An inverse shape design method for railway wheel profiles

Optimisation of a railway vehicle–track system is a complex process. The paper presents a procedure for optimal design of a wheel profile based on geometrical wheel/rail contact characteristics such as the rolling radii difference (RRD). The procedure uses optimality criteria based on an RRD function. The criteria account for stability of wheelset, cost efficiency, minimum wear of wheels and rails as well as safety requirements. The shape of the wheel profile approximated by a piecewise cubic Hermite interpolating polynomial is varied during the optimisation process to satisfy the optimality criteria. A numerical technique called multipoint approximations based on response surface fitting (MARS) has been chosen as an optimisation method. The proposed optimum design procedure has been applied to improve the performance of metro trains in Rotterdam (RET), The Netherlands. The trains were suffering from severe wheel tread wear and as a result of that from lateral vibrations (hunting). Using the proposed procedure, a new wheel profile has been obtained and applied to the RET metro trains. The results of the optimisation have shown that the performance of a railway vehicle can be improved by improving the contact properties of the wheel and rail. After the application of the optimised wheel profile, the instability of the metro trains has been eliminated and the lifetime of the wheels has been increased from 15,000 to 120,000 km.     

Reduction of train-induced building vibrations by using open and filled trenches

A numerical investigation on the effectiveness of open and in-filled trenches in reducing the building vibrations due to passing trains is presented. Particularly, a two-dimensional soil-structure system containing the cross-section of a railway embankment, the underlying soil, a trench barrier and a nearby six-storey building is considered. For the analysis, a time domain coupled boundary element-finite element algorithm is employed. Unlike most of the previous formulations, this model completely considers the soil-structure interaction effects and directly determines the effect of the wave barrier on the structural response. The effects of geometrical and material properties of the trench and its backfill material on the structural response are investigated. The results point out that using a trench barrier, a reduction level up to 80% of the building vibrations and internal forces can be achieved. Increasing the depth or the width of a trench may improve its reduction effect and a softer backfill material results in a better isolation effect.     

融合可拓语义和模糊综合评价的地铁列车外观设计方法

为进一步提升和彰显地铁列车外形中的地域文化特征,提出了一种基于专家和用 户视角的融合可拓语义和模糊综合评价的地铁列车外观设计方法。基于可拓语义提出了文化基 元概念,构建了涵盖文化载体、文化特征和文化价值的三元组,给出了地铁列车外观设计中的 可拓语义分析与表征步骤;基于模糊综合评价法来评估地铁列车外观设计方案的文化特征,给 出了评估流程,并以一款低速 B2 型成都地铁列车外观设计为例,结合专家和用户调查,从文化 提取与表征、方案设计和方案评估 3 方面对所提方法的可行性进行了验证。研究结果表明：该 方法能够有效将典型文化元素以语义符号的形式融入地铁列车的外观设计,有助于提升设计方 案的地域文化特征。     

城市有轨电车引发的建筑结构振动响应

为分析城市有轨电车运行引发的建筑结构振动舒适度,基于MATLAB设计结构振动舒适度的计算程序,可结合结构健康监测系统的监测数据对建筑结构的振动舒适度进行分析。采用某有轨电车运行中的实测数据,分析车辆段和行车段电车引发的振动,研究有轨电车的振动响应特性。分析结果表明：有轨电车运行引发的高频振动传至上盖结构几乎已完全消散;上盖结构的振动频率集中在16~20 Hz区间,以有轨电车的低频振动和结构相关附属机器的振动为主。减小有轨电车的行驶速度、增加建筑物与振动源的距离或控制楼内附属机器的振动可明显控制振动。在加速过程中,电车与地面和轨道会产生共振,因此存在振动加速度级的极大值。     

地铁车辆车顶吊挂元件动态试验工装设计

为研究地铁车顶吊挂元件所用连接件的连接参数和疲劳特性,设计一套地铁车辆车顶吊挂元件动态试验工装。工装固定在振动试验台上,模拟地铁车辆车顶局部吊挂梁的安装结构,测试车顶吊挂梁连接件在模拟振动环境下的连接参数,为地铁车辆常用紧固件连接参数的选定提供依据。为验证工装的力学特性是否满足试验要求,利用有限元软件校核工装强度,并在其频域内进行随机振动疲劳分析,计算结果表明工装的静强度和疲劳寿命均满足试验要求。     

Hidden roles of the train driver: A challenge for metro automation

In the year 2014, the Helsinki Metro is planned to be fully automated. This automation means that the metro trains will be computer-driven and monitored remotely from a stationary control room. To investigate the challenges related to this scenario, we decided to study the ways in which the current train drivers contribute to the metro system. We conducted three separate but interrelated studies, which were based on the Core-Task Analysis method. Our results suggest that there is much more to driving the metro train than meets the eye. The drivers do not only operate the train on track and its doors at stations, but they also contribute to a variety of other important, albeit more hidden, functions in the metro system. For example, the drivers anticipate, observe, interpret, and react to events in the surrounding environment. Furthermore, they are a significant interaction link between different actors of the metro system. Our conclusion is that if the identified critical roles of the drivers are not accounted for, a migration to a fully automated metro system can affect the quality of service and raise safety issues. In addition to automated metros, the results of this research can be applicable to automation implementations also in other domains.     

Critical velocity of a load moving on a beam with a sudden change of foundation stiffness: Applications to high-speed trains

The transient dynamic response of a beam supported on a foundation with sudden stiffness change and subjected to a force moving with constant velocity is analysed. The abrupt change is located at the mid-section of the beam of finite length. Two analytical approaches are implemented. In the first one, the response is obtained by finite integral transformations incorporating global modes of vibration, while in the second the analytical responses of each half of the beam are linked by continuity conditions. The values obtained are used to study the influence of the abrupt change on the critical velocities. The analyses carried out enable to reach results and draw conclusions directly related to the knowledge of ground vibrations induced by high-speed trains.     

基于复杂网络的轨道交通网络结构特性研究

本文首创性的运用复杂网络理论比较全面地分析了北京城市轨道交通网络的静态结构特性,动态加权结构特性.主要以2015年北京市地铁路网为基础,建立起轨道交通网络样本,通过计算度与度分布、平均路径长度、介数等网络统计特性分析了轨道交通网络的静态结构特性;并首次在静态网络拓扑的基础上结合了2015年北京地铁路网断面客流信息,通过计算点强度及其分布、节点加权介数、介数与点强度相关性等统计指标分析了网络的动态特性.从而解释了各个因素之间的相互作用和对北京轨道交通网络结构上的影响,为以后轨道交通的建设和运营提供了一些指导性的建议.     

基于VS2008的制动系统试验台调试程序开发

首先介绍了制动系统试验台的硬件设计,在此基础上进行了试验台调试程序的设计,并重点讲述了指示灯界面及与PLC通信的实现。在调试程序完成后,通过串口调试助手验证了调试程序的正确性和可行性。     

Efficient predictive vibration control of a building‐like structure

This paper presents the design of a model predictive controller (MPC) based on Laguerre functions for vibration control. The controller is tested in a building‐like structure consisting on a three‐story building with a passive vibration absorber. The structure is connected to an electromagnetic shaker, which excites the support of the superstructure, providing forces with a wide range of excitation frequencies, including some resonance frequencies of the structure. The overall controller is a hybrid vibration absorber conformed of (i) an active absorber, that is a predictive vibration control scheme, synthesised to actively attenuate the vibratory system response via (ii) a passive absorber, known as a tuned mass damper (TMD), located over the third story building to reduce the vibrations caused by harmonic forces acting on the base of the structure. The proposed predictive control strategy proves to be effective and efficient, improving system's performance with guaranteed stability and feasibility. Experimental and numerical results are included to illustrate the overall system performance.     

Analysis of traffic-induced vibrations by blind source separation with application in building monitoring

The paper presents an approach that may enable the separation of the vibrations induced by underground traffic from the vibrations induced by other sources, based on Second Order Blind Identification (SOBI) algorithm. The signals recorded in different locations of an instrumented building are mixed signals from different internal and external vibration sources. The blind source separation algorithm will estimate the independent vibration sources together with their mixing model. This model can be used to determine the contribution of each source in different measurement points, to evaluate the effect of the vibration sources and their potential for building damage. The above approach has been tested in simulation and on a building subject to different traffic forms.     

地铁列车车内低频结构噪声仿真

建立某地铁列车车体结构和车内声腔有限元模型,进行声固耦合模态分析,得到车体结构和车内声腔的模态特征。将车体动力学模型计算得到的车体振动激励施加于声固耦合模型中,分析地铁列车车内低频噪声和车身板件声压贡献量,得到对观察点声压贡献较大的板件,有针对性地提出车体结构改善方案,降低观察点处的噪声,为地铁列车车内噪声优化提供指导。     

采用预测控制的地铁节能优化控制算法

本文针对地铁列车自动运行系统(automatic train operation,ATO)一般运行情况以及晚点延迟发车情况下的节能问题,基于预测控制算法设计了地铁节能优化控制算法.利用预测控制算法的在线滚动优化特性,通过设计含有能量消耗趋势优化项的控制目标函数,控制算法能够针对节能目标实现快速动态调整.通过调节目标函数中各优化项权重的相对大小,节能算法可以在满足列车时间与路程运行指标的同时,达到降低能耗的目的.在MATLAB平台上利用真实车辆模型对提出的节能优化控制算法进行了仿真,在列车不延迟与延迟的情况下,算法都很好地平衡了跟踪目标与节能目标,为地铁能耗动态优化控制提供了可行方案.     

Exploring the spatiotemporal structure of dynamic urban space using metro smart card records

The wide application of pervasive computing technology has allowed for the emergence of big data on spatial behavior and therefore provides an opportunity to explore dynamic urban space. In this paper, an eigendecomposition method is proposed to capture the common patterns of passengers’ variation over time among all metro stations as well as to explore the spatial heterogeneity of the dynamic space around the metro stations based on the common patterns with low dimensional structures. Using Shenzhen as a case study, four datasets for check-in/check-out and weekday/weekend are decomposed to obtain the principal components (PCs) and eigenvectors. The first several PCs are the most common patterns of passengers’ variation over time among all metro stations, while the corresponding elements in the eigenvectors, referred to as EigenStation in this paper, can describe the characteristics of the metro station. The decomposition result is evaluated at both the aggregation and individual station levels, and the result demonstrates that the first two elements of the EigenStation can approximate the original dataset. The EigenStation vector angle, i.e., ω, is used to represent the structure of the EigenStation, and its value is highly related to the land use structure around the metro stations. The proposed method can provide deep insight into static and dynamic urban spaces, which can help improve urban planning around metro stations.     

Local energy minimization in optimal train control

The calculation of optimal driving strategies for on-board control of freight trains is a challenging task. In this paper we calculate the critical switching points for a globally optimal strategy on a track with steep gradients using a new local energy minimization principle. The method has been used successfully in Australia to calculate optimal switching points and hence provide in-cab advice to train drivers on long-haul freight trains.     

神经元膜电位对信息的编码

神经元膜电位的放电活动是神经编码的基础。然而,目前对于神经元电活动对神经信息的编码方式,至今尚未形成一个完整的认识。传统的编码理论认为神经系统以离散的动作电位放电序列进行信息的表达和传递,主要研究动作电位的发放频率和放电活动的时间模式。基于该理论,对神经元放电序列所携带的信息已经出现了一些定量的计算方法,但这些方法还很难应用到大规模神经元网络的计算当中。本研究以神经元的膜电位为研究对象,展示了如何量化膜电位序列所携带的信息,并将该计算结果与传统放电序列方沣的计算结果进行了对比分析,其结果取得了很好的一致性。本研究为神经活动信息量的定量计算提供了一种新的思路和方法。     

Quantifying variability in neural responses and its application for the validation of model predictions

A rate code assumes that a neuron's response is completely characterized by its time-varying mean firing rate. This assumption has successfully described neural responses in many systems. The noise in rate coding neurons can be quantified by the coherence function or the correlation coefficient between the neuron's deterministic time-varying mean rate and noise corrupted single spike trains. Because of the finite data size, the mean rate cannot be known exactly and must be approximated. We introduce novel unbiased estimators for the measures of coherence and correlation which are based on the extrapolation of the signal to noise ratio in the neural response to infinite data size. We then describe the application of these estimates to the validation of the class of stimulus-response models that assume that the mean firing rate captures all the information embedded in the neural response. We explain how these quantifiers can be used to separate response prediction errors that are due to inaccurate model assumptions from errors due to noise inherent in neuronal spike trains.     

Generation of optimal schedules for metro lines using model predictive control

This paper presents a new methodology for computation of optimal train schedules in metro lines using a linear-programming-based model predictive control formulation. The train traffic model is comprised of dynamic equations describing the evolution of train headways and train passenger loads along the metro line, considering the time variation of the passenger demand and all relevant safety and operational constraints for practical use of the generated schedule. The performance index is a weighted sum of convex piecewise-linear functions for directly or indirectly modelling the waiting time of passengers at stations, onboard passenger comfort, train trip duration and number of trains in service. The proposed methodology is computationally very efficient and can generate optimal schedules for a whole day operation as well as schedules for transition between two separate time periods with known schedules. The use and performance of the proposed methodology is illustrated by an application to a metro line similar to the North-South line of São Paulo Underground.     

I-bus智能照明系统在轨道交通中的应用

针对轨道交通中传统的照明控制方式的不足,简单介绍了智能照明系统的概念和特点,并详细说明了I-bus智能建筑控制系统的工作原理,构成、功能及其优势.具体阐述了I-bus智能建筑控制系统在轨道交通照明系统中的具体应用方案,从而实现轨道交通照明系统的智能化运营.     

动态资源感知的并行化模糊测试框架

针对现有的并行模糊测试在测试效率、资源利用率以及异常处理上的局限性,本文围绕测试资源的生成、使用及容错三个方面提出了一种动态资源感知的系统化解决方案。针对测试环境在大规模和多场景两个维度快速搭建的需求,提出一种基于云平台的动态构建方法,加快测试环境部署,提高有效fuzz时间;针对并行模糊测试中资源利用率低的问题,提出一种多层次并行度动态调整的资源配置策略,优化整体测试资源配置并提高单机负载;针对大规模并行测试中节点易发生故障的问题,提出基于优先级调度的容错处理方法。最后,本文设计并实现了一个基于四级流水线并行处理结构的通用模糊测试框架。实验证明,该框架能够有效提高并行模糊测试的测试效率和资源利用率,实现系统的有效容错。