| In recent years,fiber Bragg grating tilt sensors have played an increasingly important role in structural health monitoring.However,buildings and facilities that require tilt monitoring are usually affected by irregular wind vibration or vibration from the surrounding dynamic machines,and the tilt sensors are also sensitive to these vibration signals,resulting in inaccurate measurement of the tilt state of the target object,or even false alarms.In order to eliminate the interference of external vibration on the tilt measurement,the existing scheme is to configure an additional vibration compensation device for the tilt sensor,and use a complex filtering denoising algorithm to filter out the vibration signal,resulting in a more complicated process for tilt monitoring.Additionally,the internal structure of tilt sensors is prone to damage during transportation,rendering them unusable and increasing monitoring costs.To address these issues based on the practical engineering demands,this paper has developed a vibration-resistant FBG tilt sensors technology,which is detailed as follows:(1)The significance of tilt information monitoring was expounded,and the shortcomings of current commonly used tilt monitoring methods were analyzed.The existing FBG tilt sensors were classified and summarized,and preliminary design ideas for fiber Bragg grating-based tilt sensors were proposed to address some existing problems.(2)A vibration-resistant tilt sensor based on fiber Bragg grating has been developed,and a reasonable temperature compensation scheme for the sensor has been selected.A vibration reduction connection structure of cantilever beam + isolation spring + mass block is proposed,and damping fluid is injected into the sensor as a vibration reduction material to solve the problem that traditional FBG tilt sensors are easily affected by external vibrations.A special protective structure is designed inside the sensor,which can fix the mass block inside the sensor when transporting the tilt sensor,protecting the internal structure of the sensor from damage.(3)Four FBG tilt sensors were prepared according to the structure designed in this paper,and an additional FBG tilt sensor with a rigid fixed connection between the cantilever beam and the mass block was made for control experiments.Static measurement indicator tests were conducted on the prepared sensors,including tilt calibration experiment,creep resistance test,and temperature compensation characteristic test.Through processing and analyzing the experimental data,it can be concluded that the maximum tilt measurement sensitivity of the FBG tilt sensor designed in this paper is 112.743 pm/°,the tilt measurement accuracy is 0.0266°,and the resolution is 8.87×10-4°.At the same time,it also has excellent creep resistance and temperature compensation capabilities.(4)A comparative experiment was conducted on the vibration-resistant performance of five FBG tilt sensors with different internal configurations under two vibration modes.The experimental results show that the FBG tilt sensor designed in this paper has excellent resistance to sudden and sustained vibration interference.A control experiment was conducted with damping fluid viscosity as the variable to explore the relationship between damping fluid viscosity and sensor tilt response time.The results show that by flexibly adjusting the viscosity of the damping fluid inside the sensor,the desired vibration-resistant stability and measurement accuracy of the sensor can be ensured to meet the requirements of different monitoring tasks. |
