塔机群无线实时通信的研究

针对现代施工现场环境复杂、随机塔机分布、塔机之间实现物理连接困难且价格昂贵等问题,将工业无线通信技术应用到塔机群控制系统中。首先在令牌总线网的基础上提出了一种基于令牌传递的无线通信方式;然后在其基础上加入了自主进入与退出系统和故障检测功能;最后给出了该无线通信流程和帧格式。研究结果表明,该无线通信方式在保证系统实时性与快速性的同时,使系统具有良好的可扩展性。     

基金会现场总线令牌机制的研究

基金会现场总线之所以能进行确定性通信依靠的是它的令牌机制.该文研究了基金会现场总线的令牌机制的基本原理,并且进一步研究了在网络负荷增大的情况下令牌机制采取的一些网络优化的措施.     

基于现场总线ARCNET的远程故障监测管理系统

根据超级接线凹印机的应用要求和ARCNET总线令牌传输协议研制了基于网络技术的远程故障监测系统。论述了该系统的集散式结构，提出采用ARCNET令牌总线信息流侦听和主机冗余技术建立系统程序的算法模型和实现策略。经实际应用，系统能准确反映和分析设备的运行状态，有效减少设备故障停机率。     

ASP平台安全认证技术的研究与实现

为满足应用服务提供商平台集成多种异构应用系统的实际需求,提出了一种采用统一安全认证技术进行轻量级应用集成的解决方案。该方案采用目录服务数据库,统一存储用户身份和权限信息,使用会话令牌保证用户身份的持久有效性,通过策略代理保护应用服务资源的安全,并对用户的访问进行统一授权和控制。为实现用户在平台和应用系统之间的单点登录,提出了令牌和代理相结合进行身份信息传递与验证的实现方案,尤其是解决了跨域单点登录的难题。该方案已成功应用于上海电信理想商务应用服务提供商平台。     

令牌目的循环时间TTR对现场总线PROFIBUS测控周期的影响

在对PROFIBUS的令牌总线协议深入分析的基础上,讨论了影响基于PROFIBUS的现场总线系统的测控周期的因素,通过对令牌目的循环时间TTR不同设置对测控周期时间影响的具体分析,得出两个主要的结论:(1 )测控周期是在一定范围内随着TTR的增加而增加,之后将不随TTR变化;(2 )将TTR置于令牌的最小周转时间W时,高优先级任务能获得最短实时响应,但低优先级任务将得不到响应处理。文中还详细描述了一个具有两个主站、五个从站的实验系统的构成和实验过程,实验结果与理论分析一致     

轨道交通大区供电模式中的近区速动方案

为了在轨道交通大区供电模式下快速切除故障并避免越级跳闸,本文提出了一种基于光纤纵差与过流保护配合的近区速动方案。此方案保护仪表过交互近区令牌等信息,精确定位故障点,迅速隔离故障,为健康区域尽快恢复供电服务。     

基于双口RAM IDT7025的双机通讯设计

针对数控机床控制发展中的新要求提出并设计了一种新型的控制方案,即运用双口RAM实现PCI总线与DSP的通讯,以提高控制效率和实时性。应用令牌传递方案解决了双口RAM的仲裁控制逻辑问题,并且利用CPLD对数据总线接口进行了扩展。     

基于令牌环的两层工业无线测控网络系统的设计与实现

为应对工业无线测控需要而提出的单跳令牌环网受无线模块通信距离限制,无法满足实际工业应用需求。为了延长通信距离,扩大令牌环网应用范围,提出一种在基于原令牌环协议的基础上挂接主从的两层无线监控网络WICN-TL(Wireless Indus-trial Control Network-Two Layers),介绍了其协议模型的拓扑结构及通信流程,将该协议在基于IEEE802.15.4a的硬件平台NanoNET上加以实现,并接入PROFIBUS-DP现场总线系统,在某污水处理厂进行了实地测试。测试结果表明,该协议具有良好的通信能力和较大的覆盖范围,能够适应工业环境的应用需要。     

串行总线分布式控制系统

分布式控制系统广泛应用于工业生产过程中。设计了一种分布式的、采用令牌总线机制的小型工业监控网络。重点介绍了网络通信的设计与实现过程。     

基于离散时间排队理论的PROFIBUS总线性能分析

现场总线协议的实时性是评价总线性能的关键因素。该文根据PROFIBUS令牌总线协议原理,利用离散时间休假排队理论,建立了一个具有时间限量DMAP／M／1休假排队模型,然后对该模型进行了详尽的分析,求出了响应等待时间的数学表达式,给出了仿真结果。该文的研究为分析和优化令牌总线协议提供了理论依据。     

基于Slave_B并行传输模式的双绞线LON节点

为解决LonWorks节点在复杂对象中控制能力较弱的问题,介绍了一种利用单片机AT89S51和神经元芯片MC143150构成主机型节点的设计过程.主机AT89S51与从机MC143150之间采用Slave_B并行传输模式,数据通信通过传递虚拟令牌得以实现,解决了数据总线冲突问题.节点利用FTT-10双绞线收发器搭建的节点网络接口,通过iLON100服务器构建的主干式网络实现了节点实时性高的多进程、多任务的并行处理.在电力系统的实际应用表明基于Slave_B并行传输模式的LonWorks节点运行稳定可靠.     

A study on multivariable process control using message passing across embedded controllers

Multivariable process control forms an important part of modern day control. While hardwired controllers still constitute the basic component of such control systems, with reducing communication latencies, controllers on the network are being mooted as a viable alternative. These controllers promise a large number of advantages in terms of reduction in wiring and greater flexibility in implementing supervisory control systems. In this paper, a study is presented which shows that UDP (User Datagram Protocol) can actually be used for real-time multivariable process control. Latency reduction algorithms used in high performance message passing systems have been used.     

Discrete event control system design using automation Petri nets and their ladder diagram implementation

As automated manufacturing systems become more complex, the need for an effective design tool to produce both high-level discrete event control systems (DECS) and low-level implementations becomes more important. Petri nets represent the most effective method for both the design and implementation of DECSs. In this paper, automation Petri nets (APN) are introduced to provide a new method for the design and implementation of DECSs. The APN is particularly well suited to multiproduct systems and provides a more effective solution than Grafcet in this context. Since ordinary Petri nets do not deal with sensors and actuators of DECSs, the Petri net concepts are extended, by including actions and sensor readings as formal structures within the APN. Moreover, enabling and inhibitor arcs, which can enable or disable transitions through the use of leading-edge, falling-edge and level of markings, are also introduced. In this paper, the methodology is explained by considering a fundamental APN structure. The conversion of APNs into the IEC1131-3 ladder diagrams (LD) for implementation on a PLC is also explained by using the token passing logic (TPL) concept. Finally, an illustrative example of how APNs can be applied to a discrete manufacturing problem is described in detail.     

A systematic approach for the sequence controller design in manufacturing systems

This paper presents a systematic approach for the design and implementation of the sequence controller in manufacturing systems. By employing the IDEF0, we construct the simplified Petri net controller (SPNC) through the material flow diagram and the information flow diagram. Then, the ladder logic diagram (LLD) can be transformed from the SPNC through the token passing logic (TPL). The proposed approach, including the IDEF0, SPNC, and TPL tools, leads to the standard IEC1131-3 LLD for PLC implementation. Finally, an application of a stamping process is provided to illustrate the design procedure of the developed approach .     

Performance Analysis of Auction-Based Distributed Shop-Floor Control Schemes from the Perspective of the Communication System

A growing level of interest in academia and industry centers on the paradigm of distributed shop-floor control in which task and resource allocation in the manufacturing system is accomplished in a distributed manner through message passing and auction-based decision making among autonomous entities. Due to the prominent role played by the communication system in this paradigm, it is important to consider the requirements and performance characteristics of the communication system during the design and evaluation of distributed shop-floor control schemes. In this paper, we propose a two-phase methodology for analyzing auction-based shop-floor control schemes from the perspective of the communication system. In the first phase, the control scheme is modeled as a closed queueing network and performance measures related to the auctioning process and the communication system are obtained rapidly using asymptotic bounding analysis and mean value analysis. Control schemes identified as attractive in the first phase are then evaluated in greater detail during the second phase, using a discrete event simulation model. We illustrate this methodology using two-class and four-class control schemes and discuss insights learned about the impact of various control-scheme-related factors on the performance of the auctioning process and the communication system.     

集装箱外焊缝自动抛丸清理设备检测控制系统设计

针对集装箱外焊缝自动抛丸清理设备,设计了检测控制系统。该系统利用PLC作为控制核心,采用激光测距传感器来检测垂直焊缝。传感器被固定在生产线的一侧,集装箱在生产线上流水性通过。当焊缝经过激光传感器前时,激光传感器会检测到距离突变,通过算法可判断出焊缝经过的时刻。在此基础上,PLC可以控制抛头,使磨料准确地抛打清理焊缝。