| Acceleration detection is an important technique in seismic monitoring,structural health monitoring and resource exploration.As the basic part of the earthquake monitoring system,the sensor's performance directly determines the earthquake monitoring effect of the seismic network,which is of great significance to earthquake monitoring and early warning,protecting people's life safety and reducing unnecessary economic losses.However,the application of traditional electrical sensors in practical engineering is seriously restricted because of their susceptibility to electromagnetic interference,cumbersome wiring and fast signal attenuation in long-distance transmission environment.Due to its high sensitivity,anti-electromagnetic interference and low transmission loss,FBG has become one of the most promising research directions in the field of optical fiber acceleration sensor.However,at present,FBG acceleration sensor has the problems of low sensitivity of low-frequency measurement and cross crosstalk of vibration acceleration caused by temperature.Therefore,this paper proposes a low-frequency FBG acceleration sensor based on L-shaped rigid beam and cross reed,and its main work is as follows:(1)Based on the theoretical model using Solidworks software to L-shaped rigid beam structure modeling,the low frequency of FBG accelerometer sensitivity and natural frequency of the structure of theoretical derivation formula to get get the key structural parameters affect the performance of the,and parameter optimization analysis,simulation analysis was carried out on the structure model using COMSOL software.(2)Analysis based on L-shaped rigid beam problems of the low frequency of FBG acceleration sensor,its structure size is too large,the sensor quality of 290 g,and sensitivity and natural frequency of the sensor in theory analysis,is the bearing-spring system is regarded as the ideal state,namely ignoring friction bearing rotation.Based on the above two problems,two optimization objectives are proposed:one is to miniaturize the sensor structure;the other is to replace the original bearing-spring system with two symmetrical cross reeds to eliminate the friction of bearing rotation.A low frequency FBG acceleration sensor based on a cross reed was designed,its structure was modeled,its sensitivity and natural frequency theoretical formula was deduced,and its parameters were optimized and simulated.(3)Physical processing and packaging of the two sensors,the sensor vibration test system and temperature test system,test the main performance indicators of the two sensors.The L-shaped rigid beam structure has a natural frequency of 57 Hz and a flat sensitivity response in the low frequency band of 3-35 Hz.The dynamic range is89.83 d B,the sensitivity is 1241.85 pm/g,the fitting determination coefficient R~2is0.9997,and the transverse crosstalk is-26.20 d B.And the natural frequency of the cross reed sensor structure is 65.49 Hz,the measurement range of frequency band is3-45 Hz,the dynamic range is 84.94 d B.The sensitivity of sensor is 1498.29 pm/g,the fitting determination coefficient R~2is 0.9998,and the relative standard deviation of the sensor repeatability is 0.89%.The crosstalk is-33.99 d B.Compared with the L-shaped rigid beam structure,the natural frequency of the cross reed structure increases by 14.89%,the available frequency band widens by 31.25%,the dynamic range decreases by 5.44%,the sensitivity increases by 24.88%,and the ability to resist transverse interference increases by 29.73%. |
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