Study On Effects Of High-Speed Trains Dynamics Parameters And Their Applications

Based on accumulations of theory, technology and experiences of high-speed railway for nearly half a century, miracles of high-speed railway have been happening. High-speed trains are developed step by step, with strong technical inheritance and continuity. There are some technical architectures for high-speed trains in the world, due to different service demand, running environment and technology systems. Take a bogie design for example, structural characteristics at different speed grade bogie are not the same. For the higher speed bogie, it’s more simple and contains components with clear division of work and modular designs. Systemic structure determines its function. Bogie design concepts or methods at the same speed grade have a lot in common. The higher the speed is, the more the common design views are. Further performance improvements of high-speed bogie with convergence structural characters must depend on its parameters. Systemic parameters values determine its performance. Vibration characteristics of bogie, carbody or trains are decided by the coordination between stiffness/damping parameters of suspension system and structural properties. Except for the preferred design values, performances are supported by limiting parameter performance degradation in service. Effective approaches are condition monitoring and maintenance. Range of parameters affects performance. Mastering effects of parameters and features of their deterioration in service, are basic terms to control vehicle dynamics performance domains.Funded by the subproject of National Basic Research Program of China(973)-Key Basic Problems Research of High-speed Train for Safety Operation (2007CB714700),’High-speed wheel/rail dynamic behavior and its performance evolvement rule’, and the subprojects of National Science and Technology Pillar Program in the11th Five-year Plan Period-Key Technology Research and Equipment Development of High-speed Train(2009BAG12A00),’High-speed train generality foundation and its system integration technology’&’High-speed bogie technology’, research works in this paper can be summarized as follows:(1) Developments of high-speed trains and bogies around the world are described according to different nationality and speed grade. Design consensus of high-speed bogie are extracted. Combining with practical operation and maintenance of high-speed trains, the significances to study features of vehicle complete parameters in the design and service period can be shown. In view of current researches related to dynamics parameters to control lateral, vertical, longitudinal movements of a high-speed vehicle and parameter performance degradation happened in the operation, skeleton of this study and main contents are determined.(2) Models for a wheel, a vehicle, and a train are built on the basis of the multi-body system dynamics theory. Indexes of vehicle three major dynamics performances and vehicle vibration frequency are pointed out. Vehicle parameters are classified as structural parameters and suspension parameters. Orthogonal experiment design method and the comprehensive experimental method are both used to study the effects on performances of the vehicle passing through the straight and curved tracks.(3) Sensitivity of parameters can be analyzed by sensitivity analysis, curve fitting and the method to determine parameter domain based on impacts. Effect of a single parameter is discussed firstly, combining with influences of extreme fault conditions on stability. And then, remarkable impact factors of nonlinear critical speed are found, such as sprung mass Mc, equivalent conicity λe.damping of anti-hunting damper Csx, damping of secondary lateral damper Csy, longitudinal stiffness of primary swing arm Kpx. Influences of multi-parameters combination, such as two structural parameters (Mc-λe), three suspension para.mcters(Csx-Csy-Kpx), and combination of structural and suspension parameters(Mc-Csx-Kpx&λe-Kpx-Kpy). are studied. Vehicle stability can either be enhanced or weakened by the simultaneous changing of multi-parameters, which is different from the influence of single parameter. Different expression methods are used to show the right range of parameters and the way for further improvement, such as two-dimension figures&tables and three-dimension domain method.(4) Research ideas for stability are also applied to the study of parameters influences on vehicle safety, riding comfort and vibration frequency characteristics. Performances on straight and curved tracks are both simulated under two speed grades300km/h&350km/h. Unsprung mass Mw, along with the factors Mc, Csx and Kpx, affects safety indexes observably, which include wheel load reduction ratio, derailment coefficient and wheeset lateral force. Vehicle lateral Sperling index is related to parameters Mc, Csx and Kpx, while for vertical Sperling index, vertical stiffness and damping of air spring device are important. The interactions among structural and suspension parameters on vehicle safety and comfort can not be ignored. There are multi-indexes to evaluate vehicle safety and comfort, which can be considered as more constraints conditions for the determining of parameter range.(5) Five types of track random irregularities are introduced to analyze vehicle displacement and acceleration responses. It is necessary to control track regularity status in operation. Vehicle vibration frequency involves hunting frequency and suspension self-vibration frequency in this paper. Running speed is taken as one of the analysis objects and there are in-depth simulations and bench test studies on hunting frequency.(6) Actual design range of vehicle parameters, operating range and maintainance range are all discussed. Features of high-speed bogie maintenance and fault distribution in service are investigated. Combined with the conclusion about the effects, safety status of a vehicle and status of its structural and suspension parameters are discussed.(7) Based on effects of parameters on stability, a control idea is put forward, which is an open-loop control strategy and describes the design concept of vehicle stability clearly. Coupled with vehicle characteristics in service, a closed-loop control concept is introduced by adding some rapid adjustment strategies for unstable phenomenon in operation. Take speed-upgraded vehicles of CRH series as examples, validity of design improvements, which are conducted by the control strategy for stability, can be fully demonstrated by bench test and field test, so does the engineering significance of strategy.(8) A control idea for vehicle comfort is carried out on account of the effects. It is also an open-loop control method, which starts from the control of’inputs’, and then controls transfer path of’system features’(intermediate processes), so that the good’output’can be gained. The control strategy is also verified by the speed-upgraded vehicles.