The effect of spring pads in the secondary suspension of railway vehicles on bogie yaw resistance

This paper deals with properties of bogie yaw resistance of an electric locomotive with secondary suspension consisting of flexi-coil springs supplemented with tilting spring pads. Transversal stiffness of a sample of a spring/pad assembly was measured on a dynamic test stand of the University of Pardubice (Czech Republic) and the results were applied into a multi-body model of the locomotive created in the simulation tool ‘SJKV’. On the basis of the simulation results, a detailed analysis of the bogie yaw resistance was performed in order to explain the effect in dynamic behaviour of the locomotive when the moment against bogie rotation (and therefore the distribution of guiding forces on individual wheels, as well) is influenced with the vehicle speed in a certain curve. Results of this analysis show that the application of suspension elements with strongly directionally dependent transversal stiffness into the secondary suspension can just lead to a dependency of the bogie yaw resistance on cant deficiency, i.e. on the vehicle speed in curve. This fact has wide consequences on the vehicle dynamics (especially on the guiding behaviour of the vehicle in curves) and it also points out that the current method of evaluation of the bogie yaw resistance according to relevant standards, which is related with assessment of the quasistatic safety of a railway vehicle against derailment, is not objective enough.     

A real-time posture monitoring method for rail vehicle bodies based on machine vision

Monitoring vehicle operation conditions has become significantly important in modern high-speed railway systems. However, the operational impact of monitoring the roll angle of vehicle bodies has principally been limited to tilting trains, while few studies have focused on monitoring the running posture of vehicle bodies during operation. We propose a real-time posture monitoring method to fulfil real-time monitoring requirements, by taking rail surfaces and centrelines as detection references. In realising the proposed method, we built a mathematical computational model based on space coordinate transformations to calculate attitude angles of vehicles in operation and vertical and lateral vibration displacements of single measuring points. Moreover, comparison and verification of reliability between system and field results were conducted. Results show that monitoring of the roll angles of car bodies obtained through the system exhibit variation trends similar to those converted from the dynamic deflection of bogie secondary air springs. The monitoring results of two identical conditions were basically the same, highlighting repeatability and good monitoring accuracy. Therefore, our monitoring results were reliable in reflecting posture changes in running railway vehicles.     

Study on dynamic characteristic analysis of air spring with auxiliary chamber

The characteristics of air springs, such as the effects of bellows and those of heat transfer on spring constant and damping factor, have been studied. However, auxiliary chambers and pipes are required in addition to air springs, to vary spring constant in the case of spring rate change by electronically controlled air suspension systems of a vehicle. Few reports have dealt with the effects of auxiliary chambers and pipes. In our study, the relation between vibration frequency and spring reaction has been investigated to clarify the effects of pipes on dynamic spring constant. Our proposed model has proved effective in understanding the phenomena.     

Research on the mechanism of a newly developed levitation frame with mid-set air spring

To reduce the vehicle/guideway-coupled vibration and improve the levitation stability of medium–low-speed maglev vehicle, a new type of levitation frame with air springs installed in the middle of the longitudinal beams is developed. This levitation frame with mid-set air spring (LFMAS) is studied comparatively with the levitation frame with end-set air spring (LFEAS) in electromagnetic levitation mode. The coupling degrees of the two kinds of frames are analysed by vertical motion equations; the energy consumptions for levitation control system to overcome the spring resistance in the whole adjustment process are calculated by the energy method; and the vibration accelerations are compared by dynamics analysis and bench test. The equations indicate that the LFMAS has a better decoupling effect and lower energy consumption than that of the LFEAS in any adjustment process. Simulation and test results show that the LFMAS can effectively reduce the vibration acceleration at a low-speed and achieve a better levitation stability in working conditions, validating that the LFMAS has a better levitation performance and adaptability to the guideway, which is attributed to the mechanical decoupling of the levitation module. It is expected that this new levitation frame will be very helpful in enhancing levitation stability and the ride index of medium–low-speed maglev vehicle.     

大客车空气弹簧动态特性的试验分析

空气弹簧具有变刚度特性，其振动频率要比钢板弹簧低得多。对客车用空气簧动态特性进行了试验分析。结果表明，空气弹簧在多种载荷工况下特性曲线具有相似性，说明一种空气弹簧适合于多种载荷的汽车；空气弹簧的动刚度主要取决于激励频率，在低频范围内幅值比较小，高频范围内幅值比较大。     

基于腔体单元和Rebar单元的空气弹簧性能分析

建立了空气弹簧有限元离散模型,研究了空气弹簧内压-位移、容积-位移、最大外径-位移以及载荷-位移关系,仿真结果与实测结果对比表明,两者具有很好的一致性。研究了工作高度和帘线角度对空气弹簧承载能力、刚度特性以及空气弹簧在工作过程中直径变化的影响,结果表明空气弹簧的工作高度和帘线角度是影响空气弹簧性能的重要因素。     

空气弹簧的使用要求及故障分析

空气弹簧因其良好的非线性特性在车辆上得到广泛的应用,但其在使用中却容易产生故障。本文介绍空气弹簧的使用要求,并分析空气弹簧故障产生的主要原因及防范措施。     

Hunting stability analysis of high-speed train bogie under the frame lateral vibration active control

In this paper, we study a multi-objective optimal design of three different frame vibration control configurations and compare their performances in improving the lateral stability of a high-speed train bogie. The existence of the time-delay in the control system and its impact on the bogie hunting stability are also investigated. The continuous time approximation method is used to approximate the time-delay system dynamics and then the root locus curves of the system before and after applying control are depicted. The analysis results show that the three control cases could improve the bogie hunting stability effectively. But the root locus of low- frequency hunting mode of bogie which determinates the system critical speed is different, thus affecting the system stability with the increasing of speed. Based on the stability analysis at different bogie dynamics parameters, the robustness of the control case (1) is the strongest. However, the case (2) is more suitable for the dynamic performance requirements of bogie. For the case (1), the time-delay over 10?ms may lead to instability of the control system which will affect the bogie hunting stability seriously. For the case (2) and (3), the increasing time-delay reduces the hunting stability gradually over the high-speed range. At a certain speed, such as 200?km/h, an appropriate time-delay is favourable to the bogie hunting stability. The mechanism is proposed according to the root locus analysis of time-delay system. At last, the nonlinear bifurcation characteristics of the bogie control system are studied by the numerical integration methods to verify the effects of these active control configurations and the delay on the bogie hunting stability.     

A signal-based fault detection and classification method for heavy haul wagons

This paper proposes a signal-based fault detection and isolation (FDI) system for heavy haul wagons considering the special requirements of low cost and robustness. The sensor network of the proposed system consists of just two accelerometers mounted on the front left and rear right of the carbody. Seven fault indicators (FIs) are proposed based on the cross-correlation analyses of the sensor-collected acceleration signals. Bolster spring fault conditions are focused on in this paper, including two different levels (small faults and moderate faults) and two locations (faults in the left and right bolster springs of the first bogie). A fully detailed dynamic model of a typical 40t axle load heavy haul wagon is developed to evaluate the deterioration of dynamic behaviour under proposed fault conditions and demonstrate the detectability of the proposed FDI method. Even though the fault conditions considered in this paper did not deteriorate the wagon dynamic behaviour dramatically, the proposed FIs show great sensitivity to the bolster spring faults. The most effective and efficient FIs are chosen for fault detection and classification. Analysis results indicate that it is possible to detect changes in bolster stiffness of ±25% and identify the fault location.     

Carbody elastic vibrations of high-speed vehicles caused by bogie hunting instability

In particular locations of the high-speed track, the worn wheel profile matched up with the worn rail profile will lead to an extremely high-conicity wheel–rail contact. Consequently, the bogie hunting instability arises, which further results in the so-called carbody shaking phenomenon. In this paper, the carbody elastic vibrations of a high-speed vehicle in service are firstly introduced. Modal tests are conducted to identity the elastic modes of the carbody. The ride comfort and running safety indices for the tested vehicle are evaluated. The rigid–flexible coupling dynamic model for the high-speed passenger car is then developed by using the FE and MBS coupling approach. The rail profiles in those particular locations are measured and further integrated into the simulation model to reproduce the bogie hunting and carbody elastic vibrations. The effects of wheel and rail wear on the vehicle system response, e.g. wheelset bifurcation graph and carbody vibrations, are studied. Two improvement measures, including the wheel profile modification and rail grinding, are proposed to provide possible solutions. It is found that the wheel–rail contact conicity can be lowered by decreasing wheel flange thickness or grinding rail corner, which is expected to improve the bogie hunting stability under worn rail and worn wheel conditions. The carbody elastic vibrations caused by bogie hunting instability can be further restrained.     

单列列车通过无辅助坑道长大铁路隧道时空气阻力计算方法研究

对单列列车通过无辅助坑道长大铁路隧道时的空气阻力计算方法进行探讨,建立基于非恒定流和车头车尾压差的空气阻力计算公式,在通过现场试验对此方法进行验证后进行大量工况的计算,分析隧道长度、阻塞比、列车速度和列车长度对列车空气阻力的影响。计算结果表明：影响隧道内列车空气阻力最主要的因素是列车速度,其次分别为阻塞比、隧道和列车长度。     

Stability enhancement of a high-speed train bogie using active mass inertial actuators

In this study, a method regarding frame lateral vibration control based on the state feedback of an additional oscillator is proposed, so as to improve the bogie hunting stability. The multi-objective optimisation method (MOOP), with two objective functions of the stability index and control effort, is solved by the NSGA-II algorithm to obtain the feedback gains. The frame lateral vibration control can effectively improve the bogie hunting stability according to the linear and non-linear analysis of a high-speed train bogie, in which a fault of the yaw damper and time delay in the control system are considered. The effect of the oscillator suspension parameters and time delay on the system stability and robustness are analysed. The results show that the damped vibration frequency of the oscillator should be equal to the bogie hunting frequency, but a harder oscillator suspension can be used to improve the hunting critical speed margin of the bogie control system. However, just as how the feeding the frame states back directly, a hard oscillator suspension will lead to instability in the control system at a certain time delay. Therefore, the improvement of bogie hunting stability and reduction of control system stability must be considered when optimising the oscillator parameters. For the 350?km/h train bogie covered in this study, the optimal mass, natural frequency and damping ratio of the additional oscillator are acquired.     

空调进风口前端水管理及相应进风阻力关系

为了使空调前端进风口设计的更加合理,文章在确定进气格栅支撑板上排水口的位置及大小的情况下,通过CFD模拟前端水管理及前端进风口的阻力,并通过更改进气格栅的面积、开孔位置及增加挡板高度等方法,来满足水管理和进气阻力的要求。得出水管理与进气阻力之间关系：前端水管理设计比较理想,会牺牲前端进风阻力,使前端进风阻力增大;相反,为了使前端进风阻力更加合理,减小前端进风阻力,会牺牲前端水管理的性能。二者相互影响,相互制约。     

公路隧道双洞互补式通风系统横通道角度研究

依托某公路隧道研究通风横通道角度对双洞互补式通风系统的影响。通过数值模拟,分析不同角度工况下分流3通与汇流3通因阻力损失不同而引起的送风量差别,提出联络风道中汇流3通因阻力损失是确定横通道角度的关键。计算表明,在通风风速较大时,随横通道角度的减小,汇流3通段阻力损失会急剧变大;横通道角度为60°时,有利于通风网络的气流组织。     

汽车用膜式空气弹簧的非线性有限元分析

简述空气弹簧在汽车空气悬架使用中的优点,采用非线性有限元分析技术分析空气弹簧的非线性特性,得到不同帘线角的空气弹簧在不同载荷作用下的形变特性。     

Influence of temperature on the tyre rolling resistance

Temperature is a very important factor controlling rolling resistance of road vehicle tyres. There are at least three different temperatures that may be considered as important factors controlling thermal conditions of the rolling tyre. The most common measure of the thermal conditions during tyre rolling is ambient air temperature. The other two are: pavement temperature and “tyre” temperature. Tyre temperature is the most difficult to establish, as temperatures of different parts of rolling tyres differ considerably, thus there is a problem to obtain representative values. In the authors’ opinion, air temperature is the most universal and reliable parameter to measure. The article presents results obtained in the Technical University of Gdańsk during laboratory and road measurements of different car tyres rolling on different pavements. The knowledge of rolling resistance characteristics is important for modelling car dynamics as well as fuel consumption. It is also necessary to establish proper test conditions in the future standardized on-road method of measuring rolling resistance. The results indicate that generally each tyre and pavement combination is influenced by the air temperature in a unique way, but at the same it is possible to propose some general influence factors that may be used to normalize measurements to the standard temperature of 25 °C.     

汽车悬架用空气弹簧的非线性有限元分析

讨论了空气弹簧的材料、几何、接触、载荷等非线性力学特征，提出了运用非线性有限元法对空气弹簧进行结构分析的思路，并对某型汽车空气弹簧进行了充气变形与刚度特性分析，刚度特性的有限元分析结果与试验结果吻合较好。     

弹性元件在汽车悬架上的应用

阐述了应用于汽车悬架上的钢板弹簧、螺旋弹簧、扭杆弹簧、气体弹簧的功用特性、结构特点及应用实例,指出弹性元件在悬架装置中起传递垂直支承力、缓和不平路面经轮胎传给车架的冲击振动幅值和降低频率的作用,保持车辆行驶的稳定性,满足乘坐舒适陛的要求。     

Theoretical Comparison Between Different Configurations of Radial and Conventional Bogies

This article compares the dynamic behaviour of different configurations of radial and conventional two-axle bogies. In general, the design parameters for a better curve negotiation are not compatible with those for good stability. As the main target of this article is to compare the curving performances of different bogies under the same design basis, several bogie configurations with the same level of stability, obtained by choosing proper primary suspension stiffnesses, have been used. The comparison includes a conventional bogie and three radial bogies with differing self-steering and forced-steering principles in three different passenger services: High Speed, Regional and Mass Transit. The analysis has been concentrated on parameters such as stability, lateral wheel-track forces in curve and wheel wear indices. The results show that the radial bogie configurations studied do not make significant contributions in general applications with regard to a conventional bogie. It is only under specific running conditions and types of service that some radial bogie configurations provide advantages with respect to the conventional bogie.     

Theoretical Comparison Between Different Configurations of Radial and Conventional Bogies

This article compares the dynamic behaviour of different configurations of radial and conventional two-axle bogies. In general, the design parameters for a better curve negotiation are not compatible with those for good stability. As the main target of this article is to compare the curving performances of different bogies under the same design basis, several bogie configurations with the same level of stability, obtained by choosing proper primary suspension stiffnesses, have been used. The comparison includes a conventional bogie and three radial bogies with differing self-steering and forced-steering principles in three different passenger services: High Speed, Regional and Mass Transit. The analysis has been concentrated on parameters such as stability, lateral wheel-track forces in curve and wheel wear indices. The results show that the radial bogie configurations studied do not make significant contributions in general applications with regard to a conventional bogie. It is only under specific running conditions and types of service that some radial bogie configurations provide advantages with respect to the conventional bogie.