Abstract
In this work, a fiber Bragg grating (FBG) sensing system which can measure the transient response of out-of-plane point-wise displacement responses is set up on a smart cantilever beam and the feasibility of its use as a feedback sensor in an active structural control system is studied experimentally. An FBG filter is employed in the proposed fiber sensing system to dynamically demodulate the responses obtained by the FBG displacement sensor with high sensitivity. For comparison, a laser Doppler vibrometer (LDV) is utilized simultaneously to verify displacement detection ability of the FBG sensing system. An optical full-field measurement technique called amplitude-fluctuation electronic speckle pattern interferometry (AF-ESPI) is used to provide full-field vibration mode shapes and resonant frequencies. To verify the dynamic demodulation performance of the FBG filter, a traditional FBG strain sensor calibrated with a strain gauge is first employed to measure the dynamic strain of impact-induced vibrations. Then, system identification of the smart cantilever beam is performed by FBG strain and displacement sensors. Finally, by employing a velocity feedback control algorithm, the feasibility of integrating the proposed FBG displacement sensing system in a collocated feedback system is investigated and excellent dynamic feedback performance is demonstrated. In conclusion, our experiments show that the FBG sensor is capable of performing dynamic displacement feedback and/or strain measurements with high sensitivity and resolution.
Highlights
Fiber Bragg grating (FBG) sensors possess many excellent properties such as small size, mass-production at low cost, and immunity to electro-magnetic interference (EMI)
The fiber Bragg grating (FBG) sensor used in our experiment is fabricated with full-width at half maximum (FWHM) of approximately 0.13 nm and reflectivity of less than 90% to avoid distortions and saturations of the responses
We investigate the feasibility of utilizing a fiber Bragg grating (FBG) displacement sensor to perform active vibration suppression of a smart cantilever beam
Summary
Fiber Bragg grating (FBG) sensors possess many excellent properties such as small size, mass-production at low cost, and immunity to electro-magnetic interference (EMI). Since many FBGs can be inscribed into a single fiber, they have multiplexing ability to detect several different positions in the same structure simultaneously. FBG sensors are mounted on or imbedded in structures. Detecting out-of-plane point-wise displacement can’t be achieved without work-around methods such as bonding an FBG sensor to a cantilever structure to indirectly measure the displacement responses [4,5]. Indirect sensing methods are still not capable of measuring point-wise displacement. Due to the different modes of the cantilever structures, indirect sensing methods are not suitable for dynamic measurements
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