• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.11a
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• pp.567-568
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• 2010

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.4
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• pp.399-405
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• 2009

The focal plane image stabilization for a satellite camera is one of the an effective method which can increase the satellite camera's image quality by removing the motion disturbance of a focal plane. The objectives of this article are to introduce the concept of the focal plane image stabilization and determine the best driving conditions of the actuator for the response and thrust. Under various driving condition the experiments have been performed to investigate the response and thrust characteristics of the piezoelectric driven stick-slip actuator of the focal plane image stabilizing device. From experiments, the best driving frequency and duty ratio for the magnesium slider are 70 kHz and 27%, respectively.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.6
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• pp.550-557
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• 2008

Delamination damage at a bolt hole in a composite stiffened panel was detected using a built-in piezoelectric active sensor array. Various signal processing techniques were used to detect an invisible small scale delamination around a fastener hole due to localized transverse loading. A built-in piezoelectric sensor array was used to generate diagnostic signals and to measure response signals. Then, the response signals were processed to extract damage-sensitive features. Damage indexes were calculated to estimate the severity and location of the damage from the features.

• Composites Research
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• v.22 no.6
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• pp.7-12
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• 2009

This paper deals with a fabrication method of composite hinge mechanisms for flapping-wing micro air vehicles. The fabrication process includes curing process of Graphite/Epoxyprepregs, laser cutting for high fabrication repeatability, laminating of Graphite/Epoxy prepregs with Kapton film which is used for flexure, and so on. The fabricated hinge mechanism was attached with PUMPS actuators and the measured flapping angle was $173^{\circ}$ when driving voltage was 300V 170Hz.

• Composites Research
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• v.20 no.6
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• pp.21-27
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• 2007

Low-velocity impact damage in a composite stiffened panel was detected using built-in piezoelectric active sensor arrays. Using these piezoelectric active sensors, various diagnostic signals were generated to propagate Lamb waves through the structure and the responses were picked up to detect changes in the structure's vibration signature due to the damage. Three algorithms - ADI(Active Damage Interrogation), TD RMS (Time Domain Root Mean Square) and STFT (Short Time Fourier Transform) - were examined to express the features of the signal changes as one damage index. From damage detecting tests, two impact induced delaminations were detected and the location was estimated with the algorithms and diagnostic signals.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.2
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• pp.139-146
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• 2009

In this study, an assessment is made for the helicopter vibration reduction of composite rotor blades using an active twist control concept. The piezoceramic shear actuation mechanism along with elastic couplings of composite blades is used for vibration reduction. The rotor blades are modeled as composite box-beams with actuator layers bonded on the outer surfaces of the thin-walled section. The governing equations of motion for helicopter blades are obtained using Hamilton's principle. A time domain unsteady aerodynamic theory with free wake model is used to obtain the airloads. Various rotor configurations with different elastic couplings with appropriate actuator placement are used to investigate the hub vibration characteristics. Numerical results show that a substantial reduction of $N_b$/rev hub vibration can be achieved using the optimal control algorithm.

• Proceedings of the KIEE Conference
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• summer
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• pp.1281-1284
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• 2004

본 논문에서는 백라이트로 사용되는 CCFL의 점등을 위한 인버터를 연구대상으로 하였다. CCFL의 고전압 점등을 위해 다층 longitudinal 모드구조의 압전세라믹을 이용하였다. CCFL의 점등은 공진특성을 이용하는 것이므로 기계적인 공진주파수와 스위칭 주파수가 거의 일치할 수 있도록 L-C공진회로를 설계하였다. 인버터의 토플로지는 플라이백 기법을 적용하였으며 이를 위해서 권선의 배치에 의해 손실을 고려한 고주파 트랜스포머를 설계하였다. 시뮬레이션 및 실험 결과를 통하여 이에 대한 타당성을 입증하였다. 이로부터 공진주파수 48[kHz], 점등전압 600[V] 및 점등전류 6[mA] 얻었으며, 적용된 CCFL 램프사양은 관직경 $2.2{\phi}$와 관길이 314[mm], 압전세라믹 $43{\times}5.5{\times}2.3[mm]$를 이용하였다.

• Proceedings of the KIEE Conference
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• 2003.10b
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• pp.95-97
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• 2003

소형화, 정밀화 되어 가는 산업 추세에 의해 정밀 위치 제어용 엑츄에이터가 요구 되어지고 있다. 이로 인해 생산 및 유지비용이 적은 소형화된 마이크로 위치제어용 엑츄에이터를 개발하였다. 이 엑츄에이터의 설계를 위해서는 해석 기법이 요구되어진다. 그래서 엑츄에이터의 해석 방법을 정식화 하였고, 이를 이용한 해석을 통해 설계를 하였으며 제작을 하였다. 해석방법은 3차원 유한 요소법을 이용하였고, 이를 이용해 소형 마이크로 위치제어용 엑츄에이터의 특성을 해석하였으며, 그 결과는 제작된 엑츄에이터의 실험을 통해 검증되었다. 이 엑츄에이터는 적층 된 압전 세라믹과 두개의 전자석으로 구성되어 있으며, 적층된 압전 세라믹에 의한 변위와 두개의 전자석의 동기화된 동작에 의해 작동이 된다.

• Journal of the Korea Institute of Military Science and Technology
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• v.12 no.4
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• pp.491-499
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• 2009

The determination of response characteristics for pressure sensors is routinely limited to static calibration against a deadweight pressure standard. The strength of this method is that the deadweight device is a primary standard used to generate precise pressure. Its weakness lies in the assumption that the static and dynamic responses of the sensor in question are equivalent. Differences in sensor response to static and dynamic events, however, can lead to serious measurement errors. Dynamic techniques are required to calibrate pressure sensors measuring dynamic events in milliseconds. In this paper, a dynamic calibration using negative going dynamic pressure is proposed to determine dynamic pressure response for piezoelectric sensors. Sensitivity and linearity of sensor by the dynamic calibration were compared with those by the static calibration. The uncertainty of calibration results and the goodness of fit test of linear regression analysis were presented. The results show that the dynamic calibration is applicable to determine dynamic pressure response for piezoelectric sensors.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.421-428
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• 2004

Acoustic response control of a corner-pinned plate using piezoelectric wafers was studied, both theoretically and experimentally. Three different sizes of aluminum alloy plates were used and available ball joints were employed to hold the plate at the four corners. The plate with the largest aspect ratio showed the largest and most clear responses to the acoustic excitation in the range of frequencies (0～200Hz), and sound pressure levels (80～100dB) as predicted. The reduction of the acoustic response of the plate by piezoelectric actuator was very significant, more than expected, but abatement of the sound transmission through the plate was only slightly altered by the piezoelectric actuator. This work is an original work extending earlier work with doors excited by acoustic fields. The important difference is the used of ball joints to simulate the joints.