Research On Sensitized FBG Accelerometer Based On Straight Circular Flexible Hinge

Faced with the demand for vibration monitoring in the field of online monitoring and fault diagnosis,compared with electrical sensors,fiber Bragg grating(FBG)accelerometers have been valued for their advantages of anti-electromagnetic interference,long-distance transmission and distributed measurement.The sensitivity and natural frequency of the FBG accelerometer will restrict each other.The sensitivity of the medium-high frequency FBG accelerometer is often low,and the low sensitivity will reduce the vibration measurement resolution of the sensor.In addition,in order to expand the application of FBG accelerometers in aerospace and other fields,the research on accelerometer miniaturization is of great significance,but the current miniaturized FBG accelerometers also face problems such as low sensitivity.For this reason,this paper proposes a medium-frequency high-sensitivity FBG accelerometer and a miniaturized high-sensitivity FBG accelerometer based on straight circular flexible hinge,which are theoretically analyzed,simulated and optimized,and tested in real objects.The main research contents of this paper are as follows:(1)A medium-frequency high-sensitivity FBG accelerometer based on the serial structure of multiple straight circular hinges is proposed.The mechanical model of the sensor is constructed according to the mechanics theory,the sensitivity and natural frequency formula of the sensor are deduced,and the influence of structural parameters on the performance of the sensor is numerically analyzed by using Matlab software.In order to realize the high-sensitivity of the accelerometer,the simulation and optimization design of the sensor is carried out by using Workbench software,and the size of the sensor is determined.And the modal analysis and harmonic response analysis simulation are used to verify the performance of the accelerometer with the determined size.(2)A high-sensitivity miniaturized FBG accelerometer based on straight circular hinge and T-shaped mass structure is designed.The sensor mechanics model is constructed according to the mechanics theory,and the sensor sensitivity and natural frequency formulas are deduced.According to the principle of miniaturization,some parameters of the sensor are determined,and the influence of other structural parameters on the performance of the sensor is numerically analyzed by using Matlab software.In order to realize the miniaturization and high sensitivity of the sensor,the optimized design of the sensor was carried out using Workbench software,and the size of the sensor was determined.The sensor size is 25 mm × 21 mm × 9 mm,and the weight of the inertial mass is 8.619 g.And the performance of the miniaturized FBG accelerometer of determined size is verified by simulation.(3)The package design and fabrication of the medium-frequency FBG accelerometer are studied,and the performance of the accelerometer is calibrated.The test results show that the natural frequency of the medium-frequency FBG accelerometer is about 2800 Hz,and the average sensitivity in the operating frequency range of 50 Hz to 1000 Hz is 21.8 pm/g,which is basically consistent with the simulation and theoretical calculation results.The lateral interference of the sensor is less than 5%.And the temperature sensitivity coefficient of the sensor is only 0.3 pm/°C.The accelerometer has higher sensitivity and better overall performance.(4)Design the package of the miniaturized FBG accelerometer,and make a real object for testing.The test results show that the miniaturized FBG accelerometer has a good linear relationship under different excitation frequencies,the natural frequency of the sensor is about 1000 Hz,and the average sensitivity in the operating frequency range of 30 Hz to 400 Hz is 62.6 pm/g,which is basically consistent with the simulation and theoretical calculation results,and the lateral interference of the sensor is less than 5%.