Remote Monitoring System Development Based On Siemens S7-400PLC

Nowadays, a lot of cold-rolled production equipments are operated by the PLCcontrol, whether PLC can work properly is a direct impact on the quality and productionof cold-rolled sheet. The technicians who are responsible for commissioning andmaintenance need to diagnose the PLC program quickly when it fails, and analyze andcorrect the errors in the process of production. However, sometimes the technicians arenot in the production site, and can not come back to deal with the error at the first time.Therefore, whether we can effectively implement remote monitoring for PLC isparticularly important.Because of the diversity and complexity of the network environment, some remotemonitoring systems with using traditional VPN protocol can not pass through the networkaddress translation(NAT), proxy server and firewall to communicate, they are affected bythe limitations of the network and always can not work normally. Softether VPN is a newVPN protocol, through the analysis of its principle and the test of practical engineeringconnection, it’s proved that in any network conditions, Softether VPN client can set up aconvenient, safe and high speed VPN session with the server. At the same time, the use of3G technology also extends the wireless bandwidth and improves the real-timeperformance of the system.Using configuration software or OPC server to write a PC monitoring software forPLC is always poor real-time performance and high cost. According to the site with usingthe Siemens S7-400series PLC, LIBNODAVE library and VB are full used to develop anEthernet communication-based monitoring software independently, and optimizes thecommunication between PC and PLC. Meanwhile, using TeeChart to design real-timemonitoring curve function, which can directly reflect the dynamics of the observed data.This monitoring software based on LIBNODAVE is greatly facilitating real-time dataacquisition and storage, error analysis and debugging. It has the characters of simpleoperation, flexible data exchange, high real-time and strong independence. The successful development of remote monitoring system based on PLC greatlyfacilitates the technicians, reduces the cost of company, creates a good economicbenefit, and has very important realistic significance to build enterprise remote fault publicservice platform.