Design,analysis and performance evaluation of a third order distributed protocol for platooning in the presence of time-varying delays and switching topologies

This paper is concerned with the problem of designing a decentralized consensus protocol for platooning of non-identical vehicles in the presence of heterogeneous time-varying communication delays. The proposed control protocol makes use of a state feedback and to this aim drivetrain dynamics are modeled as third-order linear systems. Necessary and sufficient conditions for convergence and exponential stability, derived by using an appropriate Krasovskii functional, demonstrate the ability of the platoon in reaching the required regime with an exponentially bounded behavior. The proposed LMI-based approach allows to estimate both delay margin and decay rate. Moreover, convergence is proven under switching communication network topologies by means of a Lyapunov-Razumikhin function, and the assessment of a string stable behavior has been also theoretically investigated. High-fidelity simulations with Plexe show the effectiveness of the theoretical results in different driving conditions and in the presence of external disturbances and communication impairment. Different communication channel models are used in the validation stage to further prove robustness of the proposed methodology with respect hard delay and packets losses.     

基于向量Liapunov函数的时滞车辆跟随系统稳定性分析

为了提高自动化高速公路车辆纵向跟随控制系统的稳定性,建立了关于车辆跟随误差的具有时间滞后的无限维非线性关联大系统模型,应用向量李雅普诺夫函数对大系统的稳定性进行了分析。以大系统的孤立子系统的稳定性条件为基础,在假定系统满足全局Lipschitz条件的情况下,得到了此类大系统指数稳定的充分性判据。该判据是与时间滞后量无关的显式判据,可方便地应用于车辆纵向跟随控制器的设计。     

The impacts of changing flight demands and throughput performance on airport delays through the Great Recession

Several significant events between 2007 and 2009 impacted flight demands and the abilities of the three major New York area airports to handle demand. This paper assesses the results of applying a probabilistic simulation method – which isolates the individual contributions of changes in flight demand and changes in airport throughput performance to changes in flight delays – to diagnose how these different events may have caused operational changes at these airports, and in turn, how the results may be used to inform policies for appropriate countermeasures. The analysis revealed two key observations. Firstly, certain patterns in throughput performance shifts caused the most significant delays, and were more likely to have been caused by controller staffing issues rather than caps. Secondly, relatively constant average delays from one year to the next may result from significant demand drops accompanied by large throughput performance degradations at an airport. This suggests that not only operational limitations on capacity encourage airlines to reduce schedules, but that changed demands can also impact throughput performance. Overall, the analysis indicates that caps may not have provided their fully intended delay benefits. Although they successfully reduced overall flight demands at LGA and JFK, they also directly limited throughput performance at critical times, in turn limiting delay benefits. In addition, demands at the busiest times of the day appear to be relatively inelastic to these operational limitations, insofar as demand profiles at EWR and JFK remained “peaky” in 2008 and 2009. Also, the recession was largely responsible for reducing demands at the airports in 2009, but the delay benefits of this were dampened by a corresponding throughput performance degradation. Based on the above observations, a more direct demand management policy combined with policies that focus on maintaining high staffing capabilities at critical times of the day may be considered, to reduce the likelihood of major queue formation on days that do experience sustained demands. The results also suggest that a more flexible caps system, particularly during times of heavy queues, could be explored. Although airport practitioners have keen understandings of how their airports operate, without the support of quantitative analysis tools, it can be more difficult to argue the need for appropriate countermeasures. An analysis such as the one presented here can provide the detailed quantitative substantiation required to build cases for these targeted policy directives and infrastructure investments.     

Connected cruise control: modelling,delay effects,and nonlinear behaviour

Connected vehicle systems (CVS) are considered in this paper where vehicles exchange information using wireless vehicle-to-vehicle (V2V) communication. The concept of connected cruise control (CCC) is established that allows control design at the level of individual vehicles while exploiting V2V connectivity. Due to its high level of modularity the proposed design can be applied to large heterogeneous traffic systems. The dynamics of a simple CVS is analysed in detail while taking into account nonlinearities in the vehicle dynamics as well as in the controller. Time delays that arise due to intermittencies and packet drops in the communication channels are also incorporated. The results are summarised using stability charts which allow one to select control gains to maintain stability and ensure disturbance attenuation when the delay is below a critical value.     

Analyzing passenger train arrival delays with support vector regression

We propose machine learning models that capture the relation between passenger train arrival delays and various characteristics of a railway system. Such models can be used at the tactical level to evaluate effects of various changes in a railway system on train delays. We present the first application of support vector regression in the analysis of train delays and compare its performance with the artificial neural networks which have been commonly used for such problems. Statistical comparison of the two models indicates that the support vector regression outperforms the artificial neural networks. Data for this analysis are collected from Serbian Railways and include expert opinions about the influence of infrastructure along different routes on train arrival delays.     

Optimum Capacity for Intermodal Container Terminals

Abstract

Achievement of a desirable level of customer service at intermodal terminals mainly depends on the efficient loading and unloading of trains without delays. The efficiency of the transfer between the modes in the terminal area can have a significant effect on these delays. In this article, an analytically based simulation model is developed to investigate delays of trains for different service configurations. Simulation outputs are used to find an optimum balance of the cost of train delays and variation from the desired level of service. Data from the Acacia Ridge Terminal in Brisbane, Australia are used to validate and test the model.     

地铁发布晚点信息存在的问题和优化建议

通过持续改进设备和优化人员运作,地铁发生5min以上晚点的事件已经大幅减少,但是晚点无法完全避免。地铁受设备故障或者外部事件影响造成列车晚点时,要及时发布晚点信息。发布晚点信息既要保证乘客知情权,便于乘客调整出行计划,同时要确定合理发布范围,不扩大负面影响。以广州地铁为例,分析现在存在的问题和困难,通过量化计算晚点乘客延误总量的方法,提出按照乘客实际感受发布晚点信息、优化晚点信息发布预案、引导乘客绕行晚点地点等措施,有效减少故障影响。     

Door-to-door travel times in RP departure time choice models: An approximation method using GPS data

A common way to determine values of travel time and schedule delay is to estimate departure time choice models, using stated preference (SP) or revealed preference (RP) data. The latter are used less frequently, mainly because of the difficulties to collect the data required for the model estimation. One main requirement is knowledge of the (expected) travel times for both chosen and unchosen departure time alternatives. As the availability of such data is limited, most RP-based scheduling models only take into account travel times on trip segments rather than door-to-door travel times, or use very rough measures of door-to-door travel times. We show that ignoring the temporal and spatial variation of travel times, and, in particular, the correlation of travel times across links may lead to biased estimates of the value of time (VOT). To approximate door-to-door travel times for which no complete measurement is possible, we develop a method that relates travel times on links with continuous speed measurements to travel times on links where relatively infrequent GPS-based speed measurements are available. We use geographically weighted regression to estimate the location-specific relation between the speeds on these two types of links, which is then used for travel time prediction at different locations, days, and times of the day. This method is not only useful for the approximation of door-to-door travel times in departure time choice models, but is generally relevant for predicting travel times in situations where continuous speed measurements can be enriched with GPS data.     

我国航班时刻资源的分布研究

采用中国民航局发布的航班计划数据,分别从航空公司、机场、地区空管局三个角度统计分析我国航班时刻资源的分布情况。通过计算航空公司在各个时间段的起飞降落班次情况、各个机场的计划航班和最大容量差距情况和七大空管局在各时段的航班情况,得到南方航空公司占有的航班时刻资源最多,北京首都机场的航班时刻资源最为紧张,华东、中南、华北区域是我国最繁忙的区域的结果。作者还进一步从航班时刻的角度分析了影响航班准点率,造成航班延误的因素,并给出了相关的对策建议。     

面向航班延误的停机位实时指派优化模型

为解决航班延误造成机场停机位占用冲突问题,在对延误等级进行划分的基础上,以最小化机坪冲突概率,旅客变更登机口步行距离和指派至远机位的旅客数为目标,构建停机位实时指派的多目标优化模型,设计带精英策略的非支配排序遗传算法(NSGA-Ⅱ)求解.利用我国某大型机场的实际运行数据进行仿真验证.结果表明：在机位占用冲突得到成功化解的基础上,旅客变更登机口的平均步行距离减至102.9 m,指派至远机位的旅客数减至0人;所提出的停机位实时指派模型在保证机坪安全运行的前提下,能有效优化旅客乘机体验,提升机坪运行效率,为繁忙机场停机位资源调度提供决策支持.