車床上料機械手結構設計

車床上料機械手結構設計,車床上料機械手結構設計,車床,機械手,結構設計 河南理工大學萬方科技學院 本科畢業(yè)設計（論文）中期檢查表 指導教師： 職稱： 副教授 所在院（系）： 教研室（研究室）： 機制教研室 題 目 車床上料機械手結構設計 學生姓名 專業(yè)班級 學號 一、選題質量：（主要從以下四個方面填寫：1、選題是否符合專業(yè)培養(yǎng)目標，能否體現(xiàn)綜合訓練要求；2、題目難易程度；3、題目工作量；4、題目與生產(chǎn)、科研、經(jīng)濟、社會、文化及實驗室建設等實際的結合程度） 所選題目符合專業(yè)培養(yǎng)目標，能夠體現(xiàn)綜合訓練要求；該題目略有難度，工作量比較大；題目與生活貼近，能夠解決一定的現(xiàn)實問題，該畢業(yè)設計不僅能加強專業(yè)知識和技能，同時更能夠為今后進入該行業(yè)做好準備，及時的發(fā)現(xiàn)不足，為今后的事業(yè)打下基礎，開發(fā)的成品網(wǎng)站也能夠為同學們今后溝通感情提供一個有效的平臺。 2、 開題報告完成情況： 1、在指導老師的建議下，查閱并翻閱了大量有關機械手的資料，了解了于此有關 的問題的最新資料，并將收集到的資料及相關信息整理備用； 2、初步完成定稿； 3、在實習中收集、分析原始資料，確定設計方案、確定結構； 4、合理設計了動力系統(tǒng)和控制單元系統(tǒng)； 5、完成PLC程序的設計。 三、階段性成果： 1、開題報告已經(jīng)完成，并已經(jīng)交給指導老師檢查且合格； 2、各個零部件的選擇已經(jīng)完成，零部件的選擇均是按照相關標準進行，現(xiàn)正在 對各零部件進行計算和校核； 3、圖紙繪制工作已經(jīng)接近尾聲，現(xiàn)正對圖紙進行檢查和修改以確保最終圖紙無誤。 四、存在主要問題： 1.某些觀點和見解尚未成熟，理論與研究方法存在一些問題，待進一步查閱相關資料； 2就問題有針對性地查閱相關資料，還需要進行修改完善； 3論證的邏輯不夠嚴密，沒有詳細實際的數(shù)據(jù)； 4文章的語言文字生澀，有一些錯別字，病句，格式不夠規(guī)范； 5圖紙繪畫的不標準，標注不夠清楚，對繪圖軟件不熟練。 五、指導教師對學生在畢業(yè)實習中，勞動、學習紀律及畢業(yè)設計（論文）進展等方面的評語： 指導教師： （簽名） 年 月 日 2 河南理工大學萬方科技學院機械設計制造及其自動化專業(yè)實習報告 河南理工大學萬方科技學院 畢業(yè)實習報告 專業(yè)：機械設計制造及其自動化 班級：姓名： 學號：指導老師： 目錄 一、實習目的及意義 二、實習任務 三、實習時間 四、實習地點 五、實習企業(yè)概況 六、實習內容 七、畢業(yè)設計準備 八、總結與評價 九、參考文獻 一、實習目的及意義 機械設計制造及其自動化專業(yè)是一門實踐性很強的專業(yè)，畢業(yè)實習是本科教學計劃中非常重要的一個教育環(huán)節(jié)，是學生在校學習期間理論聯(lián)系實際、增長實踐知識、培養(yǎng)自身各方面能力的重要手段和方法。通過實習了解本專業(yè)發(fā)展前沿，涉獵相關學科知識，使機械設計制造及其自動化專業(yè)的學生初步具有科學研究與解決工程實際問題的能力、較強的實踐動手能力和創(chuàng)新意識的高級應用型人才。畢業(yè)實習是大學本科專業(yè)學習中不可缺少的重要部分，通過一段時間的生產(chǎn)實習后，使自己具備足夠的技能，應付將來市場的挑戰(zhàn)并保持強勁的競爭力，并為下一步的畢業(yè)設計打下堅實的基礎。 二、實習任務 認真學習實習大綱，提高對實習的認識，做好思想準備；認真完成實習內容，按規(guī)定記實習筆記，撰寫實習報告，收集相關資料； 三、實習時間 2012年2月至2012年3月 四、實習地點 鄭州市紅星機械廠 五、實習企業(yè)概況 鄭州中原金山機械廠是專業(yè)的水磨石機、水磨石設備廠家，水磨石磚機等新型建材設備開發(fā)制造的專業(yè)生產(chǎn)廠家。 金山機械廠的產(chǎn)品設計充分吸收國內外先進技術水平，并考慮中國國情，將國外先進的制造工藝技術、質量控制技術和中國知名企業(yè)的嚴格管理制度相結合，關鍵的電控元器件和液壓、氣動部件采用國際知名品牌和優(yōu)質產(chǎn)品，以保證向客戶提供質量優(yōu)良、運行可靠的設備，保證客戶以最小的投資獲取最大的利益。金山機械廠作為水磨石機的專業(yè)生產(chǎn)廠家，已建立起金山特色的科研、生產(chǎn)、銷售、服務體系，彩瓦機、彩磚機、磨石磨磚機、藝術圍欄機、石材設備系列產(chǎn)品，用戶遍布全國，出口國外許多國家。理念：誠信、優(yōu)質、創(chuàng)新誠信：對員工真誠，對客戶真誠，重合同、守信譽。優(yōu)質：擁有優(yōu)質的員工，向社會提供優(yōu)質的產(chǎn)品、技術、服務，向職工提供優(yōu)質的工作環(huán)境和福利待遇。創(chuàng)新：追求技術不斷進步，產(chǎn)品的不斷更新，服務的不斷完善。理念：誠信、優(yōu)質、創(chuàng)新...... 六、實習內容 （一）實習的具體內容 我是2012年2月來到河南省鄭州市中原金山機械廠的，接待我們的是人事部的孫經(jīng)理，初次見面，就感覺孫經(jīng)理是位很和藹、很親切的領導。而在接下來的日子里的接觸也證實了這點。我們被安排在動力部實習，動力部主要是負責機械維護及其機械維修方面的工作。我們也主要是學習這些方面的知識和相關的工作經(jīng)驗。剛來的時候，我們畢竟沒有什么經(jīng)驗，只能跟著師傅學習，在對公司機器修理及維護過程中，自己認真觀察各種機器，最直接的就是工藝。對我們即將畢業(yè)的人來說，這方面還是很好辦的。后面，由于對機器有了了解，我能對產(chǎn)品加工中特定的工藝動作怎么實現(xiàn)的進行思考。這樣能加速學習理解和知識的積累。因為我們要常進車間去，所以多車間的生產(chǎn)狀況也都有一個大概的了解。金山主要是水磨石機器,水泥瓦機，水磨石磚機,水磨石設備,水磨石機，這其中給我印象最深刻的是成品車間，主要是因為這個車間的設備最容易出現(xiàn)故障，可能是因為它里面的設備比較陳舊吧。當然其他車間有些東西也是要時常要更換的。 這是第一次正式與社會接軌踏上工作崗位，開始與以往完全不一樣的生活。每天在規(guī)定的時間上下班，上班期間要認真準時地完成自己的工作任務，草率敷衍了事。凡事得謹慎小心，否則隨時可能要為一個小小的錯誤承擔嚴重的后果付出巨大的代價，再也不是一句對不起和一紙道歉書所能解決。 　工作中我發(fā)現(xiàn)做任何事不能單蠻干，應合理應用各種常識來解決問題，同時也要注意團隊合作。任何一個廠都有一套嚴格緊密的生產(chǎn)體系，在體系中每個環(huán)節(jié)都是緊緊相扣，每個環(huán)節(jié)的工作人員都應該嚴格遵守規(guī)章制度。年輕不是用來揮霍的，而是我們拼搏的資本。我不想碌碌無為終了此生。我想有個幸福的家庭和人生。所以我會一直朝著我的目標走去。保持一顆樂觀豁達，積極進取的心，對生活充滿希望，相信“蒼天不負有心人”。 （二）實習中資料的收集與總結 1 鑄造 按曲軸鑄造工藝進行 2 熱處理 正火 3 銑兩端面 總長為265mm 銑床 4 車兩端工藝搭子外圓 直徑φ45mm 車床 5 鉆主軸頸中心孔 車床 6 鉆連桿軸頸中心孔 正對連桿中心 7 檢驗 8 粗車三個連桿軸頸 留余量2.6mm 車床 七、畢業(yè)設計準備 一、機械手的工作原理 （一）機械手的概述 機械手是在機械化、自動化生產(chǎn)過程中發(fā)展起來的一種新型裝置。近年來，隨著電子技術特別是電子計算機的廣泛應用，機器人的研制和生產(chǎn)已成為高技術領域內迅速發(fā)展起來的一門新興技術，它更加促進了機械手的發(fā)展，使得機械手能更好地實現(xiàn)與機械化和自動化的有機結合。 機械手雖然目前還不如人手那樣靈活，但它具有能不斷重復工作和勞動、不知疲勞、不怕危險、抓舉重物的力量比人手大等特點，因此，機械手已受到許多部門的重視，并越來越廣泛地得到了應用，例如： （1）機床加工工件的裝卸，特別是在自動化車床、組合機床上使用較為普遍。 （2）在裝配作業(yè)中應用廣泛，在電子行業(yè)中它可以用來裝配印制電路板，在機械行業(yè)中它可以用來組裝零部件。 （3）可在勞動條件差，單調重復易子疲勞的工作環(huán)境工作，以代替人的勞動。 （4）在危險場合下工作，如軍工品的裝卸、危險品及有害物的搬運等。 （5）宇宙及海洋的開發(fā)。 （6）軍事工程及生物醫(yī)學方面的研究和試驗。 （二）機械手的工作方式 機械手電氣控制系統(tǒng)，除了有多工步特點之外，還要求有連續(xù)控制和手動控制等操作方式。工作方式的選擇可以很方便地在操作面板上表示出來。當旋鈕打向回原點時，系統(tǒng)自動地回到左上角位置待命。當旋鈕打向自動時，系統(tǒng)自動完成各工步操作，且循環(huán)動作。當旋鈕打向手動時，每一工步都要按下該工步按鈕才能實現(xiàn)。以下是設計該機械手控制程序的步驟和方法。 1、機械手傳送工件系統(tǒng)示意圖，如圖1所示。 圖1 機械手傳送示意及操作面控制器 如圖1所示機械手能實現(xiàn)手動、回復位、單步、單周期和連續(xù)等五種工作方式。手動工作方式時，用各按鈕的點動實現(xiàn)相應的動作；回復位工作方式時，按下“回復位”按鈕，則機械手自動返回原位；單步工作方式時，每按一次起動按鈕機械手向前執(zhí)行一步；選擇單周期工作方式時，每按一次起動按鈕，機械手只運行一個周期就停下；連續(xù)工作方式時，機械手向前執(zhí)行一步；只要按下起動按鈕，機械手就會連續(xù)循環(huán)動作，直到按下停止按鈕，機械手才會最后運行到原位并停下；而在傳送工件的過程中，機械手必須升到最高位置才能左右移動，以防止機械手在較低位置運行時碰到其它工件。 圖2 機械手傳送示意及操作動作傳送圖 圖3 機械手傳送示意及操作動作執(zhí)行圖 如圖2，3、其功能是將工件從A移送到B處。氣動機械手的升降和左右移動分別使用了雙線圈的電磁閥，在某方向的驅動線圈失電時能保持在原位，必須驅動反方向的線圈才能反向運動。上升、下降對應的電磁閥線圈分別是YV2、YV1，右行、左行對應的電磁閥線圈分別是YV3、YV4。機械手的夾鉗使用單線圈電磁閥YV5，線圈通電時夾緊工件，斷電時松開工件。通過設置限位開關SQ1、SQ2、SQ3、SQ4分別對機械手的下降、上升、右行、左行進行限位，而夾鉗不帶限位開關，它是通過延時1.7s來表示夾緊、松開動作的完成的。 二、機械手控制的硬件設計 （一）輸入和輸出點分配表及原理接線圖 表1 機械手傳送系統(tǒng)輸入和輸出點分配表 名 稱 代號 輸入 名 稱 代號 輸入 名 稱 代號 輸出 啟動 SB1 X0 夾緊 SB5 X10 電磁閥下降 YV1 Y0 下限行程 SQ1 X1 放松 SB6 X11 電磁閥夾緊 YV2 Y1 上限行程 SQ2 X2 單步上升 SB7 X12 電磁閥上升 YV3 Y2 右限行程 SQ3 X3 單步下降 SB8 X13 電磁閥右行 YV4 Y3 左限行程 SQ4 X4 單步左移 SB9 X14 電磁閥左行 YV5 Y4 停止 SB2 X5 單步右移 SB10 X15 原點指示 EL Y5 手動操作 SB3 X6 回原點 SB11 X16 連續(xù)操作 SB4 X7 工件檢測 SQ5 X17 表1 機械手傳送系統(tǒng)輸入和輸出點分配表 圖3、機械手硬件控制連線圖 （二）控制程序 操作系統(tǒng) 操作系統(tǒng)包括回原點程序，手動單步操作程序和自動連續(xù)操作程序，如圖3所示。 圖4、機械手操作系統(tǒng)程序 其原理是： 把旋鈕置于回原點，X16接通，系統(tǒng)自動回原點，Y5驅動指示燈亮。再把旋鈕置于手動，則X6接通，其常閉觸頭打開，程序不跳轉（CJ為一跳轉指令，如果CJ驅動，則跳到指針P所指P0處），執(zhí)行手動程序。之后，由于X7常閉觸點，當執(zhí)行CJ指令時，跳轉到P1所指的結束位置。如果旋鈕置于自動位置，（既X6常閉閉合、X7常閉打開）則程序執(zhí)行時跳過手動程序，直接執(zhí)行自動程序。 回原位程序 回原位程序如圖4所示。用S10~S12作回零操作元件。應注意，當用S10~S19作回零操作時，在最后狀態(tài)中在自我復位前應使特殊繼電器M8043置1。 圖5、回原位狀態(tài)轉移圖 手動單步操作程序 如圖5所示。圖中上升/下降，左移/右移都有聯(lián)鎖和限位保護。 圖6、手動單步操作程序 自動操作程序 自動操作狀態(tài)轉移見圖6所示。當機械手處于原位時，按啟動X0接通，狀態(tài)轉移到S20， 圖7、自動操作狀態(tài)轉移圖 驅動下降Y0，當?shù)竭_下限位使行程開關X1接通，狀態(tài)轉移到S21，而S20自動復位。S21驅動Y1置位，延時1秒，以使電磁力達到最大夾緊力。當T0接通，狀態(tài)轉移到S22，驅動Y2上升，當上升到達最高位，X2接通，狀態(tài)轉移到S23。S23驅動Y3右移。 移到最右位，X3接通，狀態(tài)轉移到S24下降。下降到最低位，X1接通，電磁鐵放松。為了使電磁力完全失掉，延時1秒。延時時間到，T1接通，狀態(tài)轉移到 S26上升。上升到最高位，X2接通，狀態(tài)轉移到S27左移。左移到最左位，使X4接通，返回初始狀態(tài)，再開始第二次循環(huán)動作。 在編寫狀態(tài)轉移圖時注意各狀態(tài)元件只能使用一次，但它驅動的線圈，卻可以使用多次，但兩者不能出現(xiàn)在連續(xù)位置上。因此步進順控的編程，比起用基本指令編程較為容易，可讀性較強。 7、機械手傳送系統(tǒng)梯形圖 如圖7所示。圖中從第0行到第27行為回原位狀態(tài)程序。從第28行到第66行，為手動單步操作程序。從第67行到第129行為自動操作程序。這三部分程序（又稱為模塊）是圖3的操作系統(tǒng)運行的。 回原位程序和自動操作程序。是用步進順控方式編程。在各步進順控末行，都以RET結束本步進順控程序塊。但兩者又有不同?；卦怀绦虿荒茏詣臃祷爻跏紤B(tài)S1。而自動操作程序能自動返回初態(tài)S2。 三、梯形圖及指令表 （一） 梯形圖 上升 右移 上限位 夾緊 下限位 下降 狀態(tài)轉移開始 自動方式初始狀態(tài) 上限位 下降結束 上升 放松 下限位 下降 右移限位 夾緊 下降限位 下降 左行限位 左行 松開 夾緊 上升1/2限位 右移限位 下降 右移 翻轉 上升 回原位初始狀態(tài) 圖8、機械手傳送系統(tǒng)梯形圖 （二）指令表 八、總結與評價 機械手的控制對于很多場合需求很大，不論是機床使用的小型系統(tǒng)還是流水線上的這類設備，其基本動作要求類似，所以控制的實現(xiàn)也可以相互借鑒。 對于控制程序的編寫，這里給出的只是一種實現(xiàn)手段，使用可編程控制器還有其他的方法可以實現(xiàn)這樣的控制，針對所用的具體系統(tǒng)的情況，設計人員可以選用不同的方法來編寫程序。 機械手高效的工作效率，準確的定位精度，以及簡單的結構及控制方式是人手不能替代的，機械手的使用也將越來越廣泛。 九、參考文獻 [1] 鄔依林等：非接觸式IC卡在酒店收費系統(tǒng)中的應用[J]，佛山科學技術學院學報(自然科學版)，2002. [2] 金偉正等：基于非接觸式IC卡、考勤機的研究[J]，武漢工業(yè)學院學報，2001。 [3] 馬秀麗等：一種非接觸式射頻卡、基站讀寫電路的設計與應用[J]，金卡工程，2003。 [4] 鄔依林等：基于非接觸式IC卡收費機的設計[J]。廣東教育學院學報，2OO4。 [5].何立民：單片機應用系統(tǒng)設計，北京，北京航空航天大學出版社,1995。 [6] 周航慈：單片機程序設計技術，北京，北京航空航天大學出版社.1992。 [7] 沈宇超等：射頻識別技術及其發(fā)展現(xiàn)狀，電子技術應用，1999。 [8] 汪建主編：MCS一96系列單片機原理及應用技術[M]，武漢：華中科技大學出版社(第2版)，2004。 [9] 沈宇超等：射頻識別技術及其發(fā)展現(xiàn)狀[J]，電子技術應用，1999。 [10] 李琚門：感應式IC卡系統(tǒng)及其應用[J]，電子產(chǎn)品世界，2000。 17 河南理工大學萬方科技學院本科畢業(yè)論文 摘　　要 本課題是為普通車床配套而設計的上料機械手。工業(yè)機械手是工業(yè)生產(chǎn)的必然產(chǎn)物，它是一種模仿人體上肢的部分功能，按照預定要求輸送工件或握持工具進行操作的自動化技術設備，對現(xiàn)實工業(yè)生產(chǎn)自動化，推動工業(yè)生產(chǎn)的進一步發(fā)展起著重要的作用。因而具有強大的生命力受到人們的廣泛重視和歡迎。實踐證明，工業(yè)機械手可以代替人手的繁重勞動，顯著減輕了工人的勞動強度，改善勞動條件，提高勞動生產(chǎn)率和自動化水平。工業(yè)生產(chǎn)中經(jīng)常出現(xiàn)的笨重工件的搬運和長期頻率、單調的操作，采用機械手是有效的。此外，它能在高溫、低溫、深水、宇宙、放射性和其他有毒、污染環(huán)境條件下進行操作，更現(xiàn)實其優(yōu)越性，有著廣泛的發(fā)展前途。 本課題通過應用autoCAD技術對機械手進行總體方案設計和液壓傳動原理設計，確定了機械手的坐標形式和自由度，確定了機械手的技術參數(shù)。同時，設計了機械手的夾持手部結構，設計了機械手的手腕結構，設計了機械手的手臂結構。他能實際自動上料運動，上料機械手的運動速度是按著滿足生產(chǎn)率的要求來設定。 關鍵詞：機械手；手部設計；結構設計； Abstract This topic is designed for ordinary lathe supporting the feeding manipulator. Industrial manipulator is the inevitable outcome of the industrial production, it is a kind of imitation upper part of the body, according to the predetermined requirement function of conveying work-piece or operated holding tools to reality technical equipment, automation, promote industrial production automation of the further development of industrial production plays an important role. Thus has strong vitality wide attention by the people and welcome. Practice has proved, industrial robots can replace the hands of heavy labor, significantly reduce the labor intensity of the workers, improve working conditions, and improve labor productivity and automation level. Industrial production in the bulky workpiece often appear handling and long-term frequency, drab operation, using manipulator is effective. In addition, it can be in high temperature, low temperature and deep water, the universe, radioactive and other toxic, environmental pollution condition of operation, the more realistic its superiority, has wide development prospect This topic through the application of manipulator in overall autoCAD technology design and hydraulic transmission principle design of manipulator, sure, and freedom coordinates determined the technical parameters of manipulator. Meanwhile, the design of clamping manipulator hand structure, design of manipulator wrist structure, design of manipulator arm structure. He can actual automatic feeding movement of the manipulator, feeding velocity according to satisfy the requirement is set to productivity. KeyWords：manipulator；handing structure ；structure design II 河南理工大學萬方科技學院本科畢業(yè)論文 外文資料與中文翻譯 外文資料： Visualization of PLC Programs using XML M. Bani Younis and G. Frey Juniorprofessorship Agentenbased Automation University of Kaiserslautem P. 0. Box 3049, D-67653 Kaiserslautem, Germany Abstract - 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. INTRODUCTION Programmable 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. With 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 environments Visualization 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 61131 Since 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 software 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 APPROACH The 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 VISUALIZATION XML (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. Using 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 transforming XML not only to another XML or HTML but to many other user-friendly formats. Before the advent of XSLT, the transformation of XML to any other format was only possible through custom applications developed in a procedural language such as C++, Visual Basic or, Java. This procedure lacked the generality with respect to the structural variation of XML documents. Capitalizing on the concept that the custom applications for the transformations are all very similar, XSLT evolved as a high-level declarative language [9]. XSLT functions in two steps. In the first step, it performs a structural transformation so as to convert the XML into a structure that reflects the desired output. The second stage is formatting the new structure into the required format, such as HTML or PDF (cf. Fig. 3 ). The most important advantage of this transformation is that it allows a simple and easily-conceivable representation of the document or data structure embedded inside the well-structured but hard-to-understand XML to be produced. When HTML is chosen as the format of the transformed produce it is possible to use the extensive ability of HTML to produce an easily-conceivable and attractive visualization of a program. Every XML document has its own syntax and vocabulary. Therefore, in addition to being well-formed, the XML document needs to conform to a set of rules. According to W3C recommendations this set of rules has to be defined either through a Document Type Definition (DTD) or an XML Schema. The rules defined in a DTD or an XML Schema state the hierarchical and structural constraints of the XML document. The DTD is for defining the document grammars; more recently a number of alternative languages have been proposed. The W3C XML Schema language replicates the essential functionality of DTDs, and adds a number of features: the use of XML instance syntax rather than an ad hoc notation, clear relationships between schemas and namespaces, a systematic distinction between element types and data types, and a single-inheritance form of type derivation. In other words schemas offer a richer and more powerful way of describing information than what is possible with DTDs. Fig. 4 shows the XML technologies discussed above and the connection between them. V. AN APPROACH FOR THE VISUALIZATION OFPLC PROGRAMS A. Overview Since Instruction List (IL) is the most commonly used PLC language in Europe, the presented approach is based on this language. The proprietary IL dialect Siemens STEP 5 and the standardized version according to IEC 61131-3 are considered. The generation of XML documents showing different aspects of a PLC program is realized in the following three steps (cf. Fig. 5): 1. Transformation of the PLC program to an XML document 2.Validation of the XML against the XML Schema which sets the syntax of the XML 3.Identification of the Instruction elements of the transformed XML according to the instruction set of the source PLC These three steps are discussed in sub-sections B to D respectively. Sub-section E explains the visualization of the different XMLs obtained during the preceding steps. Throughout this Section an example is used to illustrate the presented concepts. Fig. 6 shows a PLC code written in Instruction List Siemens S5. The PLC code is written in atabular form where each row element is either a delimited list consisting of address, label, instruction, operand and description or a comment. Kommentar : Autor Erstellt :15.07.2003 Geaendert am: B1B:O NETZWERK 1 EMPFANGEN SLAVE 3 VON MASTER NAME :EMPE'MAST 0005 :U M98.7 ABFRAGE OB EMPFANG MOEGLICH 0006 0007 :SPB= MOOl 0008 0009 :A DB140 EMPFANGSFACH IST DB 140 OOOA :L KF+20 LAENGE DES DATENPAKETS oooc :T DLO OOOD :L KF+O ZIELNUMMER O=MASTER OOOF :T DRO 0010 0011 :UNM98.7 FANGEN WIEDER ERLAUBEN 0012 :S M98.7 0013 MOOl :NOP 0 0014 0015 :BE BAUSTEIN ENDE Fig. 6 A PLC program written in Siemens S5 Instruction List B. Conversion of a PLC Program inio a well-formed XML Given a PLC program in ASCII format and in a tabular structure with separate columns for addresses, labels, instructions, operands and descriptions delimited by whitespaces, XSLT can convert it into a well-formed XML document. The XML document obtained through this transformation is a hierarchically structured document. Fig. 7 shows the XML document obtained through the transformation of the PLC code of Fig. 6. The XML document is structured in a hierarchy in which the root element is the IL Code Block representing the whole PLC code. Each of the rows of the PLC code is contained within a corresponding ILRow element which is M e r smtctured into child elements. Note: The structure chosen for the XML representation of IL-Code is oriented at the working proposal of the PLCopen. C. XML Validation against the XML Schema The XML obtained as a result of the previous processing can be validated using a validating parser that confirms that the XML document in addition to being well-formed conforms to the set of syntactic rules defined in context of the PLC programming language. D. rdenhpcation of instructions This step in the process of visualization of PLC programs using XML ensures that the XML document to be used for visualization contains only valid instructions.XSLT can be used to transform the well-formed and valid Xh4L to another XML which as a result of identification on instructions has an additional attribute appended to the instruction tags. This attribute notifies whether the instruction is a valid instruction of the concerned instruction set. This transformation procedure is also capable of attaching attributes to the instruction tags that declares a classification of the instructions into predefined classes. The instruction identification of the transformed XML proofs the semantic of the XML in accordance with the operation types of the PLC programming language. In the example of this section, (cf. Fig. 8), the new XML contains additional attributes which classify the instructions according to the type of operation it represents. The STEPS instructions are categorized into eleven different types of operations e.g. logical, jump, load or transfer operation assignment, etc. (Instruction instructionId='Logical Operation") U -. SPB- BE Fig. 8 A new transformed XML showing only the inslructions and the corresponding instruction ID E. Visualization of XML Both of the XML documents generated above can be transformed into HTML or other readable documents with the help of XSL. An ingenious XSL can be designed so as to produce an HTML which can convey the logical and other features of the PLC program in an easily conceivable form. Moreover, the DOM structure embedded in the XML (cf. Fig. 9), also enables the user to navigate through the PLC programs in an easy way. For the example the visualization is done in HTML. This visualization is done for the transformed XML after the validation of it's syntax as a table where the child elements of the ILRow are the columns of this table. The XML after the instruction identification is transformed using the XSL, where the instruction and the instruction Id, obtained after extracting the XML according to the type of operations are visualized in a table containing two columns (Instruction, Instruction Id) in HTML. The HTML structures suggested here are not the only possibilities, with which the XML can be visualized, but they give a very easy practical option for the user's grasp of the PLC code. Fig. IO shows the same PLC code as shown in Fig. 4 as a HTML document converted &om the XML document shown in Fig. 7 using XSL. This visualization enables a better understanding of the PLC program. Fig. 11 shows the special visualization of instruction ids given in the XML of Fig. 6. VI. CONCLUSIONS AND OUTLOOK Re-engineering of PLC programs needs a formal approach to be developed. In this paper one way to solve this task is introduced. Based on a given PLC program written in Instruction List a step-wise transformation to a formal representation is proposed. Since this process will not be fully automatic, the need for flexible visualization of intermediate steps is derived. XML is presented as a flexible, standardized means to serve as data format for the description of the PLC code. The corresponding technology of XSL transformations and the Document Object Model are presented as tools for the variety of customized visualization tasks during the