1493-全自動立式過濾機的設(shè)計嚴(yán)浩,全自動,立式,過濾機,設(shè)計,嚴(yán)浩 0目錄第一章、設(shè)計題目…………………………………… （1）第二章、設(shè)計意義…………………………………… （3）第三章、方案選擇…………………………………… （6）第四章、過濾部分的設(shè)計…………………………… （7）4.1過濾桶的設(shè)計……………………………………… （7）4.2傳 動部件設(shè)計………………………………… （12）4.3電動機的選擇…………………………………… （18）4.4閥門的選擇與設(shè)計………………………………… (19）4. 5傳感器的選擇與信號檢測………………………… （22）4.6控制面板的設(shè)計…………………………………… （23）第五章、控制部分的設(shè)計……………………………… （24）5.1 控制系統(tǒng)的選擇………………………………… （24）5.2 工藝流程……………………………………… （26）5.3 PLC接線圖………………………………………… （27）5.4程序梯形圖以及語句表…………………………… （28）第六章、設(shè)計的應(yīng)用…………………………………… （33）第七章、設(shè)計心得……………………………………… (35)第八章、參考文獻(xiàn)…………………………………… (36)附錄：外文翻譯及文獻(xiàn)1一、設(shè)計題目題目：全自動立式過濾機的設(shè)計關(guān)鍵詞：過濾機;結(jié)構(gòu);;控制系統(tǒng)；可編程序控制器；摘要：隨著水資源的缺乏和水污染的日益嚴(yán)重，廢水的過濾與分離能很好的解決廢水的處理與重復(fù)利用的問題，實現(xiàn)良好的經(jīng)濟(jì)效益和社會效益。但傳統(tǒng)的過濾分離設(shè)備占地空間大，連續(xù)生產(chǎn)能力低，自動化程度不高，造成人力物力財力的浪費。本文以自行開發(fā) 50m3/h處理量全自動白清洗過濾器為基礎(chǔ)，提出了全自動自清洗過濾器的各操作參數(shù)的設(shè)計思想和方法，并建立了過濾過程中過濾器的模型，借此確定控制系統(tǒng)的控制參數(shù)。主要工作內(nèi)容如下;研制設(shè)計了一臺處理量為50m3/ h、工作壓力為 1.6-2.5 Mpa，要求過濾精度為 0.1-200μm,過濾總面積為 10㎡，電動機功率為 5.5KW，工作溫度為-5℃-105℃的全自動自清洗過濾器。該過濾器在運行過程中無須停運以清洗過濾元件，整機體積較小，精度可調(diào)節(jié)，適合于各類工業(yè)生產(chǎn)。本文給出了這種過濾器的整體設(shè)計方法以及設(shè)計圖紙，并對過濾器內(nèi)部過濾機理進(jìn)行分析，討論了幾個過濾參數(shù)，并應(yīng)用于過濾器控制系統(tǒng)設(shè)計之中。title: Automatic vertical filter machine designKey Words: filter，structure; control system；Programmable enfroller；Abstract：As short of water resource and more and more serious situation of water pollution, filtration and separation have been the best way to settle the problem of Reuse of waste water and realization of well economy benefit and social benefit.But there are several disadvantages in these raditional filters such as great volume,discontinuous production, lack of automation, great waste of manpower, materialresources, financial. Based on design of automatic self-cleaning filter on industrial scale (50 m3/h), the design and optimization procedures of several operation parameters are presented and a model of filter is obtained as well,then to calculate control parameters of control system.The main research contents are following as:A auto control self-cleaning filter on industrial scale( 50m 3/h) , work pressure(1.6-2.5Mpa) , filtration accuracy(0.1-200μm), filtration surface(10㎡) , Motor power(5.5 KW) and work temperature(-5 ℃ - 105 ℃)has been designed . auto control self-cleaning filter drive itself to clean completely by its pressure of filtrated liquid and without stop.Volume of the filteris so little and precision can be modulated to fit for kinds of industry produce. In this paper, a suit of drawing and design procedures of such filter has been given.Mechanism during filtration in the filter has been studied are obtained2二、設(shè)計意義過濾機是利用多孔性過濾介質(zhì)，截留液體與固體顆?；旌衔镏械墓腆w顆粒，而實現(xiàn)固、液分離的設(shè)備。過濾機廣泛應(yīng)用于化工、石油、制藥、輕工、食品、選礦、煤炭和水處理等部門。 中國古代即已應(yīng)用過濾技術(shù)于生產(chǎn)，公元前二百年已有植物纖維制作的紙。公元 105年，蔡倫改進(jìn)了造紙法，他在造紙過程中將植物纖維紙漿蕩于致密的細(xì)竹簾上，水經(jīng)竹簾縫隙濾過，一薄層濕紙漿留于竹簾面上，干后即成紙張。 最早的過濾大多為重力過濾，后來采用加壓過濾提高了過濾速度，進(jìn)而又出現(xiàn)了真空過濾。20 世紀(jì)初發(fā)明的轉(zhuǎn)鼓真空過濾機實現(xiàn)了過濾操作的連續(xù)化。此后，各種類型的連續(xù)過濾機相繼出現(xiàn)。間歇操作的過濾機因能實現(xiàn)自動化操作而得到發(fā)展，過濾面積越來越大。為得到含濕量低的濾渣，機械壓榨的過濾機得到了發(fā)展。 用過濾介質(zhì)把容器分隔為上、下腔，即構(gòu)成簡單的過濾器。懸浮液加入上腔，在壓力作用下通過過濾介質(zhì)進(jìn)入下腔成為濾液，固體顆粒被截留在過濾介質(zhì)表面形成濾渣(或稱濾餅 )。 過濾過程中過濾介質(zhì)表面積存的濾渣層逐漸加厚，液體通過濾渣層的阻力隨之增高，過濾速度減小。當(dāng)濾室充滿濾渣或過濾速度太小時，停止過濾，清除濾渣，使過濾介質(zhì)再生，以完成一次過濾循環(huán)。 液體通過濾渣層和過濾介質(zhì)必須克服阻力，因此在過濾介質(zhì)的兩側(cè)必須有壓力差，這是實現(xiàn)過濾的推動力。增大壓力差可以加速過濾，但受壓后變形的顆粒在大壓力差時易堵塞過濾介質(zhì)孔隙，過濾反而減慢。 懸浮液過濾有濾渣層過濾、深層過濾和篩濾三種方式。濾渣層過濾是指在經(jīng)過過濾初期后，形成了初始濾渣層，此后，濾渣層對過濾起主要作用，這時大、小顆粒均被截留；深層過濾是指過濾介質(zhì)較厚，懸浮液中含固體顆粒較少，且顆粒小于過濾介質(zhì)的孔道，過濾時，顆粒進(jìn)入后被吸附在孔道內(nèi)的過濾；篩濾是過濾截留的固體顆粒都大于過濾介質(zhì)的孔隙，過濾介質(zhì)內(nèi)部不吸附固體顆粒的過濾方式，例如轉(zhuǎn)筒式過濾篩濾去污水中的粗粒雜質(zhì)。 在實際的過濾過程中，三種方式常常是同時或相繼出現(xiàn)。過濾機的處理能力取決于過濾速度。懸浮液中的固體顆粒大、粒度均勻時，過濾的濾渣層孔隙較為暢通，濾液通過濾渣層的速度較大。應(yīng)用凝聚劑將微細(xì)的顆粒集合成較大的團(tuán)塊，有利于提高過濾速度。 對于固體顆粒沉降速度快的懸浮液，應(yīng)用在過濾介質(zhì)上部加料的過濾機，使過濾方向與重力方向一致，粗顆粒首先沉降，可減少過濾介質(zhì)和濾渣層的堵塞；在難過濾3的懸浮液(如膠體) 中混入如硅藻土、膨脹珍珠巖等較粗的固體顆粒，可使濾渣層變得疏松；濾液粘度較大時，可加熱懸浮液以降低粘度。這些措施都能加快過濾速度。 過濾機按獲得過濾推動力的方法不同，分為重力過濾器、真空過濾機和加壓過濾機三類。重力過濾器是借助懸浮液的重力和位差，在過濾介質(zhì)上形成的壓力作為過濾的推動力，一般為間歇操作。 真空過濾器是在濾液出口處形成負(fù)壓作為過濾的推動力。這種過濾機又分為間歇操作和連續(xù)操作兩種。間歇操作的真空過濾機可過濾各種濃度的懸浮液，連續(xù)操作的真空過濾機適于過濾含固體顆粒較多的稠厚懸浮液。 加壓過濾器以在懸浮液進(jìn)口處施加的壓力，或?qū)裎锪鲜┘拥臋C械壓榨力作為過濾推動力，適用于要求過濾壓差較大的懸浮液，也分為間歇操作和連續(xù)操作兩種。 過濾機應(yīng)根據(jù)懸浮液的濃度、固體粒度、液體粘度和對過濾質(zhì)量的要求選用。先選擇幾種過濾介質(zhì)，利用過濾漏斗實驗，測定不同過濾介質(zhì)和不同壓差下的過濾速度、濾液的固體含量、濾渣層的厚度和含濕量，找出適宜的過濾條件，初步選定過濾機類型，再根據(jù)處理量選定過濾面積，并經(jīng)實際試驗驗證。 正在發(fā)展的新型過濾設(shè)備有：機械力壓榨過濾設(shè)備；能實現(xiàn)無濾渣層過濾的動態(tài)過濾機；洗選煤炭污水處理、化工和石油工業(yè)用的大型過濾設(shè)備。 在過濾理論研究方面，濾渣層過濾阻力和孔隙率的測算、過濾速度、過濾設(shè)備的模擬和放大、稀薄液體澄清過濾和動態(tài)過濾機理，以及過濾介質(zhì)的研究，都是重要的課題。利用電子計算機控制過濾操作是過濾設(shè)備的發(fā)展方向。4三、方案選擇㈠循環(huán)方案：管道系統(tǒng)如下圖：圖 3-1F1——清洗水入口閥 F2——待濾液入口閥 F3——循環(huán)液入口閥F4——循環(huán)液出口閥 F5——流向控制閥 F6——沖洗閥 F7——排氣閥 F8——排渣閥F9——成品出口閥 F10——余液出口閥 F11——取樣閥S1——循環(huán)視筒 S2——正常工作視筒5此過濾過程有四個過濾階段，預(yù)過濾過程，過濾過程，濾余液過程，反沖洗過程。預(yù)過濾過程：待濾液由 F2 進(jìn)入泵內(nèi)，經(jīng) F3（此時 F1、F5 關(guān)閉）進(jìn)入循環(huán)視筒，然后從 F4 進(jìn)入過濾桶進(jìn)行過濾，此時 F9 關(guān)閉，過濾液經(jīng) F5 再次進(jìn)入循環(huán)桶。過濾過程：待濾液由 F2 進(jìn)入泵內(nèi)，經(jīng) F3（此時 F1、F5 關(guān)閉）進(jìn)入循環(huán)視筒，然后從 F4 進(jìn)入過濾桶進(jìn)行過濾（期間可以通過 S1 觀察過濾循環(huán)過程）濾液由 F7 再次進(jìn)入循環(huán)桶，直至完全過濾通過 S2 經(jīng) F9 流出（可以從 F11 中取樣檢驗，從而調(diào)整濾網(wǎng)密度） 。濾余液過程：收到“ 管高壓差 ”信號后，開始反沖洗過程前的約 1Min 內(nèi)，打開 F10將管道內(nèi)的余液濾出以方便反沖洗，防止堵塞反沖洗管道。反沖洗過程：當(dāng)“ 管高壓差 ”達(dá)到預(yù)定壓力值或者達(dá)到預(yù)定時間后， F2、F3 關(guān)閉，將 F1 打開，清洗水從 F1、F7 進(jìn)入過濾桶中進(jìn)行清洗，洗出的濾渣從 F8 中排出。㈡雙管道一次過濾方案：管道系統(tǒng)如下：圖 3-2過濾：閥 1、閥 4 開啟，閥 2、閥 3 關(guān)閉；反沖洗：：閥 2、閥 3 開啟，閥 1、閥 4 關(guān)閉6過濾過程：過濾液由泵泵入，經(jīng)過閥 1 后進(jìn)入過濾桶過濾，濾后液經(jīng)過視筒后從閥 4 排出（閥 2、閥 3 處于關(guān)閉狀態(tài)） ；反沖洗過程：清洗水由泵泵入，經(jīng)過閥 2 以及視筒后，對過濾桶進(jìn)行反沖洗，濾渣由閥 3 處排出（閥 1、閥 4 處于關(guān)閉狀態(tài)） 。㈢方案比較：方案 1 原理教簡單，管道系統(tǒng)相對較為復(fù)雜，但是過濾精度較高，可靠性較強，由于采用循環(huán)過濾且用閉環(huán)控制，待網(wǎng)內(nèi)外壓差值滿足排放條件時，指揮排污閥進(jìn)行排污，使過濾精度得以提高；并且采用先進(jìn)的控制方式和優(yōu)質(zhì)的信號轉(zhuǎn)換器從而具有性能穩(wěn)定，維護(hù)管理方便，日常維護(hù)少，只須做定期維護(hù)即可等特點，具有明顯的實用價值、經(jīng)濟(jì)價值和推廣價值。方案 2 原理簡單，過濾和反沖洗裝置簡單，但是由于過濾和反沖洗管道共用較多且沒有排除管道余液的設(shè)計，故過濾精度難以保證，維護(hù)較多以及容易發(fā)生堵塞等情況。綜上所述，最終方案選取為方案 1 為基本方案。7四、過濾部分的設(shè)計⒈過濾桶的設(shè)計① 過濾盤的設(shè)計過濾精度為 0.5-100μm，故濾網(wǎng)采用滌綸布料可以達(dá)到要求而且表面光滑，再在上涂上一層硅藻土增加過濾流量，水面上部采用氣壓，壓強大小為 1.6MPa，最大可達(dá)到 2.5MPa，可以使過濾更加快捷。濾后液通過下部孔流出，從取樣閥中取樣調(diào)節(jié)流速從而保證過濾精度，達(dá)到保準(zhǔn)后，打開 F10，完成過濾。另外該系統(tǒng)在-5 ℃——105℃的范圍內(nèi)工作。已知條件：過濾面積：10㎡；正常工作壓力 1.6MPa、最大工作壓力 2.5MPa。⑴.選定過濾介質(zhì)的半徑（R） ，厚度（H） ，片間間隙（ h）以及片數(shù)（N）分別為：R=0.4m、H=0.03m h=0.02m， 每一片的過濾面積為：S=∏*R*R=3.14*0.4*0.4=0.502㎡。N=10㎡/S=10㎡/0.502㎡=19.9所以片數(shù)需要 20 片才能滿足過濾需要，也因此過濾濾芯長度（過濾部分）應(yīng)等于20*（H+h ）+ 頂部密封片厚度+頂部螺母厚度=20*0.05+0.02*2+0.02=1.06m⑵.過濾片零件圖8圖 4-1② 計算內(nèi)壓圓筒殼體的壁厚⑴已知 Pg=1.6MPa由壁厚計算公式：cticPDP???][2/*??- 計算厚度 ；mm?P - 計算壓力；Mpac- 焊接接頭系數(shù);?- 材料的許用應(yīng)力;t][?在已知設(shè)計溫度下 16MnR 的許用應(yīng)力，在厚度為 6~16mm 時，[ =170Mpa;t]?在厚度為 16～36mm 時，[ =163Mpa;t]?焊接接頭系數(shù) ；85.0??設(shè)定 圓筒內(nèi)徑 D =1000mm； 腐蝕裕量 C =2mm；i 2設(shè)計厚度； 材料的許用應(yīng)力 =170Mpa （厚度為 6~16 時） ，筒體厚度計算；t][?=1.6*1000/（2*170*0.85-1.6）=5.5mm；cticPP???2/*?=5.5+2=7.5mm；dC?由鋼材標(biāo)準(zhǔn)規(guī)格，圓整可得壁厚為 10㎜；??⑵ 圓筒的半徑由濾餅半徑確定取 R=500mm;⑶ 圓筒中固定空心軸一端的頂尖高度為 150mm；頂尖的直徑 =50mm； 錐角 =50°??H =H +h1=1100+150=1250mm；總 1⑷ 圓筒邊緣設(shè)計，邊緣厚度 =20mm；B=35mm；?凸緣高度 H=10mm；9⑸ 固定頂尖板的厚度 =10mm；長度 L=120mm；寬度 B=120mm； ?但容器制成后必須經(jīng)過壓力試驗合格后才能交付，壓力的目的主要是檢查加工制造工藝的問題和焊縫的強度，以及各連接面的緊密性等。對壓力試驗一般都用水壓試驗。對水壓試驗時，筒體相應(yīng)壓力的驗算公式為：σ=P 水[D+（S-C）]/[2（S-C）Ф]按規(guī)定水壓試驗壓力 P 水=1.5MPa；故：σ=P 水[D+（S-C）]/[2（S-C）Ф]=1.5*[900+（10-1.8）]/[2*（10-1.8）*0.7]=115MPa又 σs=σ*Ns，其中 Ns查表所得為 1.6，故 σs=115*1.6=184MPaΣs 與水壓系數(shù)的積為 0.9σs=164MPa由于 115 MPa＜164MPa,故筒體強度滿足水壓試驗的要求。10③過濾桶的結(jié)構(gòu)設(shè)計過濾桶設(shè)計是整個管道系統(tǒng)的重點。直接從桶上引出的有 5個管道（底部 3個管道、頂部 2個管道）：（1）桶底正中引出的濾后管，然后連接 S2（正常工作視筒） ，再接上 2個閥門——F9（成品出口閥，正常工作是從這流出成品液）和 F11（取樣閥，用于剛開始工作是取出樣品，從而確定各項參數(shù)） ；（2）桶底斜錐面引出排渣管，引出后分成 2個方向——一個是反沖洗時使用的排渣管，上面安裝著 F8（排渣閥） ；另一個是循環(huán)過濾的循環(huán)管，通過 F5（流向控制閥，單向閥）使壓力過大時形成循環(huán)過濾；（3）桶內(nèi)靠壁處裝有反沖洗管道，連接 F7（沖洗閥）后也分成 2個方向——一個直接連到水泵上；另一個接上 F10（余液出口閥）其作用是在濾余液過程中將管道以及過濾桶的液體流出；（4）桶頂?shù)囊粋€循環(huán)管道向上連接 S1（循環(huán)視筒）和 F4（循環(huán)液出口閥）接到循環(huán)桶底部；（5）桶頂?shù)牧硪粋€循環(huán)管道向上連接 F7（排氣閥）和壓力表，然后接到循環(huán)桶頂部，以保持過濾桶以及循環(huán)筒壓力的正常（1.6MPa～2.5MPa） 。11④循環(huán)桶的設(shè)計1、結(jié)構(gòu)介紹循環(huán)筒的工作原理比較簡單，需要設(shè)計的參數(shù)也較少，主要分為 2 管道：其中一條的作用——待濾液通過 F2（待濾液入口閥） 、水泵、F3 （循環(huán)筒入口閥）從循環(huán)桶下部泵入，在循環(huán)桶上部壓力的作用下從右邊下方的循環(huán)出口通過 F4 后進(jìn)入過濾桶過濾；另外一條是頂部的管道，上面連接 F7（排氣閥）和壓力表和過濾桶頂部連接在一起以保持壓力。2、循環(huán)桶的容量設(shè)計 因為循環(huán)桶所受壓力不是很大，且不是全封閉的，所以可以不許校核桶壁承受應(yīng)力。設(shè)定桶壁厚 =3mm；桶高度 H=1200mm；半徑 R=400mm；容積 V=0.65m ；? 3122、傳動部件設(shè)計1 帶傳動的設(shè)計⑴確定計算功率 Pca由《機械設(shè)計》表 8-7查得工作情況系數(shù) K =1.0,A故 P = K P=1.0*5.5kw=5.5kwcaA⑵選擇 V帶的帶型根據(jù) P ，n 由《機械設(shè)計》教材由圖 8-11選用 A型ca⑶確定帶輪的基準(zhǔn)直徑 d 并驗算帶的速度①初選小帶輪的基準(zhǔn)直徑 d ，由表 8-6和表 8-8，取小帶輪的基準(zhǔn) d =140mm1 1②驗算帶速 V= * d *n/60*1000= *140*1440/60*1000=10.6m/s??因為 5 m/s (Instruction instructionId='Logical Operation")U-.43SPB-BEFig. 8 A new transformed XML showing only the inslructions and thecorresponding instruction IDE. 可視化的XML上述所產(chǎn)生的兩種XML文件可轉(zhuǎn)化為HTML或在XSL的幫助下轉(zhuǎn)換為其他可讀的文件。一個巧妙的XSL可以被設(shè)計用來產(chǎn)生一個可以容易想象的轉(zhuǎn)達(dá)PLC程序的邏輯或者其他特征的HTML文件。此外， DOM的結(jié)構(gòu)在嵌入在XML中 （參見圖9 ） ，也可讓使用者用一個簡單的方法瀏覽PLC程序。例如在HTML中做的可視化程序 。這可視化已經(jīng)完成XML的轉(zhuǎn)換，他作為一個表中的子元素去驗證的語法。指示鑒定后的XML被轉(zhuǎn)化成使用XSL轉(zhuǎn)化，取得那里的指示和身份指示后，根據(jù)該行動的類型提取的XML在 HTML表載列了兩欄（指示，指令編號）是在可視化的。HTML結(jié)構(gòu)的建議，這不是唯一的可能性，其中的XML可以可視化，但他們提供一個很容易的切實可行的方案，那就是為用戶把握的PLC代碼。圖 10顯示了相同的PLC的代碼，在圖 4他作為一個HTML文檔轉(zhuǎn)換XML文檔，顯示的圖 7使用的XSL 。這可視化，更好地了解PLC程序成為可能。圖 11顯示了在圖 6中的XML教學(xué)入侵檢測系統(tǒng)特殊的可視化。六 結(jié)論和展望 重新設(shè)計的PLC程序需要一個正式的辦法加以發(fā)展。在本文章中，是來解決這個任務(wù)一個方法的介紹。在給出了書面指示PLC程序的基礎(chǔ)上，在清單的通過一個明確步驟轉(zhuǎn)型為被建議的正式代表。由于這個過程不會完全自動，有必要采取靈活的可視化中間步驟。XML是作為一種靈活的，標(biāo)準(zhǔn)化的手段來充當(dāng)數(shù)據(jù)格式來描述的PLC代碼。相應(yīng)的XSL轉(zhuǎn)換和文檔對象模型的技術(shù)是作為工具，在重整過程為各種定制可視化任務(wù)。44基于XML的描述PLC程序的進(jìn)一步轉(zhuǎn)變，將適用于最后得出一個完全形式化描述原PLC的代碼。這將是在成立一個有限自動機。在這個計劃過程中，他們通過一個知識庫確定共同的介素的結(jié)構(gòu)和正規(guī)化， 七 致謝我們想感謝萊茵蘭-普法爾茨飛行情報區(qū)的創(chuàng)新，為辦學(xué)我們的工作下，項目編號616 。八 參考文獻(xiàn)1 、L.巴雷西，米毛里，甲蒙蒂，和 皮茲 主編“PLC的設(shè)計 編程和代碼生成”，收錄在IEEE 會議，并在cybernefics smczooo 上出版第 2437 -2 442頁。 2 、 g.弗雷和L. 里茲 ， “形式化方法在PLC編程 ” ，在IEEE結(jié)論對系統(tǒng)，人與控制論（ smc'zooo ） ， Nashville ，美國， 2000年10月。 第2431年至2436頁 3 、米巴尼尤尼斯和G.弗雷， “形式化現(xiàn)有的PLC程序：一項調(diào)查” ，在2003年，里爾（法國） ，號文件中S2 -的R - 00 - 0239 ， 2003年7月。 4 、國際電工委員會，國際電工技術(shù)委員會的國際標(biāo)準(zhǔn)1131-3 ，可編程控制器，第3部分，編程語言， 1993年。 5 、在萬維網(wǎng)財團(tuán)： htfp ; / / www.w3.org/ 6 、 XML的主頁： hftp ： / / xml.com / 7 、 r. kliewer ，逆向工程，馮steuerungssojiware.ph.d 。論文， 德國Kaiserslautern大學(xué)生產(chǎn)自動化研究所, 1999年。 8 、米凱， XSLT的-程序參考員。45Visualization of PLC Programs using XMLM. Bani Younis and G. FreyJuniorprofessorship Agentenbased AutomationUniversity of KaiserslautemP. 0. Box 3049, D-67653 Kaiserslautem, GermanyAbstract - Due to the growing complexity of PLC programs there is an increasing interest in the application of formal methods in this area. Formal methods allow rigid proving of system properties in verification and validation. One way to apply formal methods is to utilize a formal design approach in PLC programming. However, for existing software that has to be optimized, changed, or ported to new systems .There is the need for an approach that can start from a given PLC program. Therefore, formalization of PLC programs is a topic of current research. The paper outlines a re-engineering approach based on the formalization of PLC programs. The transformation into a vendor independent format and the visualization of the structure of PLC programs is identified as an important intermediate step in this process. It is shown how XML and corresponding technologies can be used for the formalization and visualization of an existing PLC program.I. INTRODUCTIONProgrammable Logic Controllers (PLCs) are a special type of computers that are used in industrial and safety critical applications. The purpose of a PLC is to control a particular process, or a collection of processes, by producing electrical control signals in response to electrical process- related inputs signals. The systems controlled by PLCs vary tremendously, with applications in manufacturing, chemical process control, machining, transportation, power distribution, and many other fields. Automation applications can range in complexity from a simple panel to operate the lights and motorized window shades in a conference room to completely automated manufacturing lines.46With the widening of their application horizon， PLC programs are being subject to increased complexity and high quality demands especially for safety-critical applications. The growing complexity of the applications within the compliance of limited development time as well as the reusability of existing software or PLC modules requires a formal approach to be developed [I]. Ensuring the high quality demands requires verification and validation procedures as well as analysis and simulation of existing systems to be carried out [2]. One of the important fields for the formalization of PLC programs that have been growing up in recent time is Reverse-engineering [3]. Reverse Engineering is a process of evaluating something to understand how it works in order to duplicate or enhance it. While the reuse of PLC codes is being established as a tool for combating the complexity of PLC programs, Reverse Engineering is supposed to receive increased importance in the coming years especially if exiting hardware has to be replaced by new hardware with different programming environmentsVisualization of existing PLC programs is an important intermediate step of Reverse Engineering. The paper provides an approach towards the visualization of PLC programs using XML which is an important approach for the orientation and better understanding for engineers working with PLC programs. The paper is structured as follows. First, a short introduction to PLCs and the corresponding programming techniques according to the IEC 61131-3 standard is given. In Section Ⅲ an approach for Re-engineering based on formalization of PLC programs is introduced. The transformation of the PLC code into a vendor independent format is identified as an important first step in this process. XML and corresponding technologies such as XSL and XSLT that can be used in this transformation are presented in Section IV. Section V presents the application of XML for the visualization of PLC programs and illustrates the approach with an example. The final Section summarizes the results and gives an outlook on future work in this ongoing project.Ⅱ PLC AND IEC 61131Since its inception in the early ‘70s the PLC received increasing attention due to its success in fulfilling the objective of replacing hard-wired control equipments at machines. Eventually it grew up as a distinct field of application, research and development, mainly for Control Engineering. IEC 61 131 is the first real endeavour to standardize PLC programming languages for industrial automation. In I993 the International Electrotechnical Commission [4] published the IEC 61131 Intemational Standard for Programmable Controllers. Before the standardization PLC programming languages were being developed as proprietary programming languages usable to PLCs of a special vendor. But in order to enhance compatibility, openness and interoperability among different products as well as to promote the development of tools and methodologies with respect to a fixed set of notations the IEC 61131 standard evolved. The third part of this standard defines a suit of five programming languages:Instruction List (IL) is a low-level textual language with a structure similar to assembler. Originated in Europe IL is considered to be the PLC language in which all other IEC61 131-3 languages can be translated.Ladder Diagram (LO) is a graphical language that has its roots in the USA. LDs conform to a programming style borrowed from electronic and electrical circuits for implementing control logics.Structured Text (STJ is a very powerful high-level language. ST borrows its syntax from Pascal, augmenting it with some features from Ada. ST contains all the essential elements of a modem programming language.Function Block Diagram (FBD) is a graphical language and it is very common to the process industry. In this language controllers are modelled as signal and data flows through function blocks. FBD transforms textual programming into connecting function blocks and thus improves modularity and 47software reuse.Sequential Function Chart (SFC) is a graphical language. SFC elements are defined for structuring the organization of programmable controller programs.One problem with IEC 61 131-3 is that there is no standardized format for the project information in a PLC programming tool. At the moment there are only vendor specific formats. This is also one reason for the restriction of formalization approaches to single programs or algorithms. However, recently the PLC users’ organization PLCopen (see http://www.plcopen.org) started a Technical Committee to define an XML based format for projects according to IEC 61131-3. This new format will ease the access of formalization tools to all relevant information of a PLC project.Ⅲ. RE-ENGINEERING APPROACHThe presented approach towards re-engineering (cf. Fig.1) is based upon the conception that XML can be used as a medium in which PLC codes will be transformed.This transformation offers the advantage of obtaining avendor independent specification code. (Even if the PLCopen succeeds in defining a standardized format for PLC applications, there will remain a lot of existing programs that do not conform to this standard.) Based on this code a step-wise transformation to a formal model (automata) is planned. This model can then be used for analysis, simulation, formal verification and validation, and finally for the re-implementation of the optimized algorithm on the same or another PLC.Since re-engineering of complete programs will, in most cases, be only a semi-automatic process, intermediate visualization of the code is an important point. At different stages of the process different aspects of the code and/or formal model have to be visualized in a way that a designer can guide the further work. XML with its powerful visualization and transformation tools is an ideal tool for solving this task.IV. XML AS A TOOL FOR VISUALIZATIONXML (extensible Markup Language) is a simple and flexible meta-language, i.e， a language for describing other languages. Tailored by the World Wide Web Consortium (W3C) as a dialect of SGML [S], XML removes two constraints which were holding back Web developments [6]. The dependence on a single, inflexible document type (HTML) which was being much abused for tasks it was never designed for on one side; and the complexity of full SGML, whose syntax allows many powerful but hard-to-program options on the other side.While HTML describes how data should be presented, XML describes the data itself. A number of industries and scientific disciplines-medical records and newspaper publishing among them-are already using XML to exchange information across platforms and applications. XML can be tailored to describe virtually any kind of information in a form that the recipient of the information can use in a variety of ways. It is specifically designed to support information exchange between systems that use fundamentally different forms of data representation, as for example between CAD and scheduling applications.48Using XML with its powerful parsers and inherent robustness in terms of syntactic and semantic grammar is more advantageous than the conventional method of using a lexical analyzer and a validating parser (cf. Fig. 2, [7]).The conventional method of analysis of program code requires a scanner (lexical analyser) which generates a set of terminal symbols (tokens) followed by a parser thatchecks the grammatical structure of the code and generates an object net. In the object net the internal structure of the program is represented by identified objects and the relations between them. Both the scanner and the parser to be used in this method are document oriented which implies that analysis of different types of documents requires rewriting the generated code for the scanner and the parser. An example of an application of this method can be found in [8].The most promising aspect of using XML instead is that XML and its complementary applications for transformations are standardized so as to provide maximum flexibility to its user.The XML based method is advantageous, since the lexical specification is an invariant component of XML; therefore the well-formedness is independent from the respective individual application.Hence, an XML-Parser also can transfer well-shaped XML documents in an abstract representation called Document Object Model (DOM) without using a grammar. DOM is an application programming interface (APII) for valid HTML and well-formed XML documents. It defines the logical structure of documents and the way a document is accessed and manipulated. In the DOM specification, the term "document" is used in a broad sense increasingly. XML is used as a way of representing many different kind of information that may be stored in diverse systems, and much of this would traditionally be seen as data rather than as documents. Nevertheless, XML presents this data as documents, and the DOM can be used to manage this data［5］ .XSLT, the transformation language for XML is capable of trans