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12 October 2010 Development and application of a low-frequency FBG vibration sensor
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Dynamic monitoring is part of bridge structural health monitoring. Real-time and online monitoring for bridge's dynamic performance is an important technology means for model updating, damage detection of structure and security evaluation of bridge. Nowadays dynamic monitoring system is generally installed on new long-span bridges. Vibration sensor is key part of the technology means. Vibration of a large-scale bridge belongs to low frequency one, but traditional electromagnetic vibration sensors are restricted for use in the field due to such defects as signal unable to long distance transmission, hard to measure ultra-low frequency vibration, so it is inevitable and imminent to develop a novel-type vibration sensor instead of them. Aiming at the above-mentioned problems, the author in the paper develops a low-frequency vibration sensor with double-cantilever beam structure, based on fiber Bragg grating (FBG) and matching filtering demodulation. Some experiments are done to study its sensing properties and the results indicate that it has good temperature compensation, its natural frequency is about 35Hz, measurement bandwidth from 0.1Hz to 20Hz, sensitivity is 1000mv/g or so, linearity degree is over 0.9992, repeatability is superior to 2.4%, acceleration measurement range is 1g, and cross anti-interference is 5.6%. Such sensors have been successfully used on Wuhan Tianxingzhou Yangtze River Bridge(WTYRB). The most transmission distance of measurement signal is 10km or so and the lowest measurement frequency is 0.24 Hz. The application results show it can detect accurately dynamic properties of vital areas of the bridge and can meet the demands for dynamic measurement. To sum up, the sensor developed in the paper can overcome the shortcomings of electromagnetic sensors and has very good sensing properties, so it is very suitable to be used for low-frequency vibration measurement.
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Qiu-ming Nan "Development and application of a low-frequency FBG vibration sensor", Proc. SPIE 7659, 5th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Smart Structures and Materials in Manufacturing and Testing, 76590L (12 October 2010);

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