Research And Implementation Of PLC Function Block Compling System Based On IEC61131-3 Standard

The programming language of industrial control system is moving towards standardization and openness.The International Electrotechnical Commission released the IEC61131-3 standard in 1993 to standardize the programming language of control systems.Functional block diagram language is one of the languages specified in this standard,which can be used for all kinds of PLC programs which are linked by graphical instructions in sequence.The function block diagram can not be directly identified by PLC,and it needs to be compiled into the target program that can be recognized by PLC.This compilation system that converts functional block programs into target programs is called a functional block compilation system.In view of the lack of researches on the compilation methods of functional blocks at home and abroad at present,the supporting instruction types are not comprehensive enough and the compilation error-checking function is not perfect,etc.This paper takes PLC_Config,the PLC programming software of DCCE,as the development platform,and studies and designs a PLC functional block compilation system with comprehensive error-checking and strong compilation function.Firstly,the composition and edit rules of functional block program are analyzed.The overall design scheme of PLC function block compilation system is proposed.The whole compilation system is divided into three parts: program storage,program checking,and program compilation.Program storage is to storage and read a functional block program through an XML file.Program checking is to check functional block program thoroughly and give the result of inspection.Program compilation is to convert a functional block program into the target program that can be directly executed by PLC.Each part completes the compilation system function through mutual cooperation.An example of functional block program is given,which lays a foundation for further research.Secondly,the PLC variable storage area is divided and the basic types of variables are defined.The storage method and storage format of the function block program file are given.Starting from the function block program edit rules,this paper designs four inspection methods: lexical check,grammar check,semantic check and editing function check.While checking the program,the error location and error information prompt are given in the compilation information bar,which ensures the accuracy and reliability of the program compilation.Then,the key technology of PLC function block compilation is studied.For the problems of more instruction types and more series-parallel,this paper proposes a new compilation algorithm.The algorithm introduces AOV graph and multi-fork tree structure to model the functional block program,defining a universal PLC instruction structure,and solving the compilation problem of different types of instructions and multi-output programs.The processing method of special instruction(such as communication instruction,control instruction and interrupt instruction)and PLC function block program execution are studied.Finally,the PLC function block compiling system is verified.Examples of different functional block programs are used to verify program storage,program checking,and program compilation.The results show that the compilation system can realize the storage,checking and compilation of all kinds of functional blocks,and satisfy the control requirements of the actual application.