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This paper explores some critical issues in modeling network traffic flow for predictive user optimal dynamic traffic assignment. They include the role of FIFO (first-in-first-out) in link, path and network traffic dynamics, minimal set representation of link traffic evolution, and consistency conditions for link models. It is found that (1) link FIFO plays a central role in modeling link, path and network traffic flow evolution, and (2) the dimension of a minimal state set that adequately describes link traffic flow under FIFO is two. Moreover, two sufficient FIFO conditions are provided, and pitfalls in using these conditions to enforce FIFO are pointed out. Finally, ramifications of these findings to DTA modeling are also discussed. 相似文献
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配置区域极点的约束方差动态输出反馈控制 总被引:4,自引:1,他引:3
在随即控制问题中,控制系统的稳态状态方差及闭环极点是分别表征控制系统稳、暂态特性的两个重要性能指标.这里所研究的是,设计一个动态输出反馈控制器,使闭环系统的稳态状态方差不大于允许的上界,同时闭环极点位于期望的圆形区域中.文中给出了期望控制器的存在条件及其解析表达式,并提供了相应的数值例子. 相似文献
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动态交通分配与信号控制的组合模型及算法研究 总被引:7,自引:0,他引:7
This paper presents a generalized bi-level programming model of combined dynamic traffic assignment and traffic signal control, and especially analyzes a procedure for determining the equilibrium queuing delays on saturated links for dynamic network signal control satisfying the FIFO (first-in-first-out) rule. The chaotic optimal algorithm proposed in this paper can not only present the optimal signal settings, but also calculate, at each interval, the link inflow rates and outflow rates for the dynamic user optimal problem, and provide real-time information for the travelers. Finally, a numerical example is given to illustrate the application of the proposed model and solution algorithm, and comparison shows that this model has better system performance. 相似文献
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LIAN Ai-Ping GAO Zi-You 《自动化学报》2005,(5)
This paper presents a generalized bi-level programming model of combined dynamic traffic assignment and traffic signal control,and especially analyzes a procedure for determining the equilibrium queuing delays on saturated links for dynamic network signal control satisfying the FIFO (first-in-first-out)rule.The chaotic optimal algorithm proposed in this paper can not only present the optimal signal settings,but also calculate,at each interval,the link inflow rates and outflow rates for the dynamic user optimal problem,and provide real-time information for the travelers.Finally,a numerical example is given to illustrate the application of the proposed model and solution algorithm, and comparison shows that this model has better system performance. 相似文献
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饱和路网中动态交通分配和控制一体化建模研究 总被引:3,自引:0,他引:3
对饱和路网中动态交通分配和交叉口信号控制的一体化建模进行了研究 .描述了一个双层规划问题 .上层以动态用户均衡为目标建立分配模型 ,下层以系统最优为目标进行信号设置 .考虑了饱和路段上的车辆排队行为和驾驶员路径选择行为 ,并在模型中加以描述 .最后将遗传算法与传统的非线性最优规划方法相结合求解了一体化模型 相似文献
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针对高速网络流量并行处理的需求,提出一种流级别的高效动态流量划分算法DTP-PM.讨论了DTP-PM算法设计的基本思想,并分析了其中的关键问题-会话表设计.为提升算法性能,通过定义会话标识符设计了会话表的哈希函数PRH,同时应用MTF启发法改进会话表的哈希冲突解决方法.在引入负载度量化网络流量分析负载轻重程度的基础上,给出流量划分算法DTP-PM的实现流程.借助高速网络流量样本对该算法性能进行了实验评估.实验结果表明,DTP-PM算法在均衡性和高效性方面明显优于经典的流量划分算法. 相似文献
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The CONTRAM Dynamic Traffic Assignment Model 总被引:1,自引:0,他引:1
CONTRAM is a computer model of time-varying traffic in road networks, which takes as input the network definition and time-varying demand for travel between a set of origin and destination zones, and outputs the resulting network flows, routes and travel times. It combines a macroscopic time-sliced traffic model with disaggregate dynamic assignment of traffic, so is intermediate between macroscopic equilibrium and microscopic models. The paper details the methods used, including time-dependent queuing which plays a central role, and the treatment of network definition, user classes, road capacities, signals and coordination, vehicle emissions, Intelligent Transport Systems and research lines. 相似文献
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A Strategic Model for Dynamic Traffic Assignment 总被引:2,自引:1,他引:1
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软实时系统有着广泛的应用,如在线游戏、股票交易、传感器网络数据处理等.在这类应用中,通常有多个服务节点来响应外界大量的软实时请求.为了保证服务质量及防止系统超载,这些节点的CPU需要满足一定的使用率限制.为此,首先提出了异构集群系统中基于负载平衡的CPU使用率动态模型,其次在算法设计上将反馈控制理论引入其中并提出了针对异构实时集群系统的基于反馈的使用率控制算法.实验结果证明,该算法在引入负载平衡机制的异构实时集群系统中运行良好,系统节点间负载均衡并且各节点的CPU使用率能稳定地运行在限定状态. 相似文献
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S. Travis Waller David Fajardo Melissa Duell Vinayak Dixit 《Networks and Spatial Economics》2013,13(4):427-443
This work introduces a novel formulation of system optimal dynamic traffic assignment that captures strategic route choice in users under demand uncertainty. We define strategic route choice to be that users choose a path prior to knowing the true travel demand which will be experienced (therefore users consider the full set of possible demand scenarios). The problem is formulated based on previous work by Ziliaskopoulos (Transp Sci 34(1):37–49, 2000). The resulting novel formulation requires substantial enhancement to account for path-based flows and scenario-based stochastic demands. Further, a numerical demonstration is presented on a network with different demand loading profiles. Finally, model complexity, implications on scalability and future research directions are discussed. 相似文献
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Caixia Li Sreenatha Gopalarao Anavatti Tapabrata Ray 《Networks and Spatial Economics》2017,17(3):841-860
The approximation of the traversal cost is a critical component of dynamic traffic assignment model. In link based traffic assignment, it assumes that the constraints sets are linear or convex and it is not realistic in general traffic networks. Comparing with the link based model, the path cost in the objective function of the path based traffic assignment model is implicitly nonlinear or non-convex, which is difficult to solve. In this paper, a path based traffic assignment model combining the generalized expansion method in M/G/c/c model with the point queue model is proposed to extend the link traversal cost to the travel cost along the path. Comparing with the link based model without considering intersection effects, this proposed path based model can take into account queuing delays between intersections and it is easy to implement. In order to validate the proposed path based model, a comparative experiment is implemented by comparing with the traditional travel cost models in Sydney traffic networks. Taking into account travel flow changes and blocking time, the proposed path based model is more effective for travellers from the uncongested traffic to congested traffic networks. In addition, the results from traffic assignment model show that the proposed model can achieve feasible results. 相似文献
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A review of analytical formulations of the dynamic traffic assignment problem is presented, focusing on the authors' experience with variational inequality approaches. Solution algorithms and computational issues requiring additional study are discussed. 相似文献
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对一类用极大代数描述的离散事件动态系统,本文得到了能用输出反馈任意配置其周期的充分必要条件.证明了一个系统如果能用输出反馈任意配置周期,那么它是能达能观的. 相似文献
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一种网络异常实时检测方法 总被引:30,自引:0,他引:30
传统的网络管理工具通常根据预先设定的阈值来报警,这种方法虽然简单,但适应性不好.因此出现了网络异常检测技术,有时异常检测技术不但能发现网络故障,而且具有预警的效果[1];该文介绍了一种新的实时网络流量异常检测方法,转换网络流量观测值序列并假定序列的局部是平稳的,然后建立AR模型,定义一个统计量来检测异常.结果表明,该检测方法具有GLR测试方法所没有的优点. 相似文献
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Networks and Spatial Economics - 相似文献