【作者】 陈本源；

【导师】 周祖德；

【作者基本信息】 武汉理工大学 ， 通信与信息系统， 2010， 博士

【摘要】 交换技术的出现不仅提高了以太网的通信速率和带宽,也为以太网支持工业通信提供了新的途径。但是,将交换式以太网直接应用于工业控制领域还存在相当多理论和实践的问题。本文重点研究基于交换式以太网的实时工业通信的相关理论和关键技术,在深入分析面向工业通信的交换式以太网实时特性的基础上,针对交换式以太网构建控制网络所存在的诸多理论和技术问题,从静态和动态两方面提出解决方案。主要研究工作如下：(1)面向工业通信的交换式以太网实时特性分析。时延是影响控制网络性能最主要的一个因素。针对网络控制系统中最常用的拓扑结构和数据特性,基于统计网络演算建立系统在不同调度策略下的时延模型。利用该模型计算控制网络中实时数据的时延分布和统计上界,并与确定性网络演算得出的时延上确界进行比较,评价该上确界的悲观程度。(2)基于交换式以太网的控制网络拓扑结构优化(静态解决方案)。通过分析影响控制网络实时性能的诸多因素及其内在联系,给出归一化的拓扑结构优化的评价指标。将该问题转化为一个多目标优化问题,充分考虑到控制网络的通信特点。提出改进的擂台赛算法用以构造进化群体的非支配集,并综合运用支配关系法和目标函数组合求积法对个体进行评价,以减小算法的开销。实验研究表明最终解在流量本地化和均衡方面以及交换机物理端口使用率平衡方面,都较其他算法有着较大的改进。此外,为实际控制网络设计与优化问题提出一个新性能指标的估算方法。(3)面向实时工业通信的交换机设计(基于网络节点的动态解决方案)。针对基于虚拟输出排队的输入队列交换机应用于控制网络所面临的诸多困难,提出一种新的输入队列交换机结构,并根据新的结构设计了一种基于记录矩阵和需求矩阵的信元传输顺序控制方案,解决了以往交换机中存在的信元行为及时延的不确定性问题。考虑控制网络中的流量特征,还提出了两级调度机制,链接调度提供了分级服务,交换调度实现了端口匹配。后者是一种分层的结构性匹配调度算法,层数的设置提供了在调度率和复杂度之间折衷的手段。仿真实验证明,较现有的结构性调度算法,本算法具有更高的调度率,同时所提出的交换机结构及其调度策略为控制网络的数据通信提供了确定性的实时保障。(4)分布式带宽分配策略研究(基于端节点的动态解决方案)。交换式以太网应用于控制领域所面临的主要问题之一是如何以尽量小的代价来实现其支持典型的工业通信的目的。结合控制网络的通信特点,提出了一套基于时隙的分布式带宽分配策略。给出了节点通信任务和带宽资源的模型、调度策略中信息传输的控制方法和调度算法。通过实验分析和比较,该策略在满足了各通信任务实时需求的同时,解决了当前分布式调度策略中存在的诸如不能灵活应对通信任务频繁变化、任务调度率和带宽利用率低等问题。(5)交换式以太网在网络化数控系统中的应用研究。以工业控制中的一个典型应用——网络数控服务系统为对象,分析了网络实时系统中各通信任务之间以及通信任务与其他任务之间的协调设计问题,并通过实验证明了设计方案的有效性。更多还原

【Abstract】 The emergence of the switching technology not only improves the transmission rate and bandwidth of Ethernet but also provides many new features for the industrial communication support. However, there are quite a few theorical and technological problems in applying the switched Ethernet to industrial field directly. This dissertation mainly studies the related theories and key technologies on the switched-Ethernet-based real-time industrial communication. After the deep analysis of the industrial communication oriented switched Ethernet’s temporal characteristics, this dissertation proposes solutions from both static and dynamic aspect to solve the problems in the control networking based on switched Ethernet. The main work is as follows:(1) Analysis of the industrial communication oriented switched Ethernet’s temporal characteristics. Delays have great influences on the control network’s performance. Topologies most in use and data characteristics of the network control system are considered and corresponding delay models under different scheduling policies are derived based on stochastic network calculus. Then the distribution of delays and stochastic upper bound on delays of real-time data in the control network are calculated. The results are compared with the guaranteed upper bound on delays derived by deterministic network calculus and the pessimism of the bound is evaluated.(2) Optimization of the control networks’ topology based on switched Ethernet (static solution). Factors that affect the real-time performance of the industrial control network are presented in detail, and optimization criteria with their internal relations are analyzed. After the definition of performance parameters, the normalized indices for the evaluation of the topology optimization are proposed. The topology optimization problem is formulated as a multi-objective optimization problem and the evolutionary algorithm is applied to solve it. Special communication characteristics of the industrial control network are considered in the optimization process. In respect to the evolutionary algorithm design, an improved arena algorithm is proposed for the construction of the non-dominated set of the population. In addition, for the evaluation of individuals, the integrated use of the dominative relation method and the objective function combination method, for reducing the computational cost of the algorithm, are given. Simulation tests show that the performance of the proposed algorithm is preferable and superior compared to other algorithms. The final solution greatly improves the following indices:traffic localization, traffic balance and utilization rate balance of switches. In addition, a new performance index with its estimation process is proposed.(3) A switch design for the real-time industrial communication (dynamic solution in switches). Considering the challenges in the application of the virtual-output-queue based input-queue switches to control network, this dissertation proposes a new switch structure. Accordingly, a method for the cell sequence control based on the record matrix and demand matrix is designed, which eliminates the uncertainty of cells’ behavior and delay in switches. The characteristics of the traffic in control network are taken into account and a two-level scheduling mechanism is proposed. The link scheduler provides the class of service while the switch scheduler is responsible for the match. In the latter scheduler, a layered frame-based match algorithm is designed. The layer mechanism provides a compromise between the schedulable ratio and complexity. Simulation results show that the algorithm achieves a higher schedulable ratio compared with other frame-based algorithms and the switch structure with its scheduling strategy can provide better deterministic real-time guarantees.(4) Study on the distributed bandwidth allocation strategy (dynamic solution in end nodes). One of the main problems of applying the switched Ethernet to control applications is how to adapt it to the typical industrial communication with least changes. Considering the communication characteristics of the control network, this dissertation proposes a distributed bandwidth allocation strategy based on the time-slot. Models of communication tasks and bandwidth resources in the network control system based on switched Ethernet together with the control methods of the message transmission and the scheduling algorithm of the strategy are provided. Existing distributed scheduling proposals often cannot deal with the situation that communication tasks change frequently and both schedulable ratio and bandwidth utilization are low. By the experimental analysis and comparisons, the proposed strategy guarantees the transmission of the real-time communication tasks with their deadlines, and furthermore it solves the above problems of existing proposals.(5) The application of switched Ethernet to networked numerical control system. Finally, the dissertation takes a typical application in industrial control-the service-oriented network numerical control system as an example to analyze the coordination design of communications tasks and other tasks in the implementation of network real-time systems. And the effectiveness of the task design is proved by experiments.更多还原