The Study And Realization On Running System Of SoftPLC Based On PC

At present, SoftPLC technology based on PC is a new control technology and one of main research interests in industrial automation and control technology, which has a great many advantages of open control system, stronger data processing and network communication capacity comparing with traditional PLC, but also meets need of modern industry automation.The so-called softPLC technology which uses PC as hardware support platform is using software to realize the traditional PLC basic function. That is to say, the PLC control function is sealed in the software, and the software is run in the PC environment. The control system has same function as PLC, actually it has all of advantages of PC. According to structure of the traditional PLC, the soft PLC system is generally divided into the editing system and the running system. The running system is core of softPLC, its function is to complete execution of the procedure and the input/output processing. The paper mainly studies the running system, and based on implement process of the system carries on the following work:1.Correlation technique of the softPLC system design is studied, including virtual machine technology, COM/DCOM technology and OPC technology. The international standard IEC61131-3 is analyzed, and the necessity of using this standard in the design of soft PLC system is described.2.The composition and the running principle of the traditional PLC is instructed particularly, also the characteristic and the trend of development of the traditional PLC is discussed. So the paper instructs the architecture and the software model of the soft PLC, compares three kind of control plan of the softPLC system, and determines support platform of the softPLC running system. The comparison to softPLC and traditional PLC is carried on to prove superiority of the softPLC control based on PC.3.The composition and principle of work of virtual machine is analyzed, and the data construction and memory form of the target code is introduced, the target code is provided by the development system. So according to the IEC61131-3 international standard and referring to Simens S7-200 command system, virtual machine instructions system of the soft PLC run-time system is designed, and the software implement method of virtual machine is explained in detail.4.The duty and correspondence mechanism of every correspondence interface of the softPLC running system is introduced, and the implement method of each correspondence interface is explained in detail.5.The running system is tested, it mainly includes running timeliness, accuracy and the reliability of the virtual machine, and whether every correspondence interface can work normally is tested. The result shows that the system function met the anticipated requirements and run well. At last, we point out the advantages of the design and the parts need improved on and look forward the foreground of the SoftPLC.