE bearings are then profitable. On the other hand, permanent magnet bearings are unstable. For example, the levitated ring of the axial bearing with opposite magnetic fields of Fig. 1 is stable axially, but unstable radially. It has been, however, verified that a permanent magnet system may become stable under peculiar conditions. As an example, if the above-mentioned levitated ring is subjected to a parametric axial excitation, its radial instability can be removed. In our opinion, it may also be possible that stability is obtained by exploiting microstructural properties of ferromagnetic materials, especially of RE, like dimensional and magnetic changes if subjected to mechanical stresses. Then, in this paper, the stability of the levitated member of an RE axial ring bearing is investigated by a suitable exploitation of magnetoelastic properties of the ring.

磁悬浮轴承磁路结构分析与数学模型建立方法

介绍了磁悬浮轴承系统构成和工作原理,从控制电流的性质、受控自由度数、悬浮力产生方式、作用力方式、磁极布置形式等方面对磁悬浮轴承进行了比较与分析,给出了基于等效磁路法的磁悬浮轴承悬浮力数学模型建立方法和步骤,为该类轴承磁路结构设计和建立数学模型提供了参考。