弹性轨道上三自由度磁悬浮列车的动力特性分析

通过对弹性变形轨道上二自由度磁悬浮列车耦合系统动力特性的数值研究，给出了系统受控稳定性情形下控参数Ｇ１、Ｇ２的选取方式；讨论了控制参数Ｇ１，Ｇ２和系统特征参数对磁悬浮系统的动力特性的影响方式，分析了弹性轨道的变形特征等。     

铁路钢轨扣件系统垂向动力模型及振动特性

该文针对铁路钢轨扣件系统,分别考虑了扣压件及垫层的弹性特性,并考虑了扣件系统中扣压件的预压力,建立了详细的垂向动力分析模型,并推导了钢轨受力方程,然后基于车辆-轨道耦合动力学理论,分析了扣件系统垂向振动特性,结果表明：扣压件及垫层的弹性变形均受预扣压力及轮轨动态相互作用力的影响,扣压件及垫层作用在钢轨上的力均含有预扣压力及轮轨力的成分。因此,在铁路轨道扣件系统的动力分析与设计研究中,有必要分开考虑扣压件及垫层的弹性特性。     

齿轮-轴承系统非线性振动混沌吸引子周期轨道控制

考虑轴承支撑齿轮传动系统建立了含多间隙的系统非线性动力学模型,模型中考虑了时变啮合刚度和综合传动误差等因素。基于OGY混沌控制改进策略对高维非双曲齿轮系统实施了多周期混沌控制,采用Newton-Raphson迭代法搜寻了P1、P2、P4和P8等多组不稳定周期轨道(Unstable Periodic Orbits,UPO)不动点,求解了各UPO解对应的Jacobi矩阵特征值和局部参数敏感度矢量,结合Poincaré截面等工具解析了混沌吸引子向P10周期轨道转换时的轨道间隔及迁移特性。在2 000周期步下对混沌吸引子实施了P1、P2、P4、P8和P10等多种周期组合式控制,结果表明在状态转换阶段,尤其30周期步内控制参数摄动量发生激增,此后恢复稳定且保持与目标控制轨道相同周期的状态演化;多周期轨道持续控制时周期状态越高,控制难度越大,所需参数摄动量相应增加。研究结果在理论上有助于齿轮系统混沌响应减振控制。     

基于n阶GBT初始轴向载荷影响下FGM梁的振动特性

研究了初始轴向载荷影响下弹性地基功能梯度材料(FGM)梁的振动特性。基于一种拓展的n阶广义剪切变形梁理论(n-GBT),以轴向位移、剪切变形挠度与弯曲变形挠度为基本未知函数,应用Hamilton原理,建立了该系统自由振动问题力学模型的控制方程。引入边界控制参数,采用一种改进型广义微分求积(MGDQ)法获得了FGM梁的静动态响应。通过算例验证并给出了GBT阶次n的理想取值,丰富梁理论的同时,可供验证或改进其它各种剪切变形梁理论;提供的数值分析方法切实可行,拓展了GDQ法的使用范围。最后,着重讨论并分析了初始轴向载荷、边界条件、梯度指标、地基刚度、跨厚比等参数对FGM梁振动特性的影响。     

嵌入式轨道超弹性力学属性对轮轨动态作用的影响研究

嵌入式轨道结构内的聚氨酯填充材料具有非常明显的超弹性力学特性，对轨道系统的力学行为及振动噪声有较大影响。为研究填充材料超弹性特性对嵌入式轨道轮轨系统动力特性的影响，以焊接接头不平顺为例，建立了考虑填充材料超弹性本构的嵌入式轨道三维轮轨瞬态滚动接触有限元模型，分析了焊接接头不平顺对嵌入式轨道轮轨瞬态滚动接触力学行为的影响。结果表明：考虑填充材料超弹性本构的嵌入式轨道模型可以很好的模拟高分子材料受到外力冲击时的能量转换及减振过程。焊接接头不平顺中的短波不平顺波长和波深对轮轨冲击响应的影响十分显著。轮轨冲击载荷随车速的增加而增大，所对应的轮轨动态响应主频频段也会明显上移。钢轨表面接触应力极值出现的位置与焊缝几何形状关系很大，接触斑面积和接触应力的峰值基本出现在焊缝的低塌处。聚氨酯填充材料在对于较低频率(400 Hz以下)的振动的抑制作用不明显，对500～2 000 Hz的高频振动具有良好的抑制作用，嵌入式轨道的减振特性表现出一定的频率相关性。     

考虑弹性的高速旋转轮对振动特性研究EI北大核心CSCD

轮对弹性变形和旋转振动对轮轨系统运行安全性影响需要从理论上进行深入研究。利用ANSYS有限元分析软件对轮对弹性化处理后,在SIMPACK多体动力学软件中建立了包含高速旋转弹性体轮对的车辆系统动力学模型。采用数值方法,得到了轮轴弹性弯曲变形量以及不同轨道不平顺激扰下轮对垂向振动加速度响应等。结果表明,考虑弹性和旋转振动后,轮对车轴发生弯曲变形效应明显且中部变形量最大,车辆运行速度对车轴弯曲变形量和轮轨附加动力有一定的影响,轮对垂向振动加速度频谱出现与旋转速度相关的频率特征。本文方法和结果对揭示轮对真实运动特征和研究高速轮轨安全性具有良好的指导意义。     

新型自复位桥梁墩柱节点的局部稳定性研究

为了更好地控制结构震后残余变形,增强桥梁结构自复位性能,最大限度地强化震后继续服役的能力和增加再修复的可能,该文基于性能设计的理念,给出一种新型自复位桥梁墩柱节点体系的基本概念,并选取该体系的典型模型进行截面弹性承载力、滞回特性、设计控制参数等力学性能进行初步的推导和分析。研究结果初步表明,该自复位桥梁墩柱节点结构受力明确,构造合理巧妙,由于嵌合式接头限制了体系最小势能位置,能够帮助结构复位,震后残余变形小,震后弹性承载力不下降,能够满足对结构性能的更高要求。     

考虑弹性的高速旋转轮对振动特性研究

轮对弹性变形和旋转振动对轮轨系统运行安全性影响需要从理论上进行深入研究。利用ANSYS有限元分析软件对轮对弹性化处理后,在SIMPACK多体动力学软件中建立了包含高速旋转弹性体轮对的车辆系统动力学模型。采用数值方法,得到了轮轴弹性弯曲变形量以及不同轨道不平顺激扰下轮对垂向振动加速度响应等。结果表明,考虑弹性和旋转振动后,轮对车轴发生弯曲变形效应明显且中部变形量最大,车辆运行速度对车轴弯曲变形量和轮轨附加动力有一定的影响,轮对垂向振动加速度频谱出现与旋转速度相关的频率特征。本文方法和结果对揭示轮对真实运动特征和研究高速轮轨安全性具有良好的指导意义。     

地震波频谱特性对高速列车动态脱轨行为的影响

为研究地震下高速列车的动态响应及地震波频谱特性对车辆动态脱轨行为的影响,发展了一种地震激励下车辆/轨道耦合动力学数值模型,车辆模型被简化为考虑悬挂非线性特性的35自由度多刚体系统,板式轨道被视为由钢轨、扣件系统、轨道板及CA砂浆层组成的弹性支承结构,钢轨被视为连续弹性离散点支承基础上的Timoshenko梁,轨道板用三维实体有限元模拟。采用移动轨下支承模型分析离散的轨枕支承对系统动力响应的影响,地震波被简化为周期性的横向正弦波加入计算模型中。基于仿真计算,对地震情况下高速列车的动力响应进行了详细分析,并重点分析了地震波频谱特性对高速车辆动态脱轨机理的影响。分析结果表明：地震波的频谱特性对车辆的动态响应、脱轨机理及车辆的运行安全有着重要的影响。     

齿轮-轴承系统非线性混沌控制参数摄动与轨道偏差分析

针对齿轮-轴承系统混沌响应减振控制问题,建立了含多间隙的系统非线性振动模型,模型中考虑了齿侧间隙、轴承径向间隙等非线性激励因素。通过系统状态模型与变分转换求解了Jacobi矩阵与敏感度矢量,结合微分流形理论和OGY(Ott-Grebogi-Yorke)控制法对混沌吸引子高周期轨道控制不稳定维数变异情形改进控制条件;采用Newton-Raphson数值法搜寻到混沌吸引子内部镶嵌的P8和P10等不稳定周期轨道不动点,发现二者Jacobi矩阵特征值谱中均存在模为1的临界复共轭特征根,目标周期轨道表现非双曲性。以轴承预载荷为名义控制参数,对P1、P2、P4、P8和P10等周期的多阶段控制表明状态迁移点附近存在短暂混沌瞬态振荡,高周期轨道控制精度下降、轨道偏差增高,控制稳定后参数摄动按受控周期轨道状态规律演化。     

线路不平顺对高速磁浮铁路动力响应特性的影响

基于动力有限元和耦合振动理论建立了高速磁浮列车-轨道梁动力学模型。通过仿真计算得到了高速磁浮线路确定性不平顺及随机不平顺对系统动力指标影响规律,提出了控制磁浮线路不平顺的参考建议。     

Sup-Resonant Response of a Nonautonomous Maglev System With Delayed Acceleration Feedback Control

A maglev system with delayed acceleration feedback control is disturbed by the deflection of flexible guideway, and resonant response may take place. We have investigated sup-resonant response of the maglev system by employing center manifold reduction and the method of multiple scales. We present the dynamic model and expand it to a third-order Taylor series. Taking time delay as its bifurcation parameter, we discuss the condition for the occurring of Hopf bifurcation. We apply center manifold reduction to get the PoincarÉ normal form of the nonlinear system and employ the perturbation technique to study sup-resonant response of the system. This yields the sup-resonant periodic solution of the normal form. We analyze the stability condition of the free oscillation in the solution and discuss the relatonship between guideway excitation and periodic solution. Finally, numerical results show how time delay, control, and excitation parameters affect the system response. With the proper system parameter, the free oscillation may vanish and only the periodic solution plays a part. Time delay can control amplitude of the forced oscillation. The appearance of the chaos phenomenon can also be governed by regulating time delay. And judiciously selecting a control parameter makes it possible to suppress the response.      

轨道梁在磁浮列车以共振速度通过时动力响应分析

该文研究了高速磁浮列车运行引起的轨道梁动力响应问题。采用模态综合技术建立了梁墩体系模型,推导了高速磁浮列车轨道梁运动方程,运用迭代技术求解了列车轨道梁系统动力学方程,计算分析了高速磁浮列车通过24m简支轨道梁引起的动力响应,结果表明:随着运行速度提高,轨道梁动力响应相应提高,在350km/h左右存在一阶二次谐波共振;当列车运行速度超过400km/h时,轨道梁和列车动力响应将被显着放大,为避免轨道梁出现一阶一次共振现象,在设计上,应使轨道梁的一阶自振频率远高于磁浮列车与轨道梁的特征频率(即设计速度与车长比值)。     

磁浮车辆-桥梁耦合系统随机振动分析的时域显式方法研究

轨道不平顺所引起的磁浮车辆-桥梁耦合系统随机振动问题是磁浮列车行驶过程中需要关注的重点问题之一,传统的随机振动方法在解决这类问题时存在工作量大、计算效率低等问题。分别从磁浮车辆系统和桥梁系统出发,建立磁浮车辆系统响应和桥梁系统响应关于车桥相互作用电磁力的时域显式表达式;利用车轨间的电磁力方程及几何相容条件,构建电磁力关于轨道不平顺的时域显式表达式;进一步推导得到轨道不平顺作用下磁浮车辆系统和桥梁系统关键动力响应显式表达式。在此基础上,利用统计矩运算法则,直接获得磁浮车辆系统和桥梁系统关键响应的演变统计矩;也可以利用轨道不平顺的数字生成技术,结合随机模拟法,获得车桥耦合系统关键响应的统计信息。在上述过程中,由于车桥耦合系统关键动力响应的显式表达式已先行构建完毕,因此大幅提升了随机振动分析的计算效率。以二自由度磁浮车辆与桥梁耦合模型为例,阐明了方法列式过程。磁浮列车过多跨简支梁桥的数值算例结果表明,时域显式法具有理想的计算精度和效率。     

高架轨道梁结构特性对磁浮系统的动力影响

以德国Transrapid磁浮列车系统为基础,采用现有的磁浮车辆垂向模型,建立了有限元轨道梁模型、磁浮车轨垂向耦合系统模型及其振动微分方程.在此基础上,针对德国在上海的磁浮项目,主要就轨道梁的型式(简支和连续)、支承刚度及轨面不平顺波长对磁浮车辆-轨道耦合系统动力响应的影响等进行了分析.     

Influence of Thermal Conductivity on Guidance Force Decay of HTS Bulk Exposed to AC Magnetic Field Perturbation in a Maglev Vehicle System

Bulk superconductors have great potential for various engineering applications, especially in a high-temperature superconducting (HTS) maglev vehicle system. In the vehicle system, the stable levitation can be achieved without any complex control system owed to the pinning effect of the bulks. However, the HTS bulks in the vehicle system were always exposed to the time-varying external magnetic field, which was generated by the inhomogeneous surface magnetic field of the NdFeB guideway. In our previous work, we studied the guidance force decay characteristics of the YBCO bulk over the NdFdB guideway used in the HTS maglev vehicle system by an experiment in which the AC external magnetic field generated by an electromagnet was used to simulate the time-varying external magnetic field caused by the inhomogeneity of the guideway, and calculated the guidance force decay as a function of time based on an analytic model. In this paper, we investigated the influence of thermal conductivity on the guidance force decay of HTS bulk exposed to AC field perturbation in the maglev vehicle system and tried to adopt a method to suppress the decay. From the results, it was found that the guidance force decay rate was higher for the bulk with the lower thermal conductivity. So, we could reduce the guidance force decay of the HTS bulk exposed to the AC external magnetic field perturbation in the maglev vehicle system by improving the thermal conductance of the bulks.     

Magnet Guideways for Superconducting Maglevs: Comparison Between Halbach-Type and Conventional Arrangements of Permanent Magnets

The characteristics of the permanent magnets composing the guideway in superconducting magnetic levitation devices are very important for their performance in terms of levitation force and stability. From a model based on minimizing the magnetic energy in the superconductor and considering realistic parameters of actual maglev devices, we calculate the levitation and guidance forces and stability arising from both conventional arrangements and recently proposed Halbach-like arrangements. When a comparison is carefully made under similar conditions, we conclude that not always complicated arrangements based on Halbach arrays bring significant improvements with respect to some simpler arrangements that also provide large force. These results may help improving the design of actual maglev devices.     

3D-Modeling Numerical Solution of Guidance Force of HTSC Bulk Above Permanent Magnetic Guideway

This paper presents a 3D-modeling numerical method to simulate the electromagnetic behavior of high-temperature superconductors (HTSC) while the bulk departs from the center line of the guideway. In this paper, for a typical superconducting levitation style with a bulk superconductor suspended above a permanent magnet guideway (PMG), the guidance characteristics of the system were investigated computationally followed by experimental work. Based on the proposed 3D-modeling numerical solutions of electromagnetic behavior of a HTS bulk sample, we used the grid multiplexing technology in which the meshing nodes inside the HTS bulk represent the centers of pinning to simulate flux pinning of HTS bulk. The resolved code of the 3D-modeling of high-temperature maglev was developed with the FORTRAN language. Comparisons between the experimental and numerical results indicated the effectiveness of the method utilized in the paper.     

Magneplane power supply costs

Means are studied to bring propulsion power from commercial utility lines and distribute it and control it to the LSM propulsion winding in the guideway. Switched sections of propulsion winding from 0.25 km to 2.5 km long are considered and cost variations explored. Magneplane guideway for this study propagates a fixed frequency travelling magnetic wave on which vehicles with superconducting magnets for LSM and maglev are inserted and removed by adjustable frequency sections at station stops. Costs reported reflect only fixed frequency main-line. Several variable parameters are considered. These include length of LSM winding which will be energized by each PCU, number of winding sections per PCU, utility supply voltage, and capacitor compensation of winding inductance to reduce thyristor current. Estimated costs are presented to show the influence of variation in the parameters. Future cost trends are considered. System power efficiencies are presented and their influence on selection of non-optimum system cost is considered. Development of thyristor switching technology for tuned series RLC high power circuits is recommended.     

Influence of the Vertical Inclination of Permanent Magnet Guideway on Levitation Characteristics of Hts Maglev System

In the application of high temperature superconducting (HTS) magnetic levitation (maglev) system under vertical inclination of permanent magnetic guideway (PMG), the component of the total weight of levitation body above the PMG will be changed. Therefore, the influence of the vertical inclination of PMG on levitation characteristics of HTS maglev system cannot be ignored, such as the levitation gap, the levitation force, guidance force and driving force of the linear motor. In order to investigate the influence of the vertical inclination angle on levitation characteristics of the HTS maglev system, a HTS maglev launch platform has been designed and fabricated for the investigation the influence of vertical inclination angle between the range of 0° and 18° on the levitation and guidance and driving force parameters of the HTS maglev launch platform. Experimental results show that the levitation gap was the main levitation characteristic for HTS maglev system under vertical inclination of PMG, which increased with increment of the vertical inclination angle. However, the levitation force, and the driving force of the linear motor decreased. The guidance force could not be influenced by the increment of levitation gap. The experimental results are helpful toward improving the running performance of the HTS Maglev launch system.