基于嵌入式的光纤光栅解调系统

发布时间：2018-03-03 12:52

  本文选题：F-P滤波器　切入点：光纤光栅　出处：《南昌航空大学》2017年硕士论文　论文类型：学位论文

【摘要】：光纤光栅传感器较传统的电学传感器,具有抗电磁干扰能力强、耐腐蚀、精度高、结构简单且价格低廉等优点,在石油化工,航空航天,建筑结构等领域具有广泛应用。光纤光栅传感技术的关键是解调系统,开发设计一套低成本、便携式的解调系统对于拓展光纤光栅传感技术的应用范围具有重要意义。本文首先从光纤光栅传感器的理论研究出发,在详细分析比较了常见的五种光纤光栅解调方式的基础上,选择可调谐光纤法布里-珀罗(FFP)滤波器作为本系统的解调方法,并设计解调系统的总体方案。根据光纤光栅解调系统的总体设计方案,完成了光纤光栅解调系统的软硬件开发,具体内容如下:在系统硬件设计上,选择STM32F4芯片处理核心,设计并实现了可调谐FFP驱动放大电路和SD卡硬件电路,解决了容性负载导致的驱动波形失真问题。在系统软件设计上,首先开发完成了SD卡的驱动、DAC驱动和ADC驱动,并针对各个模块的驱动利用上位机进行调试,使模块达到预期的状态。然后完成了uC/OS-III嵌入式实时操作系统和Fatfs文件系统的移植工作,利用操作系统来管理系统的软硬件资源。为了配合操作系统的使用,本文设计了一种简单的内存管理方式。在数据的存储上,利用Fatfs文件系统,实现了将LCD截图以BMP格式和AD采样值以TXT格式保存在SD卡中。最后,利用GUI图形库设计了图形用户界面,完成波形图像数据显示。为了获取更高精度的光纤光栅反射谱信号,首次将并行数据采集方法应用于光纤光栅谱的采集中,并完成了3个AD并行工作的软硬件设计,提高了光纤光栅反射谱的采集点数,为高精度、高速率光谱拟合奠定了基础。为了进一步提高系统的测量精度,本文实现了嵌入式环境下的Levenberg Marquardt(LM)算法并用于光纤光栅反射谱的拟合,得到反射谱峰值的精确位置。同时,利用应力光栅对温度光栅传感器进行定标,完成环境温度到传感光栅波长的变化。较传统方案相比,本系统完全不依赖于PC,实现了数据采集存储,光纤光栅反射谱波长的拟合定标等。经测试,利用本课题提出的高速数据采集方案和实现的LM拟合算法,解调系统解调的中心波长漂移小于15pm。结合温度传感光栅的敏感系数ξ=10.3 pm/ ℃,系统解调温度分辨率小于1.5 ℃。
[Abstract]:Fiber Bragg grating (FBG) sensors have the advantages of strong resistance to electromagnetic interference, corrosion resistance, high precision, simple structure and low price. The key of fiber Bragg grating sensing technology is demodulation system, which develops and designs a set of low cost, Portable demodulation system is of great significance to expand the application of fiber Bragg grating sensor technology. Firstly, this paper starts with the theoretical research of fiber grating sensor. The tunable fiber Fabry-Perot FFP filter is selected as the demodulation method of this system, based on the detailed analysis and comparison of five common demodulation methods of fiber Bragg grating, and the tunable fiber Fabry-Perot FFP filter is selected as the demodulation method of the system. According to the overall design of the fiber grating demodulation system, the hardware and software development of the fiber grating demodulation system is completed. The specific contents are as follows: in the system hardware design, the STM32F4 chip processing core is selected. The tunable FFP driver amplifier circuit and SD card hardware circuit are designed and implemented to solve the problem of waveform distortion caused by capacitive load. In the system software design, the SD card driver driver and ADC driver are first developed. According to the driver of each module, the module is debugged by the host computer to make the module achieve the expected state. Then, the transplant of the uC/OS-III embedded real-time operating system and the Fatfs file system is completed. In order to cooperate with the use of the operating system, this paper designs a simple memory management method. In the data storage, the Fatfs file system is used. The LCD screenshots are saved in the SD card in BMP format and AD sampling value in TXT format. Finally, the graphical user interface is designed by using the GUI graphics library to display the waveform image data. The parallel data acquisition method is applied to the acquisition of fiber grating spectrum for the first time, and the hardware and software design of three AD parallel work is completed, which improves the collection points of fiber Bragg grating reflectance spectrum and is of high precision. In order to further improve the measurement accuracy of the system, the Levenberg Marquardt LM algorithm in embedded environment is implemented and used to fit the reflection spectrum of fiber Bragg gratings, and the exact position of the peak value of the reflection spectrum is obtained. The temperature grating sensor is calibrated by stress grating to change the temperature from the ambient temperature to the wavelength of the sensor grating. Compared with the traditional scheme, the system is completely independent of PC-dependent, and realizes the data acquisition and storage. The wavelength fitting calibration of fiber Bragg grating reflectance spectrum, etc. By testing, using the high speed data acquisition scheme and the LM fitting algorithm proposed in this paper, The center wavelength shift of demodulation system is less than 15pm.The sensitivity coefficient of temperature sensing grating is 10. 3 pm/ 鈩，

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