Application And Study On Communication Between Monitoring Computer And PLC

The programmable controller that now abbreviated to PLC is a kind of universal industrial control apparatus, which takes microprocessor as its core, and integrates microcomputer technology, automation technology and communication technology. PLC is widely used in industrial control for its strong function, high reliability, modular structure and etc. By connecting personal computers(PCs) to a PLC network, strong data processing ability and many customer services, such as an excellent interface, monitoring system programmers and displaying control charts can be provided, which help users knowing the data quickly. These functions are based on communication between PLC and host computer, so communication is the mainly researched part in this paper.There are six chapters in this paper, in which Chap.5 and Chap.6 are the most important parts. The first chapter briefly introduces the research background and assignment. Being basic parts, Chap.2 and Chap.3 tell about PLC control system and some theories of PLC communication and network, moreover the idea of communication about line vehicle is provided. Chap.4 discusses the communication mode, protocol and orders. In order to solve the problem of distance monitoring and saving history data of line vehicle, the paper provides PLC free port protocol and communication interface program in Visual Basic 6.0. In this paper we also apply the theory of database, frequency converter and sensor. Chapter 6 summarizes the whole paper and discusses possible future developments of the monitoring function.To the question of line vehicle apparatus, the paper introduces real time monitoring mode. On the basis of communication between monitoring computer and PLC, the theory of Visual Basic 6.0, free port orders, database and etc is applied, excellent monitoring interface is designed and the communication program of PC and S7-200 PLC is compiled. Compared to monitoring mode of configuration software, this computer monitoring system is more flexible, economical, saving more storage space, providing communication secure for more professional monitoring applications and being helpful to other PLC. The work is important for guiding practical applications.