【機械類畢業(yè)論文中英文對照文獻翻譯】PLC概述【word英文3701字8頁word中文翻譯6779字6頁】
【機械類畢業(yè)論文中英文對照文獻翻譯】PLC概述【word英文3701字8頁word中文翻譯6779字6頁】,機械類畢業(yè)論文中英文對照文獻翻譯,word英文3701字8頁,word中文翻譯6779字6頁,機械類,畢業(yè)論文,中英文,對照,對比,比照,文獻,翻譯,plc,概述,word,英文,中文翻譯
中文譯文
1 PLC概述
可編程控制器是60年代末在美國首先出現的，當時叫可編程邏輯控制器PLC（Programmable Logic Controller），目的是用來取代繼電器。以執(zhí)行邏輯判斷、計時、計數等順序控制功能。提出PLC概念的是美國通用汽車公司。PLC的基本設計思想是把計算機功能完善、靈活、通用等優(yōu)點和繼電器控制系統(tǒng)的簡單易懂、操作方便、價格便宜等優(yōu)點結合起來，控制器的硬件是標準的、通用的。根據實際應用對象，將控制內容編成軟件寫入控制器的用戶程序存儲器內,使控制器和被控對象連接方便。
70年代中期以后，PLC已廣泛地使用微處理器作為中央處理器，輸入輸出模塊和外圍電路也都采用了中、大規(guī)模甚至超大規(guī)模的集成電路，這時的PLC已不再是僅有邏輯(Logic)判斷功能，還同時具有數據處理、PID調節(jié)和數據通信功能。國際電工委員會(IEC)頒布的可編程控制器標準草案中對可編程控制器作了如下的定義：可編程控制器是一種數字運算操作的電子系統(tǒng)，專為在工業(yè)環(huán)境下應用而設計。它采用了可編程序的存儲器，用來在其內部存儲執(zhí)行邏輯運算，順序控制、定時、計數和算術運算等操作的指令，并通過數字式和模擬式的輸入和輸出，控制各種類型的機械或生產過程。可編程控制器及其有關外圍設備，易于與工業(yè)控制系統(tǒng)聯成一個整體，易于擴充其功能的設計。
可編程控制器對用戶來說，是一種無觸點設備，改變程序即可改變生產工藝。目前，可編程控制器已成為工廠自動化的強有力工具，得到了廣泛的普及推廣應用。
可編程控制器是面向用戶的專用工業(yè)控制計算機，具有許多明顯的特點。
①可靠性高，抗干擾能力強；
②編程直觀、簡單；
③適應性好；
④功能完善，接口功能強
2 PLC的歷史
1968年，Richard E. Morley創(chuàng)造出了新一代工業(yè)控制裝置可編程邏輯控制器(PLC),現在，PLC已經被廣泛應用于工業(yè)領域，包括機械制造也、運輸系統(tǒng)、化學過程設備、等許多其他領域。初期可編程控制器只是用一種類似于語言的軟件邏輯于代替繼電器硬件邏輯，并且使開發(fā)時間由6個月縮短到6天。
雖然計算機控制技術已經產生，但是PLC控制因為它的高性能、成本低、并且對惡劣的環(huán)境有很強的適應能力而在工業(yè)控制的廣泛應用中保持優(yōu)勢。而且，盡管硬件的價格在逐漸下跌，據估計，根據Frost和Sullivan對PLC市場的調查研究表明，每年銷售硬件的價格要比銷售PLC的價格（一千五百萬）至少多出八十億美元。PLC的創(chuàng)造者Richard E. Morley十分肯定的認為目前PLC市場是一個價值五十億的工業(yè)
雖然PLC廣泛應用于工業(yè)控制中，PLC控制系統(tǒng)的程序依然和語法有關。和軟件過程一樣，PLC的軟件設計也以同樣的方式會遇到軟件錯誤或危機。Morley在演講中著重強調了這個方面。
如果房子建造的像軟件過程一樣，那么僅僅一只啄木鳥就可以摧毀文明。特別的，PLC程序要解決的實際問題是消除軟件錯誤和減少老式梯形邏輯語言的花費。盡管PLC的硬件成本在繼續(xù)下降，但是在工業(yè)控制上減少梯形邏輯的掃描時間仍然是一個問題，以至于可以用到低耗時的PLC。
一般來說，和其他領域相比生產PLC的周期要短很多。例如，在實踐中，VISI設計是一種有效的計算機輔助設計。PLC不需要使用目前的以軟件設計為基礎軟件工程方法論，因為PLC程序要求對軟件和硬件搜都要考慮到。因此，軟件設計越來越成為花費動力。在許多的工業(yè)設計工程中，多數人力分配給了控制系統(tǒng)設計和安裝，并且他們被要求對PLC進行程序測試和錯誤排除。
再者，PLC控制系統(tǒng)不適合設計對適應性和重構有越來越多要求的生產系統(tǒng)。一個更深入的問題是在大規(guī)模的工程中軟件越來越復雜，促使要有一個系統(tǒng)化的設計方法論。
主題的客觀性是為PLC自動控制系統(tǒng)建立一個系統(tǒng)化的軟件設計方法論。這個設計方法論包括以狀態(tài)轉換模型為基礎的精確的描述，這個轉臺轉換模型是自動控制系統(tǒng)的抽象系統(tǒng)。方法論還包括一個逐步的設計過程，并且要設置一個設計規(guī)則，這樣才能為一個成功的設計提供導向和方法。這項研究的真正目的是找到一個減少控制軟件發(fā)展過程的不穩(wěn)定性的方法，也就是說，減少程序和調試時間以及他們的變化，以增強自動控制系統(tǒng)的適應性，并且通過調整軟件使得軟件可以再度使用。這樣的目的是為了克服目前程序策略的不足之處，而目前的程序策略是以個人軟件開發(fā)者的經驗為基礎的。
3 現今的PLC
從結構上分，PLC分為固定式和模塊式兩種。固定式PLC包括CPU板、I/O板、顯示面板、內存塊、電源等，這些元素組合成一個不可拆卸的整體。模塊式PLC包括CPU模塊、I/O模塊、內存、電源模塊、底板或機架，這些模塊可以按照一定規(guī)則組合配置。
在使用者看來，不必要詳細分析CPU的內部電路，但對各部分的工作機制還是應有足夠的理解。CPU的控制器控制CPU工作，由它讀取指令、解釋指令及執(zhí)行指令。但工作節(jié)奏由震蕩信號控制。
運算器用于進行數字或邏輯運算，在控制器指揮下工作。寄存器參與運算，并存儲運算的中間結果，它也是在控制器指揮下工作。CPU速度和內存容量是PLC的重要參數，它們決定著PLC的工作速度，IO數量及軟件容量等，因此限制著控制規(guī)模。
中央處理器(CPU)是PLC控制器的大腦。通常CPU本身就是一個微控制器。起先是8位微控制器例如8051,現在發(fā)展為16位和 32位微控制器。你會發(fā)現大部分由日本制造商制造的PLC中是日立和Fujicu的微控制器,西門子的微控制器多應用在歐洲的PLC中,摩托羅拉生產的微控制器則獨占美國市場。CPU同樣關注通信, PLC控制器,操作程序的執(zhí)行,監(jiān)督記憶設置的輸入和輸出等部分的關聯性。
PLC使用系統(tǒng)存儲器（現在大部分采用閃存技術了）用于過程控制系統(tǒng)。除了這個操作系統(tǒng)之外，它還包括一個由梯形圖翻譯成而進制形式的用戶程序?？觳列痛鎯ζ鳎‵LASH memory）的內容只有在改變用戶程序的時候可以被改變。PLC控制器比快擦型存儲器使用得更早，EPROM存儲器比快擦型存儲器也更早，快擦型存儲器必須用紫外線（UV，Ultra-Violet Ray）燈擦除，并在編程器上進行編程。由于快擦型存儲器技術的應用，使得這個過程大大縮短了。在應用程序開發(fā)中，通過一個串行電纜可以對程序存儲器進行重新編程。
用戶存儲器被分成具有特殊功能的塊。一部分存儲器用來存儲輸入和輸出狀態(tài)。一個輸入的實際狀態(tài)存儲狀態(tài)存儲在專用存儲器位上，為“1”或者“0”。每一個輸入和輸出在存儲器中都有一個相應的位。另外一部分存儲器用來存儲用戶程序中的變量的內容。例如，定時器值，或者記數器值存放在存儲器的這個部分。
PLC控制器可以通過計算機（通常方式）重新編程，但是也可以通過人工編程器9控制臺）編程。實際上，這意味著，如果你有編程所需要的軟件，早期PLC控制器可以通過計算機進行編程。今天的傳輸計算機是工廠自己對PLC控制器進行重新編程的理想設備。這對于工業(yè)企業(yè)來說是非常重要的。一旦系統(tǒng)修改結束，將正確的程序重新讀入PLC控制器也是非常重要的。定期檢查PLC中的程序是否改變是非常好的事情。這有助于避免車間發(fā)生危險情況（一些汽車制造商已經建立了通信網絡，可以定期檢查PLC中的程序，以保證運行的程序都是正確的）。
幾乎所有用于為PLC控制器編程的程序都擁有各種不同的選項，例如系統(tǒng)輸入/輸出（I/O線）的強制開關，程序實時跟蹤以及圖表驗證。圖表驗證對于理解、定義失敗和故障非常必要。程序員可以添加標記，書日和輸出設備名稱，以及對于查找錯誤或者對于系統(tǒng)維護很有用的注釋。添加注釋和標記可以使技術人員（不僅僅是開發(fā)人員）很快理解梯形圖。注釋和標記甚至還可以準確地引用零件號，如果需要更換零件的話。這將加快由于損壞零件而引起的任何問題的修理速度。響應的舊方法是這樣的，開發(fā)系統(tǒng)的人必須保護這個程序，他旁邊再沒有人知道系統(tǒng)是怎樣完成的。正確的、備有證明文件的梯形圖使任何技術人員都能徹底理解系統(tǒng)的功能。
電源是為中央處理單元提供電源的。大部分PLC控制器的工作電壓為24VDC或者220VAC。在有些PLC控制器上，你可以看見作為獨立模塊的電源。用戶必須確定從I/O模塊取出多大電流來保證電源提供適當的電流。不同的模塊使用不同的電流量。
該電源一般不用于啟動外部輸入或輸出。用戶必須提供獨立的電源來啟動PLC控制器的輸入和輸出，因為這樣可以保證PLC控制器的所謂“純電源”。使用純電源意味著工業(yè)環(huán)境中的電源不會嚴重影響它。有些較小的PLC控制器從與PLC控制器集成在一起的小電源為它們的輸入提供電壓源。
4 PLC的設計標準
一個系統(tǒng)化的設計PLC程序的方法可以克服傳統(tǒng)程序生產控制系統(tǒng)的缺點，并且在一些工業(yè)應用總有很大的不同。自動控制系統(tǒng)是狀態(tài)模型用公式語言或等價的語言描述的。公式描述對被控制的系統(tǒng)的行為提供一個精確的描述。可以通過分析估計看狀態(tài)模型是否達到想要的目標。第二，為狀態(tài)模型的描述提供結構描述，這個結構描述可以說明邏輯要求和如細節(jié)安全規(guī)則的限制。第三，好的控制系統(tǒng)設計是對自動控制代碼生成有益的——一種能夠產生可執(zhí)行的控制軟件的能力，不同的邏輯控制器可以減少程序掃描時間和執(zhí)行那個時間。特別的，這個主題與隨后的部分的是有關的。
在現代制造業(yè)中，系統(tǒng)是用過程和結果的革新來描述的，并且因此不得不改變系統(tǒng)性能以快速做出反應。因此，一個大的挑戰(zhàn)是提供技術以限制自動控制系統(tǒng)對變化需要和新機會的反應，所以，設計和操作知識可以實時的被再次利用，在工業(yè)實踐中提供了一個重要的競爭面。
研究表明，在自動化系統(tǒng)中，程序實現的方法已經與計算機資源應用的急速增長不能匹配。例如，可編程邏輯控制器（ＰＬＣ）程序仍然依靠一種方便的有邏輯梯形圖的程序實現模式。結果，程序上的延遲和資源成了生產工業(yè)過程的主要絆腳石。在可編程邏輯控制器程序設計過程中，測試和調試可能會占用超過百分之五十的人力。在發(fā)展和傳播“ＳＴＡＴＥ－ＯＦ－ＴＨＥ－ＡＲＴ”已經形成標準[IEC 60848, 1999; IEC-61131-3, 1993; IEC 61499, 1998; ISO 15745-1, 1999]，但是，基本上這些標準都不能參與有效的程序和系統(tǒng)設計方面知識的革新。
系統(tǒng)的方法通過使用原有的軟件模塊，有助于增加設計自動化的水平，同時也將提供一種可管理的大規(guī)模系統(tǒng)設計的方法。同樣的，它也將改善軟件的質量的可靠性，以及關系到系統(tǒng)的較高安全標準，尤其是這些對環(huán)境有危害影響的，比如：機場控制、公共鐵路運輸。
軟件工業(yè)被認為是系統(tǒng)性能的破壞者和系統(tǒng)復雜性的產生者。逐漸下降的硬件價格，破壞了對通過優(yōu)化程序獲得的軟件性能的需要。其結果是，一方面造成了大量而低效率的程序代碼，另一方面并沒有獲得高的硬件性能。其次，軟件變得難以掌握其程度的復雜；在現代自動化系統(tǒng)中，軟件設計和保持系統(tǒng)本質幾乎變得不可能。尤其是，可編程邏輯控制器（ＰＬＣ）程序設計從二十五年前的兩條主線，發(fā)展到現在的成千上萬條?，F在安全性增加了，例如，關于防火的新措施，以及現代自動化系統(tǒng)的柔韌性增加了程序設計過程的復雜性。因此，軟件的使用周期花費是總共花費的一個固定不變的增長部分。百分之八十到九十的花費用于軟件維護、調試、優(yōu)化（改進）、和擴展以滿足不斷變換的需求。
目前，大部分設計研究的主要焦點都集中在機械和電子產品上。這種有目的性的研究產生了一個副產品，就是通過推廣這中研究到系統(tǒng)工程設計領域，從而加固了我們對設計理論和技巧的基本理解。針對大規(guī)模和復雜系統(tǒng)的系統(tǒng)設計理論并沒有成熟。尤其是，對如何簡化一個繁冗而復雜的設計任務這一問題，仍然沒有被科學的處理。而且，正在設計理論和代表計算機科學及運籌學研究的認識論結果之間構建一條橋梁，這樣的具體應該是邏輯硬件電路設計。
從邏輯學的角度來看，可編程邏輯控制器（PLC）的軟件設計類似與集成電路的硬件設計?，F代超大規(guī)模集成電路設計（Very Large Scale Integration--VLSI）是及其復雜的，一個集成電路一般有幾百萬個晶體管，而且產品開發(fā)周期大都三年左右。設計過程一般都分成局部功能塊設計和系統(tǒng)設計兩個階段。在局部功能塊設計階段，單個功能將被設計出來，并予以驗證。在系統(tǒng)設計階段，所有功能塊都將被整合起來，整個系統(tǒng)行為特性和功能將會通過仿真形式加以測試。一般來說，所有部分都完全的驗證是不可能的。因此，統(tǒng)計學可以作為可編程邏輯控制器（PLC）設計的一個例子，并有可能影響邏輯硬件設計。
5 AK 1703 ACP
AK 1703 ACP憑借著一貫創(chuàng)新的精神與穩(wěn)定的技術，在以穩(wěn)定為基礎的產品平臺中，擁有高級的功能性和適應性。
ACP（自動化，控制和保護）系統(tǒng)概念保證了AK 1703 ACP功能的實現。穩(wěn)定的功能性使得自動化控制，遠程控制和通信協(xié)議三者完美結合?？缮壍男阅芘c多種冗余結構，使得AK1703 ACP可以完美處理各種功能要求。
AK 1703 ACP擁有適合現代化自動控制的綜合的遠程控制技術：
? 水電站遠程控制與中控設備
? 擁有自治功能的自動控制單元
? 數據節(jié)點, 設備控制站, 尖端科技
? 擁有現場或遠程外圍設備
? 為后面板安裝而設計的19英寸設備
? 專為多種現場應用和高產品要求設計的中間產品
? 多種通信手段
? 簡潔的編程
? 唯一的設備插座
? 開放型系統(tǒng)體系結構
? 可升級的冗余
? 智能終端- TM 1703
AK 1703 ACP基本外部設備原件擁有兩個基本系統(tǒng)原件CP-2010/CPC25（主控原件）和CP-2012/PCCE25（處理和通信原件），一個總線最多可以連接16個外圍設備原件。
CP-2010/CPC25 特征與功能
系統(tǒng)功能：
? 核心元件，協(xié)調所有系統(tǒng)功能
連接所有基本功能原件的中心站點
? 時間管理
自動控制單元的中控時鐘設定并保持自身時鐘的時間，分辨率為10ms通過互聯網或當地的服務通信進行同步
? 冗余在處理與通信中為自動控制單元選擇并轉變冗余單元通過SCA-RS外部冗余開關支持選擇與轉變功能通過外接系統(tǒng)實現選擇與支持,例如控制系統(tǒng)
? 與SAT TOLLBOX連接在閃存卡里存儲固件和參數
通信：
? 通過相應的協(xié)議原件與高級或附屬自動控制單元進行通信
? 為數據流自動選擇路徑
? 優(yōu)先基本數據的傳輸(優(yōu)先級控制)
? 為每個聯檢站設立自己的循環(huán)緩沖器和處理信息(數據保持)
? 為冗余通信提供路徑與對方站的冗余進行通信
? 通過撥號上網方式對特殊應用實施特殊功能為可進行冗余的站點進行測試具有處理功能的外圍設備：
? 通過Ax 1703外圍設備串口總線自發(fā)地將信息傳輸到外圍設備單元自動控制功能：
? 通過CAEX+按照IEC 61131-3協(xié)議創(chuàng)建的可自由定義的擁有開閉環(huán)控制功能的用戶程序512KB的用戶程序空間 大約50000個可變信號源,2000個常用信號源10ms的循環(huán)時間網上測試可隨時下載
? 冗余的開閉環(huán)功能控制通過冗余線路進行同步通過Ax 1703外圍設備串口總線在開閉環(huán)控制功能與外圍接口單元之間不斷傳輸處理信息。
6 SIEMENS可編程序控制器
SIMATIC S7-300系列PLC適用于各行各業(yè)、各種場合中的檢測、監(jiān)測及控制的自動化，其強大功能使其無論在獨立運行中，或相連成網絡皆能實現復雜控制功能。
該產品具有光電隔離，高電磁兼容；具有很高的工業(yè)適用性，允許的環(huán)境溫度達60℃；具有很強的抗干擾、抗振動與抗沖擊性能，因此在嚴酷的工作環(huán)境中得到了廣泛的應用。
自由通訊口方式也是S7-300型PLC的一個很有特色的功能，它使S7-300型PLC可以與任何通訊協(xié)議公開的其它設備、控制器進行通訊，即S7- 300型PLC可以由用戶自己定義通訊協(xié)議（例ASCII協(xié)議），波特率為1。5Mbit/s（可調整）。因此使可通訊的范圍大大增加，使控制系統(tǒng)配置更加靈活、方便。任何具有串行接口的外設，例如：打印機或條形碼閱讀器、變頻器、調制解調器（Modem）、上位PC機等都可連接使用。用戶可通過編程來編制通訊協(xié)議、交換數據（例如：ASCII碼字符），具有RS232接口的設備也可用PC/PPI電纜連接起來進行自由通訊方式通訊。
當上位機脫機時，在下位機控制下，整個系統(tǒng)能正常運行。
上位機即圖文控制中心，主要由PC機和激光打印機組成，采用SIMATIC WINCC軟件平臺，采用全中文操作界面，人機對話友好。管理人員和操作者，可以通過觀察PC機所顯示的各種信息來了解當前和以往整個冰蓄冷自控系統(tǒng)的運行情況和所有參數，并且通過鼠標進行設備管理和執(zhí)行打印任務。
WINCC軟件在自動化領域中可用于所有的操作員控制和監(jiān)控任務?？蓪⑦^程控制中發(fā)生的事件清楚地顯示出來，可顯示當前狀態(tài)并按順序記錄，所記錄的數據可以全部顯示或選擇簡要形式顯示，可連續(xù)或按要求編輯，并可輸出打印報表和趨勢圖。
WINCC 能夠在控制過程中危急情況的初發(fā)階段進行報告，發(fā)出的信號既可以在屏幕上顯示出來，也可以用聲音表現出來。它支持用在線幫助和操作指南來消除故障。某一 WINCC工作站可專門用于過程控制以使那些重要的過程信息不被屏蔽。軟件輔助操作策略保證過程不被非法訪問，并提供用于工業(yè)環(huán)境中的無錯操作。
WINCC 是MICRSOFT WINDOWS98或WINDOWS NT4。0操作系統(tǒng)下，在PC機上運行的面向對象的一流32位應用軟件，通過OLE和ODBC視窗標準機制，作為理想的通訊伙伴進入WINDOWS世界，因此WINCC可容易地結合到全公司的數據處理系統(tǒng)中。
7 通信
通信對于個人自動單元是很重要的。在過去的幾年里，我們聽到許多關于生產自動化協(xié)議的事情，并且許多公司已經加入大有成功希望的事業(yè)。然而，當一個完整的生產自動化協(xié)議說明書沒有及時出現時許多公司都很失望。Larry Kotare說:”現在，生產自動化協(xié)議仍然是生產中一個發(fā)展的對象，一個說明書并不是最終的結果。例如，雖然當新的生產自動化協(xié)議MAP3.0版本使用之時以MAP2.1版本為基礎的產品將會被汰，但是現在人們仍然將產品用于MAP2.1版?！?
由于這些原因，許多PLC廠家緊盯著MAP的最新結果。如歐姆龍公司正在進行一個有關MAP兼容性的項目。但是歐姆龍生產部門總經理Frank Newborn說由于缺少一個固定的標準，歐姆龍的產品并不涉及到MAP。
由于工業(yè)PLC無論何時不可能廣泛的涉及到MAP，生產廠家正在考慮專用網絡。根據Sal Probanzano說法，用戶擔心如果他們廣泛的應用生產廠家將會收回MAP，這樣將會留下一個不支持通信的交流框架。
英文原文
1 PLC overview
Programmable controller is the first in the late 1960s in the United States, then called PLC programmable logic controller (Programmable Logic Controller) is used to replace relays. For the implementation of the logical judgment, timing, sequence number, and other control functions. The concept is presented PLC General Motors Corporation. PLC and the basic design is the computer functional improvements, flexible, generic and other advantages and relay control system simple and easy to operate, such as the advantages of cheap prices combined controller hardware is standard and overall. According to the practical application of target software in order to control the content of the user procedures memory controller, the controller and connecting the accused convenient target.
In the mid-1970s, the PLC has been widely used as a central processing unit microprocessor, import export module and the external circuits are used, large-scale integrated circuits even when the PLC is no longer the only logical (IC) judgment functions also have data processing, PID conditioning and data communications functions. International Electro technical Commission (IEC) standards promulgated programmable controller for programmable controller draft made the following definition : programmable controller is a digital electronic computers operating system, specifically for applications in the industrial design environment. It used programmable memory, used to implement logic in their internal storage operations, sequence control, timing, counting and arithmetic operations, such as operating instructions, and through digital and analog input and output, the control of various types of machinery or production processes. Programmable controller and related peripherals, and industrial control systems easily linked to form a whole, to expand its functional design. Programmable controller for the user, is a non-contact equipment, the procedures can be changed to change production processes. The programmable controller has become a powerful tool for factory automation, widely popular replication. Programmable controller is user-oriented industries dedicated control computer, with many distinctive features.
First, high reliability, anti-interference capability;
Second，programming visual, simple;
Third, adaptability good;
Fourth functional improvements, strong functional interface.
2 History of PLC
Programmable Logic Controllers (PLC), a computing device invented by Richard E. Morley in 1968, have been widely used in industry including manufacturing systems, transportation systems, chemical process facilities, and many others. At that time, the PLC replaced the hardwired logic with soft-wired logic or so-called relay ladder logic (RLL), a programming language visually resembling the hardwired logic, and reduced thereby the configuration time from 6 months down to 6 days [Moody and Morley, 1999].
Although PC based control has started to come into place, PLC based control will remain the technique to which the majority of industrial applications will adhere due to its higher performance, lower price, and superior reliability in harsh environments. Moreover, according to a study on the PLC market of Frost and Sullivan [1995], an increase of the annual sales volume to 15 million PLCs per year with the hardware value of more than 8 billion US dollars has been predicted, though the prices of computing hardware is steadily dropping. The inventor of the PLC, Richard E Morley, fairly considers the PLC market as a 5-billion industry at the present time.
Though PLCs are widely used in industrial practice, the programming of PLC based control systems is still very much relying on trial-and-error. Alike software engineering, PLC software design is facing the software dilemma or crisis in a similar way. Morley himself emphasized this aspect most forcefully by indicating
If houses were built like software projects, a single woodpecker could destroy civilization.
Particularly, practical problems in PLC programming are to eliminate software bugs and to reduce the maintenance costs of old ladder logic programs. Though the hardware costs of PLCs are dropping continuously, reducing the scan time of the ladder logic is still an issue in industry so that low-cost PLCs can be used.
In general, the productivity in generating PLC is far behind compared to other domains, for instance, VLSI design, where efficient computer aided design tools are in practice. Existent software engineering methodologies are not necessarily applicable to the PLC based software design because PLC-programming requires a simultaneous consideration of hardware and software. The software design becomes, thereby, more and more the major cost driver. In many industrial design projects, more than of the manpower allocated for the control system design and installation is scheduled for testing and debugging PLC programs.
In addition, current PLC based control systems are not properly designed to support the growing demand for flexibility and reconfigurability of manufacturing systems. A further problem, impelling the need for a systematic design methodology, is the increasing software complexity in large-scale projects.
The objective of this thesis is to develop a systematic software design methodology for PLC operated automation systems. The design methodology involves high-level description based on state transition models that treat automation control systems as discrete event systems, a stepwise design process, and set of design rules providing guidance and measurements to achieve a successful design. The tangible outcome of this research is to find a way to reduce the uncertainty in managing the control software development process, that is, reducing programming and debugging time and their variation, increasing flexibility of the automation systems, and enabling software reusability through modularity. The goal is to overcome shortcomings of current programming strategies that are based on the experience of the individual software developer.
3 Now of PLC
From the structure is divided into fixed PLC and Module PLC, the two kinds of PLC including CPU board, I/O board, display panel, memory block, power, these elements into a do not remove overall. Module type PLC including CPU module, I/O modules, memory, the power modules, bottom or a frame, these modules can be according to certain rules combination configuration.
In the user view, a detailed analysis of the CPU's internal unnecessary, but working mechanism of every part of the circuit. The CPU control works, by it reads CPU instruction, interprets the instruction and executes instructions. But the pace of work by shock signal control.
Unit work under the controller command used in a digital or logic operation.In computing and storage register of computation result, it is also among the controller command and work. CPU speed and memory capacity is the important parameters for PLC , its determines the PLC speed of work, IO PLC number and software capacity, so limits to control size.
Central Processing Unit (CPU) is the brain of a PLC controller. CPU itself is usually one of the microcontrollers. Aforetime these were 8-bit microcontrollers such as 8051, and now these are 16-and 32-bit microcontrollers. Unspoken rule is that you’ll find mostly Hitachi and Fujicu microcontrollers in PLC controllers by Japanese makers, Siemens in European controllers, and Motorola microcontrollers in American ones. CPU also takes care of communication, interconnectedness among other parts of PLC controllers, program execution, memory operation, overseeing input and setting up of an output.
System memory (today mostly implemented in FLASH technology) is used by a PLC for a process control system. Aside form. this operating system it also contains a user program translated forma ladder diagram to a binary form. FLASH memory contents can be changed only in case where user program is being changed. PLC controllers were used earlier instead of PLASH memory and have had EPROM memory instead of FLASH memory which had to be erased with UV lamp and programmed on programmers. With the use of FLASH technology this process was greatly shortened. Reprogramming a program memory is done through a serial cable in a program for application development.
User memory is divided into blocks having special functions. Some parts of a memory are used for storing input and output status. The real status of an input is stored either as “1”or as “0”in a specific memory bit/ each input or output has one corresponding bit in memory. Other parts of memory are used to store variable contents for variables used in used program. For example, time value, or counter value would be stored in this part of the memory.
PLC controller can be reprogrammed through a computer (usual way), but also through manual programmers (consoles). This practically means that each PLC controller can programmed through a computer if you have the software needed for programming. Today’s transmission computers are ideal for reprogramming a PLC controller in factory itself. This is of great importance to industry. Once the system is corrected, it is also important to read the right program into a PLC again. It is also good to check from time to time whether program in a PLC has not changed. This helps to avoid hazardous situations in factory rooms (some automakers have established communication networks which regularly check programs in PLC controllers to ensure execution only of good programs).
Almost every program for programming a PLC controller possesses various useful options such as: forced switching on and off of the system input/outputs (I/O lines), program follow up in real time as well as documenting a diagram. This documenting is necessary to understand and define failures and malfunctions. Programmer can add remarks, names of input or output devices, and comments that can be useful when finding errors, or with system maintenance. Adding comments and remarks enables any technician (and not just a person who developed the system) to understand a ladder diagram right away. Comments and remarks can even quote precisely part numbers if replacements would be needed. This would speed up a repair of any problems that come up due to bad parts. The old way was such that a person who developed a system had protection on the program, so nobody aside from this person could understand how it was done. Correctly documented ladder diagram allows any technician to understand thoroughly how system functions.
Electrical supply is used in bringing electrical energy to central processing unit. Most PLC controllers work either at 24 VDC or 220 VAC. On some PLC controllers you’ll find electrical supply as a separate module. Those are usually bigger PLC controllers, while small and medium series already contain the supply module. User has to determine how much current to take from I/O module to ensure that electrical supply provides appropriate amount of current. Different types of modules use different amounts of electrical current.
This electrical supply is usually not used to start external input or output. User has to provide separate supplies in starting PLC controller inputs because then you can ensure so called “pure” supply for the PLC controller. With pure supply we mean supply where industrial environment can not affect it damagingly. Some of the smaller PLC controllers supply their inputs with voltage from a small supply source already incorporated into a PLC.
4 PLC design criteria
A systematic approach to designing PLC software can overcome deficiencies in the traditional way of programming manufacturing control systems, and can have wide ramifications in several industrial applications. Automation control systems are modeled by formal languages or, equivalently, by state machines. Formal representations provide a high-level description of the behavior of the system to be controlled. State machines can be analytically evaluated as to whether or not they meet the desired goals. Secondly, a state machine description provides a structured representation to convey the logical requirements and constraints such as detailed safety rules. Thirdly, well-defined control systems design outcomes are conducive to automatic code generation- An ability to produce control software executable on commercial distinct logic controllers can reduce programming lead-time and labor cost. In particular, the thesis is relevant with respect to the following aspects.
In modern manufacturing, systems are characterized by product and process innovation, become customer-driven and thus have to respond quickly to changing system requirements. A major challenge is therefore to provide enabling technologies that can economically reconfigure automation control systems in response to changing needs and new opportunities. Design and operational knowledge can be reused in real-time, therefore, giving a significant competitive edge in industrial practice.
Studies have shown that programming methodologies in automation systems have not been able to match rapid increase in use of computing resources. For instance, the programming of PLCs still relies on a conventional programming style with ladder logic diagrams. As a result, the delays and resources in programming are a major stumbling stone for the progress of manufacturing industry. Testing and debugging may consume over 50% of the manpower allocated for the PLC program design. Standards [IEC 60848, 1999; IEC-61131-3, 1993; IEC 61499, 1998; ISO 15745-1, 1999] have been formed to fix and disseminate state-of-the-art design methods, but they normally cannot participate in advancing the knowledge of efficient program and system design.
A systematic approach will increase the level of design automation through reusing existing software components, and will provide methods to make large-scale system design manageable. Likewise, it will improve software quality and reliability and will be relevant to systems high security standards, especially those having hazardous impact on the environment such as airport control, and public railroads.
The software industry is regarded as a performance destructor and complexity generator. Steadily shrinking hardware prices spoils the need for software performance in terms of code optimization and efficiency. The result is that massive and less efficient software code on one hand outpaces the gains in hardware performance on the other hand. Secondly, software proliferates into complexity of unmanageable dimensions; software redesign and maintenance-essential in modern automation systems-becomes nearly impossible. Particularly, PLC programs have evolved from a couple lines of code 25 years ago to thousands of lines of code with a similar number of 1/O points. Increased safety, for instance new policies on fire protection, and the flexibility of modern automation systems add complexity to the program design process. Consequently, the life-cycle cost of software is a permanently growing fraction of the total cost. 80-90% of these costs are going into software maintenance, debugging, adaptation and expansion to meet changing needs.
Today, the primary focus of most design research is based on mechanical or electrical products. One of the by-products of this proposed research is to enhance our fundamental understanding of design theory and methodology by extending it to the field of engineering systems design. A system design theory for large-scale and complex system is not yet fully developed. Particularly, the question of how to simplify a complicated or complex design task has not been tackled in a scientific way. Furthermore, building a bridge between design theory and the latest epistemological outcomes of formal representations in computer sciences and operations research, such as discrete event system modeling, can advance future development in engineering design.
From a logical perspective, PLC software design is similar to the hardware design of integrated circuits. Modern VLSI designs are extremely complex with several million parts and a product development time of 3 years [Whitney, 1996]. The design process is normally separated into a component design and a system design stage. At component design stage, single functions are designed and verified. At system design stage, components are aggregated and the whole system behavior and functionality is tested through simulation. In general, a complete verification is impossible. Hence, a systematic approach as exemplified for the PLC program design may impact the logical hardware design.
5 AK 1703 ACP
Following the principle of our product development, AK 1703 ACP has high functionality and flexibility, through the implementation of innovative and reliable technologies, on the stable basis of a reliable product platform.
For this, the system concept ACP (Automation, Control and Protection) creates the technological preconditions. Balanced functionality permits the flexible combination of automation, telecontrol and communication tasks. Complemented with the scalable performance and various redundancy configurations, an optimal adaptation to the respective requirements of the process is achieved.
AK 1703 ACP is thus perfectly suitable for automation with integrated telecontrol technology as:
? Telecontrol substation or central device
? Automation unit with autonomous functional groups
? Data node, station control device, front-end or gateway
? With local or remote peripherals
? For rear panel installation or 19 inch assembly
? Branch-neutral product, therefore versatile fields of application and high productstability
? Versatile communication
? Easy engineering
? Plug & play for spare parts
? Open system architecture
? Scalable redundancy
? The intelligent terminal - TM 1703The Base Unit AK 1703 ACP with Peripheral Elements has one basic system element CP-2010/CPC25 (Master control element) and CP-2012/PCCE25 (Processing and communication element) one bus line with max. 16 peripheral elements can be connected.CP-2010/CPC25 Features and Functions System Functions:
? Central element, coordinating all system services Central hub function for all connected basic system elements
? Time management Central clock of the automation unitSetting and keeping the own clocks time with a resolution of 10msSynchronization via seri d communication via LAN or local
? Redundancy Voting and change-over for redundant processing and communication elements of the own automation unit Supports voting and change-over by an external SCA-RS redundancy switch Supports applicational voting and change-over by an external system, e .g. a control system
? SAT TOLLBOX|| connectionStoring firmware and parameters on a Flash Card
Communication:
? Communication via installable protocol elements to any superior or subordinate automation unit
? Automatic data flow routing
? Priority based data transmission (priority control)
? Own circular buffer and process image for each connected station(data keeping)
? Redundant communication routes Communication with redundant remote stations
? Special application specific functions for dial-up traffic Test if stations are reachable Process Peripherals:
? Transmission of spontaneous information objects from and to peripheral elements, via the serial Ax 1703 peripheral bus
Functions for Automation:
? Open-/closed-loop control function for the execution of freely definable user programs which are created with CAEX plus according to IEC 61131-3,e.g.using function diagram technology 512KB for user program Approx 50.000 variables and signals,2.000 of them retained Cycle of 10ms or a multiple there of Online test Loadable without service interruption
?Redundant open-/closed-loop control functions Synchronization via redundancy link
Tran
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