【正文】 ]. The project included a plete replacement of the installed functionality. This included the D/3 as well as the integration of the DESY field bus SEDAC and the temperature conversion in VME. The project started promising. But soon technical and organizational problems were pushing the schedule to it’s limits which were determined by the HERA shutdown scheduled at that time. The final acceptance test at the vendors site showed dramatic performance problems. Two factors could be identified as the cause of these problems. The first one was related to the under estimated CPU load of the 6th grade polynomial temperature conversion running at 1 Hz. The second one was the additional CPU load caused by the plex functionality of the existing D/3 system. Here it was underestimated that each digital and analog input and output channel had it’s own alarm limits in the D/3 system. In a SCADA like system as Cube the base functionality of a channel is to read the value and make it available to the system. Any additional functionality must be added. Last not least the load on the network for polling all the alarm limits – typically for a SCADA system – was also driving the network to it’s limits. Finally the contract with Orosi was canceled and an upgrade of the D/3 system was the only possible solution. It was finally carried out in march 2003.In any case it should be mentioned that the Cube approach had the advantage of a homogeneous configuration environment (for the Cube front end controllers) – pared with heterogeneous environments for ‘pure’ SCADA systems.SCADA (PVSSII)The H1 experiment at the HERA accelerator decided to use PVSSII for an upgrade of their slow control systems[3]. The existing systems were developed by several members of the H1 collaboration and were difficult to maintain. The decision to use PVSS as a replacement was driven by the results of an extensive survey carried out at CERN by the Joint Controls Project [4]. PVSS is a ‘pure’ Supervisory And Data Acquisition System (SCADA). It provides a set of drivers for several field buses and generic socket libraries to implement munication over TCP/IP. The core element is the so called event manager. It collects the data (mostly by polling) from the I/O devices and provides an event service to the attached management services like: control manager, database manager, user interface, API manager and the built in HTTP server. The PVSS scripting library allows to implement plex sequences as well as plex graphics. Compared with other SCADA systems PVSS es with one basic feature: it provides a true object oriented API to the device’s data. One major disadvantage of SCADA systems is the fact that two databases, the one for the PLC and the one for the SCADA system must be maintained. Integrated environments try to overe this restriction. EPICS EPICS has emerged at DESY from a problem solver to a fully integrated control system. Starting from the data collector and number cruncher for the cryogenic control system, EPICS made it’s way to bee the core application for the DESY utility group. In addition it is used wherever data is available through VME boards or by means of Industry Pack (IP) modules. For those cryogenic systems which are not controlled by the D/3 system EPICS is used with it’s plete functionality. In total about 50 Input Output Controller (IOC) are operational processing about 25 thousand records. 1 EPICS as a SCADA System The utility group ( water, electrical power, pressed air, heating and air conditioning) is using a variety of PLC’s spread out over the whole DESY site. EPICS is used to collect the data from these PLC’s over Profuse (FMS and DP) and over Ethernet (Siemens H1 and TCP). The IOC’s provide the interfaces to the buses and collect the data. The built in alarm checking of the EPICS records is used to store and forward alarm states to the alarm handler (ale) of the EPICS toolkit. In addition tools like the channel archive and the graphic display (dm2k) are used. The default name resolution (by UDP broadcast) and the directory server (name server) are used to connectclient and server applications over TCP. All of these are basically SCADA functions. The textual representation of all configuration files ( for the IOC, the graphic tool, the alarm handler and the archive) provides a flexible configuration scheme. At DESY the utility group has developed a set of tools to create IOC databases and alarm configuration files from Oracle. This way the controls group provides the service to maintain the EPICS tools and the IOC’s while the users can concentrate on the equipment being controlled. 2 EPICS as a DCS System Besides the basic ponents of a SCADA system EPICS also provides a full flavored Input Output Controller (IOC). The IOC provides all of the function a DCS system requires, such as: a standard set of properties implemented in each record, built in alarm checking processed during the execution of each record。這其中，雖然我遇到了很多問題，但通過查閱相關資料、請教老師和與同學討論將這些問題一一解決，從而使我對大學三年所學到得知識有了進一步的加深和拓展，并且學會了西門子S7200是如何在溫度控制中應用的，相信這一定會對以后走上工作崗位的我有很大的幫助。用PLC控制除了能解決以上問題以外，還具有以下特點： ①控制條理清楚，接線簡單明了。往MPI網(wǎng)添加一個新節(jié)點時，應該切斷MPI網(wǎng)的電源。MPI是多點通信接口（Multi plain Interface）的簡稱?？刂瞥绦蛄鞒虉D如圖42所示：開始系統(tǒng)初始化綠燈亮，系統(tǒng)運行取實際溫度變量TT是否滿足條件 YN PID調節(jié)Y調節(jié)是否成功 N紅燈/黃燈亮，喇叭響 圖42 控制程序流程圖 通信系統(tǒng)隨著計算機網(wǎng)絡通信技術的發(fā)展，自動控制方式由傳統(tǒng)的集中控制向多級分布式方向發(fā)展，PLC的通信和聯(lián)網(wǎng)功能也越來越強。（3）系統(tǒng)診斷①快速瀏覽CPU的數(shù)據(jù)和用戶程序在運行中的故障原因。③ 模塊的參數(shù)設置。（4）STEP7的幫助功能按FI鍵便可以得到與它們有關的在線幫助。（1）編程語言3種基本的編程語言:梯形圖(LAD)、功能塊圖(FBD)和語句表(STL)。計算機的通信卡CP56ll(PCI卡)、CP55ll或CP5512(PCMCIA卡)將計算機連接到MPI 或PROFIBUS 網(wǎng)絡?？梢园醋止?jié)(PIB或PQB)、字(PIW或PQW)或雙字(PID或PQD)存取，不能以位為單位存取PI和PO。4. 計數(shù)器(C)存儲器區(qū)計數(shù)值(0一999) 可以用二進制或BCD碼方式讀取。在掃描循環(huán)中，用戶程序計算輸出值，并將它們存入過程映像輸出表(process image output，PIQ).在循環(huán)掃描結束時將過程映像輸出表的內容寫入數(shù)字量輸出模塊。(2) BLOCK(塊):指定一個塊用作輸入和輸出，實參應為同類型的塊 。(2) 結構(STRUCT)將一組不同類型的數(shù)據(jù)組合在一起，形成一個單元.(3) 字符串(SRTING)是最