• Title, Summary, Keyword: EFPI

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Vibration Measurement and Flutter Suppression Using Patch-type EFPI Sensor System

  • Kim, Do-Hyung;Han, Jae-Hung;Lee, In
    • International Journal of Aeronautical and Space Sciences
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    • v.6 no.1
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    • pp.17-26
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    • 2005
  • An optical phase tracking technique for an extrinsic Fabry-Perot interferometer (EFPI) is proposed in order to overcome interferometric non-linearity. Basic idea is utilizing strain-rate information, which cannot be easily obtained from an EFPI sensor itself. The proposed phase tracking system consists of a patch-type EFPI sensor and a simple on-line phase tracking logic. The patch-type EFPI sensor comprises an EFPI and a piezoelectric patch. An EFPI sensor itself has non-linear behavior due to the interferometric characteristics, and a piezoelectric material has hysteresis. However, the composed patch-type EFPI sensor system overcomes the problems that can arise when they are used individually. The dynamic characteristics of the proposed phase tracking system were investigated, and then the patch-type EFPI sensor system was applied to the active suppression of flutter, dynamic aeroelastic instability, of a swept-back composite plate structure. The proposed system has effectively reduced the amplitude of the flutter mode, and increased flutter speed.

Papers : Simultaneous Measurement of Strain , Temperature , and Vibration Using Fiber Optic Sensor (논문 : 광섬유 센서를 이용한 변형률, 온도, 진동의 동시 측정)

  • Gang,Hyeon-Gyu;Bang,Hyeong-Jun;Hong,Chang-Seon;Kim,Cheon-Gon
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.30 no.1
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    • pp.44-48
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    • 2002
  • In this paper, we demonstrated the simultaneous measurment of triple parameters such as strain, temperature, and vibration using single FBG/EFPI hybrid sensor. The FBG/EFPI sensor system for the strain and temperature measurement and the EFPI sensor system for the the vibration measurement were combined by a wavelength division multiplexer. The optical source of FBG/ EFPI sensor system is a wavelength-swept fiber laser(WSFL) and that of an EFPI sensor system is a laser diode. We performed the simultaneous measurement of thermal strain, temperature, and vibration of a aluminum beam placed in a thermal chamber and validated the efficiency of the constructed measurment system.

Measurement of Dynamic Strain of Structures Using a Gold-deposited EFPI (금 증착된 광섬유 외부 패브리-페로 간섭( EFPI ) 센서를 이용한 구조물의 동적 변형률 측정)

  • Kim, Dae-Hyeon;Gang, Hyeon-Gyu;Hong, Chang-Seon;Kim, Cheon-Gon
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.30 no.2
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    • pp.52-58
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    • 2002
  • Measurment of dynamic strain is important to monitor structural integrity. In this paper, the new type of EFPI is proposed to measure the dynamic strain. The second reflecting surface of fiber in this new sensor is deposited gold on to increase its reflectivity. So, it is called the gold-deposited EFPI (G-EFPI) in this paper. In order to explain the principle of measurement of the dynamic strain, two models for the loss of intensity are proposed and an experiment is performed. If a cavity between two reflecting surface increases, the loss of the light that passes through the cavity increases, causing a subsequent decrease in the output intensity of the sensor. Conversely, if the cavity decreases, the amount of loss decreases and the output intensity increases. Also the optimal length of the cavity is proposed to manufacture the G-EFPI with high sensitivity. Finally, the dynamic strainof a composite specimen was measured successfully using the G-EFPI.

Development of Fiber Optic Total Reflected Extrinsic Fabry-Perot Interferometric Sensor for Structural Strain Measurement (구조물의 변형률 측정을 위한 광섬유 TR-EFPI 센서의 개발)

  • Kwon, In-Bum;Choi, Man-Yong;Moon, Hahn-Gue;Kim, Min-Soo
    • Journal of Sensor Science and Technology
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    • v.9 no.2
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    • pp.96-105
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    • 2000
  • Fiber optic TR-EFPI(total reflected extrtinsic Fabry-Perot interferometric) sensor was developed to measure the strain of structures, such as building, bridge, aircraft, etc. It has been difficult to distinguish the increase and decrease of the strain from the conventional fiber optic EFPI sensor because their signals only have a sinusoidal wave pattern related to the change of strain. Also, the absolute strain could not be measured by the simple fiber optic EFPI sensor. In this study, in order to measure the magnitude of strain with the direction of strain, the fiber optic sensor was simply constructed with the total reflected EFPI sensor probe. This probe was manufactured with a single mode fiber and a mirror coated fiber in a silica glass capillary tube. The output signal of this fiber optic TR-EFPT sensor can give the information about the magnitude and the direction of strain. The loading-unloading test was performed by the universal testing machine with alluminum beam specimen to compare the strain from fiber optic TR-EFPI sensor with the value from electrical strain gauge. In the result of this experiment. the strain from fiber optic TR-EFPI sensor had a good agreement with the values from the electrical strain gauge.

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Strain Analysis in GFRP Cross-Ply Laminates Using TR-EFPI Optical Fiber Sensor (광섬유 TR-EFPI 센서를 이용한 GFRP 직교 적층판의 변형률 해석)

  • 우성충;최낙삼;권일범
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.150-153
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    • 2003
  • Longitudinal strains({$varepsilon}_x$) of the core and skin layers in glass fiber reinforced plastic(GFRP) cross-ply composite laminates have been studied using the embedded optical fiber sensor of totally-reflected extrinsic Fabry-Perot interferometer(TR-EFPI). Foil-type strain gauges bonded on both the upper and lower surfaces were used for the measurement of the surface strains. Both TR-EFPI sensor and strain gauge bonded on the specimen surface showed excellent agreement within -0.0086 ~ +0.0302% strain. It was shown that values of {$varepsilon}_x$ in the interior of the surface layer and the core layer measured by embedded TR-EFPI sensor was significantly higher than that of the specimen surface measured by strain gauges. The experimental results were ascertained with finite element analysis. Embedded TR-EFPI optical fiber sensor could measure accurately the internal strains which were different from the surface.

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Strain and Temperature Measurement using Transmission-type EFPI Optical Fiber Sensors (투과형 EFPI 광섬유 센서를 이용한 변형률 및 온도의 측정)

  • Kim, Sang-Hoon;Lee, Jung-Ju;Huh, Jeung-Soo
    • Journal of Sensor Science and Technology
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    • v.10 no.1
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    • pp.9-15
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    • 2001
  • The extrinsic Fabry-Perot interferometric (EFPI) optical fiber sensor shows good sensitivity and resolution, and has many advantages over optical fiber sensors of other types. However, this EFPI optical fiber sensor has a disadvantage that the distinction of measuring directions is difficult due to the measurement method by using only fringe counting. In this paper, the transmission-type extrinsic Fabry-Perot interferometric (TEFPI) optical fiber sensor was developed, which has been improved by the additional function and whose measuring system is different from that of the conventional EFPI optical fiber sensor. Then the application result of the TEFPI optical fiber sensor to the strain and temperature measurement was explained in detail.

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Real-time Measurement of Precision Displacement using Fiber Optic EFPI Sensor (광섬유 EFPI 센서를 이용한 실시간 고정밀 변위 측정)

  • 박상욱;김대현;김천곤;홍창선
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.154-157
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    • 2003
  • Precision displacement of less than a few nm resolution was measured in real-time using fiber optic EFPI sensor. The novel method for real-time processing of analyzing EFPI output signal was developed and verified. Linearity in the mean values of interferometric light intensity among adjacent fringes was shown, and the sinusoidal approximation algorithm that estimates past and coming fringe values was verified through the linearity. Real-time signal processing program was developed, and the intensity signal of the EFPI sensor was transformed to the phase shift with this program. The resolution below 0.4 ~ 10 nm in the displacement range of $0 ~ 300\mu\textrm{m}$ was obtained by reducing the photodetector noise using low-pass filter and signal averaging. The nano-translation stage with a Piezo-electric actuator and the EFPI sensor system was designed and tested. This stage successfully reached to the desired destination in $15\mu\textrm{m}$ range within 1 nm accuracy.

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Application of a fiber optic TR-EEPI sensor to detect deformation and failure in composite materials (복합재료의 변형 및 파손탐지를 위한 광섬유 TR-EFPI 센서의 적용)

  • 박래영;권일범;최낙삼
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.31-34
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    • 2002
  • A study on the method that can measure the internal strain of composite materials is performed to monitor the health status of composite structures. A fiber optic sensor was constructed using the total reflected extrinsic Fabry-Perot interferometer(TR-EFPI) probe with a broadband light source. Result obtained from electrical strain gage adhered on the aluminum beam specimen was compared with that from the fiber optic TR-EFPI sensor and showed a good agreement. It was found that fiber optic TR-EFPI sensor system was adequate for monitoring the strain and thus failure processes in the interior of composite materials.

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Cure Monitoring of Composite Laminates Using Fiber Optic Sensors (광섬유 센서를 이용한 복합재료 적층판의 성형 모니터링)

  • Gang, Hyeon-Gyu;Gang, Dong-Hun;Park, Hyeong-Jun;Hong, Chang-Seon;Kim, Cheon-Gon
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.30 no.2
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    • pp.59-66
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    • 2002
  • In this paper, we present the simulataneous monitoring of the strain and temperature during cures f various composite laminates using fiber Bragg grating/extrinsic Fabry-Perot interferometric (FBG/EFPI) hybrid sensors. Three types of graphite/epoxy composite were used : a undirectional laminate, a symmetric cross-ply laminate, and a fabric laminate. Two FBG/EFPI hybrid sensors were embedded in each laminate at different directions and different locations. We performed the real time monitoring of fabrication strains and temperatures at two points within the composite laminates during cure process in an autoclave. Throuhg these experiments, FBG/EFPI sensors proved to be an efficient choice for smart cure monitoring of composite structures.

Development of nano-positioner using fiber optic EFPI sensor (광섬유 EFPI 센서를 이용한 나노 이송장치의 개발)

  • Park, Sang-Wuk;Kim, Dae-Hyun;Kim, Chun-Gon
    • Journal of Sensor Science and Technology
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    • v.14 no.5
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    • pp.302-307
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    • 2005
  • Precision displacement of less than a few nm resolution was measured in real-time using fiber optic EFPI sensor. The novel method for real-time processing of analyzing EFPI output signal was developed and verified. Linearity in the mean values of interferometric light intensity among adjacent fringes was shown and verified the sinusoidal approximation algorithm that estimates past and coming fringe values. Real-time signal processing program was developed and the intensity signal of the EFPI sensor was transformed to the phase shift with this program. The resolution below $0.36{\sim}8.6$ nm in the displacement range of $0{\sim}300{\mu}m$ was obtained. The nano-positioner with a piezoelectric actuator and the EFPI sensor system was designed and tested. The positioner successfully reached to the desired destination within 1 nm accuracy.