The Research And Realization Of Data Communication In Wireless Sensor Network Applied In Bridge Structural Health Monitoring System

Wireless sensor network combines sensor technology, wireless communication technology, embedded computing and distributed information processing technology together. It uses a variety of integrated micro sensor nodes to monitor environment or objects, sending the information collected wirelessly. Wireless sensor network connects the physical world and the human society. Currently, it has been used in many fields. Structural health monitoring system based on wireless sensor network not only retains the advantages of wired monitoring system, but also solves many problems in wired monitoring system, such as high cost, complicated wiring and difficulties in system maintenance.Taizhou Yangtze River Highway Bridge is a three-tower two-span steel box girder bridge. Many of its technologies used in the course of construction are the first applications of their kinds in the country. Specially, the middle steel tower has a unique shape and complex stress state. Thus, to establish a comprehensive structural health monitoring system on the bridge to long-time on-line monitor and guide the maintenance of the bridge has a great significance. The research described in the article is conducted on the Taizhou Bridge structural health monitoring system based on wireless sensor network.Firstly, this paper introduces the framework of the Taizhou Bridge structural health monitoring system and describes hardware and software used in the system briefly, for example, the wireless sensor node with the high-precision sensing board used to obtain three-directional acceleration data, the high-performance base station platform, the embedded operating system for developing wireless sensor network applications. Besides, the layout of the entire monitoring system on the bridge is illustrated.Network protocol stack for wireless sensor network usually has five layers, including physical layer, data link layer, network layer, transport layer and application layer, corresponding to the five-layer protocol stack for Internet. IEEE 802.15.4 is the protocol formulated for the low-rate wireless personal area network, and has become the de facto standard for the physical layer and the data link layer in the WSN protocol stack. Taizhou Bridge health monitoring system customs MAC layer protocol based on IEEE 802.15.4. As for the transport layer, we design a polling-based protocol suitable for the star topology of the system. By controlling data transmission process between base station and sensor nodes, we effectively reduce the mutual interference in channels and increase the reliability of wireless communication.Compared with the transmission of the wired network, the wireless transmission is more prone to error. Reflection, diffraction and scattering of the signal waveform will result in fast fading and inter-symbol interference. Besides, the noise from other nodes or systems in the same or adjacent frequency bands will impact the quality of wireless communication. Taizhou Bridge structural health monitoring system is a real-time monitoring platform, demanding high accuracy and completeness of data transmission. Taking into account existing error control methods and the polling-based transmission mode, we propose a group-ACK ARQ mechanism. It can effectively improve the reliability of the communication system.