主辅一体化厂级FCS在1050 MW机组的设计应用

研究主辅一体化厂级FCS控制系统应用,分析FCS的数字化、网络化和信息化等先进技术,重点研究FCS系统庞大的周期性数据与非周期性数据传输的实时响应时间、实时调度策略、冗余通信等关键技术,以及工程设计原则、网段划分、安全性设计等.通过理论计算Profibus现场总线的响应时间和Profibus在任务最坏情况下响应时间的可调度性分析,计算其非周期任务响应时间指标,提高周期任务和非周期任务的响应性能;把各单元机组控制系统、辅助车间控制系统在网络和人机交互层面连接起来,实现全厂一点监控.事实证明FCS优于传统DCS,特别是其AMS深入开发利用,将使FCS成为工业控制主导.     

基于现场总线的蓄热式加热炉测控系统

加热炉是热连轧生产线的重要设备 ,近年来基于现场总线的分布式测控系统在连续加热炉中的应用越来越多。介绍了用于蓄热式加热炉的Profibus现场总线分布式测控系统的硬件构成和软件功能 ,重点讨论了加热炉回路控制方案和故障联锁分析应用软件的实现方法。     

基于RTLinux和CAMAC的硬实时测控程序设计

文章介绍了一种基于RTLinux和CAMAC系统的的硬实时测控程序设计,对测控程序的实时性能进行了分析,同时给出了此测控系统的测试结果,并讨论了在RTLinux下使测控程序满足硬实时测控所需性能的实现方法。     

Profibus总线分析仪的设计

Profibus的应用越来越广泛,在Profibus控制系统的安装、调试和查错中一个不可或缺的工具就是总线分析仪。它对整个系统的维护、试车、发现并维修故障具有重要意义。就此设计了基于PC的Profibus总线分析仪。它能对Profibus总线及接入到Profibus总线的各种设备进行在线监测、实时分析和处理。实验结果表明,Profibus总线分析仪具有广阔的应用前景。     

并行实时测控数据存储系统设计与实现

随着测控设备数量增加、数据码率的不断提高,传统的测控中心实时存储系统采用的串行化处理逻辑已经难以适应高负载的测控任务需要。采用SPMD（Single Program Multiple Data）思想,基于OpenMP和Qt设计并实现了一套并行实时测控数据存储系统框架。该系统通过引入M/M/1模型的排队系统,设计了一种适合并行实时测控数据存储系统的静态负载均衡算法,基于互斥锁完成了线程间的细粒度通信同步机制,借助于事件循环机制将Qt的信号与槽特性成功地嵌入OpenMP线程,保留了Qt图形界面良好的人机交互性能。实验结果表明该系统在高负载的情况下,相比串行测控数据存储系统而言具有更好的扩展性和实时性,能更好地利用现行单机多核系统的计算资源,获得更好的实时性能。     

现场总线在汽车质检线数据自动化采集系统中的应用

本文简要对现场总线进行了介绍，并着重就Profibus现场总线技术进行了分析，同时将该技术应用于汽车质检线数据自动化采集系统的设计，取得了良好的使用效果。实践表明，Profibus现场总线技术的应用极大地提高了数据采集系统的性能，使得系统具有较好的实时性、开放性和可扩展性.     

实时性能评价及任务参数调整

在实时多任务系统中,任务计算时间和任务周期是影响实时性能的一个重要的因素。该文在实时性能评价模型基础上,提出通过调整任务参数的方法,达到以满足系统的实时性的目的。     

Profibus DP协议在以太网上的实现研究

讨论了Profibus DP协议功能在以太网上实现的可行性,对基于以太网的实时协议进行了改进.改进的实时协议基于以太网数据链路层的LLC子层,使以太网可以适应实时通讯的要求能够应用于设备级,并且与已经存在的Profibus DP现场总线上的应用保持了兼容性.还介绍了协议的实现和性能分析.     

基于工业以太网实时协议的改进

介绍了一种基于工业以太网的实时协议，参考Profibus DP现场总线技术，基于以太网数据链路层的逻辑链路控制子层提出了一种改进方案，在以太网上实现了Profibus DP的基本功能，使以太网适应实时通信的要求和能够应用于设备级，并且与已经存在的Profibus DP现场总线上的应用保持了连续性和兼容性。最后介绍了协议的实现和性能分析。     

Profibus现场总线及冗余系统研究

现场总线技术是自动化监控领域研究的热点，代表了技术发展的方向。Profibus现场总线性能卓越。研究Profibus技术对于工业系统的自动化有重要的现场意义。本文简单介绍了Profibus现场总线的技术特点，针对防护工程对监控系统的高可靠性要求，设计了一个Profibus冗余监控网络，并用组合模型分析比较了此系统与模块级冗余系统的可靠性。在文章最后，设计实现了一个Profibus冗余从站，实验结果表明，文章提出的冗余系统设计思想完全可行，所设计的冗余从站具有较好的性能指标。     

Profibus-DP总线单主站系统报文传输延时分析

采用确定与随机Petri网建立了Profibus-DP总线单主站系统报文传输延时的模型,并在TimeNet软件环境下对其进行了仿真分析,得出了报文传输延时与目标令牌循环时间的关系;并以STEP7软件为例,说明了在实际工程中如何根据Profibus-DP总线参数合理设定目标令牌循环时间、从而使监控系统获得最好的实时性的方法。仿真结果验证了该模型的正确性。     

混合现场总线控制系统的实时性分析

根据当前混合现场总线控制系统的系统构架,对FF H1现场总线系统、Profibus-DP现场总线系统以及由它们构成的混合现场总线系统进行了实时性分析.给出了混合现场总线系统控制周期、总线宏周期和报文循环时间的设置和计算方法,为工程设计人员设计混合现场总线系统提供了重要参考依据.最后,说明了对混合现场总线进行实时性分析具有重要的理论价值和实用价值.     

移动数据库缓存模型研究

针对移动数据库系统性能有待提高的问题,提出了一种移动数据库缓存模型。采用基于消息摘要的同步算法,通过比较移动客户端与服务器消息摘要表中的消息摘要值,完成缓存同步,维护移动客户端缓存与服务器数据的一致性;该模型还考虑了数据的时效性与事务的优先级,设计了一种基于价值函数的缓存替换算法。实验结果表明,随着缓存数据个数的增加,所提算法的缓存命中率高于最近最少使用(LRU)和LA2U算法,同时随着访问频率的增加,事务的重启率低于LRU和LA2U,有效提高了移动数据库缓存的性能。     

基于消息机制的异构系统集成方案

Web服务技术可以为异构系统集成提供有力支持,但在异步调用、流程控制和事务处理等方面仍然存在许多困难。提出了基于消息机制的异构系统集成方案,设计了总线型消息控制平台,通过基于XML的格式化消息提升系统集成的能力,并在数字化校园建设中得到了应用。     

SWIFT—A new real time commit protocol

Although there are several factors contributing to the difficulty in meeting distributed real time transaction deadlines, data conflicts among transactions, especially in commitment phase, are the prime factor resulting in system performance degradation. Therefore, design of an efficient commit protocol is of great significance for distributed real time database systems (DRTDBS). Most of the existing commit protocols try to improve system performance by allowing a committing cohort to lend its data to an executing cohort, thus reducing data inaccessibility. These protocols block the borrower when it tries to send WORKDONE/PREPARED message [1, 6, 8, 9], thus increasing the transactions commit time. This paper first analyzes all kind of dependencies that may arise due to data access conflicts among executing-committing transactions when a committing cohort is allowed to lend its data to an executing cohort. It then proposes a static two-phase locking and high priority based, write-update type, ideal for fast and timeliness commit protocol i.e. SWIFT. In SWIFT, the execution phase of a cohort is divided into two parts, locking phase and processing phase and then, in place of WORKDONE message, WORKSTARTED message is sent just before the start of processing phase of the cohort. Further, the borrower is allowed to send WORKSTARTED message, if it is only commit dependent on other cohorts instead of being blocked as opposed to [1, 6, 8, 9]. This reduces the time needed for commit processing and is free from cascaded aborts. To ensure non-violation of ACID properties, checking of completion of processing and the removal of dependency of cohort are required before sending the YES-VOTE message. Simulation results show that SWIFT improves the system performance in comparison to earlier protocol. The performance of SWIFT is also analyzed for partial read-only optimization, which minimizes intersite message traffic, execute-commit conflicts and log writes consequently resulting in a better response time. The impact of permitting the cohorts of the same transaction to communicate with each other [5] on SWIFT has also been analyzed. Recommended by: Ahmed Elmagarmid     

On the analysis of a symmetric polling system with single-message buffers

A performance analysis is provided for a polling system consisting of statistically identical stations with single-message buffers and Poisson arrival streams. Switchover and message service times are assumed to be generally distributed. Some errors in the past analysis are pointed out. We express such performance measures as the mean polling cycle time, the mean message response time, and the mean number of messages at an arbitrary time in terms of the mean number of massages served in a polling cycle. Our mean message response time reduces to that for an FCFS M/G/1//N queue (machine interference model) in the limit of zero switchover time.     

Mean message waiting times in symmetric multi-queue systems with cyclic service

A new performance analysis is provided for a cyclic service system consisting of statistically identical stations where at most one message is served for any station in a cycle. We assume that the time is slotted and that the number of message arrivals at each station in any slot is independent and generally distributed. The switch-over time and message service time (integral multiples of the slot size) are also generally distributed. For this system (called limited service system) we find the mean message waiting time explicitly. In the case of Poisson arrivals we show that our mean message waiting time is greater than that for the gated service system which is greater than that for the exhaustive service system. We also summarize the corresponding results for the three types of services in continuous-time systems.     

Using optimistic atomic broadcast in transaction processing systems

Atomic broadcast primitives are often proposed as a mechanism to allow fault-tolerant cooperation between sites in a distributed system. Unfortunately, the delay incurred before a message can be delivered makes it difficult to implement high performance, scalable applications on top of atomic broadcast primitives. Recently, a new approach has been proposed for atomic broadcast which, based on optimistic assumptions about the communication system, reduces the average delay for message delivery to the application. We develop this idea further and show how applications can take even more advantage of the optimistic assumption by overlapping the coordination phase of the atomic broadcast algorithm with the processing of delivered messages. In particular, we present a replicated database architecture that employs the new atomic broadcast primitive in such a way that communication and transaction processing are fully overlapped, providing high performance without relaxing transaction correctness.     

Blocking reduction for distributed transaction processing within MANETs

Atomic commit protocols for distributed transactions in mobile ad-hoc networks have to consider message delays and network failures. We consider ad-hoc network scenarios, in which participants hold embedded databases and offer services to other participants. Services that are composed of several other services can access and manipulate data of physically different databases. In such a scenario, distributed transaction processing can be used to guarantee atomicity and serializability throughout all databases. However, with problems like message loss, node failure, and network partitioning, mobile environments make it hard to get estimations on the duration of a simple message exchange. In this article, we focus on the problem of setting up reasonable time-outs when guaranteeing atomicity for transaction processing within mobile ad-hoc networks, and we show the effect of setting up “wrong” time-outs on the transaction throughput and blocking time. Our solution, which does not depend on time-outs, shows a better performance in unreliable networks and remarkably reduces the amount of blocking.     

数据访问的事务处理中间件中等待时间的研究

数据访问的事务处理中间件主要用于分布式的数据库访问的事务处理，采用两阶段提交技术。在两阶段提交中当协调者把任务分支分配到所有的参与者后，需要在等待一定的时间再发出准备消息。等待时间的大小会对分布式系统的并发性产生影响，为了提高系统的并发性，需要对提交等待时间进行估计。该论文对于数据访问的事务处理中间件任务的类型较少的特点，提出了一种对于提交等待时间进行较准确估计的方法，且针对不同类型的数据访问(单个操作和批量操作)采用不同的时间估计，提出了长事务的概念。