光纤布拉格光栅应变传感系统可靠性的关键技术研究

发布时间：2018-06-17 17:47

本文选题：光纤布拉格光栅 + 应变传感　；参考：《重庆大学》2016年博士论文

【摘要】：光纤布拉格光栅(Fiber Bragg Grating,FBG)应变传感系统因其独特的优势,已在各行各业获得了广泛的应用。但在实际应用中,传感系统会出现不同程度的性能退化、进而产生各种类型的故障,严重影响其推广效果。这使得系统的可靠性成为了用户最关注并亟待解决的共性难题。但因其牵涉面广、技术难度高,且耗时费力、极难在理论上取得突破,因而难以受到研究人员足够的重视,是光纤传感研究领域最薄弱的环节。要在FBG应变传感系统可靠性研究上取得突破,就必须从传感器和解调仪这两个关键环节入手,从传感器与信号解调的基本原理出发,深入研究FBG传感元件在各种恶劣环境中的性能变化规律,研究传感器封装与安装的应变传递特性,研究解调方法的鲁棒性、评估解调结果的可信性。这既能为FBG传感器的制造企业提供指导,也可以为FBG传感器的用户提供使用帮助,对促进FBG传感技术、国民经济和国防事业的发展都具有重大的意义。为此,本文从FBG传感元件、应变传递和传感解调三大方面开展了深入研究,主要的研究内容如下:(1)为了提供研究FBG可靠性基本的理论与方法,总结分析了FBG结构的形成机理,提出了从光化学反应角度理解FBG折射率变化的思想;基于耦合模理论和传输矩阵法,推导了FBG光谱的仿真方法;总结分析了FBG光谱特征指标。(2)全面探索了FBG传感元件在力学、温度、和辐照环境中的性能变化规律。针对轴向、横向作用力对FBG传感特性影响研究归纳不全面的问题,分别推导了轴向、横向受力对FBG光谱的影响模型,仿真了分析轴向、横向作用力对FBG光谱影响的规律,并提出了确保FBG可靠传感的许用条件。针对弯曲对FBG传感特性影响机理不明确的问题,建立了弯曲对FBG光谱的影响模型,并结合此模型给出了确保FBG可靠传感的弯曲条件。针对长期作用力下FBG光谱恶化机理与规律不明确的问题,通过理论分析和实验得出了长期作用力下FBG光谱的恶化机理及恶化规律。针对温度使用寿命不明确的问题,建立了FBG温度寿命预测模型,并结合高温加速老化实验,低温持续实验和高低温冲击实验预测了FBG在常规应用温度环境(-40~80℃)下的寿命。针对辐照影响机理不明确的问题,建立了辐照对FBG光谱的影响模型,利用该模型揭示了辐照实验中出现Bragg波长漂移差异性的机理。(3)为了全面探讨FBG应变传感器的应变传递特性,建立了广义的应变传递模型,统一了目前形式各异的应变传递模型。针对目前应变传递特性研究存在的局限性,全面分析了粘接层对平均应变传递效率和FBG光谱的影响。在平均应变传递效率方面,基于FBG应变传递简化模型推导了四种FBG应变传递形式的平均应变传递效率,然后具体分析了粘接层材料特性和几何特征对FBG平均应变传递效率的稳定性和一致性的影响,并给出了解决稳定性和一致性的方法。在FBG光谱受粘接层的影响方面,建立了粘接层横向应力对FBG光谱的影响模型,通过仿真及实验探究了其影响规律,并给出避免FBG光谱因其发生畸变的方法。另外,从理论和实验上探讨了粘接层恶化对光谱信号的影响机理与规律。(4)为了优化FBG解调软件的解调算法、提升其鲁棒性,从传感系统的实际情况出发,建立了FBG测量光谱的恶化模型,更加全面地刻画了由FBG传感器恶化形成的光谱畸变、FBG传感系统引入的干涉噪声、基线噪声和高斯噪声。在此基础上,分析了光谱噪声对目前有代表性的解调算法的影响,并相应地提出了提高解调算法鲁棒性的改进方案。最后通过分析光谱畸变对解调算法的影响,发现了利用光谱的黄金边模抑制比进行解调结果可信性评估的方法,并通过实验证实了方法的有效性,这解决了目前在实际应用中无法得知解调结果是否可信的难题;同时也发现鲁棒性相对较高的是改进的相关算法和改进的直接寻峰解法,为用户提供了解调算法选用的参考。
[Abstract]:Optical fiber Prague grating (Fiber Bragg Grating, FBG) strain sensing system has been widely used in all walks of life for its unique advantages, but in practical applications, the sensing system will have different degrees of performance degradation, and then produce various types of failures, which seriously affect the effect of its popularization. This makes the system reliability. However, it is difficult to make a breakthrough in theory because of its wide involvement, high technical difficulty and time-consuming and laborious, so it is difficult to get enough attention by researchers. It is the weakest link in the field of optical fiber sensing research. To make a breakthrough in the reliability research of FBG strain sensing system, it must be from sensing. Starting with the two key links of the demodulator and the demodulator, from the basic principle of sensor and signal demodulation, the performance changes of FBG sensor in various harsh environments are studied, the strain transmission characteristics of the sensor package and installation are studied, the robustness of the demodulation method is studied, and the credibility of the demodulation results is evaluated. This can be transmitted to FBG. The manufacturing enterprises of the sensor provide guidance, and can provide use help for the users of FBG sensors. It is of great significance to promote the FBG sensing technology, the national economy and the development of national defense. This paper has carried out in-depth research on the three aspects of FBG sensing elements, strain transmission and sensing demodulation. The main contents are as follows: (1) The theory and method to study the basic reliability of FBG are provided, the formation mechanism of the FBG structure is summarized and analyzed. The idea of understanding the change of FBG refractive index from the photochemical reaction angle is put forward. Based on the coupled mode theory and the transfer matrix method, the simulation method of the FBG spectrum is derived and the FBG spectral characteristic index is summarized and analyzed. (2) the FBG sensing is fully explored. The influence of the axial and lateral forces on the FBG sensing characteristics is not comprehensive. The influence of axial and transverse force on the FBG spectrum is deduced, and the influence of axial and transverse force on the FBG spectrum is analyzed, and the FBG can be ensured. According to the permissible condition of sensing, in view of the problem that the influence mechanism of bending on the FBG sensing characteristics is not clear, the influence model of the bending on the FBG spectrum is established, and the bending conditions to ensure the reliable sensing of FBG are given in combination with this model. In view of the problem that the mechanism and the law of the FBG spectrum deterioration under the long-term force are not clear, the theoretical analysis and experiments have been made. The deterioration mechanism and deterioration law of FBG spectra under long term force are made. The FBG temperature life prediction model is established for the problem of the uncertain temperature service life. Combined with high temperature accelerated aging experiment, low temperature continuous experiment and high and low temperature impact test, the life of FBG under the conventional temperature environment (-40~80 C) is predicted. The mechanism is not clear, and the effect of irradiation on the FBG spectrum is established. The mechanism of the difference of Bragg wavelength shift in the irradiation experiment is revealed. (3) in order to investigate the strain transfer characteristics of FBG strain sensor, a generalized strain transfer model is established, and the strain transfer model of different forms is unified. The influence of the adhesive layer on the average strain transfer efficiency and the FBG spectrum is analyzed. The average strain transfer efficiency of four FBG strain transfer forms is derived based on the FBG strain transfer simplified model. Then the material characteristics of the adhesive layer are analyzed. And the effect of geometric characteristics on the stability and consistency of FBG average strain transfer efficiency, and a method to solve the stability and consistency is given. In the influence of the FBG spectrum on the adhesive layer, the influence model of the transverse stress on the adhesive layer on the FBG spectrum is established. The influence rules are explored by simulation and experiment, and the cause of avoiding the FBG spectrum is also given. In addition, the mechanism and law of the influence of the adhesive layer deterioration on the spectral signal are discussed theoretically and experimentally. (4) in order to optimize the demodulation algorithm of FBG demodulation software and improve its robustness, the deterioration model of the FBG measurement spectrum is established from the actual situation of the sensing system, and the FBG sensor is depicted more comprehensively. The spectral distortion caused by the deterioration, interference noise, baseline noise and Gauss noise introduced by the FBG sensing system. On this basis, the influence of spectral noise on the present representative demodulation algorithm is analyzed, and an improved scheme for improving the robustness of the demodulation algorithm is proposed. The method to evaluate the credibility of the demodulation results by using the golden edge mode suppression ratio of the spectrum is presented, and the effectiveness of the method is proved by the experiment. This solves the problem that the demodulation results cannot be trusted in the actual application, and the improved correlation algorithm and the improved direct peak seeking are also found. The solution provides users with reference to the algorithm.
【学位授予单位】：重庆大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TP212

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