Research On Wireless Sensor Network Based On Vibrating Wire Sensors

Structural health monitoring has been an important technological means to ensure the operating safety of the large civil engineering structures. The signal cables are used for the on-site data transmission of the traditional structural health monitoring system and transmit the signal sensed by the sensor to data rendezvous point. The wire transmission mode has the disadvantage of large amount of wiring, high cost of installation and maintenance and difficulty in wiring.With the rapid development of wireless communication technique and integrated micro electro mechanical systems, wireless sensing technology is more widely used. The inherent disadvantages of traditional wire transmission mode can be overcome by applying wireless sensor technique on the structural health monitoring. In order to improve the efficiency of stress monitoring, reduce the cost of installation and maintenance and promote the development of structural health monitoring, the wireless sensor technique based on the vibrating wire sensor is studied in this thesis.The main work of this thesis is as followed.(1) Structural health monitoring and wireless sensor network research literature are reviewed. Then the significance of structural health monitoring is explained and the composition, application and development of structural health monitoring system are introduced. Lastly an overview of the characteristics of wireless sensor networks and their applications in various fields are conducted.(2) Analysis of the working principle of vibrating wire sensors is conducted firstly. Then the structure, mathematical models and signal measurement principle of single coil vibrating wire sensors are introduced. Finally the comparative analysis of high-pressure and low-pressure sweep plucked two kinds of excitation principle is conducted, so as to give a further improved low pressure sweep excitation method.(3) The design and development of wireless sensor units are launched. The design and integration of wireless sensor unit hardware acquisition module, data processing and control module, wireless transceiver module and power supply module are executed via modular design based on the some hardware design principles including miniaturization, low power, low cost and high reliability. According to the stress-strain monitoring functional requirements, the design and development of wireless sensing unit embedded software are conducted combined with the principles of software design.(4) The design of wireless sensor networks is carried out. Through a comparative analysis of the characteristics of various types of wireless communication protocols, the ZigBee protocol is selected to be the communication protocol for wireless sensor networks. From the comparison of the features of three wireless communication protocol ZigBee network topology, it notes that the wireless sensor network topology structures are applicable to all types of engineering structures. Lastly the application layer data communication protocol is designed.(5) The design and development of wireless sensor network client software are carried out. According to the function which the client software needs to achieve, the client software design is completed. On this basis, the client software which has a friendly interactive interface is developed.(6) The experiments of the wireless sensor network’s performance are carried out to verify the above theory. Through wireless and wired data acquisition comparative experiments, multi-point network stability test, and wireless sensor networks power and communication distance test, the wireless sensor networks’ performance including measurement accuracy, stability, and power consumption of the communication distance is tested.To meet the demand of structural health monitoring, a sort of wireless sensing unit matched with the client software is developed based on vibrating wire sensor to accomplish the function of collecting, processing and wireless transmitting the data of sensor and comprising the network between wireless sensor units automatically, which lays a stable foundation for the effective and low-cost system for structural health monitoring. These special experiments indicate that the functions and properties of the wireless sensor unit proposed in this thesis achieve the intended targets.