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结合不锈钢膜片的特性,研制出一种微型高精度光纤布拉格光栅(FBG)土压力传感器。该传感器通过不锈钢膜片与力学传递元件将土压力转化为光纤光栅的轴向拉力,大大提高了传感器的灵敏度,有效避免了光栅受力不均引起的啁啾效应,同时减小了传感器的体积。通过理论计算,得到该传感器的压力敏感系数为29.6557nm/MPa,是裸光栅的9885倍。传感器性能测试实验证实该传感器线性度良好,实测压力敏感系数为27.5nm/MPa,略小于理论值,其主要原因是应变传递效率低于1。为进一步提高实验测量精度,采用Haar小波变换来减小因光纤光栅解调设备模数(A/D)采样速率及转换精度有限带来波长抖动所产生的仪器误差,实验数据表明经Haar小波处理后光栅中心波长的抖动幅值降为原数据的50%左右。
Combined with the characteristics of stainless steel diaphragm, a miniature high-precision fiber Bragg grating (FBG) earth pressure sensor was developed. The sensor converts the earth pressure into the axial tension of the fiber grating through the stainless steel diaphragm and the mechanical transmission element, which greatly improves the sensitivity of the sensor and effectively avoids the chirping effect caused by the uneven force of the grating and simultaneously reduces the volume of the sensor . Through the theoretical calculation, the pressure sensitive coefficient of the sensor is 29.6557nm / MPa, which is 9885 times that of the bare grating. Sensor performance test confirmed that the linearity of the sensor was good. The measured pressure sensitivity coefficient was 27.5nm / MPa, slightly lower than the theoretical value. The main reason was that the strain transfer efficiency was lower than 1. In order to further improve the experimental measurement accuracy, Haar wavelet transform was used to reduce the instrumental error caused by the wavelength jitter due to the finite sampling rate and conversion precision of A / D demodulation equipment. The experimental data show that Haar wavelet processing After the grating center wavelength jitter amplitude reduced to about 50% of the original data.