Key Technology Of Wireless Sensor Networks For Bridge Strain Monitoring

The bridge is an important infrastructure with huge investment and long service life,and the safety of the bridge is very important to the national economy.It is of great significance to monitor the bridge status and to prevent the bridge structure from being destroyed.With the development of microelectronic technology,communication technology and structure monitoring technology,the wireless monitoring of bridge status has become a hot topic in wireless technology.Compared with the traditional bridge monitoring system,the wireless bridge monitoring system has the advantages of low cost,simple maintenance,high intelligence degree and great application value.This paper studies the wireless communication technology,which is suitable for the bridge strain monitoring,the sensor deployment of the wireless bridge strain monitoring system and the development of the wireless bridge strain monitoring system.Firstly,the wireless communication technology suitable for bridge strain monitoring is studied.The classification and structure of bridge are studied,and the environment of bridge monitoring site is analyzed.In this paper,the evaluation index of wireless communication scheme is introduced,and the commonly used wireless communication technology is compared with these indexes.In order to analyze more specifically the suitable wireless communication scheme under this application background,this paper makes a comparative analysis of the CC3200 based on Wi-Fi technology,the CC2640 based on Bluetooth technology,and the CC2530 based on ZigBee technology.It is concluded that under the background of bridge strain monitoring,the ZigBee scheme is a high cost-effective wireless communication scheme,and the principle of ZigBee technology is studied.Secondly,in order to ensure the high coverage and reliability of the system,and considering the cost problem,this paper studies the deployment method of wireless sensor nodes under the background of bridge monitoring.The perception and communication models of wireless nodes are studied,including probability perception,free space propagation model,two-ray ground reflection model and shadowing model.After comparing the models,the probability sensing and shadowing models are used to set up the simulation environment.The deployment methods of wireless sensor network nodes are studied,and the specific schemes of random deployment,quadrilateral deployment and hexagon deployment are studied from the point of view of coverage.This paper introduces the simulation environment of NS2 network and its general use methods.For monitoring the whole bridge,four deployment schemes are determined by using the methods of regular hexagon and quadrilateral deployment,and the best deployment scheme is obtained by simulation with NS2,and the optimal deployment scheme is obtained by using the method of regular hexagon and quadrilateral deployment.And its reliability in rainy days,electromagnetic interference,obstacle blocking scene is investigated.In addition,in order to provide experimental reference for the prototype of the system in this paper,the deployment scheme of the system is determined,and the reliability performance is analyzed.Finally,this paper studies the wireless bridge strain monitoring system,and develops a set of prototype system which can be used for bridge strain monitoring.The prototype includes wireless sensor,router,power module,gateway,upper computer and cloud memory.The wireless sensor includes resistance strain gauge,signal conditioning module,signal acquisition module,wireless transmission module with enddevice program,router as wireless transmission module with routing program.The wireless sensor and router are powered by power supply module,and the gateway is consists of 3 wireless transmission module with coordinator programs and a main control module based on STM32F103ZET6.The upper monitor adopts Qt design to receive the signals transmitted by the gateway,sort the signals of different nodes and different channels and display their waveforms,in addition,store the data of each channel to the local and cloud server.The experiment proves that the system can monitor structural strain with high precision wirelessly,and has the function of displaying real-time signal waveform,storing data to local and cloud,and harvest solar energy.