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

• Main Authors: Kuo-Chih, Chuang, 莊國志
• Other Authors: 馬劍清
• Format: Others
• Language: en_US
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/68408836337703912482

博士 === 國立臺灣大學 === 機械工程學研究所 === 96 === 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.