Research On Characteristics Of Miniaturized Vibration Sensor Based On Fiber Bragg Grating

Natural disasters such as earthquakes and debris flows will deteriorate the health of my country’s large-scale infrastructure,resulting in increased engineering safety risks,threatening people’s health and safety and the stable and orderly economic development.Therefore,relying on the vibration sensor to pick up the characteristic parameters such as natural vibration frequency and bad vibration of large structures from time to time,and carry out structural damage identification based on low-frequency engineering vibration,is the most direct and effective way to conduct trend analysis and safety warning of large-scale engineering structure health.Compared with traditional electrical vibration sensors,fiber Bragg gratings,as a new type of passive sensing device,have the advantages of small size,high sensitivity,distributed measurement,low transmission loss,etc.It can replace electronic accelerometers under harsh environmental conditions,and can improve the ability of remote online monitoring while ensuring high-fidelity acquisition of low-frequency vibration signals.This paper takes engineering vibration acquisition as the application scenario,and takes the characteristics of the miniaturized acceleration sensor based on fiber Bragg grating as the research target.Fiber-like accelerometers,one is a low-frequency fiber grating accelerometer with three cantilever beam structure,and the other is a low-frequency fiber grating accelerometer with double-tilted cantilever beams.The structure design is studied,and a low-frequency vibration test experimental system is built to test two types of accelerometers.Low frequency vibration characteristics of the sensor.The main contents of this article are as follows:(1)Analyze the fiber Bragg grating strain and temperature sensing principle and two easy-to-implement temperature compensation methods;on the basis of the traditional electrical acceleration sensing principle,the sensitivity theoretical formula of the FBG accelerometer is deduced,which provides a basis for subsequent research work.Theoretical support,two-point adhesive axial package FBG sensing model and two-point adhesive radial package FBG sensing model are proposed,and the effect of fiber length and prestress on its natural vibration characteristics is studied by using ANSYS Workbench simulation software,which is used for subsequent FBG acceleration sensors.The design and packaging provide a theoretical basis.(2)A low-frequency fiber grating accelerometer with a three-cantilever structure is proposed to meet the actual needs of low-frequency seismic data acquisition.The theoretical model of the sensor is established and its parameters are optimized.After optimization,the mass of the sensor probe is about 138 g and the volume is about19.56 cm~3,which meets the design goal of miniaturization.The ANSYS Workbench software is used to simulate and analyze it,and then the sensor is studied through experiments.characteristic.The experimental results show that the natural frequency of the sensor is about 64 Hz,and it can be used to monitor vibration signals in the frequency range of 16-54 Hz.86 d B.(3)In order to analyze the influence of the tilt angle of the cantilever beam on the characteristics of the sensor,a low-frequency fiber grating accelerometer with double tilt cantilever beam is proposed.The theoretical model of the sensor is established,and the theoretical formula of the sensitivity of the inclined cantilever beam sensor is deduced.The structural parameters of the sensor are simulated and optimized.After optimization,the mass of the sensor probe is about 32 g and the volume is about 3.96cm~3.Fabricate the horizontal beam acceleration sensor and design a control experiment.The experimental results show that the natural frequency of the dual-inclined cantilever beam sensor is about 46 Hz,which can be used to monitor vibration signals in the frequency range of 6-30 Hz.The sensitivity of the sensor is about 4.16 pm/m·s~2,and the anti-transverse interference degree is less than 5.62%.Compared with the horizontal cantilever beam FBG accelerometer,the flat response area of the double-inclined cantilever beam FBG accelerometer is increased by about30%,but the sensitivity is reduced by about 1 times,which basically meets the needs of low-frequency vibration signal acquisition.