Vibration Characteristic Research Of Chained FBG Accelerometer Based On Circular Flexible Hinge

Vibration is generally existent in mechanical equipment and building structure,and abnormal vibration often causes equipment or structural failure.Therefore,it is of great significance for equipment and structure vibration monitoring to establish an on-line monitoring system.Compared with traditional electrical sensors,fiber Bragg grating(FBG)sensors have many advantages such as long distance transmission,on-line monitoring,anti-electromagnetic interference and corrosion resistance,and so on,which can provide favorable conditions for on-line monitoring of vibration.This paper takes a chained FBG accelerometer based on arc flexible hinge as the research object,and researches on its working principle and theoretical analysis in detail.Based on that,a mid-frequency accelerometer is developed.The main working and conclusion of this paper are as follows:(1)This paper designs a chained FBG accelerometer based on arc flexible hinge and introduces the working principle of the accelerometer.Through a certain simplified processing,the natural frequency and acceleration sensitivity of the accelerometer are analyzed by using the general equations of dynamics and the transfer matrix method separately.The calculation methods of natural frequency and acceleration sensitivity under two different theoretical models are obtained,which provide a theoretical basis for the analysis and design of the accelerometer.(2)According to the theoretical model obtained by the transfer matrix method,this paper analyzes the influence of different structural parameters on the natural frequency and sensitivity of the accelerometer.And a mid-frequency accelerometer is designed.Then the natural frequency,sensitivity and equivalent stress are analyzed by finite element analysis software ANSYS,so as to judge the merits and drawbacks of the two accelerometer theoretical models.The finite element analysis results show that the accelerometer has the natural frequency of 1829 Hz and the sensitivity of about 33.7 pm/g.Besides,the maximum equivalent stress under 1 g(9.8 m/s~2)acceleration is about 0.37 MPa in the frequency measuring range.(3)The designed chained FBG accelerometer based on the arc flexible hinge is packaged and tested.Though the test experiment,the frequency response curve of the FBG accelerometer is obtained and its sensitivity is tested.Then the directional anti-interference and damping characteristics of the accelerometer are tested.The test results show that the natural frequency of the accelerometer is about 1850 Hz,its sensitivity is about 23.99 pm/g,and the sensitivity of the cross-axis is less than 13.8%.The use of damping seal can effectively improve the frequency response curve of the accelerometer and play a protective role.(4)For the designed mid-frequency accelerometer,the natural frequency is calculated to be about 2187 Hz and the sensitivity is about 23.93 pm/g by using the theoretical model of the general equations of dynamics.Through the theoretical modal of transfer matrix method,the accelerometer has the natural frequency of about1935 Hz,and the sensitivity of about 29.68 pm/g.Both the finite element analysis results and the test results show that the two theoretical models have certain accuracy for analyzing the natural frequency and sensitivity of the FBG accelerometer.