Design And Research Of FBG Acceleration Sensor With Symmetrical L-beam Structure

Low-frequency vibration monitoring is of great significance in the field of earthquake disaster monitoring.Acceleration sensor is one of the keys in the field of earthquake disaster monitoring,and its performance is crucial to the monitoring of lowfrequency seismic signals.Fiber Bragg Grating(FBG)acceleration sensor has been a research hotspot in recent years.It has the advantages of anti-electromagnetic interference,small size,easy to carry,high accuracy,and good stability.It can replace traditional electrical sensors for low-frequency vibration signal measurement.However,the measurement of low-frequency vibration signals of less than 10 Hz has the problems of inaccurate measurement and low measurement sensitivity.In response to the abovementioned problems,this paper developed a symmetrical L-beam structure FBG acceleration sensor to realize the detection of seismic low-frequency signals.The research content includes:(1)Theoretical analysis of the principle of fiber Bragg grating sensing,analysis of the theoretical model of the FBG acceleration sensor,and the basic principle of the FBG acceleration sensor.Based on the sensing principle of fiber Bragg grating and the design of general acceleration sensor,a symmetric L-beam structure fiber Bragg grating(SLFBG)acceleration sensor is designed and proposed.The mechanical theory derives the natural frequency and sensitivity theory of SLFBG acceleration sensor formula.(2)Using MATLAB software,the influences of the three structural parameters of L-arm ratio,diaphragm thickness and mass mass on the natural frequency and sensitivity of the acceleration sensor are discussed separately,and the structural parameters of the SLFBG acceleration sensor are determined.After determining the main structural parameters L-arm ratio,diaphragm thickness and mass mass,threedimensional modeling of SLFBG acceleration sensor was performed using SOLIDWORKS,and modal analysis and static analysis of the SLFBG acceleration sensor model were performed using ANSYS finite element software.(3)Construct a test system to test the amplitude-frequency response characteristics,linear response characteristics and anti-lateral interference performance of the SLFBG acceleration sensor,and obtain the performance indicators of the sensor.The test results show that the natural frequency of the FBG acceleration sensor with a symmetrical Lbeam structure is about 27 Hz,the sensitivity is 241.2 pm/g,and the lateral interference of the sensor is less than 10%,which realizes the measurement of low-frequency vibration signals less than 10 Hz.