Research And Design On Field Network Monitoring System Based On BACnet Protocol

In the field of intelligent building, BACnet (A Data Communication Protocol for Building Automation and Control Network) has become the ISO standard by right of its opening, practicality and easy to integrate with various kinds of physical network. MS/TP(Master-Slave/Token-Passing)protocol as one of BACnet datalink layer options, widely used in BACnet field control product for its stability and reliability characteristics. With the development of industry and information in our country, it is practical to introduce the BACnet protocol into the field monitoring system in industry field. Using BACnet protocol opening and interoperability characteristic, solves the problem of private fieldbus monitoring system. Research and implementation of field monitoring based on BACnet protocol have a very important role in promoting the use and popularization of BACnet, accelerating the development process of intelligent building.On the basis of deeply study in BACnet protocol, from system designed angles, an implementation of field network monitoring system based on BACnet is presented in this paper, which solves the problem of interconnection and interoperability between monitoring system and other BACnet facilities, and constructs a complete and effective monitoring system. For the real-time performance of monitoring network, this study builds a mathematical model for MS/TP protocol, and makes series numerical value analyses on model. Analysis of the simulation results was used to identify the network parameters that influence the real-time performance of MS/TP, finally optimized algorithm was given. For the different application object of BACnet stack, this paper designs two frameworks of protocol stack and describes the implementation in detail. Later, test result including all modules indicates that this system has achieved the goal of design and satisfied the requirement of field monitoring. The main tasks of this paper include the following:(1) Proposed a field monitoring system of BACnet protocol design program, providing a better solution to the problem of interconnection and interoperability between field monitoring system and other BACnet facilities.(2) Proposed a make sure real-time algorithm by simulation based on queue theory, enhanced the real-time performance of MS/TP protocol.(3) Determined the system software structure on the basis of analysis the functions of all modules in monitoring system. Design tasks mainly including the field controller unit, local monitoring subsystem, remote monitoring subsystem and database subsystem.(4) Proposed two frameworks of BACnet protocol for different object platform, the key data structures and whole protocol stack realization details were given.