The Research And Implementation On PLC Algorithm Generation Platform Based On Component Refactoring

As one of the four pillars of modern industrial control, Programmable logic controller (PLC) is widely used both in various process control industry and mechatronics equipment. With widespread of IEC61131-3 standard and combination of software and hardware development method, PLC programming software has become an essential part of the development process. Different manufacturers of PLC only develop their own design platform, but their principles are not the same as each other. As the consequence of this phenomenon, related developers are required to master a large number of different usages and programming standards. But it introduces complexity and inconvenience to the design process. Thus, design and implement a plateform which is user-friendly and efficient for design has a great significance and marketing value.In this thesis, basic knowledge of PLC control algorithm platform is studied, and a PLC control algorithm generic platform based on component refactoring technology is designed and implemented. The platform provides design function for ladder diagram and instruction list which obey IEC61131-3 standard. AVR, ARM7, ARM10E and so on chips are supported. The work and research results can be summarized as following:(1) Based on learning PLC standard and analyzing the development of PLC programming tools, overall design for the platform is proposed to meet the system requirements. The whole platform is divided into three layers which are user interface layer, ladder diagram algorithm parse layer and data communication layer. The user interface layer provides an environment for control algorithm, which will improve the efficiency of design process. The ladder diagram algorithm parse layer is responsible for translating ladder diagram into an executable file. The data communication layer is designed for sending and receiving data between PLC and PC.(2) In order to provide easy-to-use control algorithm design environment, a ladder diagram editor is implemented based on design framwork. Control algorithm designers would design ladder diagram program layout by dragging and dropping elements without programming. Component-based software development (CBSD) methodology is introduced for designing ladder diagram. Based on analysis of theory of CBSD, common component model, embedded component model and component composition, ladder diagram component model and its assembly method are proposed. The proposed model and method are the good foundation for translating ladder diagram into other languages. In order to improve efficiency of ladder diagram program design, component refactoring method is applied to the ladder diagram design platform. Encapsulate a specific function ladder diagram into a composite component, validate and provide it to customer. This method will simplify design process and ensure ladder diagram's correctness. In addition, ladder diagram editor also provides printing service.(3) The ladder diagram program will be automatically translated into IL instruction after design process. Then the IL instruction will be compiled to executable file by using different compiler according to different chips. Finally the executable file is loaded to the PLC. Two load modes are provided, regular mode and debug mode. Under regular mode, the PLC program keeps running and only the relay status and register can be watched and updated via platform. Under debug mode, PC can send commands to control PLC program running state.(4) Design and implement three-floor lift ladder diagram program by proposed platform. Comparing traditional design methods and component-based refactoring methods, the experimental results show that applying proposed platform can improve the design efficiency, and optimize memory utilization. The platform has a wide versatility and adaptability.