Visualization of PLC Programs using XML
tidAbstract - 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 rearch. The paper outlines a re-engineering approach bad 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 ud for the formalization and visualization of an existing PLC program.
I. INTRODUCTION
母语迁移Programmable Logic Controllers (PLCs) are a special type of computers that are ud in inweakness
dustrial and safety critical applications. The purpo of a PLC is to control a particular process, or a collection of process, by producing electrical control signals in respon 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 2020考研分数线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 incread 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 Rever-engineering [3]. Rever Engineering is a process o
f evaluating something to understand how it works in order to duplicate or enhance it. While the reu of PLC codes is being established as a tool for combating the complexity of PLC programs, Rever Engineering is suppod to receive incread 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 Rever 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 bad 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 ud in this transformation are prented in Section IV. Section V prents 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.
Ⅱnegatives larainePLC AND IEC 61131
非限定性定语从句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, rearch 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 com
patibility, openness and interoperability among different products as well as to promote the development of tools and methodologies with respect to a fixed t of notations the IEC 61131resional 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 asmbler. 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.法规英文>approvement
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 esntial 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 reu.
