62全自动立式过滤机的设计
62全自动立式过滤机的设计,62,全自动,立式,过滤机,设计
湘潭大学兴湘学院毕业论文(设计)任务书论文(设计)题目: 全自动立式过滤机的设计 学号: 2006183922 姓名: 严 浩 专业: 机械设计制造及其自动化 指导教师: 文美纯 系主任: 周友行 一、主要内容及基本要求 1、了解全自动过滤机的工作原理及流程; 2、设计过滤机的内部零件,用 CAD 绘图装配图、工艺流程图 A0 两张,零件图滤盘、大皮带轮、小皮带轮、空心轴 A1 一张、 A2 三张; 3、PLC 控制系统的设计,及其编程、语句表; 4、设计说明书 8000 字以上,内容完整,计算准确; 5、外文翻译 7000 字以上; 二、重点研究的问题全自动立式过滤机的结构设计及其控制系统; 三、技术指标主要技术参数:过滤面积 10 平方米 工作压力 1.6Mpa 工作温度-5 105 电机功率 5.5KW 四、进度安排序号 各阶段完成的内容 完成时间1 查阅资料、调研 1 周2 开题报告、制定设计方案 2 周3 设计计算 35 周4 PLC 编程 68 周5 CAD 画图 912 周6 整理说明书、外文翻译 1314 周7 修改图纸和说明书 15 周8 打印图纸、毕业设计答辩五、应收集的资料及主要参考文献1文美纯,刘吉普 对全自动过滤机的探讨; 过滤与分离1997.第三期2文美纯,刘吉普,可编程序控制器在过滤器上的应用研究;过滤与分离2002.VOl12.NO43文美纯,刘吉普 新型管道过滤器的开发研究 ;过滤与分离1996.第三期4丁启圣、王惟一等.新型实用过滤技术M .北京:冶金工业出版社. 2000.1;5文棋.全自动自清洗过滤机过滤机理分析及控制系统研究. J浙江:大学硕士学位论文.2002.6;6管力明.PLC 在硅藻土过滤机上的应用J .机电工程 2004 年第 21 卷第七期.2004.7;7华东工业大学、浙江大学合编.化工容器设计M .武汉:湖北科学技术出版社.1985.6;8濮良贵、纪名刚主编.机械设计(第 8 版).M.北京:高等教育出版社.2006.5;9成大先.机械设计手册M第四版.北京:化学工业出版社.2002.8;0目录第一章、设计题目 (1)第二章、设计意义 (3)第三章、方案选择 (6)第四章、过滤部分的设计 (7)4.1过滤桶的设计 (7)4.2传 动部件设计 (12)4.3电动机的选择 (18)4.4阀门的选择与设计 (19)4. 5传感器的选择与信号检测 (22)4.6控制面板的设计 (23)第五章、控制部分的设计 (24)5.1 控制系统的选择 (24)5.2 工艺流程 (26)5.3 PLC接线图 (27)5.4程序梯形图以及语句表 (28)第六章、设计的应用 (33)第七章、设计心得 (35)第八章、参考文献 (36)附录:外文翻译及文献1一、设计题目题目:全自动立式过滤机的设计关键词:过滤机;结构;控制系统;可编程序控制器;摘要:随着水资源的缺乏和水污染的日益严重,废水的过滤与分离能很好的解决废水的处理与重复利用的问题,实现良好的经济效益和社会效益。但传统的过滤分离设备占地空间大,连续生产能力低,自动化程度不高,造成人力物力财力的浪费。本文以自行开发 50m3/h处理量全自动白清洗过滤器为基础,提出了全自动自清洗过滤器的各操作参数的设计思想和方法,并建立了过滤过程中过滤器的模型,借此确定控制系统的控制参数。主要工作内容如下;研制设计了一台处理量为50m3/ h、工作压力为 1.6-2.5 Mpa,要求过滤精度为 0.1-200m,过滤总面积为 10,电动机功率为 5.5KW,工作温度为-5-105的全自动自清洗过滤器。该过滤器在运行过程中无须停运以清洗过滤元件,整机体积较小,精度可调节,适合于各类工业生产。本文给出了这种过滤器的整体设计方法以及设计图纸,并对过滤器内部过滤机理进行分析,讨论了几个过滤参数,并应用于过滤器控制系统设计之中。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(0.1-200m), 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、设计意义过滤机是利用多孔性过滤介质,截留液体与固体颗粒混合物中的固体颗粒,而实现固、液分离的设备。过滤机广泛应用于化工、石油、制药、轻工、食品、选矿、煤炭和水处理等部门。 中国古代即已应用过滤技术于生产,公元前二百年已有植物纤维制作的纸。公元 105年,蔡伦改进了造纸法,他在造纸过程中将植物纤维纸浆荡于致密的细竹帘上,水经竹帘缝隙滤过,一薄层湿纸浆留于竹帘面上,干后即成纸张。 最早的过滤大多为重力过滤,后来采用加压过滤提高了过滤速度,进而又出现了真空过滤。20 世纪初发明的转鼓真空过滤机实现了过滤操作的连续化。此后,各种类型的连续过滤机相继出现。间歇操作的过滤机因能实现自动化操作而得到发展,过滤面积越来越大。为得到含湿量低的滤渣,机械压榨的过滤机得到了发展。 用过滤介质把容器分隔为上、下腔,即构成简单的过滤器。悬浮液加入上腔,在压力作用下通过过滤介质进入下腔成为滤液,固体颗粒被截留在过滤介质表面形成滤渣(或称滤饼 )。 过滤过程中过滤介质表面积存的滤渣层逐渐加厚,液体通过滤渣层的阻力随之增高,过滤速度减小。当滤室充满滤渣或过滤速度太小时,停止过滤,清除滤渣,使过滤介质再生,以完成一次过滤循环。 液体通过滤渣层和过滤介质必须克服阻力,因此在过滤介质的两侧必须有压力差,这是实现过滤的推动力。增大压力差可以加速过滤,但受压后变形的颗粒在大压力差时易堵塞过滤介质孔隙,过滤反而减慢。 悬浮液过滤有滤渣层过滤、深层过滤和筛滤三种方式。滤渣层过滤是指在经过过滤初期后,形成了初始滤渣层,此后,滤渣层对过滤起主要作用,这时大、小颗粒均被截留;深层过滤是指过滤介质较厚,悬浮液中含固体颗粒较少,且颗粒小于过滤介质的孔道,过滤时,颗粒进入后被吸附在孔道内的过滤;筛滤是过滤截留的固体颗粒都大于过滤介质的孔隙,过滤介质内部不吸附固体颗粒的过滤方式,例如转筒式过滤筛滤去污水中的粗粒杂质。 在实际的过滤过程中,三种方式常常是同时或相继出现。过滤机的处理能力取决于过滤速度。悬浮液中的固体颗粒大、粒度均匀时,过滤的滤渣层孔隙较为畅通,滤液通过滤渣层的速度较大。应用凝聚剂将微细的颗粒集合成较大的团块,有利于提高过滤速度。 对于固体颗粒沉降速度快的悬浮液,应用在过滤介质上部加料的过滤机,使过滤方向与重力方向一致,粗颗粒首先沉降,可减少过滤介质和滤渣层的堵塞;在难过滤3的悬浮液(如胶体) 中混入如硅藻土、膨胀珍珠岩等较粗的固体颗粒,可使滤渣层变得疏松;滤液粘度较大时,可加热悬浮液以降低粘度。这些措施都能加快过滤速度。 过滤机按获得过滤推动力的方法不同,分为重力过滤器、真空过滤机和加压过滤机三类。重力过滤器是借助悬浮液的重力和位差,在过滤介质上形成的压力作为过滤的推动力,一般为间歇操作。 真空过滤器是在滤液出口处形成负压作为过滤的推动力。这种过滤机又分为间歇操作和连续操作两种。间歇操作的真空过滤机可过滤各种浓度的悬浮液,连续操作的真空过滤机适于过滤含固体颗粒较多的稠厚悬浮液。 加压过滤器以在悬浮液进口处施加的压力,或对湿物料施加的机械压榨力作为过滤推动力,适用于要求过滤压差较大的悬浮液,也分为间歇操作和连续操作两种。 过滤机应根据悬浮液的浓度、固体粒度、液体粘度和对过滤质量的要求选用。先选择几种过滤介质,利用过滤漏斗实验,测定不同过滤介质和不同压差下的过滤速度、滤液的固体含量、滤渣层的厚度和含湿量,找出适宜的过滤条件,初步选定过滤机类型,再根据处理量选定过滤面积,并经实际试验验证。 正在发展的新型过滤设备有:机械力压榨过滤设备;能实现无滤渣层过滤的动态过滤机;洗选煤炭污水处理、化工和石油工业用的大型过滤设备。 在过滤理论研究方面,滤渣层过滤阻力和孔隙率的测算、过滤速度、过滤设备的模拟和放大、稀薄液体澄清过滤和动态过滤机理,以及过滤介质的研究,都是重要的课题。利用电子计算机控制过滤操作是过滤设备的发展方向。4三、方案选择循环方案:管道系统如下图:图 3-1F1清洗水入口阀 F2待滤液入口阀 F3循环液入口阀F4循环液出口阀 F5流向控制阀 F6冲洗阀 F7排气阀 F8排渣阀F9成品出口阀 F10余液出口阀 F11取样阀S1循环视筒 S2正常工作视筒5此过滤过程有四个过滤阶段,预过滤过程,过滤过程,滤余液过程,反冲洗过程。预过滤过程:待滤液由 F2 进入泵内,经 F3(此时 F1、F5 关闭)进入循环视筒,然后从 F4 进入过滤桶进行过滤,此时 F9 关闭,过滤液经 F5 再次进入循环桶。过滤过程:待滤液由 F2 进入泵内,经 F3(此时 F1、F5 关闭)进入循环视筒,然后从 F4 进入过滤桶进行过滤(期间可以通过 S1 观察过滤循环过程)滤液由 F7 再次进入循环桶,直至完全过滤通过 S2 经 F9 流出(可以从 F11 中取样检验,从而调整滤网密度) 。滤余液过程:收到“ 管高压差 ”信号后,开始反冲洗过程前的约 1Min 内,打开 F10将管道内的余液滤出以方便反冲洗,防止堵塞反冲洗管道。反冲洗过程:当“ 管高压差 ”达到预定压力值或者达到预定时间后, F2、F3 关闭,将 F1 打开,清洗水从 F1、F7 进入过滤桶中进行清洗,洗出的滤渣从 F8 中排出。双管道一次过滤方案:管道系统如下:图 3-2过滤:阀 1、阀 4 开启,阀 2、阀 3 关闭;反冲洗:阀 2、阀 3 开启,阀 1、阀 4 关闭6过滤过程:过滤液由泵泵入,经过阀 1 后进入过滤桶过滤,滤后液经过视筒后从阀 4 排出(阀 2、阀 3 处于关闭状态) ;反冲洗过程:清洗水由泵泵入,经过阀 2 以及视筒后,对过滤桶进行反冲洗,滤渣由阀 3 处排出(阀 1、阀 4 处于关闭状态) 。方案比较:方案 1 原理教简单,管道系统相对较为复杂,但是过滤精度较高,可靠性较强,由于采用循环过滤且用闭环控制,待网内外压差值满足排放条件时,指挥排污阀进行排污,使过滤精度得以提高;并且采用先进的控制方式和优质的信号转换器从而具有性能稳定,维护管理方便,日常维护少,只须做定期维护即可等特点,具有明显的实用价值、经济价值和推广价值。方案 2 原理简单,过滤和反冲洗装置简单,但是由于过滤和反冲洗管道共用较多且没有排除管道余液的设计,故过滤精度难以保证,维护较多以及容易发生堵塞等情况。综上所述,最终方案选取为方案 1 为基本方案。7四、过滤部分的设计过滤桶的设计 过滤盘的设计过滤精度为 0.5-100m,故滤网采用涤纶布料可以达到要求而且表面光滑,再在上涂上一层硅藻土增加过滤流量,水面上部采用气压,压强大小为 1.6MPa,最大可达到 2.5MPa,可以使过滤更加快捷。滤后液通过下部孔流出,从取样阀中取样调节流速从而保证过滤精度,达到保准后,打开 F10,完成过滤。另外该系统在-5 105的范围内工作。已知条件:过滤面积:10;正常工作压力 1.6MPa、最大工作压力 2.5MPa。.选定过滤介质的半径(R) ,厚度(H) ,片间间隙( h)以及片数(N)分别为:R=0.4m、H=0.03m h=0.02m, 每一片的过滤面积为:S=*R*R=3.14*0.4*0.4=0.502。N=10/S=10/0.502=19.9所以片数需要 20 片才能满足过滤需要,也因此过滤滤芯长度(过滤部分)应等于20*(H+h )+ 顶部密封片厚度+顶部螺母厚度=20*0.05+0.02*2+0.02=1.06m.过滤片零件图8图 4-1 计算内压圆筒壳体的壁厚已知 Pg=1.6MPa由壁厚计算公式:cticPDP2/*- 计算厚度 ;mmP - 计算压力;Mpac- 焊接接头系数;- 材料的许用应力;t在已知设计温度下 16MnR 的许用应力,在厚度为 616mm 时, =170Mpa;t在厚度为 1636mm 时, =163Mpa;t焊接接头系数 ;85.0设定 圆筒内径 D =1000mm; 腐蚀裕量 C =2mm;i 2设计厚度; 材料的许用应力 =170Mpa (厚度为 616 时) ,筒体厚度计算;t=1.6*1000/(2*170*0.85-1.6)=5.5mm;cticPP2/*=5.5+2=7.5mm;dC由钢材标准规格,圆整可得壁厚为 10; 圆筒的半径由滤饼半径确定取 R=500mm; 圆筒中固定空心轴一端的顶尖高度为 150mm;顶尖的直径 =50mm; 锥角 =50H =H +h1=1100+150=1250mm;总 1 圆筒边缘设计,边缘厚度 =20mm;B=35mm;凸缘高度 H=10mm;9 固定顶尖板的厚度 =10mm;长度 L=120mm;宽度 B=120mm; 但容器制成后必须经过压力试验合格后才能交付,压力的目的主要是检查加工制造工艺的问题和焊缝的强度,以及各连接面的紧密性等。对压力试验一般都用水压试验。对水压试验时,筒体相应压力的验算公式为:=P 水D+(S-C)/2(S-C)按规定水压试验压力 P 水=1.5MPa;故:=P 水D+(S-C)/2(S-C)=1.5*900+(10-1.8)/2*(10-1.8)*0.7=115MPa又 s=*Ns,其中 Ns查表所得为 1.6,故 s=115*1.6=184MPas 与水压系数的积为 0.9s=164MPa由于 115 MPa164MPa,故筒体强度满足水压试验的要求。10过滤桶的结构设计过滤桶设计是整个管道系统的重点。直接从桶上引出的有 5个管道(底部 3个管道、顶部 2个管道):(1)桶底正中引出的滤后管,然后连接 S2(正常工作视筒) ,再接上 2个阀门F9(成品出口阀,正常工作是从这流出成品液)和 F11(取样阀,用于刚开始工作是取出样品,从而确定各项参数) ;(2)桶底斜锥面引出排渣管,引出后分成 2个方向一个是反冲洗时使用的排渣管,上面安装着 F8(排渣阀) ;另一个是循环过滤的循环管,通过 F5(流向控制阀,单向阀)使压力过大时形成循环过滤;(3)桶内靠壁处装有反冲洗管道,连接 F7(冲洗阀)后也分成 2个方向一个直接连到水泵上;另一个接上 F10(余液出口阀)其作用是在滤余液过程中将管道以及过滤桶的液体流出;(4)桶顶的一个循环管道向上连接 S1(循环视筒)和 F4(循环液出口阀)接到循环桶底部;(5)桶顶的另一个循环管道向上连接 F7(排气阀)和压力表,然后接到循环桶顶部,以保持过滤桶以及循环筒压力的正常(1.6MPa2.5MPa) 。11循环桶的设计1、结构介绍循环筒的工作原理比较简单,需要设计的参数也较少,主要分为 2 管道:其中一条的作用待滤液通过 F2(待滤液入口阀) 、水泵、F3 (循环筒入口阀)从循环桶下部泵入,在循环桶上部压力的作用下从右边下方的循环出口通过 F4 后进入过滤桶过滤;另外一条是顶部的管道,上面连接 F7(排气阀)和压力表和过滤桶顶部连接在一起以保持压力。2、循环桶的容量设计 因为循环桶所受压力不是很大,且不是全封闭的,所以可以不许校核桶壁承受应力。设定桶壁厚 =3mm;桶高度 H=1200mm;半径 R=400mm;容积 V=0.65m ; 3122、传动部件设计1 带传动的设计确定计算功率 Pca由机械设计表 8-7查得工作情况系数 K =1.0,A故 P = K P=1.0*5.5kw=5.5kwcaA选择 V带的带型根据 P ,n 由机械设计教材由图 8-11选用 A型ca确定带轮的基准直径 d 并验算带的速度初选小带轮的基准直径 d ,由表 8-6和表 8-8,取小带轮的基准 d =140mm1 1验算带速 V= * d *n/60*1000= *140*1440/60*1000=10.6m/s因为 5 m/s (Instruction instructionId=Logical Operation)U-.43SPB-BEFig. 8 A new transformed XML showing only the inslructions and thecorresponding instruction IDE. 可视化的XML上述所产生的两种XML文件可转化为HTML或在XSL的帮助下转换为其他可读的文件。一个巧妙的XSL可以被设计用来产生一个可以容易想象的转达PLC程序的逻辑或者其他特征的HTML文件。此外, DOM的结构在嵌入在XML中 (参见图9 ) ,也可让使用者用一个简单的方法浏览PLC程序。例如在HTML中做的可视化程序 。这可视化已经完成XML的转换,他作为一个表中的子元素去验证的语法。指示鉴定后的XML被转化成使用XSL转化,取得那里的指示和身份指示后,根据该行动的类型提取的XML在 HTML表载列了两栏(指示,指令编号)是在可视化的。HTML结构的建议,这不是唯一的可能性,其中的XML可以可视化,但他们提供一个很容易的切实可行的方案,那就是为用户把握的PLC代码。图 10显示了相同的PLC的代码,在图 4他作为一个HTML文档转换XML文档,显示的图 7使用的XSL 。这可视化,更好地了解PLC程序成为可能。图 11显示了在图 6中的XML教学入侵检测系统特殊的可视化。六 结论和展望 重新设计的PLC程序需要一个正式的办法加以发展。在本文章中,是来解决这个任务一个方法的介绍。在给出了书面指示PLC程序的基础上,在清单的通过一个明确步骤转型为被建议的正式代表。由于这个过程不会完全自动,有必要采取灵活的可视化中间步骤。XML是作为一种灵活的,标准化的手段来充当数据格式来描述的PLC代码。相应的XSL转换和文档对象模型的技术是作为工具,在重整过程为各种定制可视化任务。44基于XML的描述PLC程序的进一步转变,将适用于最后得出一个完全形式化描述原PLC的代码。这将是在成立一个有限自动机。在这个计划过程中,他们通过一个知识库确定共同的介素的结构和正规化, 七 致谢我们想感谢莱茵兰-普法尔茨飞行情报区的创新,为办学我们的工作下,项目编号616 。八 参考文献1 、L.巴雷西,米毛里,甲蒙蒂,和 皮兹 主编“PLC的设计 编程和代码生成”,收录在IEEE 会议,并在cybernefics smczooo 上出版第 2437 -2 442页。 2 、 g.弗雷和L. 里兹 , “形式化方法在PLC编程 ” ,在IEEE结论对系统,人与控制论( smczooo ) , Nashville ,美国, 2000年10月。 第2431年至2436页 3 、米巴尼尤尼斯和G.弗雷, “形式化现有的PLC程序:一项调查” ,在2003年,里尔(法国) ,号文件中S2 -的R - 00 - 0239 , 2003年7月。 4 、国际电工委员会,国际电工技术委员会的国际标准1131-3 ,可编程控制器,第3部分,编程语言, 1993年。 5 、在万维网财团: htfp ; / / www.w3.org/ 6 、 XML的主页: hftp : / / xml.com / 7 、 r. kliewer ,逆向工程,冯steuerungssojiware.ph.d 。论文, 德国Kaiserslautern大学生产自动化研究所, 1999年。 8 、米凯, XSLT的-程序参考员。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 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. 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. 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 data5 .XSLT, the transformation language for XML is capable of trans
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