布拉格光纖光柵應用於壓力感測器設計與製作以及動態應變量測

Abstract

光纖感測器具有良好的機械性質以及幾何形狀特質、高靈敏度以及不受電磁波干擾等優點，因此近年來以光纖感測器做為感測器的相關研究發展相當迅速，其中又以布拉格光纖光柵感測器（Fiber Bragg Grating, FBG）最為受到重視，而其應用於量測時可搭配波長解調器進行靜態訊號的監測或是以能量調變型光纖光柵架設進行動態訊號量測，上述兩種方式若再結合分波多工器則可實現多點同時量測的技術。而數位影像相關法（Digital Image Correlation, DIC）可進行非接觸之全域量測，進年來也被廣泛應用於精密的位移及應變量測問題上，而這些量測技術本實驗室過去已投入相當多的研究，並擁有相當成熟之技術，而本文中將利用這些技術進行高精度壓力感測器之設計與開發，同時也對已有之量測技術進行改良。 本文主要應用FBG製作微小壓力感測的系統，利用薄板理論及光纖模態耦合理論模型設計FBG壓力感測器，使其可針對氣壓及液體壓力進行精密量測，並搭配實驗室過去以及新開發之波長解調技術，對微小之壓力變化進行量測與測試，可與市售之商用壓力感測器進行比較，並將其應用於液體之壓力波量測、音箱導音管之微小壓力變化量測以及風扇系統之氣壓變化量測。此外，也將理論模擬之結果與量測結果進行比較。在布拉格光纖光柵的實驗量測上，本文針對實驗室新引進之波長解調器進行詳細的測試並與其他感測技術量測之結果互相驗證比較，確認其量測結果之正確性，並引進大頻寬之傾斜式光纖光柵做為能量調變型光纖光柵之濾波器，並將其應用於大振幅波長飄移之暫態訊號量測。在本文末段則是針對FBG應用於車削加工時刀具狀態與壽命監測進行初步的評估，並提出其可行性與改良之建議。

Recently, the optical fiber sensors, especially the fiber Bragg grating (FBG) sensors, have been rapidly developed due to the advantages such as excellent mechanical properties, thin geometries, high sensitivity and electromagnetics immunity. It can be applied to static analysis by demodulating the FBG central wavelength or dynamic measurement by power modulated system, and both of them can measure multiple points in the same time with wavelength division multiplexer. On the other hand, digital image correlation (DIC), which is a non-contact and full field measurement technique, has also been used widely for measurement of displacement and strain problems. Both of them are developed in our laboratory and this thesis is going to use these techniques to design the high precision pressure sensors and improve these developed measurement techniques. The main object of this research is focused on the application of FBG on measuring small pressure changes due to the disturbance of fluid. We also use the theory of thin plate and the coupled mode theory to design FBG pressure sensors. The FBG pressure sensor we designed and manufactured can be used for measuring not only the air pressure but also the water pressure. It can detect the small pressure change by the I-MON system or the dynamic pressure change from power modulated system. Then we compared the signals, which include the water pressure, the pressure change of the loudspeaker system and the fan system, with the commercially available pressure sensors. We also compared the sensitivity and response of the FBG pressure sensor with theoretical simulation. In terms of the FBG measurement techniques, we did a series experiments and compared to other measurement system to confirm the accuracy of the signals acquired by the I-MON system. We also introduced a wide bandwidth tilted fiber Bragg grating as the filter in power modulated system to measure the high amplitude and dynamic signals. Furthermore, we evaluate the feasibility of the application of FBG on the turning tools monitoring by comparing the experiment results with the dynamometer.