The Research Of PLC Control Network Based On Ethernet

With the popularization of the network technology of computer, the dramatic change has been taking place in the worldwide industrial structure. In the field of industrial control, control network technology has already become the center of automatic technical research.The conventional control scheme has been already unable to meet the demand for modernized industrial production. With the inter combination of Ethernet/Internet technology and control technology, the distributed control network based on Ethernet have been gaining more and more extensive application in industrial processing control system, which can be taken as a superior mode of integration of scene micro-control and enterprise macroscopic decisions.In this thesis, our aim is focused on the architecture of the network of control system and the respect PLC programs for an automatic production assembly line. The control system of the line is designed based on industrial Ethernet and in which PLCs play an important role. In the system, serial-Ethernet server transforms the signal from OMRON CPM1A/CPM2A PLCs with the type RS-232 into network signals according to TCP/IP, it makes PLCs link into Ethernet. Meanwhile, the hierarchy and module design means are adopted in the system, there is much benefit from Ethernet technology and the disadvantages of fieldbus are avoided.PLCs and the human-machine interface are felicitously selected in order to satisfy the requirements of the control system. The PLC's programs with automatic pattern, half-automatic pattern and manual pattern are designed and performed respectively. The program of the human-machine interface is also discussed in detail with half-automatic pattern and manual pattern.The asynchronous WinSock of MFC in VC++ is adopted for the program of the upper controller to guarantee the communication between the upper controller and PLCs. The communication format between the PLCs and the host-computer is chosen based on the OMRON standards.As a result, by means of PLC technology, network technology, communication technology and object-oriented programming technology etc., real-time data collection and interaction are realized in our system.