光纖感測器對懸臂樑結構之振動量測研究

THE MEASUREMENTS OF VIBERTION ON A CANTILEVER BEAM BY FIBER-OPTIC SENSOR

游佩仁(Pei-Jen Yu)

指導教授 ： 何旭川 博士

元智大學/工程學院/機械工程學系/碩士(2004年)

摘要

光纖在通信之應用早為人所熟知，而光纖體積小質量輕不受電磁干擾的特性亦非常適合做為感測元件。本文主要探討光纖感測器在結構振動之量測應用，結合光彈理論與Mach-Zehnder干涉推導出光干涉強度與結構應變之關係，再由光強度週期性的變化反推結構之應變變化，進而瞭解結構振動狀態。並以懸臂樑為例說明Mach-Zehnder干涉型光纖感測器之量測方法，實驗內容包含自由振動、強制振動及基座激振三種不同振動模式，比較共振與非共振頻率之差異，探討單一頻率與雙頻率振動之量測難易度。並將光纖感測器量測所得應變與應變規量測值及有限元素數值解比較，以驗證量測的準確性。實驗結果顯示光纖感測器對單一頻率振動之量測相當準確，但對雙頻率振動，由於光干涉強度的變化比較複雜不易辨識其規律性，故量測所得誤差較大。

關鍵字

光纖感測器 ； 強制振動 ； 自由振動 ； 懸臂樑 ； 基座激振 ； Mach-Zehnder干涉儀

並列摘要

In this investigation, the application of fiber-optic senor on the measurement of structural vibration is studied. The measurement is based on the relationship between the fiber-optic strain and interferometric light intensity which is derived by using the photo-elastic theory and Mach-Zehnder interferometry. To explore the technique, the Mach-Zehnder interferometric fiber-optic sensor is used to measure the strain of a vibrating cantilever beam. The vibration test includes free vibration, forcing vibration, and base excitation. In the cases of forcing vibration and base excitation, the cantilever beam is subjected to single or double frequency at resonance or non-resonance. The strains measured by the fiber-optic sensor are compared with the results obtained by the strain gauge to examine the accuracy of the fiber-optic sensor. The experimental results show that the fiber-optic sensor is capable of measuring single-frequency vibration. However, for a multi-frequency vibration the proposed measurement technique of fiber-optic sensor is unable to obtain accurate result.

並列關鍵字

fiber-optic sensor ； force vibration ； free vibration ； cantilever beam ； Mach-Zehnder interferometry ； base excitation

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