Bifurcation analysis of an automobile model negotiating a curve

The paper deals with the bifurcation analysis of a rather simple model describing an automobile negotiating a curve. The mechanical model has two degrees of freedom and the related equations of motion contain the nonlinear tyre characteristics. Bifurcation analysis is adopted as the proper procedure for analysing steady-state cornering. Two independent parameters referring to running conditions, namely steering angle and speed, are varied. Ten different combinations of front and rear tyre characteristics (featuring understeer or oversteer automobiles) are considered for the bifurcation analysis. Many different dynamical behaviours of the model are obtained by slightly varying the parameters describing the tyre characteristics. Both simple and extremely complex bifurcations may occur. Homoclinic bifurcations, stable and unstable limit cycles (of considerable amplitude) are found, giving a sound and ultimate interpretation to some actual (rare but very dangerous) dynamic behaviours of automobiles, as reported by professional drivers. The presented results are cross-validated by exploiting handling diagram theory. The knowledge of the derived set of bifurcations is dramatically important to fully understand the actual vehicle yaw motions occurring while running on an even surface. Such a knowledge is a pre-requisite for robustly designing the chassis and for enhancing the active safety of vehicles.     

曲轴—轴承系统多工况动力学与摩擦学耦合分析

以实测示功图为计算依据,以动力学仿真软件ADAMS为工具,以某4缸柴油机的曲轴—轴承系统为研究对象,耦合分析多工况作用下曲轴—轴承系统动力学行为和摩擦学特性。得到的主要结论是:主轴颈中心径向振动响应振幅随转速提高而降低,随最小油膜厚度增大而上升,而最大油膜压力的变化规律主要取决于气缸最高燃烧压力;主轴颈中心径向振动响应振幅和最大油膜压力随负荷提高而上升,最小油膜厚度随负荷的提高而降低。     

Empirics of multi-modal traffic networks – Using the 3D macroscopic fundamental diagram

Traffic is multi-modal in most cities. However, the impacts of different transport modes on traffic performance and on each other are unclear – especially at the network level. The recent extension of the macroscopic fundamental diagram (MFD) into the 3D-MFD offers a novel framework to address this gap at the urban scale. The 3D-MFD relates the network accumulation of cars and public transport vehicles to the network travel production, for either vehicles or passengers. No empirical 3D-MFD has been reported so far.In this paper, we present the first empirical estimate of a 3D-MFD at the urban scale. To this end, we use data from loop detectors and automatic vehicle location devices (AVL) of the public transport vehicles in the city of Zurich, Switzerland. We compare two different areas within the city, that differ in their topology and share of dedicated lanes for public transport. We propose a statistical model of the 3D-MFD, which estimates the effects of the vehicle accumulation on car and public transport speeds under multi-modal traffic conditions. The results quantify the effects of both, vehicles and passengers, and confirm that a greater share of dedicated lanes reduces the marginal effects of public transport vehicles on car speeds. Lastly, we derive a new application of the 3D-MFD by identifying the share of public transport users that maximizes the journey speeds in an urban network accounting for all motorized transport modes.     

一种新的经济多段桥控制方法

以SS4电力机车主电路为例,分析了经济多段桥的传统控制方法存在的问题,介绍了一种新的经济多段桥控制方法及其控制框图,并提出了对SS4机车经济四段桥控制方法进行改造的方案,从技术经济、控制及功率因数的角度阐述了该方案的优点。     

应用面向对象程序设计方法实现列车运行图绘制

介绍面向对象编程方法,阐述用其方法完成列车运行图的绘制过程,并且介绍列车运行图编制系统中所涉及的各种问题及解决方法.     

环放路网宏观基本图信号周期敏感性分析

为揭示路网宏观基本图(MFD)对信号周期的敏感性,首先,提出一种基于GMM的宏观基本图建模方法,并在此基础上提出路网运行效率和稳定性的表征方法;其次,提出MFD 对信号周期敏感性的仿真实验设计方法;再次,以环放路网为例,进行仿真实验,分析信号周期的变化对MFD的影响,进一步揭示信号周期对路网运行效率和稳定性的影响机理. 结果表明,合理的信号周期对MFD和路网的效率及稳定性影响不大,但周期过大或过小则对MFD 和路网的运行效率及稳定性造成较大影响. 该结论可以为路网交通控制和优化提供依据.     

编制列车运行图的智能控制方法

讨论了在列车运行中,针对列车晚点、加开列车、减开列车造成的不能按图行车的实际情况,研究并提出在原有运行图基础上进行智能化调整的方法,并将调整结果反映在运行图上,实时绘制出新的运行图.这为列车运行的调整及相关参数的计算提供了方便、直观的依据,反映了计算机编制列车运行图的智能化发展趋势.     

高速铁路列车运行图编制系统的研究

当前,京沪高速客运专线的修建工作正处于可行性研究阶段,各项科研工作正在广泛而深入地进行,为了进一步研究京沪高速铁路的运营组织工作,开发了京沪高速铁路分段运行图计算机编制系统.对该系统进行了介绍,并研究了该系统中的各种处理模型,给出了算例.     

铁路列车调度运行图输出系统中面向对象的软件设计模式

当前,对于面向对象的软件设计模式是软件工程的重要研究课题之一.而基于铁路知识域的相应研究对于提高铁路系统软件的设计规范和复用性具有重要的意义.本文基于铁路列车调度运行图输出系统的研发基础上,建立了整个系统的面向对象的软件体系结构,同时析取区观察者模式,绘图环境模板模式,代理模式,策略模式四个软件设计模式.