差动式光纤布拉格光栅渗压传感器的研究

Study on the Differential Fiber Bragg Grating Seepage Pressure Sensor

为了对土壤中渗透水压力进行精确测量,根据波纹管的压力传感特性,以及等强度悬臂梁与光纤Bragg光栅的应变传感特性,设计了一种差动式光纤布拉格光栅(FBG)渗压传感器。传感器通过土壤渗透水压力推动波纹管轴向应变转化成等强度悬臂梁挠度变化,进而转化成FBG轴向应变。通过测量FBG中心波长的变化获得压力值,利用差动式结构降低了环境温度变化带来的影响。在常温条件下进行标定试验,得出升压过程中传感器的渗压灵敏度约为11.96 pm/k Pa,线性度为1.3%,重复性为2.9%;降压过程中传感器的渗压灵敏度约为10.56 pm/k Pa,线性度为4.6%,重复性为1.9%;环境温度变化对测量结果影响小于1%。试验结果表明,该光纤光栅渗压传感器能够对小量程范围内的渗压进行准确测量,同时可以通过改变波纹管及等强度梁参数将其推广到大量程的测量。

In order to accurately measure the seepage water pressure in soil,according to the pressure sensing characteristics of bellows,and the strain sensing characteristics of cantilever beams with equal strength and the strain sensing characteristics of the fiber bragg grating（ FBG）,a differential FBG seepage pressure sensor has been designed. Under the action of osmotic pressure of soil,the axial strain of bellows converted into the change of the deflection of equal strength cantilever,and converted to axial strain of FBG in further. The pressure is obtained by detecting the variation of the center wavelengths of the FBG,and the effects of environmental temperature changes are reduced by using differential structure. Under ambient temperature,in the process of boosting,calibration experiments show that the pressure sensitivity of the sensor is 11. 96 pm/k Pa,the linearity is about 1. 3%,and the repeatability is 2. 9% FS; in the process of decompression,the pressure sensitivity of the sensor is 10. 56 pm/k Pa,the linearity is about 4. 6%,the repeatability is 1. 9% FS. And the environmental temperature change influence on measurement results lower than 1%. The test results show that,the fiber grating sensor can accurately measure the osmotic pressurein a small range; it also can be promoted to the large range of measurement by changing the parameters of bellows and equal strength beam.