Research On High Sensitivity Low Frequency FBG Accelerometer

Low frequency vibration measurement technology can be used in frontiers of large building quality monitoring,earthquake tsunami monitoring and forecasting,geological exploration,various types of energy development,spacecraft,precision manufacturing,nuclear monitoring,environmental monitoring,biology,physics and materials science,which plays a pivotal role in national defense construction and national production.The fiber optic vibration sensor has the advantages of high precision,reusability,good stability and anti-electromagnetic interference,and has been a focus topic in academic and engineering circles at home and abroad in recent years.However,due to its low sensitivity,it can not be used for measuring the vibration less than 10 Hz.Therefore,high-sensitivity and low-frequency acceleration sensor is of theoretical significance and engineering application value.In order to solve the above problems,high-sensitivity low-frequency FBG accelerometer was investigated.The main contents was included as follows:?1?Structural design and theoretical analysis of FBG acceleration sensor was done.Firstly,based on the vibration principle,an improved beam structure acceleration sensor with optical fiber as elastic element is proposed.A mathematical sensing model is established.The effect of the structural design parameters such as fiber length,system elastic coefficient and mass quality on the sensing properties of FBG acceleration sensor was illustrated.The law of influence provides a theoretical basis for the acceleration sensors.?2?Production technology of FBG accelerometer was investigated.Based on the adsorption theory in the bonding principle,by increasing the contact area of the bare fiber,the packaging problem of the fiber grating under the high prestress is solved,and the design function of the acceleration sensor is realized.?3?Five kinds of high-sensitivity low-frequency FBG accelerometers were designed and manufactured,and the five kinds of accelerometers were called as the support plate double-spring double-gate and single-gate type,single-spring double-gate and single-gate type,double-spring double-gate type,vertical support plate double-spring double-gate type and large elastic coefficient double-spring double-gate type.The experiment of response characteristics,amplitude characteristics and frequency measurement was done.The results show that the double-spring double-gate and large elastic coefficient double-spring double-gate FBG accelerometers have some advantages such as wider frequency response,wider measuring range,good stability and so on.The frequency response range of the double-spring double-gate FBG accelerometer is 0.5²0 Hz and 23³0 Hz,the sensitivity is 2 711 pm.g^-1 and 3 336pm.g^-1,the measuring range is 0.1² g,and the static error is 1.8%;The frequency response range of the large elastic coefficient double-spring double-gate FBG accelerometer is 0.5 to 40 Hz,the sensitivity is 1 154 pm.g^-1,the range is 0.02 to 2 g,and the static error is 2.9%.In addition,the designed sensor can also be used for measuring the vibration frequency,and the large elastic coefficient double-spring double-gate FBG accelerometer can be used for measuring the maximum frequency range.