畢業(yè)設(shè)計(jì)(機(jī)械)外文翻譯--可視化的plc程序使用xml

1、<p>　　Visualization of PLC Programs using XML</p><p>　　M. Bani Younis and G. Frey</p><p>　　Juniorprofessorship Agentenbased Automation</p><p>　　University of Kaiserslautem</

2、p><p>　　P. 0. Box 3049, D-67653 Kaiserslautem, Germany</p><p>　　Abstract - Due to the growing complexity of PLC programs there is an increasing interest in the application of formal methods in this

3、 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 tha

4、t 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, for</p><p>　　I. INTRODUCTION</p><p>　　Programmable

5、 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

6、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, transportat

7、ion, power distribution, and many other fields. </p><p>　　With the widening of their application horizon， PLC programs are being subject to increased complexity and high quality demands especially for safety

8、-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 develop

9、ed [I]. Ensuring the high quality demands requires verification and validation procedures as well as analysis and simulation of exi</p><p>　　Visualization of existing PLC programs is an important intermediat

10、e 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

11、 programs. </p><p>　　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 appro

12、ach 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 correspon

13、ding technologies such as XSL and XSLT that can be used in this transformation are presented i</p><p>　?、?PLC AND IEC 61131</p><p>　　Since its inception in the early ‘70s the PLC received increa

14、sing 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

15、 Engineering. </p><p>　　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

16、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

17、 enhance compatibility, openness and interoperability among different products as well as to prom</p><p>　　Instruction List (IL) is a low-level textual language with a structure similar to assembler. Origina

18、ted in Europe IL is considered to be the PLC language in which all other IEC61 131-3 languages can be translated.</p><p>　　Ladder Diagram (LO) is a graphical language that has its roots in the USA. LDs confo

19、rm to a programming style borrowed from electronic and electrical circuits for implementing control logics.</p><p>　　Structured Text (STJ is a very powerful high-level language. ST borrows its syntax from Pa

20、scal, augmenting it with some features from Ada. ST contains all the essential elements of a modem programming language.</p><p>　　Function Block Diagram (FBD) is a graphical language and it is very common to

21、 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 softw

22、are reuse.</p><p>　　Sequential Function Chart (SFC) is a graphical language. SFC elements are defined for structuring the organization of programmable controller programs.</p><p>　　One problem w

23、ith 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 formali

24、zation 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

25、 IEC 61131-3. This new format will ease the acc</p><p>　?、? RE-ENGINEERING APPROACH</p><p>　　The presented approach towards re-engineering (cf. Fig.1) is based upon the conception that XML can b

26、e used as a medium in which PLC codes will be transformed.</p><p>　　This transformation offers the advantage of obtaining avendor independent specification code. (Even if the PLCopen succeeds in defining a s

27、tandardized format for PLC applications, there will remain a lot of existing programs that do not conform to this standard.) </p><p>　　Based on this code a step-wise transformation to a formal model (automat

28、a) 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.</p><p>　　

29、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 c

30、ode 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.</p><p>

31、　　IV. XML AS A TOOL FOR VISUALIZATION</p><p>　　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 Consorti

32、um (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

33、designed for on one side; and the complexity of full SGML, whose syntax allows many powerful but hard-to-program options</p><p>　　While HTML describes how data should be presented, XML describes the data its

34、elf. 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

35、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 fundam</p><p

36、>　　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.

37、 2, [7]).</p><p>　　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 that</p><p>　

38、　checks 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

39、 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 o

40、f this method can be found in [8].</p><p>　　The most promising aspect of using XML instead is that XML and its complementary applications for transformations are standardized so as to provide maximum flexibi

41、lity to its user.</p><p>　　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

42、application.</p><p>　　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 programm

43、ing 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"

44、 is used in a broad sense increasingly. XML is used as a way of representing many different kind of infor</p><p>　　XSLT, the transformation language for XML is capable of transforming XML not only to another

45、 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++,

46、 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 tra</p><p>　　XSLT func

47、tions 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 require

48、d 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

49、-structured but hard-to-understand XML to be produc</p><p>　　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 r

50、ules. 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 structur

51、al constraints of the XML document.</p><p>　　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 esse

52、ntial 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 type

53、s and data types, and a single-inheritance form of type derivation. In other words schemas offer a richer and more pow</p><p>　　V. AN APPROACH FOR THE VISUALIZATION OFPLC PROGRAMS</p><p>　　A. Ov

54、erview</p><p>　　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

55、version according to IEC 61131-3 are considered.</p><p>　　The generation of XML documents showing different aspects of a PLC program is realized in the following three steps (cf. Fig. 5):</p><p>

56、;　　1.Transformation of the PLC program to an XML document</p><p>　　2.Validation of the XML against the XML Schema which sets the syntax of the XML</p><p>　　3.Identification of the Instruction el

57、ements of the transformed XML according to the instruction set of the source PLC</p><p>　　These three steps are discussed in sub-sections B to D respectively. Sub-section E explains the visualization of the

58、different XMLs obtained during the preceding steps.</p><p>　　Throughout this Section an example is used to illustrate the presented concepts. Fig. 6 shows a PLC code written in Instruction List Siemens S5. T

59、he 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.</p><p>　　Kommentar :</p><

60、p><b>　　Autor</b></p><p>　　Erstellt :15.07.2003 Geaendert am: B1B:O</p><p>　　NETZWERK 1 EMPFANGEN SLAVE 3 VON MASTER</p><p>　　NAME :EMPE'MAST</p><p>　

61、　0005 :U M98.7 ABFRAGE OB EMPFANG MOEGLICH</p><p><b>　　0006</b></p><p>　　0007 :SPB= MOOl</p><p><b>　　0008</b></p><p>　　0009 :A DB140 EMPFANGSFAC

62、H IST DB 140</p><p>　　OOOA :L KF+20 LAENGE DES DATENPAKETS</p><p>　　oooc :T DLO</p><p>　　OOOD :L KF+O ZIELNUMMER O=MASTER</p><p>　　OOOF :T DRO</p><p><b

63、>　　0010</b></p><p>　　0011 :UNM98.7 FANGEN WIEDER ERLAUBEN</p><p>　　0012 :S M98.7</p><p>　　0013 MOOl :NOP 0</p><p><b>　　0014</b></p><p>

64、;　　0015 :BE BAUSTEIN ENDE</p><p>　　Fig. 6 A PLC program written in Siemens S5 Instruction List</p><p>　　B. Conversion of a PLC Program inio a well-formed XML</p><p>　　Given a PLC pr

65、ogram 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

66、 document obtained through this transformation is a hierarchically structured document.</p><p>　　Fig. 7 shows the XML document obtained through the transformation of the PLC code of Fig. 6. The XML document

67、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 int

68、o child elements.</p><p>　　Note: The structure chosen for the XML representation of IL-Code is oriented at the working proposal of the PLCopen.</p><p>　　C. XML Validation against the XML Schema&

69、lt;/p><p>　　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 syntact

70、ic rules defined in context of the PLC programming language.</p><p>　　D. rdenhpcation of instructions</p><p>　　This step in the process of visualization of PLC programs using XML ensures that th

71、e 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 addition

72、al 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</p><p>　　

73、The instruction identification of the transformed XML proofs the semantic of the XML in accordance with the operation types of the PLC programming language.</p><p>　　In the example of this section, (cf. Fig.

74、 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. logi

75、cal, jump, load or transfer operation assignment, etc.</p><p>　　<?xml version="l.O" encOding="ISO-8859-1" ?></p><p>　　<ILCodeBlock></p><p><b>　

76、　<ILRow></b></p><p>　　(Instruction instructionId='Logical Operation")</p><p>　　U</Instruction></p><p><b>　　</ILROW></b></p><p

77、><b>　　-.</b></p><p><b>　　<ILRow></b></p><p>　　<Instruction instructionId="Jump Operation"></p><p>　　SPB-</Instruction></p&g

78、t;<p>　　<Instruction instructionId=" special Operation</p><p>　　"> BE</Instruction></p><p><b>　　</ILROW></b></p><p><b>　　</IL

79、Row></b></p><p>　　Fig. 8 A new transformed XML showing only the inslructions and the</p><p>　　corresponding instruction ID</p><p>　　</ILCodeBlack></p><p>

80、;　　E. Visualization of XML</p><p>　　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

81、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 pr

82、ograms in an easy way.</p><p>　　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 elemen

83、ts of the ILRow are the columns of this table.</p><p>　　The XML after the instruction identification is transformed using the XSL, where the instruction and the instruction Id, obtained after extracting the

84、XML according to the type of operations are visualized in a table containing two columns (Instruction, Instruction Id) in HTML.</p><p>　　The HTML structures suggested here are not the only possibilities, wit

85、h which the XML can be visualized, but they give a very easy practical option for the user's grasp of the PLC code.</p><p>　　Fig. IO shows the same PLC code as shown in Fig. 4 as a HTML document converte

86、d &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. </p>

87、;<p>　　VI. CONCLUSIONS AND OUTLOOK</p><p>　　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

88、 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

89、 presented as a flexible, standardized means to serve as data format for the description of the PLC code. The corresponding </p><p>　　Based on the XML description of PLC programs further transformations will

90、 be applied to finally derive a completely formalized description of the original PLC code. This will be in the form of a finite automaton. During this process it is planned to identify common IL structures and formalize

91、 them via a library.</p><p>　　Gaining the Benefit of the XML Metadata Interchange (XMI) as an open industry standard that applies XML to abstract systems such as UML and referring to the classification of th

92、e instructions of IL into the eleven categories mentioned above. We can extract UML classes from this classification, as it resembles the action semantics of UML.</p><p>　　可視化的PLC程序使用XML</p><p>

93、　　米巴尼尤尼斯和G.弗雷</p><p>　　摘要:由于P LC程序日益復(fù)雜,在PLC應(yīng)用方面有越來越多的興趣愛好者。形式化方法，讓僵化的證明系統(tǒng)屬性被核查和驗(yàn)證。一個(gè)傳統(tǒng)思路的方法就是在PLC編程中設(shè)立一個(gè)正式的設(shè)計(jì)方法。不過，現(xiàn)有的軟件已被優(yōu)化，改變，或移植到新系統(tǒng).有需要找到從某一PLC程序開始的方法。因此，規(guī)范PLC程序是一個(gè)現(xiàn)在研究的熱點(diǎn)。該文章概述了基于形式化的PLC程序基礎(chǔ)上從新啟動(dòng)的方法。轉(zhuǎn)型成

94、為一個(gè)獨(dú)立的格式和可視化的結(jié)構(gòu)，在這個(gè)過程中，PLC程序的確定是作為這項(xiàng)措施的重要中間步驟。這表明如何XML和相應(yīng)的技術(shù)可用于形式化和可視化現(xiàn)有的PLC程序。</p><p><b>　　一 導(dǎo)言 </b></p><p>　　可編程邏輯控制器（PLC ）是一種特殊類型的計(jì)算機(jī)，它應(yīng)用于工業(yè)和安全的關(guān)鍵地方。應(yīng)用PLC的目的是控制某一特定的或可選擇的過程，它是通過產(chǎn)生

95、的電控制信號(hào)回應(yīng)電器中相關(guān)的輸出信號(hào)來實(shí)現(xiàn)的。應(yīng)用在制造業(yè)和化工過程控制，機(jī)械加工，交通，電力分配，以及其他許多領(lǐng)域。PLC控制有著極大的不同，自動(dòng)化應(yīng)用范圍的復(fù)雜性從一個(gè)簡(jiǎn)單的小組運(yùn)作到控制一個(gè)會(huì)議室的的燈光和自動(dòng)窗成為一個(gè)全自動(dòng)化的生產(chǎn)線。</p><p>　　隨著他們應(yīng)用PLC知識(shí)的增加，他們把PLC應(yīng)用到復(fù)雜性和品質(zhì)要求高的地方，特別是對(duì)安全性要求特別嚴(yán)格的地方。由于在有限的時(shí)間里PLCD的發(fā)展應(yīng)用日益復(fù)

96、雜，現(xiàn)有的軟件或PLC的模塊也在迅速發(fā)展，以此，需要一個(gè)正式的辦法加以規(guī)范 。為了確保高品質(zhì)的要求，我們需要檢查和驗(yàn)證程序，以及分析和模擬現(xiàn)有系統(tǒng)[ 2 ] 。其中一個(gè)重要的領(lǐng)域就是已經(jīng)在最近的時(shí)間成長(zhǎng)在規(guī)范化的PLC程序是逆向工程[ 3 ] 。逆向工程是通過評(píng)估達(dá)到了解它的運(yùn)轉(zhuǎn)過程，以達(dá)到重復(fù)或加強(qiáng)的目的。而重用的PLC守則正在建立，作為一種打擊復(fù)雜PLC程序的工具，逆向工程在今后幾年將得到越來越多的重要性，特別是如果現(xiàn)有的硬件被適用

97、于各種不同程序環(huán)境的新硬件所取代的情況下。</p><p>　　現(xiàn)有的PLC程序的可視化是逆向工程一個(gè)重要的中間步驟。本文章提供了一個(gè)方法，使用XML使PLC程序可視化，讓PLC程序工程師更容易把握方向和更好地了解。</p><p>　　該文件的結(jié)構(gòu)如下。首先，簡(jiǎn)單的介紹了PLC（根據(jù)國(guó)際電工委員會(huì)61131-3的標(biāo)準(zhǔn)是給予）和相應(yīng)的編程技巧，。在第三部分，在現(xiàn)有基礎(chǔ)上用形式化PLC程序重

98、新設(shè)計(jì)方法的介紹。PLC代碼轉(zhuǎn)型成為一個(gè)獨(dú)立的格式被確定為在這個(gè)過程中重要的第一步。XML和相應(yīng)的技術(shù)，例如XSL和XSLT（第四節(jié)可以使用的這種轉(zhuǎn)變）。第五部分提出了應(yīng)用XML的使PLC程序可視化的方法并用一個(gè)例子做出說明。最后一節(jié)總結(jié)了結(jié)果，并就今后的工作在這方面正在進(jìn)行的項(xiàng)目做了一個(gè)前景的展望。</p><p>　　二 PLC和IEC 61131</p><p>　　自從七十年代初期

99、公布于世，由于它的成功的完成目的，取代了機(jī)器上的硬連線控制設(shè)備，PLC日益受到重視，。最終它作為一個(gè)獨(dú)特的應(yīng)用領(lǐng)域成長(zhǎng)起來，它的研究和開發(fā)，主要是為控制工程。</p><p>　　IEC61131是為工業(yè)自動(dòng)化第一次真正的努力來規(guī)范PLC的編程語言。在1993國(guó)際電工委員會(huì)[ 4 ]上公布了IEC 61131作為可編程控制器標(biāo)準(zhǔn)。在標(biāo)準(zhǔn)化PLC的編程語言之前，正在制定為了個(gè)別PLC實(shí)用的專有編程語言。為了提高不同

100、產(chǎn)品的兼容性，開放性和互操作性以及為了促進(jìn)工具和方法的發(fā)展,國(guó)際電工委員會(huì)61131標(biāo)準(zhǔn)設(shè)立固定的一套符號(hào)。第三部分，定義了一個(gè)適合5種編程語言標(biāo)準(zhǔn)：</p><p>　　Originated (IL)語言是一種低層次的文本語言,其結(jié)構(gòu)類似于匯編語言。Originated語言L被視為PLC的在所有其他IEC61 131-3語言都可以翻譯語言。</p><p>　　梯形圖(L0)是一種被認(rèn)

101、為起源于于美國(guó)的圖形語言。LDS符合從電子及電器電路實(shí)施控制邏輯的編程風(fēng)格。</p><p>　　結(jié)構(gòu)化文本（ ST）是一個(gè)非常強(qiáng)大的高層次的語言。圣借從帕斯卡爾那里借用了它的語法，充實(shí)它的一些特點(diǎn)。圣包含一個(gè)現(xiàn)在編程語言多要求的所有要素。</p><p>　　功能塊圖（FBD）是一種圖形語言，在工業(yè)流程里是非常常見的。在這種語言中，控制器被認(rèn)為是可在功能塊之間流動(dòng)的信號(hào)和數(shù)據(jù)。FBD把換