Study On Vehicle Weigh-in-motion System Using Fiber Bragg Grating

The technology of the fiber grating sensing is a new sensing technology,which grew up in 1990's.Since fiber gratings can realize the multi-dot,multi-parameter and distributed sensing,and have some advantages such as high sensitivity,compact structure,low loss in signal transmission,good ability of anti-electromagnetic disturbance and corrosion resistance. The fiber grating sensing technology is developed and widely applied in many fields.Combining with the Young Expert Foundation Item of Chang'an University(YEFICU), the overall research on the fiber grating sensing technology was studied in the dissertation. The design and experiments are carried out for vehicle weigh-in-motion system,adopting the fiber grating sensing technology.The main contributions are as follows.1) The basic theory of fiber gratings and sensing are studied,and the fabrication technique is introduced in the dissertation.The progress and the current situation of fiber grating sensing technology applications are elaborated.2) The spectral characteristics of fiber grating are analyzed using the coupling-mode theory.Several common fiber grating wavelength demodulation technologies are investigated and comparisons are carried for each demodulation technologies.Based on the theoretical analysis,a sensing model of fiber gratings was established,and the strain and temperature properties of fiber gratings are also investigated.3) The vehicle weigh-in-motion technology is studied.The characteristics and the existing problems of the vehicle weigh-in-motion systems available used in nation and abroad are analyzed.A new scheme of vehicle weigh-in-motion system based on fiber grating sensing technology.The experiment results show that this system is with higher measuring accuracy and is effective and practical.4) Based on matched filtering technology,a digitalized fiber grating wavelength demodulators with high measuring accuracy and low cost.The sensors used in the fiber grating system are studied and made.The experiment results indicate that the wavelength detection range of single matched fiber grating is 4nm,and the resolution of the wavelength detection is 1pm,and the uncertainty is 5pm,which put up with the advanced level of the wavelength demodulation technology.