【作者】 崔陆军；

【导师】 陈幼平； 张冈；

【作者基本信息】 华中科技大学 ， 机械电子工程， 2010， 博士

【摘要】 在常温常压下,空气中泄漏的氢气浓度达到4%-74.5%时变得易燃易爆,所以安全、可靠且廉价的氢气测量传感技术是安全利用氢气的必要保障。迄今为止,基于不同工作原理的氢气传感器都曾报道过,在常温常压下能提供快速而有效的响应,但这些氢气传感器主要是电化学传感器,潜在的电磁干扰和电火花可能会引起灾难性的后果。而光纤氢气传感器却能同时满足安全、实时在线检测、不干扰被测环境、不产生电火花的要求。并且,还具有体积小、重量轻、柔韧性好,多点测量的特点；另外,光纤还能抗化学腐蚀、恶劣的环境温度和电磁干扰等,非常适合在这种环境中工作。本文主要对反射式光纤束氢气传感器的理论、设计和相关实验进行理论研究和实现。首先,研究了单光纤对的氢气传感器的理论特征,分析总结了各相关参数对于反射式光纤传感器的影响规律,建立了反射式光纤束氢气传感器的数学模型,为光纤在氢气传感器的应用提供了理论基础。进而给出了光纤束在反射式氢气传感器探头中的应用。与此同时,为了克服以往基于纯钯的氢气传感器发生“氢脆”现象的缺陷,大大延长了氢敏薄膜的寿命,本文研究了将银作为第二组份加入到纯钯中作为检测氢气的气敏材料,仿真分析了在氢气传感器探头中使用最佳的钯银合金的组份配比问题,建立了反射式光纤束氢气传感器的光学模型,研究了钯银合金膜厚度与氢气浓度的关系,从仿真和实验的角度找到了最佳的钯银合金反应薄膜厚度。为了能够提高反射式光纤束氢气传感器的精度和稳定性,在分析了传统典型光纤光路的优、缺点的基础上,提出一种不依赖于对光纤进行任何微细加工的光纤束的设计思路,以及反射式光纤束氢气传感器探头的设计方法,并对所设计的光纤束光路进行了研究和讨论,通过实验验证了该探头设计的合理性。提出了利用溅射方法制备钯银合金薄膜的理论模型,在模型中分析了得到理想溅射厚度和合金配比的溅射方法,讨论了在制备钯银合金膜过程中几个重要相关问题。之后利用相关检测仪器对制备的钯银合金薄膜进行了表征,得出了制备符合要求的钯银合金薄膜最佳的溅射条件。依据相关性检测的原理和反射式光纤束氢气传感器的信号特点,完成了反射式光纤束氢气传感器的微弱信号电路系统设计,设计了移相电路,相敏检波电路和除法电路等。为了进一步提高反射式光纤束氢气传感器的测量精度和抗干扰性,本文提出了基于虚拟仪器和神经网络相结合的补偿设计思路,并对反射式光纤束氢气传感器进行了补偿实验,实验结果表明：基于虚拟仪器和神经网络的补偿设计比单纯的线性拟合的输出精度高,同时尽可能地消除了由于内部和外部原因所带来的各种干扰因素,实现了反射式光纤束氢气传感器在线的非线性校正。最后,基于上述的研究,对反射式光纤束氢气传感器的样机进行了一系列实验测试,实验结果表明基于钯银合金的反射式光纤束氢气传感器具有良好的检测效果。更多还原

【Abstract】 Under room temperature and standard pressure, the air becomes to be exploded when the leaked hydrogen concentration is 4%-74.5% in air; therefore, the safe, reliable and cheap hydrogen sensing and detective technology is necessary for usage of the hydrogen. So far, many hydrogen sensors that based on different operational principle, are disscuced, the sensors could provide quick and active responses in normal temperature and pressure, electro-chemical hydrogen sensor are ordinary during the mentioned hydrogen sensors, potential electromagnetic interference and electric spark could arouse the catastrophic consequence. Optical fiber hydrogen sensor could satisfy the demand of safety, online detection, undisturbed surrounding, and no spark. At one time, the optical fiber hydrogen sensors possess the some features, for example, small volume, low weight, better pliability, suitable for multipoint detection in narrow space. On the side, the optical fiber could resist the interferences of chemical corrosion, the temperature and electromagnetic in tempest. Reflective optical fiber bundle hydrogen sensors was studied systematically in this dissertation, which includes correlative sensing theoretical modeling, developing and testing of hydrogen prototypes.Firstly, theoretical characteristics of the single optical-fiber couple were studied, the influence rules of related parameters in optical fiber couple were analysed, the model of reflective optical fiber bundle hydrogen sensor was established, and the results provide the theoretical principle for the optic-fiber bundle in hydrogen sensor. At the same time, for the sake of avoiding hydrogen embrittlement in previous hydrogen sensors, which were based on pure palladium, gas-sensing scheme which the sliver was added to the palladium was studied, and optimal proportioning in palladium-sliver was simulated, the reflective hydrogen sensor optical model was built up. The relationships between the palladium-sliver thickness and hydrogen concentration are studied; the optimum Pd-Ag thickness was validated through simulations and experiments.In order to improve sensor’s precision and stability, and the analyzing the virtues and shortcomings of typical optical fiber path, a new design of optical fiber bundle sensing probe which was independent of any microprocessing in optical fiber was bring forward, and optical path was discussed in detail, the experiments validated the justification of sensing probe.For fabricated for Pd-Ag alloy, sputtering theoretical model was put forward, and the sputtering parameters were analysed for the ideal palladium-sliver optimal proportioning and thickness of membrane. Subsequently, the relevant details in sputtering model were discussed in detail; finally, we got the optimal supptering parameters for the palladium-sliver membrane.According to the principles of weak signal detection and signal characterics of reflective optical fieber bundle hydrogen sensor, the system of weak signal detection is designed. At the same time, phase-shift circuit, phase-sensitive circuit and dividing circuit were designed.The method, which based on virtual instrument and neural network, is studied to enhance the measuring precision and anti-interference. Compared to he hydrogen sensor, experiments using the proposed method show that the higher linear precision, the method could eliminate the inside and outside interferences as possible in sensor and realize the non-linear adjustment online.Finally, the prototypes of reflective optical fiber bundle hydrogen sensor were tested; experimental results show that reflective optical fiber bundle hydrogen sensor based on palladium-sliver alloy has good detection effects.更多还原