基于光纤光栅的桥梁多参数传感技术及系统的研究

【作者】 吴朝霞；

【导师】 李志全；

【作者基本信息】 燕山大学 ， 测试计量技术及仪器， 2006， 博士

【摘要】 近年来,光纤Bragg光栅(FBG)在光纤传感和光纤通信中的应用研究引起了人们极大关注。FBG传感器由于具有不受电磁干扰、信号带宽大、灵敏度高、易于复用、重量轻、结构紧凑,易于光纤连接,实现波长绝对编码及可以把多个传感器利用各种复用技术连接成传感网络,埋入材料和结构内部或贴装在其表面,实现对其特性的多点监测等优点,所以FBG传感器在大型建筑和油井等特殊场合的安全监测方面具有极为广泛的应用前景。本文主要对基于FBG的桥梁多参数传感技术及系统设计进行了理论和实验研究,具体内容包括:从FBG的模式耦合理论出发,分别推证了其温度和应变传感模型,并详细分析了相关参数对反射谱的影响;针对应变和温度交叉敏感问题,提出了温度补偿原理和方法;为了解决FBG的长期稳定性问题,通过理论分析和实验研究得出其最佳退火参数。从土木工程应用的实际情况出发,基于FBG传感特性设计了工程化FBG光纤传感器,对其传感特性进行了实验研究。研究了FBG传感器的布设工艺,并将其在桥梁结构中进行了实际应用。结果表明所设计的工程化FBG传感器在灵敏度和稳定性方面均能满足工程长期监测的需要。FBG解调系统的研究是本课题研究的重要部分之一,在比较分析各种分布式光纤光栅传感系统的解调方案的基础上,提出了基于连续波调频技术的波长扫描解调方法,从实用的角度出发,采用宽带光源与光纤F-P腔可调谐滤波器组合的方法,设计了可调窄带光源,不仅保证了系统所需的调谐范围,又获得了较高信噪比。在FBG传感网络复用方面,提出了将光频域反射复用(OFDR)技术与波分复用(WDM)技术相结合的方法,实现分布式FBG传感网络的寻址,提高了FBG的复用容量。实验表明所设计的解调系统具有解调速度快,稳定性好的优点。在上述研究的基础上,设计了基于FBG传感器的多参数桥梁测量系统,编制了数据采集和处理软件,并将所设计的FBG传感系统成功用于斜拉桥施工阶段及成桥的监测,现场监测效果证明所设计的工程化FBG传感器可以长期有效监测钢筋混凝土结构的应变与温度变化,且性能稳定,是一种有效的结构监测敏感元件。所设计的FBG传感系统不仅准确监测结构重要部位的内部应变及车流量等参数,为桥梁结构的静、动载测试提供了准确的数据,同时也为桥梁的工作状态评估和健康诊断提供依据。从桥梁施工、竣工、运营的两年多时间里FBG桥梁监测系统表现出良好的稳定性和耐久性,能够满足钢筋混凝土桥梁结构长期监测要求,具有为健康诊断提供连续、准确信息的能力。更多还原

【Abstract】 In recent years, the applications of fiber Bragg grating (FBG) has been attracted great attention in the field of optical sensing and communication. FBG sensor has the advantages of resistance to electromagnetic interference, big signal bandwidth, high sensitivity, easy multiplexing, light weight, compact conformation, easy for fiber connection, realizing wavelength absolute coding, linking many sensors into sensing network using various multiplexing technology, realizing multi-point monitoring to achieve its properties through embedding in the internal structure of materials, or adhibiting on the surface mount, etc. These sensors have extensive prospect in the security monitoring area of the special occasions, such as the large buildings and oil wells. In this paper, the theoretical and experimental studies on multi-parameters sensing technology and system using FBG were carried on, which specifically includes:The establishment of FBG’s temperature sensing model and strain sensing model were introduced based on coupled mold theory. The effect of correlation parameter on the reflected spectrum was analyzed. Because of the coupling problem, the principle and technique for the temperature compensation of FBG sensors were given when using as strain sensor. The best annealing parameters were given by theoretical analysis and experiments.Considering the need of long-term monitoring for civil engineering, several practical FBG sensors were developed and their sensing characteristics were investigated experimentally. Such as FBG strain sensor, FBG temperature sensor and FBG accelerometer. The research indicated that the sensitivity and stability of practical FBG sensors can satisfy the needs for civil engineering long-term monitoring.Study on the characteristic of FBG demodulation system is one of the most important parts of the subject study. On the basis of analyzing several familiar demodulation techniques of distributed FBG system, a wavelength scanning demodulation system based on continuous wave tunable frequency is designed. At the same time, tunable narrow-band light source, which is composed of wide-band light source and tunable optical filter, is adopted to demodulate multiplex signals. This method not only supply wider tunable range but also afford higher signal to noise ratio. A mixture multiplexing method that combines optical frequency domain reflectometry (OFDR) and wavelength division multiplexing (WDM) is proposed to address FBG sensing array. The proposed system scheme is testified to have faster demodulation and higher stability by analyzing theoretically and researching experimentally.Based on above research, multi-parameters monitoring system based on FBG has been designed. The software of data acquisition, signal processing and analysis system have been established. The practical FBG sensors have been successfully used in monitoring during construction stage and service time. The experimental results indicate that FBG sensors can monitor the temperature and strain effectively for a long time, as well as have higher stability. So, it’s a practical structure monitoring sensor. The FBG strain sensor can monitor the strain and vehicle flux of important position accurately. FBG sensors can not only supply precision data for bridge’s static and dynamic testing but also supply gist for bridge’s working state assessment and health diagnosis. The FBG bridge monitoring system shows the outstanding stability and endurance throughout the whole process of bridge’s construction, accomplishment and service time in two years. It can satisfy the needs for long term monitoring of armored concrete structural bridge, as well as provide continuous and accurate information.更多还原