Performance And Structure Optimization Of FBG Acceleration Sensor Based On Elliptical Hinge

High-range impact accelerometers have important application value in military fields such as aerospace,weaponry and nuclear industries.However,at present,most of the sensors are electromagnetic sensors,which have the problems of electromagnetic interference,cannot realize long-term real-time on-line monitoring,large temperature drift and so on.Fiber Bragg Grating(FBG)accelerometer as a new type of sensor,using optical wavelength signal as the medium of information transmission,can make up for the above shortcomings of electromagnetic sensors,but it is inferior to electromagnetic sensors in range,sensitivity and frequency band range,which limits its application scope and field.Moreover,there are few studies on high-range FBG impact accelerometers at home and abroad.In recent years,FBG accelerometers have developed rapidly,especially for the FBG accelerometers based on circular hinges.However,the hinge modes are much monotonous and their parameters need to be refined.Considering the above points,a FBG accelerometer based on elliptical flexible hinge is proposed,and a high-range impact sensor and a low-frequency vibration sensor are designed.The main research contents and results of this paper are as follows:(1)The FBG accelerometer based on the design of elliptical flexible hinge is proposed.The mechanical model of the sensor is constructed and its theoretical formula of sensitivity and natural frequency is derived.By means of transient dynamics simulation,the stress and displacement changes of the sensor under impact load are studied,and the design theory of FBG shock accelerometer is deduced.The FBG shock accelerometer and low frequency accelerometer based on elliptical flexible hinge are designed.The parameters of the sensor are optimized by combining MATLAB and LINGO software,and the optimal structural parameters of the sensor are obtained.The validity of the sensor theoretical model is verified by the modal analysis and harmonic response analysis of the established sensor finite element model.(2)According to the above designing principle,we fabricated the FBG accelerometer,and carried out the expriment of performance evaluation.The amplitude frequency response,sensitivity and transverse anti-interference characteristics of the sensor are tested experimentally.The test results show that the natural frequencies of the FBG shock accelerometer and the low frequency accelerometer are about 980 Hz and 380 Hz,respectively,and the sensitivity is 54 pm/g and 470 pm/g respectively under low-frequency excitation conditions.The transverse anti-interference of both sensors is less than 8%.The results of performance test are similar to the theoretical design and simulation analysis results,which verifies the correctness of the theoretical model.(3)The impact test of FBG shock accelerometer is carried out,and the test results of piezoelectric accelerometer are compared.The shock response state of the sensor is analyzed,and the results indicate that the range of the sensor is at least 100 g.The lowfrequency accelerometer is applied to Guangzhou-Shenzhen high-speed viaduct section,and the self-vibration test is carried out.The first six-order modes frequency of the viaduct section are analyzed and compared with the simulation results.The analysis results show that the referred sensors in this thesis can greatly satisfy with the the demand of engineering applications,and both show great performance with high reliability and good practicability.