Study On WIM Technology Based On Chirped Fiber Bragg Grating

With the high-speed development overloading is coming from bad to worse. Harms created by overloading are destroying traffic infrastructures, bringing about frequent occurrence of traffic accidents, leading to substantial run off of taxation and toll fee etc. So, it must be effectively controlled. The technology of weight-in-motion (WIM) is an effective measure to prevent overloading, decrease traffic accident, which will provide critical contributions to the society and the economy.There are some kinds of sensors used in WIM systems such as piezoelectricity sensor, capacitance sensor, bend plant sensor and so on. But in practice these sensors have many disadvantages because of the bad conditions in the investments. For example, their measuring results shift along with the changes of temperature and time. They have low electromagnetism anti-jamming quality and corrosion, etc. In recent years, fiber grating is widely used in measurement domain. It provides new approaches for the research in WIM system. Fiber Grating sensor, which uses the property that the Bragg wavelength is sensitive to outside parameter, is a new kind of fiber optic sensor. Countering the disadvantage of FBG demodulation's high costing and slow speed, it is limited to be used in practice.In this paper, we use the advanced chirped fiber Bragg grating (CFBG) as the sensitive element for the WIM system and do a series of theoretical and experimental research. Main jobs completed are as follows:1) Introduce WIM technology and FBG sensing technology and analyze the flaw of traditional sensors.2) Analyze CFBG cantilever focusing on the working principle, manufacture technology, static calibration experiments of weighing sensor. What's more, it gives an experiment based on equal intensity beam that verifies the linear characteristic of strain to wavelength change. By the static calibration experiments' data processed from software origin, we can see that the linearity, sensitivity and repeat error can meet the design requirements from 0 to 90kN.3) Introduce the way of vehicle weighing and the composition of the vehicle weighing system. On this basis, we have static and dynamic vehicles at the scene following calibration. In static vehicle calibration, the linear fit of measured data and actual weight can attain 0.9984; in dynamic vehicle calibration, when the speed is under 20km/h, the maximum relative error is -2.83%. In summary, the WIM system based on Chirped Fiber Bragg Grating in our study has some distinctive characteristics, such as high electromagnetism anti-jamming quality, bearing corrosion and the high measurement precision. This system uses intensity demodulation, which has simple structure, faster demodulation qualities and decreases costing greatly. It will have great potential for future applications in real technology market.