变截面悬臂梁式光纤布拉格光栅压力传感器设计研究

Design and Research on Variable Cross-section Cantilever Fiber Bragg Grating Pressure Sensor

为满足煤矿井下复杂环境中围岩应力测量的实际需要,设计了一种变截面悬臂梁结构的光纤光栅压力传感器,并与等截面悬臂梁结构进行了对比。对其压力与光纤光栅漂移量的关系进行了推导;通过有限元方法分析了不同截面悬臂梁影响灵敏度大小的情况,确定了悬臂梁的尺寸;在此基础上应用数值分析和有限元分析探究了不同结构和材料参数对两种悬臂梁结构灵敏度的影响,同时与类似结构进行了对比分析。研究结果表明:设计时应选用固定端厚度相对较小、自由端厚度相对较大的变截面梁,最终选定的变截面悬臂梁厚度为固定端0.5 mm、自由端2 mm,传感器的压力灵敏度可达893.45 pm/MPa,是裸光纤光栅的294倍。在改变结构及材料参数后,变截面悬臂梁结构的压力灵敏度依然优于等截面悬臂梁,验证了传感器结构的合理性,能够满足煤矿巷道监测所需,并且在量程范围内具有良好的线性。

This study presents a fiber Bragg grating pressure sensor with a variable cross-section cantilever structure,which meets the needs of surrounding rock-stress measurements in the complex environment of a coal mine.The performances of the designed sensor and a sensor with a constant cross-section cantilever structure are compared,and the relationship between the pressure and fiber grating drift is derived.The cases affecting the sensitivity of different crosssection cantilever beams are analyzed using the finite element method,and the size of the cantilever beam is determined.The effects of different structures and material parameters on the sensitivities of the two cantilever structures are determined through a numerical and finite element analysis.The results are compared with the experimental results of a similar structure.The results showed that the variable cross-section beam should be designed with a relatively thin fixed end and a relatively thick free end.In the final variable cross-section cantilever beam,the thicknesses of the fixed and free ends were 0.5 mm and 2.0 mm,respectively.The sensitivity of the sensor reached 893.45 pm/MPa,which is294 times that of the bare fiber grating.Even after changing the structure and material parameters,the sensitivity of the variable cross-section cantilever beam was greater than that of the constant cross-section cantilever beam.The sensor structure can meet the needs of coal mine roadway monitoring and exhibits good linearity in the operating range.