Oriented Applied Research, Object Methods In Plc Programming

With the characteristic such as high reliability, high performance and can be adapted in various harsh environment, Programmable Logic Controller(PLC) is widely used in industrial control field. The traditional programming method of programmable controller is mainly based on process-oriented programming ideas, which includes the combination of logic function method based on logic algebra, the functional method based on diagram flow chart, and programming method combined with Petri nets, etc. The PLC program designed by the traditional methods has bad readability, bad code reusability, also modification difficulties. And the shortcomings are extremely obvious especially in applications with large and complex function logic. Object oriented programming method is a kind of proved effective programming method in both theory system and practical applications. To apply the object-oriented idea in PLC control field and PLC program design process is meaningful.This thesis discussed the process of PLC program design, which includes system analysis and modeling, construction and encapsulation of Class, and program design and realization, mainly based on object-oriented idea and unified modeling language (UML). We also proposed a Baking control system which PLC program was designed by object-oriented method, and then, we verified the effectiveness of the system. Our work mainly includes:(1) We introduced the related technologies of PLC, and analyzed the traditional programming process of PLC control system and the new program design process based on object-oriented method.(2) We discussed the feasibility of analysis and modeling using UML in PLC control system design, and also provided a detailed UML modeling process of PLC system.(3) We completed the encapsulation of Class with object-oriented program design method in Siemens Step7 development platform, and also discussed the coding process,in which the encapsulation of Class make the program structure of control system more clearly.(4) Finally, we analyzed and modeling a baking control system in detail based on object-oriented method and UML. We realized the system's Program and also verified the effectiveness of the object-oriented method using in PLC program design.