【作者】 江俊峰；

【导师】 张以谟； 刘铁根；

【作者基本信息】 天津大学 ， 光学工程， 2004， 博士

【摘要】 结构健康监测系统是智能结构的一个重要应用方向,日益受到人们的关注。光纤 Bragg 光栅(FBG)传感器和非本征光纤法珀(EFPI)传感器是在结构健康监测领域非常有前景的两种光纤传感器。本文从解调系统的角度组合 FBG 和 EFPI传感器进行了应变、温度双参数传感的研究,设计了综合 FBG 傅里叶变换解调方法和 EFPI 传感器低相干干涉解调方法的并行解调方案,在此基础上完成了并行解调系统的构建与实验。在工程应用方面,进行了光纤光栅在预应力钢绞线应力测量领域的应用研究,设计开发了适应大应力范围下的光纤传感系统。 1. 系统研究了光纤法珀传感及其解调的相关理论。建立了 EFPI 的传感解调模型。基于部分相干理论,以 Michelson 干涉仪作为解调干涉仪详细推导了不同精细度 EFPI 作用下的干涉仪输出,并将实验与计算结果作了对比。从系统设计的角度研究了利用组合光源增强低相干干涉信号处理能力,定义了附加信噪比,从而可获得实际信噪比要求,并进行了光源组合实验。研究了 Morlet 解析小波在提取低相干干涉条纹包络的应用,给出了 Morlet 小波尺度s的计算公式。进行了仿真计算和实测干涉图的提取实验。 2. 研究了均匀周期光纤光栅的传感模型及其傅里叶变换解调理论。依据耦合模理论推导了均匀周期光纤光栅的传输响应特性。研究了均匀周期光纤光栅的应变温度传感模型及热诱导应变、应变温度交叉灵敏度的影响。研究分析了傅里叶变换解调中的误差来源,对三种噪声做了详细分析。给出了主要伪谱的出现位置和幅度。 3. 利用传感系数矩阵的条件数研究分析了结构监测中应变、温度双参数传感的传感器组合。采用 EFPI 和 FBG 传感器组合,根据信号分离方式提出了三种应变、温度双参数传感并行解调方案,并设计了相应的并行解调系统。方案采用ASE 光源作为系统光源。采用基于交叉滚柱轴承技术的运动平台,平台由精密压电陶瓷电机驱动,并通过光栅尺编码器提供运动定位编码,利用 Mini-PMAC 控制卡实现运动扫描平台的闭环运动控制,通过 PID 控制参数,速度前馈和加速度前馈控制参数的调整实验,得到高运动分辨率和良好的运动平稳性。采用 InGaAs探测器和 AD 采集卡实现了干涉信号的采集。 4. 进行了双参数传感并行解调方案的软件设计及数据处理方法的研究。采用面向对象思想进行软件设计,根据功能要求设计了软件的整体模块化结构,设 i<WP=4>计开发了软件的主控模块和 5 个主要的 C++类。在数据处理方面详细研究了用于处理 FBG 干涉信号的多种谱估计算法,并研究了一种数据融合模型。 5. 构建了应变、温度双参数传感并行解调方案的实验系统。进行了傅里叶变换光谱的重建实验研究。讨论了系统噪声的影响。利用并行解调系统进行了光纤光栅和光纤法珀的应变实验,分别获得 16.5με 和 13.49με 的测量精度。利用并行解调系统进行了 FBG、 EFPI 组合型的双参数测量实验研究。40°C 温度下的测量应变平均测量偏差0.028με ,测量精度24.36με ,温度测量平均偏差2.05°C ,温度测量精度为1.61°C 。 6. 利用光纤光栅进行了预应力钢绞线应力测量的应用研究。研究分析了预应力钢绞线的特性,提出了与之相适应的光纤光栅安装方法。研制开发了基于光纤熔锥型 WDM 器件便携式光纤光栅解调装置。应变解调范围在 0～20000με 或±10000με ,应变分辨率为 38με 。在预应力钢绞线试验机上进行了钢绞线光纤光栅传感器应力测量试验,成功的实现了光纤光栅超过 7000με 的测量。研究了逆散射理论在环氧树脂胶分布应变测量的应用。研究了光纤光栅的分布传感模型,利用逆散射理论建立了光纤光栅复反射谱与应变分布的对应关系并对三种应变分布进行了仿真计算。工作中的主要创新点1. 提出从解调系统的角度上组合 FBG 和 EFPI 传感进行应变、温度双参数传 感,基于一套 Michelson 扫描干涉仪实现了两种传感器的双参数传感并行解 调方案,该解调方案综合了 FBG 傅里叶变换解调方法和 EFPI 传感器低相干 干涉解调方法。2. 指出在高反射率情况下,单个 EFPI 的多次反射可在干涉仪扫描时输出多个 低相干干涉峰,当这多个干涉峰不重叠时,可通过对这多个干涉峰值位置取 平均来提高测量精度;研究了固定尺度的 Morlet 小波和固定位移的 Morlet 小波分别在 EFPI 信号包络提取和 FBG 反射谱估计的应用。3. 研制开发了一套并行解调方案的光纤传感测控、数据处理软件;提出在短扫 描行程情况下利用样条函数插值获取光谱高分辨率的数据处理方法;对于 EFPI 和 FBG 干涉信号混叠输出的情况,提出利用完整干涉图和局部干涉图 分别提取 FBG 传感信息和 EFPI 传感信息的数据处理方法。4. 进行了光纤光栅用于预应力后张法中的预应力钢绞线的大量程应力测量研 究,研制开发了一种便携式光纤光栅传感系统,并研究了逆散射理论在局部 应变分布传感中的应用。更多还原

【Abstract】 Structure health monitoring system is an important application field of smartstructure and gets more and more concern. Fiber Bragg grating (FBG) sensor andextrinsic Fabry-Perot interferometer (EFPI) sensor are two kinds of optical fibersensors suit for structure health monitoring. In this paper, a research of measuringstrain and temperature simultaneously is carried out with combination of FBG andEFPI sensors from the view of demodulation system. A parallel demodulation systemis designed, which combines the Fourier transform demodulation method of FBG andlow coherence demodulation method of EFPI. Then an experiment system isestablished and a set of experiments are carried out. In the engineering application, anapplication research of FBG on stress measurement of prestressed steel strand iscarried out and a fiber sensor system used for large stress range is developed. 7. The theory of EFPI sensing and demodulation is studied. A sensing model ofEFPI is established. Based on partial coherence theory, the output of interferometerunder different finesse EFPI acting is deduced with Michelson interferometer asreceiving interferometer, and the results of experiment and computation are compared.From the view of system design, the synthesis of light source used for enhancingprocess of low coherence interference signal is studied and an additive signal to noiseratio (SNR) is defined, which helps obtain the actual demand SNR. The experiment ofsynthesis of light source is carried out. The application of Morlet wavelet to retrievethe profile of low coherence interference is discussed and a formula for deciding scaleof Morlet wavelet is provided. Simulation and experiment of retrieving profile arecarried out. 8. The sensing model and Fourier transform demodulation method of uniformperiod fiber grating are discussed in detail. The spectrum response of uniform periodfiber grating is deduced with couple mode theory. The strain and temperature responseof it is studied. The effect of strain induced by heat and cross-sensitivity betweenstrain and temperature are analyzed. The error sources of Fourier transformdemodulation method are discussed and three main noises are analyzed in detail. Theposition and amplitude of main fake spectrums are provided. iii<WP=6>9. The combinations of sensors for simultaneous measurement of strain andtemperature, which are used for structure health monitoring, are analyzed with thecondition numbers of sensing coefficient matrixes. With combination of EFPI andFBG sensors, three parallel demodulation schemes for simultaneous measurement ofstrain and temperature are proposed and designed, based on the different methods ofsignal separating. ASE light source is adopted. Motion stage is made up of crossedroller bearing, piezo linear motor, and linear encoder. The close-loop motion control isrealized with Mini-PMAC card. Through the adjust experiment of PID, velocityforward feedback and acceleration forward feedback, high motion resolution andgood stability of stage are obtained. The interference acquisition is realized withInGaAs detector and AD acquisition card. 10. The software for parallel demodulation is developed and method of dataprocess is studied. With object-oriented software development method,the wholestructure of software is designed according to the function demand, then the maincontrol module and five main C++ classes are developed. Several spectrum evaluationmethods for FBG are studied in detail and a data fusion model is proposed. 11. The experiment system of parallel demodulation for simultaneousmeasurement of strain and temperature is established. The reconstructionexperimental research of Fourier transform spectrum is carried out, the effect of noiseis discussed. With this system, strain experiment of FBG and EFPI is carried out, andprecision of 16.5 με and 13.49 με are obtained respectively. Then the experiment ofsimultaneous measurement更多还原