基于软件锁相的TDLAS光纤混合式气体传感关键技术研究

发布时间：2018-07-03 01:13

本文选题：TDLAS + SLIDT　；参考：《天津大学》2015年博士论文

【摘要】：近年来,随着科技的进步及经济的快速发展,环境污染问题成为人们日益关注的话题。气体污染作为环境污染的一个重要方面,对工业生产安全及人类的身体健康均构成严重危害。光谱吸收技术的调谐二极管激光吸收光谱(Tunable Diode Laser Absorption Spectroscopy,TDLAS)技术与波长调制/谐波检测技术相结合,以其响应时间短、探测灵敏度高、高稳定性等诸多优点,被广泛应用于有毒有害气体浓度检测。本文基于TDLAS技术,提出软件锁相方法代替硬件锁相,并对软件锁相方法中涉及的数学模型及算法进行理论和实验研究。对系统进行仪器化设计,能够对CO、CO_2和CH4气体浓度、温度和压强进行同时检测,实现了气体传感系统的多气体、多参量混合传感。本文的主要创新性工作如下:1、基于TDLAS气体浓度检测理论,本文提出了软件锁相的TDLAS气体浓度检测系统理论模型,理论分析了调制深度、调制频率、相移和系统噪声对软件锁相得到的二次谐波幅值的影响,通过仿真和理论推导得到了软件锁相系统最优调制参数理论值。2、基于针对非平稳非线性信号进行时域分解的经验模态分解(EMD)理论,本文提出了一种EMD-FCR算法用于系统信号去噪,以提高系统检测精度。将本算法与其他常用滤波算法进行了比较,结果表明,本算法大大提高了解调信号的信噪比,将系统的检测下限从原来的18ppm降低到2ppm,降低近一个数量级。3、针对气体吸收线存在部分重叠的现象,本文构建了重叠光谱拟合的数学模型,提出了一种重叠光谱分离算法,用于分离CO和CO_2的重叠光谱,实现了单个DFB激光器电流调谐下的CO和CO_2两种混合气体浓度的同时检测。4、本文提出基于气体吸收线线宽的温度和压强测量的方法。通过测量不同温度和压强下气体吸收线线宽,即可推算出待测气体的温度和压强。结合上述同时对多种气体检测研究,以及气体的温度和压强检测方法研究,本文对多种混合气体、多参量进行同时检测,实现了基于软件锁相的混合式传感。
[Abstract]:In recent years, with the progress of science and technology and the rapid development of economy, environmental pollution has become a topic of increasing concern. As an important aspect of environmental pollution, gas pollution poses serious harm to industrial production safety and human health. The tunable Diode Laser Absorption Spectroscopy (TDLAS) technique combined with wavelength modulation / harmonic detection technology has many advantages, such as short response time, high detection sensitivity, high stability and so on. It is widely used to detect the concentration of toxic and harmful gases. In this paper, based on TDLAS technology, the software phase-locking method is proposed to replace the hardware phase-locked method, and the mathematical model and algorithm involved in the software phase-locking method are studied theoretically and experimentally. The instrument design of the system can simultaneously detect the concentration, temperature and pressure of COC _ 2 and Ch _ 4 gas, and realize the multi-gas and multi-parameter mixed sensing of the gas sensing system. The main innovative work of this paper is as follows: 1. Based on the TDLAS gas concentration detection theory, this paper presents a theoretical model of the software phase-locked TDLAS gas concentration detection system. The effect of phase shift and system noise on the second harmonic amplitude obtained by software phase-locked, Based on the empirical mode decomposition (EMD) theory of time-domain decomposition for non-stationary nonlinear signals, an EMD-FCR algorithm is proposed for system signal denoising. In order to improve the system detection accuracy. The algorithm is compared with other common filtering algorithms. The results show that the signal-to-noise ratio of demodulated signal is greatly improved. The detection limit of the system is reduced from the original 18ppm to 2 ppm, and the detection limit is reduced by nearly one order of magnitude. 3. Aiming at the phenomenon of partial overlap of gas absorption lines, a mathematical model of overlapping spectral fitting is constructed, and an overlapping spectral separation algorithm is proposed. The overlapping spectrum of CO and CO _ 2 is used to separate CO and CO _ 2, and the concentration of CO and CO _ 2 mixed gas in a single DFB laser is detected simultaneously. A method of measuring temperature and pressure based on the line width of gas absorption line is presented in this paper. By measuring the line width of the gas absorption line at different temperatures and pressures, the temperature and pressure of the gas to be measured can be calculated. Combined with the research of gas detection and the temperature and pressure detection methods, the mixed sensing based on software phase locking is realized in this paper.
【学位授予单位】：天津大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：X831;O433.51

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