【正文】 l properties must be addressed individually in order to identify them in the munication protocol and last not least in the display, alarm and archive programs. In addition any kind of modifications of these embedded properties is difficult to track because two or more systems are involved. This might be one strong argument why control loops are mainly implemented on the IOC level rather than PLC’s. 1 I/O and Control Loops Complex control algorithms and control loops are the domain of DCS alike control systems. The support for sets of predefined display and controls properties is essential. If not already available (like in DCS systems) such sets of generic properties are typically specified throughout a plete control system (see namespaces). 2 Sequence/ State programs Sequence programs can run on any processor in a control system. The runtime environment depends on the relevance of the code for the control system. Programs fulfilling watchdog functions have to run on the frontend processor directly. Sequence programs for plicated startup and shutdown procedures could be run on a workstation as well. The basic functionality of a state machine can be even implemented in IEC 61131. Code generators can produce ‘C’ code which can be piled for the runtime environment. 3 Supported Hardware The support for field buses and Ethernet based I/O is a basic functionality for SCADA type systems it is mercially available from any SCADA system on the market. The integration of specific hardware with specific drivers and data conversion is the hard part in a mercial environment. Open API’s or scripting support sometimes help to integrate custom hardware. If these tools are not provided for the control system it is difficult – if not impossible to integrate custom hardware. New industrial standards like OPC allow the munication with OPC aware devices and the munication between control systems. One boundary condition for this kind of functionality is the underlying operating system. In the case of OPC it is bound to DCOM which is a Microsoft standard. UNIX based control systems have a hard time to get connected. Only control systems supporting multiple platforms can play a major role in a heterogeneous environments. As a result the limited support for custom or specialized hardware may give reason for the development of a new control system.Display and Operation Besides the frontend system the operator interfaces play a major role for the acceptance of a control system. SCADA tools e with a homogeneous look and feel throughout their set of tools. Toolkits implemented in a collaboration might vary because the individual tools were developed by different teams. 1 Graphic Synoptic displays are the advertising sign for any control system. Commercial synoptic displays e with a rich functionality and lots of special features. Starting to make use of all these features one will find out that all individual properties of the graphic objects must be specified individually. Since SCADA systems must be generic they cannot foresee that an input channel does not only consist of a value but also consists of properties like display ranges and alarm values. Defining all of these properties again and again can be a pretty boring job. Some systems allow to generate prototypes of graphic objects. These prototype or template graphics are plex and need a specialist to generate them. DCS or custom synoptic display programs can make use of the mon set of properties each I/O point provides. This predefined naming scheme will fill in all standard property values and thus only require to enter the record – or device name into the configuration tool. A clear advantage for control systems with a notion of I/O objects rather than I/O points.2 Alarming Alarms are good candidates to distinguish between different control system architectures. Those systems which have I/O object implemented also provide alarm checking on the frontend puter. Those systems which only know about I/O points have to add alarm checking into the I/O processing. While the I/O object approach allows to implement alarm checking in the native programming langu。③模塊化程序設計，便于調(diào)試，并且方便功能的改進?！?2Mbit/s，只有能夠設置為PROFIBUS 接口的MPI網(wǎng)絡才支持12Mbit/s的通信速率。 程序設計本設計是鍋爐控制，以溫度控制為主，主要是控制鍋爐內(nèi)水的溫度達到控制溫度的目的。 7的硬件組態(tài)與診斷功能（1）硬件組態(tài)① 系統(tǒng)組態(tài)：選擇硬件機架，模塊分配給機架中希望的插槽。STEP 7的授權(quán)在軟盤中。DI為背景數(shù)據(jù)塊，DIX，DIB，DIW和DID。(4) ANY :用于實參的數(shù)據(jù)類型未知或?qū)崊⒖梢允褂萌我鈹?shù)據(jù)類型的情況，占10個字節(jié)。OB塊根據(jù)操作系統(tǒng)調(diào)用的條件（如時間中斷和報警中斷等）分成幾種類型，這些類型有不同的優(yōu)先級，高優(yōu)先級的OB可以中斷低優(yōu)先級的OB。設計高級應用程序時建議使用語句表。它們定義了5種編程語言：1) 指令表IL(Instruction list):西門子稱為語句表STL.2) 結(jié)構(gòu)文本ST(Structured text):西門子稱為結(jié)構(gòu)化控制語言(SCL)。將Q與Q max（溫度允許上限）比較，若也未低于下限，則說明溫度正常，等待下一次采樣。當被控溫度超過上限或低于下限時，經(jīng)調(diào)整3分鐘后仍不能回到正常范圍，則紅燈或黃燈亮，并有聲音報警，表示溫度超過上限或低于下限。CPU221模塊不允許帶擴展模塊；CPU222模塊最多可帶2個擴展模塊；CPU224模塊、CPU226模塊、CPU226XM模塊最多可帶7個擴展模塊。，進行控制柜（臺）等硬件的設計及現(xiàn)場施工。，在選擇PLC的型號、I／O點數(shù)和存儲器容量等內(nèi)容時，應留有適當?shù)挠嗔浚岳谙到y(tǒng)的調(diào)整和擴充。 系統(tǒng)方案設計系統(tǒng)將溫度控制在50℃~60℃以內(nèi)，為了控制方便，本設計設定50℃為溫度較佳值，并依此作為被控溫度的基準值。每一次掃描所用的時間稱為掃描周期或工作周期。編程器一般分為簡易型和智能型兩類。I/O模塊集成了PLC的I/O電路，其輸入暫存器反映輸入信號狀態(tài)，輸出點反映輸出鎖存器狀態(tài)。進入20世紀80年代，隨著大規(guī)模和超大規(guī)模集成電路等微電子技術(shù)的迅猛發(fā)展，以16位和少數(shù)32位微處理器構(gòu)成的微機化PLC，使PLC的功能增強，工作速度快，體積減小，可靠性提高，成本下降，編程和故障檢測更為靈活，方便。溫度是工業(yè)生產(chǎn)對象中主要的被控參數(shù)之一。尤其是近一、二十年來，隨著先進控制理論和計算機技術(shù)的飛速發(fā)展，加之計算機各種性能的不斷增強，價格的大幅度下降，使鍋爐應用計算機控制很快得到了普及和應用。實際表明，應用于20~30噸/時中壓鍋爐的DMC一50系列微機控制系統(tǒng)，經(jīng)實測節(jié)煤率達5%以上。雖然近年來，電熱采暖、地熱采暖悄然進入尋常百姓家，但以水暖鍋爐進行采暖仍是我國最為普遍使用的冬季采暖方式。水暖鍋爐在我國已有近百年的歷史，在過去很長一段時間，我國水暖鍋爐控制一直都是人工手動控制。前饋控制就是在擾動影響到被控對象前就將其通過補償消除掉。洛陽理工學院畢業(yè)設計（論文）基于PLC的爐膛溫度控制系統(tǒng)設計畢業(yè)論文目　錄前　言 1第1章 緒論 2 課題研究的意義 2 鍋爐控制的國內(nèi)外研究現(xiàn)狀 3 本文所做工作 4第2章 PLC基礎及系統(tǒng)方案設計 5 可編程控制器基礎 5 可編程控制器的產(chǎn)生和應用 5 可編程控制器的組成 5 可編程控制器的工作原理 7 可編程控制器的分類及特點 8 系統(tǒng)方案設計 8第3章 硬件設計 9 PLC控制系統(tǒng)設計的基本原則和步驟 9 PLC控制系統(tǒng)設計的基本原則 9 PLC控制系統(tǒng)設計的一般步驟 9 PLC系統(tǒng)選型 10 系統(tǒng)控制要求 11 電氣控制系統(tǒng)電路圖 12第4章 軟件設計 14 PLC編程語言簡潔 14 PLC編程語言的國際標準 14 復合數(shù)據(jù)類型與參數(shù)類型 15 系統(tǒng)存儲器 16 STEP7的原理 17 程序設計 18 通信系統(tǒng) 19結(jié)　論 21謝 辭 22參考文獻 23附　錄 24外文資料翻譯 320前　言在經(jīng)濟科技日益金華的今天自動生產(chǎn)代替單純的手工勞動已是不可逆轉(zhuǎn)的歷史潮流，于是過程控制這門課程被提上日程在經(jīng)濟科技日益進化