Research On Multi-sensor Communication Method And Application Of Solid Structure Using Stress Wave Based On Spread Spectrum

With the progress of the large-scale industrial structures,monitoring and evaluation of structural health status has become a significant problem to be studied.With the title“Research on Multi-Sensor Communication Method and Application of Solid Structure using Stress Wave based on Spread Spectrum”,the thesis studies the new communication method using multi-sensing stress wave.It has practical significant for the rapid development of Structural Health Monitoring(SHM) for large-scale solid structure.This paper is organized as follow:(1) In order to meet the requirements of multi-sensor communication for SHM under the special environment,according to the research of stress wave communication for SHM and the application of spread spectrum at home and abroad,a new communication method using multi-sensing stress wave based on spread spectrum was proposed.(2) The proposed method utilized stress wave as message carrier. All sensors in the same area were grouped into sets of dual-channel signal according to the degree of importance.m sequence code was used as spread spectrum code to broaden baseband spectrum for distinguishing signals between the different groups.Walsh code was used as address code to distinguish different sensors in the same group.The change of carrier relative phase between the neighboring symbols was utilized to modulate transporting information. Four sub modules were designed to realize the launching function.(3)According to the receiving module of multi-sensing stress wave communication system,the received signal was synchronized before carrier synchronous demodulation.Then correlation dispreading of demodulated signal was executed by PN code of each group. Finally,the original binary signal can be recovered after the judgment of each channel to gain corresponding sensor data.(4) At last,in order to improve the stress wave communication system performance,the stress wave communication effectiveness index SWCE was proposed.The method was applied to steel strands in vibration,underwater environment,The result shows that error-free communication can be realized for 256-bit sensor information in vibration environment at SNR of 10.75 d B,indicating that stress wave communication system based on spread spectrum theory has the advantage of a high anti disturbance capability.In the condition of putting the transmitter PZT in the water,the received signal amplitude of single and double channel were increased by 20% compared to the air environment,meanwhile the value of SWCE kept basically unchanged.The result of multi-sensing stress wave communication for steel pipe in different environment shows that underwater and moist soil conditions are the best ways for stress wave communication,while the stress wave communication effectiveness is not good in the working condition of impact.The proposed method utilized stress wave as message carrier to realize multi-sensor information communication can provide a new way of data communication for SHM of offshore platform,steel strands,pipe,etc.At the same time,The new method of stress wave communication can be extended to the environment of soil and sealed container for data communication,effectively compensates for some applications in which wireless sensor network can’t work normally based on electromagnetic wave.