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时间:2021-01-21 02:52:08    下载该word文档

中文翻译:

现场总线控制系统是在自动检测控制技术和计算机网络技术飞 速发展的推动下形成的,它是现代计算机技术和通信技术和检测控 制技术的集成,人们称之为 3C( computer communication

control )技术。

本文首先分析了当前流行的 FCS网络的结构特点、技术特点和

优势,介绍了几种较为流行的现场总线,构建了企业生产的。 FCS 网络模型,并提出了在控制网络和信息网络之间加入转换接口、采 用DDE技术和使用统一的协议标准三种集成方式。

随着信息技术的飞速发展,工业过程控制领域正孕育着深刻的 变革。控制要求的不断提高,控制程度的愈加复杂使长久以来在生 产中运用的单一的经典控制理论和技术已经不能满足系统的需求, 现代化工业过程控制系统迫切地需要高级理论的支撑。与理论发展 相对滞后形成对比的是,自动化技术工具的蓬勃发展,在经历气动 仪表控制、集中式数字控制系统到集散式控制系统后形成了新一代 的网络集成式全分布的现场总线控制系统。

作为自动化领域的热点之一,现场总线己成为自动化系统与分

散的现场设备间信息交换的主要技术。 PROFIBU是国际上应用十分

广泛的工业过程现场总线,主要应用于加工自动化、过程自动化、 楼宇自动化等领域。

现场总线技术的不断发展,其在计算机集散控制领域的优势已

越来越明显。现场总线具有以下特点①快速性、实时性②开放性、 互可操作性与互用性 ; ③现场设备的智能化具有功能独立性 ; ④系统 结构的高度分散性⑤较强的抗干扰性。现场总线的最大特点是标准 化和公开性,目前国际上流行的几种现场总线均是以 OSI模型为依

据建立的,包括物理层、数据链路层和应用层等。现场总线中最具 影响力的有 5 种,分别是 FF, Profitbus, HART, CANLonWorks

西门子推出的 Profibus 总线以 IS07498 标准为基础,以开放式 系统互联网络 (OSI Open system interconnection) 作为参考模型, 定义了物理传输特性,总线存取协议和应用功能。该总线通过相应 的通讯模块,与系统内的远程控制设备以及其他厂商的单机控制设

备相连,采用控制字的方式进行通讯和控制,可节约大量控制电缆, 并且通过良好的接地处理和保护,具有极高的抗干扰能力。

随着社会生产规模的扩大、生产水平的提高,电气控制技术和液 压技术都在非常迅速的发展。电气控制从继电器控制系统发展到直 接数字控制 DDC)系统、集散控制系统DCS倒目前的现场总线控

制系统 (FCS 。现代的液压传动及控制技术已发展成一门集传动、 控制、检测、计算机一体化的完整的自动化技术,并逐步趋向数字 控制和全自动化。

文章从结合所研究的水电站的实际需要出发,将先进的现场总线 技术、以太网技术与传统的液压技术相结合,并应用到水电站闸门 监 控系统的实际设计过程中。论文根据所研究水电站闸门控制的具 体技 术要求,设计了适合该水电站的液压启闭机系统。文章对闸门 启闭机 及其控制系统的发展状况和传统液压启闭机控制系统的局限 性进行了 详细分析,并结合当前控制技术,特别是 Profibus 现场总 线控制技 术的特点,针对所研究的水电站的实际情况提出了“基于 Profibus 现 场总线控制和以太网技术的闸门监控系统”的技术方案。 并根据该方 案完成了下位机(PLC控制程序的编制和上位机监控软 件和人机界面 的组态的组态。最后通过组建上位机与 PLC的通信以 太网络和远程 I/O模块与PLC之间的总线网络,实现了整个闸门监 控系统的网络化。

通过该监控网络,可实现对该水电站分居于八个 不同坝段的闸门的运 行及运行状态的控制与监视,从而使得该监控 系统在满足水电站实际 生产的各项要求,同时还保证了该系统具有 相当的先进性。

底层控制网络不再是孤立的控制系统 ,通过工业以太网和现场

线技术实现网络集成 , 将基础自动化控制、过程控制和管理与企业 资源 计划层 ERP(Enterprise Resource Planning) 连接在一起 ; 提 高现场 数据采集能力 ,增强使用灵活性 , 有效解决了以往控制系统提 供的信息 不全, 自动化控制系统与企业管理系统之间的无缝集成问题 , 还 为实现 ERPt理和管控一体化提供了良好的必要条件。

在电气控制系统的设计过程中,采用了上位机加下位机的设计 模 式,组建了远程集中控制与现地控制相结合的控制网络。上位机 选用 功能强大的工控组态软件一一组态王和操作方便灵活的触摸屏。 下位 机则采用可靠性高的可编程控制器和先进的 Profibus 现场总线

完成对现场设备的控制。

可编程控制器 (PLC) 是以继电器逻辑控制系统为基础,逐步发展 为以处理器为中心,同时具有各类运算、控制、网络等功能的控制 系统,凭借良好的稳定性和强大的功能,使得在制造工业、电力、 运输等领域有着广泛的应用。

PLC程序在主程序循环中采用循环扫描,从而对输入变量进行 周期性的检查。程序循环通过扫描系统的输入开始,并将它们的状 态储存在固定的存储器位置(输入图像存储器)。然后一格格地执行 梯形图程序。对程序的扫描和求解不同阶梯格的逻辑决定了输出状 态。然后,保持在存储器中的输出值被用于在程序扫描终止时同时 设定和复位PLC的物理输出。如我们知道的那样,逻辑控制是 PLC

一个值得注意的性能,它可被用于有效地处理模拟数据。

1 模拟数据的采集和转换

模拟输入和输出,例如需要在线测量的压力和温度。举例来说, 温度首先由铂电阻采集。然后信号转换模块将实测电阻值转换成 1 5V的电压范围。这一转换模块的输出,最后被收集和传输回上

PLC

2 PLC的控制算法

模拟变量可以是任何受控的变量,例如在我们的卷绕系统中为 温度或压力。事实上,存在两种控制模式,自动的和手动的。在手 动模式中,操作人员根据希望的水平修改输出值;而在自动模式中, 输出值由预先设计的算法加以调节。值得指出, PLC的输出总是为 增

量值。虽然这里可采用自动调谐 PID (比例积分微分)控制器, 但在 生产的开始阶段总是用手动调谐来进行日常的初始化,在那以 后, 系统即切换到自动模式。我们强调指出,用户适应模糊逻辑控 制器 的经验在这里也被利用来进一步改善生产的绩效。我们推荐一 种在 PLC上采模糊逻辑控制器的薄膜张力控制系统,来应付卷绕系 统的不

确定性。模糊逻辑算法由基本的 PLC指令来实现。

要用固定的模型和参数来处理系统,常规的 PID就够了,但是 固定是相对的,事实上,卷绕系统的参数在一定的范围内是可变的, 因此,控制器必须有一个监控系统,用于基于现场总线鲁棒性的 PLC控制的制造系统,以获得高的性能。为此目的,我们用模糊推 理来调节PID的因子,通过这样的方法,PID的因子可以根据系统 状态和设备参数的变化加以调节。

The Fieldbus Control System (FCS) comes into being with the fast of auto-control, auto-detectionand computer network technology. And it is the integration of the modern computer technology, the communication technology and the detection control technology, which is called the 3C( computer communication control)development.

Firstly, this paper makes a detailed study on the prevalent Field Control Systems (FCS), including the characteristics of structure & technology and advantage, introduces several popular Field Buses, designs the model of field control system, and puts forward three effective methodsto integrate between the MCN & information network under different situations.

With the rapid development of information technology, a deep change hastaken placed in the industry processcontrol field. The simple control theory used in this field for years can't meet the new requirement of the system any more due to the higher control target, and a more advanced theory need to be found to support the system with higher complexity In contrast with the slow progress of the control theory, the automatic control tool experienced the evolution of pneumatic meter control, centralize data control system and distributed control system

has made a great achievement, that is the new net integrated and distributed control system---field bus control system.

Nowadays, the technology of Fieldbus has becomethe hotspot in the research field of automation and become the main method of communication and exchange of information in the DCS systems. And the Profibus is a kind of Fieldbus broadly used in many situations of process control of industry such as automation of processing,automation of machining and automationof building.

With the development of the fieldbus technology, its advantagehas becamemore and more notable in the field of computer'scentralized and

separatedcontrol. The fieldbus features:

1.Fast and real-time

2.Open, manipulate andalternate usable

3.The functional independency of the locale equipment's intelligence.

4.The highly decentralizationof system structure

5.The strong anti-jamming

At present,the most popular fieldbus in the world is based on OST model, Including physical layer, data link layer, application layer and etc. The FF, Profitbus, HART, CAN and LonWork are the most effective oneson this field.

Profitbus, proposed by SIEMENS, is based on IS07498, which refers to OSI (open system interconnection) model and defines the specialty of physical transmission, protocol of bus wire's storage and extraction, as well as application function. This bus wire connect the long-distance equipments in system and control equipment of other manufacturer. Especially, the adoption of control word used in communication and control reduced the quantity of control cable, also. The good treatments of grand and protection has an every strongcapability of anti- jamming.

With the scale of social production extends and the production horizontal exalts, the electricity control technique and the Hydraulic technique all develop very quickly. Electricity control technique developed from the relay system to the direct digit control ( DDC) systemthe dispersecontrol system(DCS) to the fieldbus control system (FCS).The modern Hydraulic control technique have developed to a complete automation which include of transmit, controltesting computer technique, and gradually turn to the digit control and fullautomatic control.

According to the actuality of the studied water power station, the thesis combine the advanced fieldbus technique, Ethernet and the traditional hydraulic technique together ,and use them to design the supervise controlling systemof the water power station. Baseon the gatecontrolling request of the water power stationdesigned the gate's hydraulic hoist system.The thesis analyzed the developmentof the gate's hoist and its control system ,and the localization of the gate's operating machine's traditional hydraulic systemaccording to today's control technique, especially the characteristics of the Profibus fieldbusthe thesis put forward the project that "the gate supervise controlling system base on the Profibus control and Ethernet technique"according to that projectcompleted PLC control procedure and the procedure of the supervise and control( supervise and control software and man-machine in terface)At last the thesis set up a Ether net n etwork for the mon itor and the PLC correspondenceof a place of honor machine and PLC and a fieldbus network for the far I/ O mold and the PLC, madethe gate supervise and control by network o the network can control the openingshutting and surveillance the circulate of the eight gates,which stand in different positionsand make the system satisfied the various requestsof that water power station'sproduction, and still guaranteedthe system had very advancedat the sametime.

Bottom layer of control net is not any longer an unaidedanode. It joins automation control system, processing controlling-management system with enterpriseresourceplanning system to apply technology of Industrial Ethernet and fieldbus, as a result, the data acquisition capacity and flexibility improved, the problem on control system information shortage and integration of auto-control system and enterprise managementsystem solved, the qualification to realize integration of ERPandmanagement-control system presented.

During the designing of the electricity control system, the thesis used the mode that made up of monitor system and control system, formatted a network that is combined by far concentrates control system and nearly control system.The monitor system choosesthe functional monitoring software the king monitor and the man-machine interface ,which operated conveniently .And the control system chooses dependablyprogrammable logic controller and advance Profibus fieldbus tocompletely control the spotequipments.

Programmable Logic Controller (PLC) is based of relay logic control system; today it has developed into a powerful control system with the central of processor and has many functions such as all kinds of calculations control and network. With its excellent stability and powerful functions, PLC is now widely used in manufacture industry, electric power field, traffic field and etc.

The PLC program uses a cyclic scan in the main program loop such that periodic checks are made to the input variables. The program loop starts by scanningthe inputs to the system andstoring their statesin fixed memory locations (input image memory). The ladder program is then executedrung-by-rung. Scanningthe program and solving the logic of the various ladder rungs determine the output states. The updated output statesare stored in fixed memory locations (output image memory). The output values held in memory are then used to set and reset the physical outputs of the PLC simultaneously at the end of the program scan.As we know, logic control is a remarkable property of PLC, and it can be applied to efficiently handle analogdata.

1) Analog data acquisition and transformation

Analog inputs and outputs such as pressure andtemperatureneed to be measuredon-line. For instance, temperatureis first acquired by the Platinum resistances.A signal transformation module then converts the measuredresistancevalue into the voltage range of 1-5V. The output of this transformation module is finally collected and transmitted back to the above PLC.

2) PLC control algorithms

The analog variables could be any controlled variable, e.g., temperatureor pressure in our winding system.As a matter of fact, there exist two control modes, auto andmanual. In the manual mode, operators modify the output values according to the desired levels; while in the auto mode, output values are regulatedby the pre-designedcontrol algorithms. It is worth mentioning that the outputs of PLC are always incremental values. Although auto-tuning PID controllers can be employed here, manual tuning is always used at the beginning of the production for routine initialization, and after that the system is switched to the auto mode. We emphasize that user's experiences oriented fuzzy logic controllers are utilized here to further improve the production performance as well. A film tension control system using fuzzy logic controller (PLC) on PLC to cope with the winding system uncertainty is proposed.Fuzzy logic algorithm is realized by basic PLC instructions.

To deal with the system with fixed model and parameter conventional PID is enough, but fixture is relative, in fact, the parameters of the winding system are variable in a definite range, therefore the controller must has a Monitoring System for PLC Controlled Manufacturing System Based on Fieldbus robustness to obtain high performance. For this purpose, fuzzy reasoning is used to adjust the factors of PID, by this way the PID factors can be adjustedaccording to the changesof system stateand plant parameters.

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