车载接触网运行状态检测装置系统设计及应用

接触网作为电气化铁路牵引供电的关键设备,其状态好坏直接影响铁路运行安全。为了在运营动车组上装备一套接触网运行状态检测装置对接触网运行状态进行全程监控,从系统的设计要求、设计原则、设计方案着手,引入非接触式的图像处理、机器视觉以及红外测温关键技术,完成装置的系统设计,同时通过静态和动态试验验证装置的性能。试验和现场的实际应用反馈表明,装置满足技术条件要求,同时装置对接触网的检测结果能够为接触网检修提供依据。     

A mesoscopic model for large-scale simulation of pedestrian dynamics

A mesoscopic pedestrian model is proposed, considering pedestrians as individuals and describing their movement by means of aggregate density-flow relationships. The model builds on a stochastic process, describing transition rates among adjacent sites on a lattice. Each lattice can contain several pedestrians. The approach is minimal and fast to simulate, and, by construction, capable of capturing population heterogeneity as well as variability in walking behaviour and en-route path choice. The model is more efficient than microscopic models, and potentially more accurate than macroscopic ones. We calibrate and validate the model using real data and carry out several numerical experiments to present its key properties and possible applications for simulation of large-scale scenarios.     

Scalable stability analysis on large connected vehicle systems subject to stochastic communication delays

In this paper large connected vehicle systems are analyzed where vehicles utilize vehicle-to-vehicle (V2V) communication to control their longitudinal motion. It is shown that packet drops in communication channels introduce stochastic delay variations in the feedback loops. Scalable methods are developed to evaluate stability and disturbance attenuation while utilizing the mean, second moment, and covariance dynamics in open chain and closed ring configurations. The stability results are summarized using stability diagrams in the plane of the control parameters while varying the packet delivery ratio and the number of vehicles. Also, the relationship between the stability of different configurations is characterized. The results emphasize the feasibility of V2V communication-based control in improving traffic flow.     

Link-based day-to-day network traffic dynamics and equilibria

A general dynamical system model with link-based variables is formulated to characterize the processes of achieving equilibria from a non-equilibrium state in traffic networks. Several desirable properties of the dynamical system model are established, including the equivalence between its stationary state and user equilibrium, the invariance of its evolutionary trajectories, and the uniqueness and stability of its stationary points. Moreover, it is shown that not only a link-based version of two existing day-to-day traffic dynamics models but also two existing link-based dynamical system models of traffic flow are the special cases of the proposed model. The stabilities of stationary states of these special cases are also analyzed and discussed. In addition, an extension is made to the case with elastic demand. The study is helpful for better understanding the day-to-day adjustment mechanism of traffic flows in networks.     

A pedestrian flow model considering the impact of local density: Voronoi diagram based heuristics approach

Local density, which is an indicator for comfortable moving of a pedestrian, is rarely considered in traditional force based and heuristics based pedestrian flow models. However, comfortable moving is surely a demand of pedestrian in normal situations. Recently, Voronoi diagram had been successfully adopted to obtain the local density of a pedestrian in empirical studies. In this paper, Voronoi diagram is introduced into the heuristics based pedestrian flow model. It provides not only local density but also other information for determining moving velocity and direction. Those information include personal space, safe distance, neighbors, and three elementary characteristics directions. Several typical scenarios are set up to verify the proposed model. The simulation results show that the velocity-density relations and capacities of bottleneck are consistent with the empirical data, and many self-organization phenomena, i.e., arching phenomenon and lane formation, are also reproduced. The pedestrians are likely to be homogeneously distributed when they are sensitive to local density, otherwise pedestrians are non-uniformly distributed and the stop-and-go waves are likely to be reproduced. Such results indicate that the Voronoi diagram is a promising tool in modeling pedestrian dynamics.     

The results of the pantograph–catenary interaction benchmark

This paper describes the results of a voluntary benchmark initiative concerning the simulation of pantograph–catenary interaction, which was proposed and coordinated by Politecnico di Milano and participated by 10 research institutions established in 9 different countries across Europe and Asia. The aims of the benchmark are to assess the dispersion of results on the same simulation study cases, to demonstrate the accuracy of numerical methodologies and simulation models and to identify the best suited modelling approaches to study pantograph–catenary interaction. One static and three dynamic simulation cases were defined for a non-existing but realistic high-speed pantograph–catenary couple. These cases were run using 10 of the major simulation codes presently in use for the study of pantograph–catenary interaction, and the results are presented and critically discussed here. All input data required to run the study cases are also provided, allowing the use of this benchmark as a term of comparison for other simulation codes.     

混合动力汽车行星耦合传动系统的图论建模及动力学分析

建立了混合动力汽车行星耦合传动系统的图论模型。采用行星耦合机构邻接矩阵和构件邻接矩阵的组合来描述图论模型,并根据邻接矩阵输出编码来判断传动系统的同构方案。在考虑行星耦合机构和各构件的转动惯量的基础上,基于图论模型分别对单、双排行星耦合机构传动系统进行运动学和动力学分析,为后续性能分析和传动方案优选奠定了基础。     

重载汽车-路面-路基垂向耦合动力学模型

为了研究路面不平度激励下移动重载汽车、路面结构和路基的动力相互作用,将重载汽车简化为由弹簧和阻尼器并联的匀速移动多自由度刚体模型,面层简化为离散基层块体支撑的带内部阻尼连续薄板模型,基层简化为支撑于粘弹性路基上的离散块体模型,并采用Wilson-θ法对建立的重载汽车-路面-路基垂向耦合动力学模型求解,同时验证模型的可靠性.研究结果表明:移动重载汽车产生的动力效应显著,五轴汽车产生的轮胎接地力和路面动位移最大,随着后轴轴重的增加,轮胎接地力和路面位移呈线性增加;随着行车速度增加,轮胎接地力峰值和路面动位移峰值增加,但路面动位移均值变化较小;路面不平度等级由A级降为D级时,轮胎接地力放大倍数增大了1倍多,且路面动位移峰值增幅达72％;路基刚度对轮胎接地力影响较小,但路面位移的影响则较为显著.     

喷水推进轴流泵三元水力设计

基于环量的三元设计方法和计算流体动力学,研究了叶片数、叶片流向环量中心位置与叶片出口边环量对叶轮性能的影响,分析了导叶进口边和出口边环量对喷水推进轴流泵性能的影响,通过合理地控制这些因素,设计了一种效率高、空化性能好的喷水推进轴流泵。在流量为56.2m3·s-1时,泵的扬程为35.9m,功率为21 465kW,效率为92.3%,可见,设计泵的性能优良,效率高。研究结果表明:增加叶片数能够有效减小单叶片转矩,当叶片数从5个增加到7个时,单叶片转矩减小了21%;叶片环量中心靠近出口边,有利于提高叶轮的空化性能,当环量中心从叶片弦长的0.3处移动到0.7处时,叶轮吸力面空化面积减小80%;叶轮出口边环量斜率会影响叶轮效率,当斜率分别为0.8、1.0和1.2时,叶轮效率逐步提高;当出口边环量从0.40增加到0.50时,叶轮的扬程和功率近似线性增加,扬程增加19.9%,功率增加19.5%;随着导叶进口边环量与出口边环量的比值的增大,泵效率先增大后减小,当比值为0.93时,泵的效率最高;导叶出口边环量分布会影响泵的效率、出口不均匀度和出口周向动能,当导叶出口边环量为-0.05时,泵的效率最高,出口不均匀度和出口周向动能最小。     

喷水推进轴流泵主体设计及性能分析

针对喷水推进轴流泵流道设计、轴流泵叶轮和导叶体设计进行计算研究,运用CAD软件进行了轴流泵建模设计,利用CFD软件求解了轴流式喷水推进泵内的流场,得出了喷泵的水力性能及内部流场的流动情况,直观地检验了喷泵设计的合理性和可行性,研究结果和结论可为喷水推进装置的整体化设计提供参考.