【作者】 朱琴跃；

【导师】 刘友梅； 谢维达；

【作者基本信息】 同济大学 ， 载运工具运用工程， 2008， 博士

【摘要】 随着计算机通信和网络控制技术、智能微机控制技术、嵌入式电子控制技术、现场总线技术以及故障诊断技术的快速发展,现代列车控制系统已从集中型的直接数字控制系统发展成为基于网络的分布式车载微机控制系统。列车网络控制系统应用多种总线技术,将分布在全列车上的计算机应用系统或完成特定功能的智能设备互连起来,是一种典型的实时分布式控制系统。列车通信网络TCN(Train Communication Network)就是运用于其中进行信息交换的数据通信平台,列车通信网络标准IEC61375-1则是IEC为车载数据通信而制定的一项国际标准,旨在为各种列车控制应用建立一个标准的信息通信平台。TCN标准将列车通信网络定义成两级分层结构,各个车辆间的数据通信网络称为绞线式列车总线WTB,同一车辆内部或固定编组的不同车辆间各种设备之间的数据通信网络称为多功能车辆总线MVB。通过TCN技术将复杂的列车控制功能下放到不同的层次,简化了列车网络控制系统的结构,实现了真正意义上的分布式列车控制。与一般的信息通信网络相比,列车通信网络本质上属于工业控制局域网的范畴,也可以看作是应用于列车控制这个特定场合的现场总线。作为一种典型的实时分布式控制网络技术,列车通信网络的实时性非常重要,它直接影响着整个列车控制系统的性能,因此和列车通信网络实时性相关的许多关键技术问题都值得深入研究,以便形成有关列车网络实时通信调度机制、实时性能评价等方面的理论建模和分析方法,为实际应用及优化网络性能提供理论指导。为此,本论文首先对列车通信网络的发展历程及列车网络技术的国内外研究现状进行了阐述,指出我国在列车通信网络实时性理论研究方面存在的不足:然后在分析并总结一般现场总线实时调度理论和方法的基础上,以MVB和WTB总线为研究对象,对列车通信网络有关实时性问题的理论和方法进行了深入研究,研究结果和内容主要概括为以下几个方面:在列车通信网络中,实时调度过程是总线协议中最为重要的内容之一。对于列车网络总线周期信息的实时调度而言,如何对其通信过程进行系统的理论建模以及如何构建实时调度表是研究列车通信网络实时性技术的首要关键问题。从分析MVB和WTB两种总线的基本通信原理入手,对它们各自周期信息的实时通信调度机制分别进行了深入的研究。根据它们周期信息通信的特点,分别提出了相应的实时调度时间表的构建算法;同时,对MVB和WTB周期信息实时调度算法的可调度性分析进行了研究,通过求取周期信息最长响应时间的方法,给出了实时调度有效性判定条件。最后,设计了相应程序对文中所提算法和方法进行了仿真实现,通过实例分析证明了所建模型的正确性。对于列车通信网络中偶发性的非周期信息而言,其通信调度机理及其响应时间特性也在某种程度上影响着列车网络的实时性。由于MVB和WTB采用了两种完全不同的方式进行非周期信息的调度,MVB采用基于冲突的事件仲裁机制进行消息事件的查询和发送,而WTB则采用按序轮询的方式进行非周期信息的传输。为此,论文对MVB和WTB非周期信息通信时的响应时间特性进行了研究,分别提出了非周期信息最长响应时间的计算方法。论文中通过对具体实例的分析,验证了所提算法的正确性,有效地评估了极端情况下非周期信息的响应时间特性。列车通信网络性能的分析是改进和优化网络实时性能的基础,同时也是提供稳定的网络服务质量Qos的前提和保证。为此,论文针对列车通信网络的各项性能指标,提出了网络实时性能参数以及其它各项网络平均性能指标的计算方法,并进行了仿真分析。以MVB为例,重点利用排队论对其实时性能指标—信息平均传输时延进行了建模和分析;同时,对列车通信网络的利用率、传输效率、吞吐量等平均性能的计算方法也进行了仔细研究,并通过仿真分析验证了所建模型的正确性。仿真结果也进一步指出了影响列车通信网络性能的主要因素,可以对实际应用中优化网络性能起到很好的指导作用。通过上述对列车网络通信调度机制以及网络总体性能的分析和评价可以看出,现有MVB和WTB网络实时性能的提高和优化还值得展开进一步的研究。为此,论文以MVB为研究对象,首先对其周期信息特征轮询周期与最多可配置逻辑端口数之间的关系进行了研究,提出了确保所有周期信息均能满足实时响应要求的约束条件。然后,对现有MVB非周期通信调度策略进行了优化研究,提出了基于过程数据从帧填充法的SFS方法,对提高列车通信网络中紧急非周期信息的实时性能进行了尝试和探索。最后,论文提出了有待进一步研究和完善的方向。更多还原

【Abstract】 With the rapid technical development of computer communication and network, intelligent computer, embedded microelectronics, fieldbus and fault diagnosis, the modern train control system has been developed from the central digital control system to distributed computer system which is based on networked control system on board. The train networked control system which is a typical real-time distributed control system can interconnect all the intelligent applications and special smart devices with various fieldbus technologies so as to exchange information and share the resource. TCN (train communication network) is the special network used within the control system. To be a standard platform for exchange information, IEC defined an international network specification named IEC61375-1 which comprises MVB(Multifunction Vehicle Bus) and WTB(Wired Train Bus). WTB is a kind of standard communication bus which was defined in TCN to connect vehicles in a train, while MVB is another kind of standard bus designed for interconnection equipment within a vehicle or within different vehicles in closed train sets. The use of TCN technology not only simplifies the structure of train networked control system but also achieves the real distributed train control by making complex control functions down to the different level.As an industrial control network in essence, train communication network can also be used as a specific fieldbus in train control application compared with the general communication network. From the view point of typical real-time distributed control network, real-time characteristic is very important for train communication network, which affects the performance of whole train control system. So many key problems relevant to the real time characteristic of train communication network are worth studying. It is expected that the modeling and analyzing of the real time communication scheduling as well as the real time characteristic will be achieved, and these results will provide some useful guidance for application.At the beginning of the dissertation, phytogeny of train communication network and its research status are presented, and existent real-time problem of train communication network is also indicated. In the body of the dissertation, on analyzing the real time scheduling theory and methods of fieldbus, the real time problem of train communication network is researched. The m ajor contributions in the dissertation can be described as follows:Real-time schedule process is one of the most important thing in the train communication network. As for the real-time schedule of periodic messages, it is the key problem that how to model for the communication process and which kind of real-time schedule time table could be set up. From the point of analyzing the basic communication scheduling mechanisms, the real-time schedule mechanism of MVB and WTB are further researched respectively. Firstly, the algorithms for constructing the real-time schedule table of MVB and WTB are introduced according to the characteristics of the periodic messages traffic. Secondly, the algorithm schedulability of periodic messages is proposed and the condition judging the validity of the schedule time table built is also given by analyzing the worst-case response time. Finally, the algorithms and methods proposed in this dissertation are validated by some programs, and the validity of the model built is showed by the example of application.The communication scheduling mechanism of sporadic messages and its response time characteristic can affect the real-time performance of train communication network. Based on quite different sporadic messages scheduling mechanism, the arbitration scheme based collision can be used to transfer MVB messages whereas WTB adopts the method of polling. The response time characteristic of sporadic communication on MVB and WTB is analyzed, and consequently the computation method to the worst-case response time is introduced. Moreover, the algorithms proposed in this dissertation are validated by some examples of application, and the validity about the response time of the sporadic messages is evaluated.To analyze the network performance is a basis for improvement and optimization of the network performance, and can be guaranteed to provide stable quality of network service. The method to calculate the real-time performance and other average characteristic parameters is introduced, and simulation based on these parameters is also made. The modeling and analysis of the average transmission delay are studied especially with queue by example of MVB. Then the methods to compute the average network performance such as utilization, transmission efficiency and throughput of train communication network are particularly studied. The validity of the model is validated by simulation. The simulation results point out the key cause which affects the train communication network performance, and it provides a good guidance for optimization the network performance.On analyzing the scheduling mechanism and whole performance of the train communication network, there are many problems which is relating to the improvement and optimization of the real time performance of train communication network are worth studying. To guarantee the real-time requirement of all messages, the constraint between the individual period and maximal logical ports of the sporadic messages is put forward. Then the SFS method based on process data slave frame stuffing is proposed, which improves the real-time performance of urgent sporadicmessages in train communication network.Finally, the future research works are discussed.更多还原