Monitoring System Based On Profibus And As-i Road Tunnel

National Expressway Network Program has been discussed and passed by State Department on 17th December, 2004. It indicates the development of expressway enters a new history phase in China. More highway tunnels and tunnels groups will be constructed in the future 30 years. Because of the particularity of the tunnel traffic circumstance, Highway Tunnel Surveillance and Control System (HTSCS) need to be built to ensure tunnels' smooth traffic and safe run.As the 5th generation control system, Fieldbus Control System (FCS) combines the technologies of computer, communication, control and network. Its simple structure, high reliability, open character, interoperability, interchange character, low setting expenditure and easy maintainability made it be one of the hot spots of automation field and thoroughly change the traditional industrial surveillance and control mode. It is inevitable to adopt fieldbus technology in the development of HTSCS.The dissertation introduces the actualities and development trend of HTSCS, the conception of fieldbus and its development tendency. Then the structures and communication protocols of PROFIBUS and AS-i were presented in detail. The composing and its each part's function of HTSCS were expatiated, in the foundation of these, we put forward a HTSCS based on PROFIBUS and AS-i. The HTSCS based on PROFIBUS and AS-i is designed in general. And we use SIMATIC STEP7 to configure the network, to design the surveillance and control program of the field control level and to diagnose the network. The abnormal incidents' process in surveillance and control center and the realized function of the HTSCS were researched. Finally we analyzed the reliability of the HTSCS and set forth the measures to enhance its reliability from the aspects of its field control level and device level.