Recently, health and usage monitoring systems (HUMS) are being studied to monitor the real-time condition of aircrafts during flight. HUMSs can prevent aircraft accidents and reduce inspection time and cost. Fiber Bragg grating (FBG) sensors are widely used for aircraft HUMSs with many advantages such as light weight, small size, easy-multiplexing, and EMI immunity. However, commercial FBG interrogators are too expensive to apply for small aircrafts. Generally the cost of conventional FBG interrogators is over $20,000. Therefore, cost-effective FBG interrogation systems need to be developed for small aircraft HUMSs. In this study, cost-effective low speed FBG interrogator was applied to full-scale small aircraft wing structure to examine the operational applicability of the low speed FBG interrogator to the monitoring of small aircrafts. The cost of the developed low speed FBG interrogator was about $10,000, which is an affordable price for a small aircraft. 10 FBG strain sensors and 1 FBG temperature sensor were installed on the surface of the full-scale wing structure. Load was applied to the tip of the wing structure, and the low speed interrogator detected the change in the center wavelength of the FBG sensors at the sampling rate of 10Hz. To assess the applicability of the low-cost FBG interrogator to full-scale small aircraft wing structure, a temperature-compensated strain measurement algorithm was verified experimentally under various loading conditions of the wing structure with temperature variations.
Optical fibers can be used as promising sensors in smart structures due to their novel characteristics. This paper presents
a wavelength division multiplexing (WDM) technique in order to improve the application capacity of single reflective
grating based fiber optic sensors to monitor large industrial structures at multiple points. The models are appropriate for
the general extrinsic fiber optic sensors such as the grating panel-based fiber optic sensor. The manufactured WDM fiber
optic sensor system was examined in order to demonstrate the feasibility for two parameter detections at two points using
mirror mounted grating based fiber optic sensor.
This paper discusses an applicable fiber-optic accelerometer composed of a transmissive grating panel, a reflection mirror, and two optical fibers with a separation of quarter grating pitch as transceivers that monitor the low-frequency accelerations of civil engineering structures. This sensor structure brings together the advantages of both a simple sensor structure, which leads to simplified cable design by 50% in comparison with the conventional transmission-type fiber optic accelerometer, and a stable reflected signals acquisition with repeatability in comparison to the researched grating-reflection type fiber optic accelerometer. The vibrating displacement and sinusoidal acceleration measured from the proposed fiber optic sensor demonstrated good agreement with those of a commercial laser displacement sensor and a MEMS accelerometer without electromagnetic interference. The developed fiber optic accelerometer can be used in frequency ranges below 4.0 Hz with a margin of error that is less than 5% and a high sensitivity of 5.06 rad/(m/s)2.
Optical fibers can be used as a promising sensors in smart structures thanks to their novel characteristics. In particular,
its immunity to electromagnetic interference (EMI) makes the sensor suitable for use in electronic environments. In
order to inspect the reliability of a structure, it is essential to characterize the dynamic responses of the structure. An
accelerometer associated with optical fiber makes it possible to conduct real-time structural health monitoring under high
electromagnetic environments. This paper describes an optimal design of a novel fiber optic accelerometer using one
grating panel for the application to civil engineering structures. The fiber optic sensor design was optimized to have the
best sensitivity to the motion of the reflective grating using two optical fibers in the quadrature. The reflected optical
signal of the sensor is influenced by the reflective grating pattern and optical fiber-grating distance. In this paper, several
simulations and experiments were carried out to evaluate the characteristics of the output signals according to the grating
pattern and the distance between the optical fiber and the grating for a fixed fiber core diameter. Through comparison of
the results between the simulations and the experiments, the optimum design of the grating-pattern was determined to
obtain a stable and periodic sine wave as the output signal. Furthermore, it was demonstrated that the output signals
reflected by one grating panel could be used for the final parameter-measurement.
The ionic polymer metal composite actuators have the best merit for large deformation and bio-mimetic motion generation. In this study, the noble patterning methods of multiple electrodes have been developed for the realization of the bio-mimetic fish-like locomotion by actuating the multiple electrodes. There are so many fabrication methods for patterning and depositing the platinum electrodes including electroless chemical reduction, physical sputtering, e-beam deposition and electroplating. Generally, the ionic-polymer metal composite actuator has been fabricated in electroless plating technique, while it needs very long fabrication time and shows poor repeatability in the actuation performance. Therefore the several fabricating methods are newly investigated by combining electroless plating, photolithograpy, physical sputtering, and electroplating techniques capable of precisely patterning and actuating of the multiple electrodes. Present results show that the initial composite between the Nafion polymer membrane and the platinum electrode is very important for the better bending performance. Consequently, the mixing the electroless chemical reduction and sputtering or electroplating can be a promising candidate for the better bending performance, although the patterned shape of the multiple electrodes may be coarse in the fabricating process of the electroless plating with masking tapes. However, the sputtering and electroplating methods with a photolithography technique can be incorporated in the precise design of MEMS devices, while the actuation performance may be slightly reduced.