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機械與電氣工程學院
畢業(yè)設計（論文）外文翻譯
所在學院： 機電學院
班 級： 08機自6班
姓 名： 沈玉萍
學 號： 08141010626
指導教師： 龔方
合作導師：
2011年 12 月 9 日
原文：
DCS-Based Process Control Simulating System
Abstract: A distributed control system (DCS) based on two-layer networks for experimental teaching is presented in this paper. Three sets of equipments are used as process objects with their parameters such as pressure, temperature, level and flow rate being controlled variables. This system has multiform training functions. Students can not only set up basic experiments about the process control, but can also design complicated control system. The result of 4 years' use shows: it is an ideal engineering simulating system for students major in industrial automation.
Key Words: DCS, process control, simulating system, experimental teaching, network
1.INTRODUCTION
Control education is an integral part of the community's activities and one of its most important mechanisms for transition and impact. In 1998, the National Science Foundation (NSF) and the IEEE Control Systems Society (CSS) jointly sponsored a workshop in control engineering education which made a number of recommendations for improving control education . One of them is about experiments. Experiments continue to form an important part of a control education and projects should form an integral part of the curriculum for both undergraduate and graduate students . The idea of using distributed control system for process control emerged in the 1970s. Now it is widely used in manufacturing,chemicalindustry,papermaking, textile, food processing,power,etc.DCS integrating advanced computer, control, communications and CRT technologies has played an important role in raising technological level, reducing cost, and making production more flexible and integrated. So, it is very important to establish a DCS simulating system in university. We have set up the system in 2002. The system can bring more understanding of real-world problems to the students.
2.SYSTEM BUILDUP
Most modern industrial process control system adopts two-layer network topological structure. The lower one- field bus comes close to the process and the upper one-Ethernet mainly locates inside control room. Such structure disperses control and centralizes management and operation. Our system bases just this structure with the benefits of letting students familiar with current industrial network control. As shown in Figure 1, our system consists of 16 operator stations, one I/O station and 3 sets of process equipments.
2.1 The Distributed Computer System
From Figure 1 we can see that the distributed computer system is connected by two-layer networks. The monitoring network is implemented via 10M/100M pen Ethernet. The TCP/IP protocol is used. The buses connected by I/O stations and operator stations are information channels for plantwide supervision and control. According to the specifications of a process, the web server linked to Internet can also be set to achieve remote monitor. This network is arranged redundantly so the system proves reliable. The field network interconnected by I/O station and its I/O modules uses Profibus-DP and transmits a variety of information and parameters in real time.
The operator stations are general-purpose PCs. They act as engineering stations when used for off-line configuration, so 16 students can program at the same time. While for on-line use the students can monitor and control the process on these PCs. The I/O station is a domestic product developed by Beijing Hollysys Co., Ltd. Its design adopts standardization and modularization.The I/O station based on high-performance microprocessors and mature control algorithms can response as soon as possible to the internal and external events. It has 5 local modules i.e. two FM148 analog input cards, one FM151 analog output ard, one FM161 digital input card and one FM171 digital output card. Each card has particular microprocessor responsible for its control, test, calculation and diagnosis, thus, enhancing its selfcontrol level and dramatically improve its reliability and safety. The station or modules can be shifted without disturbance in case of trouble. Therefore, the system is able to control in real time and with high quality.
2.2Process Equipments
Process control is an important course of automatic major . After learning the theories in the classroom, the students have an eager for digesting and understanding. The control community has a strong history of impact on many important problems and industry involvement will be critical for the eventual success of the future directions. How to imitate industrial process is an important concern. We have built 3 sets of equipments representing pressure process, level process, temperature and flow rate process individually. The three sets of equipments can also be used for normal instrumentation control or direct digital control. All the connections are wired to the panel, so does the I/O station. The process equipments can be flexibly linked to different controller by plug contacts on the panels. There are different kinds of transducers installed on the process to provide a variety of signals such as tempera-ture, level, pressure and flow rate .These signals are analog inputs to DCS. The final operating elements include electric heater, switching components and control valves . DCS outputs analog or digital signals to the elements. The combination of the process equipments with the distributed computer system explores the frontiers of control, including increased use of computing, communications and networking, as well as exploration of control in application domains
3.SOFTWARE CONFIGURATION AND OPERATION
In the computer-control field, it has been customary to overcome some of the programming problems by providing table-driven software. A user of the DCS is provided with a configuration package that allows the user to generate a DCS system simply by configuring, so very little effort is needed to program. The package providing device, database, control scheme, graph and report forms configuration is run off-line on the engineering station. Configuration of the DCS is implemented from up to down by conforming to hardware structure. It is divided into the following 5 steps :
Devices registration to configure system hardware, including: the number of I/O stations or operator stations along with their network addresses and each I/O station's hardware such as data transmission card, I/O card;
Database configuration to define signal points and parameters set;
Control scheme configuration classified as conventional configuration which provides many control blocks like feedback, cascade, ratio and self-defined one that is programmed in real time control language similar to BASIC;
Graph configuration to make various pictures such as survey, standard display, adjust, control, trend, flow chart, alarm displayed on high-resolution color CRT and compound windows more abundant and menu-function more live; this configuration to configure diagrams for operator to monitor and control the process in real-time;
Report forms configuration to provide statistic report of the process. Before running the software, all the configurations must be compiled, linked and downloaded to the operators where several networked PC sharing the overall workload are able to monitor and control all aspects of process from a variety of live displays and friend interactions. Or the operator will run the system downloaded last time. The operator is extended with flat sealed film keyboard, touch screen, and global mouse to let operations easier. Through the man-machine interaction the process data can be collected, analyzed, recorded and controlled in real time; the system structure and configure loops can be modified on line; local breakdown can be fixed on line. Once the process is abnormal, the hardware will self diagnose and inform the operator stations that personnel around the field find the breakdown and that the indicator lamps on cards on I/O station shows the fault location. Such dual means of indication together with breakdown alarm and hot plug-in plug-out make it possible to fix breakdown on line and to run system safely and reliably.
4 .EXPERIMENTAL PROJECTS
Our DCS simulating system can train 16 students at the same time. The training functions are versatile from hardware and software configuration to complicated system design and debug. By I/O station 11 inputs from the 3 sets of equipments are measured and controlled, 7 control valves and 1 electric heater of the processes are manipulated in real time to implement temperature, pressure, level and flow rate control, breakdowns are detected and the system is maintained. Live measured values and status indications reveal the current situation. Process operators monitor and control the long-distance processes from their own consoles . The students operate the system as if they are in the real-world industrial automation. The flow chart of temperature and flow rate control sys-tem is shown in Figure 2. T1, T2 are measured temperature of the inner and outer water tank. FT1, FT2 are flow rate of the water into the inner and outer tank. WVL1 and WVL2 are two outputs from the I/O station to change the open range of the valves. ZK is a switch for turning on or off the electric heater. This system control is made up of 2 single variable closed-loops (T1-control and FTI Control),1cascade (T1-T2) and 1proportion(FT1-FT2) loop.All loops adopt normal PID which parameters can be dynamic adjusted from the operator station. The four control loops and main chart of the system can be easily shifted by pressing the buttons on the bottom of the graph as shown in Fig 2.
5 .CONCLUSION
The result of 4 years' use for both undergraduate and graduate shows: experimental training is especially efficient to help students understand the technique of industry process, the dynamic characters of the control system and to improve students' ability to operate and control the process. The convenient hardware connections make the DCS teaching system easily operated and the effortless software configuration renders different control algorithms implemented flexibly. Besides basic experiments about the process control, students have also designed complex control system to meet stricter product specifications.
譯文：
基于DCS過程控制仿真系統(tǒng)
摘要
本文提出的是一個建立在實驗教學雙層網(wǎng)絡上的分布式控制系統(tǒng)（DCS）。其中配備三套設備，用于監(jiān)測實驗過程對象中自身的流量、水平、溫度的次數(shù)變量。該系統(tǒng)具有多種形式的培訓職能，學生不僅可以設立有關控制程序的基本實驗，而且還可以設計復雜的控制系統(tǒng)。經(jīng)過4年的使用結果表明：DCS過程控制仿真系統(tǒng)是一個非常理想的工程模擬系統(tǒng)，我們可以利用它做工業(yè)自動化的學習研究。
關鍵詞：DCS、過程控制，仿真系統(tǒng)，實驗教學，網(wǎng)絡
1. 緒論
控制系統(tǒng)的教育機構是社會體系中的組成部分，在有舉足輕重的位置，它是一個重要的轉變和影響機制。在1998年，美國國家科學基金會（NSF）和電氣和電子工程師控制系統(tǒng)協(xié)會（CSS）聯(lián)合舉辦教育控制工程教育研討會，本提出了如何改善控制系統(tǒng)的教育機構的若干建議，其中就有關于實驗的提議。研究人員表明DCS過程控制系統(tǒng)應當始終作為控制系統(tǒng)學習的重要組成部分，應作為對本科生和研究生課程的組成部分。上世紀70年代，分布式控制系統(tǒng)就出現(xiàn)在過程控制應用之中。到現(xiàn)在，它被廣泛用于制造，化工，造紙，紡織，食品加工，電力等各種領域。分布式控制系統(tǒng)結合了先進的計算機，控制，通信和CRT技術，為生產(chǎn)技術水平不斷提高，減少成本起到重要的作用，使得生產(chǎn)更具有靈活性和綜合性。如此看來，我們在大學期間，建立一個DCS仿真系統(tǒng)是非常重要的。在2002年，我們成功建立了這個系統(tǒng)。該系統(tǒng)的建立，可以讓學生更多的了解實際遇到的問題。
2. 系統(tǒng)建立
大多數(shù)現(xiàn)代工業(yè)過程控制系統(tǒng)都是采用兩層網(wǎng)絡拓撲結構。系統(tǒng)采用一個較低的現(xiàn)場總線來關閉進程，用一個以太網(wǎng)來控制整個系統(tǒng)操作，使用這種分散式結構控制和集中管理和運作。我們的系統(tǒng)就是基于這樣的機構上，可以更有利于學生熟悉目前的工業(yè)控制。如圖1，我們的系統(tǒng)包括16個操作站，一個I / O站和3套加工設備
2.1分布式計算機系統(tǒng)
我們從圖1的分布式計算機系統(tǒng)可以看出，分布式計算機系統(tǒng)是由2層網(wǎng)絡連接組成。該監(jiān)測網(wǎng)絡是通過10M/100M以太網(wǎng)實施控制，并在TCP / IP協(xié)議下使用。系統(tǒng)由總線連接各個I/O站點，操作員站連接所有信息渠道，可以在整個系統(tǒng)范圍進行監(jiān)督和控制。依據(jù)整個過程的結構，在網(wǎng)絡服務器鏈接到互聯(lián)網(wǎng)的
條件下，也可以設置實現(xiàn)遠程控制。該網(wǎng)絡采用冗余安排，以便使得系統(tǒng)絕對的可靠。外部網(wǎng)絡通過I/O總站連接到系統(tǒng)，并在I/O模塊中使用現(xiàn)場總線段落準確的傳輸各種信息和參數(shù)
操作站作為工程總站，通過主機的控制，在不在現(xiàn)場的情況下，可以讓16名學生同時進行工程訓練，而且學生可以使用電腦程序通過網(wǎng)絡對這些操作進程監(jiān)視和控制。該系統(tǒng)I/O控制站是基于北京和利時發(fā)展有限公司的產(chǎn)品，它的設計采用標準化和模塊化。該I / O站的基于高性能微處理器和成熟的控制算法，能盡快回應系統(tǒng)內部和外部的各種操作。它由5個本地模塊組成，即兩個FM148模擬輸入卡，一FM151模擬輸出卡，一卡FM161數(shù)字輸入和一個FM171數(shù)字輸出卡。每個卡都具有其特定的微處理器，負責不同的控制，測試，計算和診斷，由此來加強系統(tǒng)自身的控制水平，大大提高了它的可靠性和安全性。在糟糕的情況下，這樣的控制站可以一直啟動無干擾模式。由此可見，這樣的系統(tǒng)可以保證高品質的且非常準確的控制
2.2工藝設備
過程控制是一個非常重要并且艱巨的工程。學生通過課堂理論學習之后，需要進一步去消化和理解。而這個控制系統(tǒng)在過去很多年里影響到很多重要事件，
而在未來的發(fā)展方向主要與各個行業(yè)的合作，這將是最終取得成功的關鍵。如何去模仿工業(yè)過程是一個重要的問題。我們已建立3個獨立設備，分別用于代表壓力加工設備，工藝水平，溫度和流量水平。并且這3套的設備也可用于正常儀表控制或直接數(shù)字控制。所有設備都通過線路連接到控制面板，同時也連接到I/O站點，并且可以自由的與控制面板上的任何插頭連接。在過程控制系統(tǒng)中安裝有各種不同的傳感器，用于監(jiān)測如溫度，真實姿態(tài)，液位，壓力和流量，給控制站反饋多種信息。這些信息通過模擬輸入到DCS，然后通過電熱水器，開關元件，和控制閥等操作元件控制整個過程，形成一個反饋系統(tǒng)。然后集散控制系統(tǒng)輸出模擬或數(shù)字信號的元素。這套控制系統(tǒng)設備是與分布式計算機控制系統(tǒng)結合而進行的前沿探索，包括增加使用的計算，通信和網(wǎng)絡，以及在應用程序的控制等等。
3. 軟件配置和運行
在計算機控制領域，已經(jīng)克服了驅動軟件編程的一些問題。DCS系統(tǒng)為用戶提供一個配置包，允許生成一個簡單的DCS系統(tǒng)配置，所以用戶可以很輕松的設計方案。這個提供有設備，數(shù)據(jù)庫，控制計劃，圖形和報表配置的系統(tǒng)包在工程站內可以離線運行，DCS的配置是順應硬件結構從上網(wǎng)下實現(xiàn)的。它分為一下5個步驟：
設備登記系統(tǒng)硬件配置，其中包括跟蹤其網(wǎng)絡的I / O站或操作站地址和每個I / O站的硬件，如數(shù)據(jù)傳輸卡，I / O卡
數(shù)據(jù)庫配置來定義信號點和參數(shù)設置
控制計劃配置列為常規(guī)配置，提供許多反饋控制塊，梯級，比率和自定義，這是類十余BASIC語言的實施控制程序。
用圖像來顯示各種諸如調查，標準顯示，調整，控制，趨勢，流程圖的數(shù)據(jù)，然后用高分辨率彩色顯像管和更豐富的復合窗口和菜單功能顯示操作現(xiàn)場，用此配置來配置運行圖，一檢查和控制實時處理。
報告提供的統(tǒng)計表格配置的進程。在運行該軟件下，所有的配置都將被編譯，鏈接并下載到運營商，這個運行商必須有幾個聯(lián)網(wǎng)的電腦用于共享整體工作情況，以便可以監(jiān)視和控制現(xiàn)場展示各種進程的所有方面?；蛘呓?jīng)營者將運行系統(tǒng)下載最后一次。經(jīng)營者擴展了平面密封薄膜鍵盤，觸摸屏和鼠標，讓所有行動更容易。通過人機互動的過程中可以收集數(shù)據(jù)，分析，記錄和實時控制;該系統(tǒng)結構和配置的循環(huán)可以被修改，在線，本地故障可在線修復。一旦這個過程是不正常的，硬件會自動診斷并通知操作員站，現(xiàn)場工作人員圍繞故障進行查找，并在卡片上我指示燈/ O站顯示故障位置。這種雙重手段的跡象說明具有連接故障報警和熱插件插件可以實現(xiàn)在線修正線路故障，使得系統(tǒng)運行的更加安全可靠。
4. 實驗項目
我們的DCS仿真培訓系統(tǒng)可以讓16名學生同時操作。培訓職能對硬件和軟件配置復雜的系統(tǒng)設計和調試都是通用的。I / O站的11個輸入點由3臺進行測量和控制的設備，7個控制閥和一個電加熱器的進程實現(xiàn)的。用于實時操作執(zhí)行溫度，壓力，液位，流量的控制和故障檢測和系統(tǒng)的維護。現(xiàn)場測量值和狀態(tài)的跡象表明目前系統(tǒng)的運行狀況。自身的操作站可以處理系統(tǒng)運行的過程監(jiān)控和控制，學生操作該系統(tǒng)，猶如他們是在現(xiàn)實工業(yè)自動化操作中。溫度和流量控制系統(tǒng)，透射電鏡流程圖如圖2所示：T1和T2用來測量的內，外水箱的溫度。FT1和FT2 用來顯示內外水箱的水流流速。WVL1 and WVL2 是兩個從I/O站輸出的數(shù)值，控制閥門開啟程度。ZK是一個打開或關閉電加熱器的開關。該系統(tǒng)的控制是由2個單變量閉合回路（T1控制和FTI控制）、一個串聯(lián)(T1-T2)、一個比例循環(huán)(FT1-FT2)構成。所有的回路采用從操作站動態(tài)調整的常規(guī)PID。四個控制回路和系統(tǒng)的主要圖表可以很容易地轉向按本圖底部的按鈕，如圖2所示。
5.結論
在4年的本科和研究生的使用結果表明：實驗培訓可以非常有效的讓學生了解產(chǎn)業(yè)的工藝技術，而這個控制系統(tǒng)的動態(tài)特性，更可以提高學生的操作和控過程的能力。便捷的連接，使DCS的硬件教學系統(tǒng)操作非常簡便，同時簡便的軟件配置使得實施不同的控制算法變的非常靈活。除了對于過程控制的基本實驗，學生們還設計了復雜的控制系統(tǒng)，以滿足更嚴格的產(chǎn)品規(guī)格。