多維高解析度布拉格光纖光柵動態位移及應變量測系統之研發並應用於暫態波傳之量測

Development of Multidimensional, High Resolution Fiber Bragg Grating Dynamic Displacement and Strain Sensing System for Measurement of Transient Wave Propagation

莊國志(Kuo-Chih, Chuang)

指導教授 ： 馬劍清

國立臺灣大學/工學院/機械工程學研究所/博士(2008年)

https://doi.org/10.6342/NTU.2008.03278

摘要

本論文提出一套可以量測單點面外或面內動態位移之布拉格光纖光柵感測系統的架設方法，並分別搭配長週期光纖光柵濾波器或布拉格光纖光柵濾波器發展一個全光纖式之高靈敏度動態訊號解調系統。為了驗証所提出系統之動態量測能力，本研究首先在積層式壓電致動器之定位控制問題中，利用提出之布拉格光纖光柵感測器搭配高解析度之布拉格光纖光柵濾波器來回授壓電致動器的端點位移，進行系統識別，並以三種不同的控制法則來驗証感測器的量測能力與在定位控制系統中應用的可行性。所有的量測都同時與雷射都卜勒振動儀比較。實驗顯示所提出之光纖系統的位移感測靈敏度可達 5 mV/nm。接著我們搭配可解調較大範圍之長週期光纖光柵濾波器量測懸臂梁與懸臂板受鋼珠正向撞擊所引發之面外暫態位移，並利用快速傅利葉轉換得到懸臂結構的共振頻率。我們進一步以光學全域式的振幅變動電子斑點干涉術及有限元素分析所得到的振動振形與共振頻率資訊解讀由布拉格光纖光柵感測系統所量測到的暫態訊號。量測結果顯示激振位置與模態節線的關係會影嚮暫態訊號。本文最後以三個正交之布拉格光纖光柵量測固體同一點上受鋼珠正向或側向撞擊產生之三維位移之波傳訊號，驗証提出之面內布拉格光纖光柵位移感測器的暫態量測能力。我們並以布拉格光纖光柵應變感測器配合與應變規的比較，研究解調系統對動態應變的解調能力。因此，由三維波傳量測的實驗，証明所提出之光纖光柵感測系統具有多維、高解析度、單點或多點的量測能力。

關鍵字

面外/面內布拉格光纖光柵位移感測器 ； 定位控制 ； 雷射都卜勒振動儀 ； 振幅變動電子斑點干渉術 ； 多維量測 ； 暫態波傳

並列摘要

A method for setting up a fiber Bragg grating (FBG) sensor which can measure the point-wise, out-of-plane or in-plane dynamic displacement is proposed. A multiplexing demodulation system based on a single long-period fiber grating (LPFG) or an FBG filter is used in this study. First, the FBG displacement sensor is employed as a feedback sensor in a multilayer piezoceramic actuator tracking control system. The dynamic measurement ability of the proposed FBG sensor is demonstrated by the system identification experiment and various control strategies. The experimental results compared with a laser Doppler vibrometer (LDV) simultaneously show that the proposed sensor system can serve as a feedback control sensor which has a displacement sensitivity of 5 mV/nm. We further measure the dynamic response of a cantilever beam or a cantilever plate subjected to impact loadings. An optical amplitude-fluctuation electronic speckle pattern interferometry (AF-ESPI) technique and FEM numerical calculations are used to provide full-field vibration mode shapes and resonant frequencies of the cantilever structures. The amplitudes of the frequency spectrums are emphasized from the mode shapes and impact locations. Finally, we employ three orthogonal FBG displacement sensors to measure the three-dimensional displacements for transient wave propagation in a solid. The experimental results also indicate the excellent dynamic measurement ability of the proposed in-plane FBG strain sensor.

並列關鍵字

Out-of-plane/In-plane FBG displacement sensor ； tracking control ； LDV ； AF-ESPI ； multidimensional measurement ； wave propagation

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