Performance evaluation of switched Ethernet for real-time industrial communications

The real-time industrial network, often referred to as fieldbus, is an important element for building automated manufacturing systems. Thus, in order to satisfy the real-time requirements of field devices such as sensors, actuators, and controllers, numerous standard organizations and vendors have developed various fieldbus protocols. As a result, the IEC 61158 standard, including Profibus, WorldFIP, and Foundation Fieldbus, was recently announced as an international standard. These fieldbus protocols have an important advantage over the widely used Ethernet (IEEE 802.3) in terms of the deterministic characteristics. However, the application of fieldbus has been limited due to the high cost of hardware and the difficulty in interfacing with multivendor products. In order to solve these problems, the computer network technology, especially Ethernet, is being adopted by the industrial automation field. The key technical obstacle for Ethernet for industrial applications is that its nondeterministic behavior makes it inadequate for real-time applications, where the frames containing real-time information, such as control command and alarm signal, have to be delivered within a certain time limit. Recently, the development of switched Ethernet shows a very promising prospect for industrial applications due to the elimination of uncertainties in the network operation that leads to the dramatically improved performance. This paper focuses on the application of the switched Ethernet for industrial communications. More specifically, this paper presents the performance evaluation of the switched Ethernet on an experimental network testbed along with an implementation method for using the switched Ethernet for industrial automation.  

具有随机通讯时延的离散网络化系统的H∞滤波器设计

由于传感器和滤波器是通过有限带宽的网络连接的,因此系统的测量数据经常会出现时延,而且时延是随机的.本文讨论了具有一步随机通讯时延的离散网络化系统的H∞滤波器设计问题.利用线性矩阵不等式方法设计线性滤波器使得滤波误差系统是均方意义下指数稳定并具有给定的H∞性能.滤波器参数通过凸优化技术求解一个线性矩阵不等式得到.数值仿真表明设计方法的有效性.  

Multiprocessor scheduling with communication delays

This paper adresses certain types of scheduling problems that arise when a parallel computation is to be executed on a multiprocessor. We define a model that allows for communication delays between precedence-related tasks, and propose a classification of various submodels. We also review complexity results and optimization and approximation algorithms that have been presented in the literature.  

群体动力学与协调控制研究中的若干问题

群体行为是自然界和社会中常见的现象, 探讨群体合作行为的机制和工程应用具有重要的意义. 本文从系统与控制的角度讨论当前群体动力学与协调控制研究中的一些基本问题, 评述文献中常见的群体系统模型, 分析群体系统的动态行为和系统关联拓扑结构之间的关系, 时变拓扑与连通性、通信时滞、以及外部作用的影响等. 给出在非对称耦合、时滞等情况下, 系统的聚集-振荡复杂行为的数值仿真结果.  

分布式实时数据库的通讯延迟模型与协议

本文通过建立分布式实时数据库系统中的一个网络通讯延迟模型,对它的时间开销进行了分析,指出实现实时通讯的可行性.同时给出了通讯协议ECSMA/CD(extend carrier sense multiple access/collission detection)的算法,为数据或消息的实时传送提供了一种机制.  

具有时延的多个体系统的一致性问题综述

考察了具有时延的多个体系统的一致性问题．根据不同的分析方法，介绍了关于具有通信时延的多个体系统一致性问题的结果，并对各种分析方法的特点进行了比较．此外，对具有输入时延的多个体系统的现有一致性结果也作了介绍．最后评述了该研究领域存在的问题以及今后的研究方向．  

离散时间系统的多智能体的一致性

动态多智能体系统的一致性是复杂动力学系统中很有现实意义的问题.假设智能体连接网络拓扑是无向、固定和连通的,而且个体之间信息传递存在通信时廷,分析了一个动态移动多智能体离散时间系统.应用广义Nyquist判据研究具有通信时延的多智能体离散时间系统,得到了保证系统达到一致的充分条件.最后应用计算机仿真验证了该结论的有效性.  

EPA的实时性能分析与计算

文章在深入分析EPA网络周期数据传输原理的基础上,讨论了周期数据在EPA网络的端到端传输过程及在端点的处理过程中的通信延迟构成,并以一个典型的微网段构成的EPA网络为例,对EPA网络的周期数据通信延迟进行了定量计算,从而得出EPA网络所能达到的实时性指标,并指出了改善EPA网络实时性能的措施。  

通信延迟下的多UUV协同定位——基于航迹预测的实时更新算法

研究了主从式多无人水下航行器(UUV)协作系统的协同定位方式,并针对协同定位过程中存在的水声通信和探测时延问题,提出了基于主UUV航迹预测的无状态逆推的非等间隔实时更新(ⅡRU)定位方法,用于提高从UUV的协同定位精度.该方法采用统计建模方法对主UUV航迹进行预测,用于从UUV相对距离量测的实时更新,并基于非等间隔滤波,设计了针对不同类型传感器的实时滤波方法.仿真结果验证了所提定位算法在存在通信时延下的有效性.  

传感器网络通信延迟的实时预测

针对使用CSMA/CA通信机制的无线传感器网络提出一种通信延迟估计算法。利用链路质量具有时间和空间相关性的特点建立组合的链路模型，预测链路可靠性，使用简化的冲突概率模型预测信道竞争延迟，结合预测的链路可靠性得到通信延迟。分析了算法的开销，在ns2模拟器上对信道竞争延迟预测算法进行了模拟，结果表明预测算法能够比较准确地预测网络的竞争延迟。