Research And Design Of Wireless Sensor Networks For Structural Health Monitoring

Wireless Sensor Network (WSN) is a new type of network made up of sensors, microprocessors and wireless communication interfaces. As the development of sensors technology, microelectronic technology, embedded computing technology and wireless communication technology, Wireless sensor network have a rapid develop speed and become a new computer interdisciplinary field. Sensor nodes are randomly located in an area self-organized to be a network, which is essentially a large scale, and resource limited distributed system. A wireless sensor network based data acquisition system promises enormous benefits such as ease and flexibility of deployment in addition to low maintenance and deployment costs.Structural Health Monitoring (SHM) focuses on developing technologies and systems that assess integrity of structures such as buildings, bridges, aero-space structures and off-shore oil rigs. Different from the general environmental monitoring, SHM implementations continuously collect structural vibration data from various locations in the structure (induced by ambient sources e.g., moving vehicles, winds) for analysis. In theory, since the interesting structural modes are in the tens of Hz, it would be sufficient to sample a structure at about 50 Hz. This results in an insufficient number of samples for robust reconstruction of the frequency spectrum. Thus, SHM needs to sample at higher rates, which stresses the communication and processing limits of mote-class devices.The main contents of this dissertation are following:(1) We selected the transceiver CC2420 and MCU Atmega128 as key chip set and designed the hardware platform which adapt to IEEE802.15.4 and ZigBee Specification. Attached to this card is a highly sensitive tri-axial accelerometer MMA7260 that is capable of sensing up to three channels (3-axes) of vibration data.(2) On the software side, this paper detailed analyses and studies the principle and implementation of CTP data collection protocol in TinyOS2.0 . The CTP routing protocol and SMAC link layer protocol are used for self-organizing and high-quality wireless data communication.(3)The data compression algorithm based on wavelet lift is presented. It is improved and implemented on the TinyOS system and hardware platform. Through experiments and contrast, this approach can achieve good results, and thus break through the bottleneck of communication bandwidth, and achieve the purpose of improving the sampling frequency.(4) We design and implement a background monitoring software. The software can monitor data, route information, communicate status and so on.