• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.713-721
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• 2004

Variable air intake and variable exhaust nozzle of hypersonic engines are designed and tested in this study. Dimensions for variable geometry air intake, ram combustor and variable geometry exhaust nozzle are defined based on the requirements of a pre-cooled turbojet engine. Hypersonic Ramjet Engine is designed as a scaled test bed for each component. Actuation forces of moving parts for variable intake and variable nozzle are reduced by balancing the other force in the opposite direction. A demonstrator engine which includes variable intake and variable nozzle is designed and the components are fabricated. Composite material with silicone carbide is applied for high temperature parts under oxidation environment such as leading edge of the variable intake and combustor liner. Internal cooling structure is adopted for both moving and static parts of the variable nozzle. Pressure recovery and mass capture ratio of the variable intake at Mach 5 is obtained by a hypersonic wind tunnel test. Flow characteristics of the variable nozzle are obtained by a low temperature flow test. Wall temperature and heat flux of the nozzle at Mach 3 is obtained by a firing test. As results, the intake and the nozzle are proved to be used at designed pressure and temperature environment.

• Smart Structures and Systems
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• 제7권1호
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• pp.1-13
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• 2011

It has been shown in the literature that active adjustment of the intake area of a jet engine has potential to improve its fuel efficiency. This paper presents the design and control of a novel proof-of-concept active jet engine intake using Nickel-Titanium (Ni-Ti or Nitinol) shape memory alloy (SMA) wire actuators. The Nitinol SMA material is used in this research due to its advantages of high power-to-weight ratio and electrical resistive actuation. The Nitinol SMA material can be fabricated into a variety of shapes, such as strips, foils, rods and wires. In this paper, SMA wires are used due to its ability to generate a large strain: up to 6% for repeated operations. The proposed proof-of-concept engine intake employs overlapping leaves in a concentric configuration. Each leaf is mounted on a supporting bar than can rotate. The supporting bars are actuated by an SMA wire actuator in a ring configuration. Electrical resistive heating is used to actuate the SMA wire actuator and rotate the supporting bars. To enable feedback control, a laser range sensor is used to detect the movement of a leaf and therefore the radius of the intake area. Due to the hysteresis, an inherent nonlinear phenomenon associated with SMAs, a nonlinear robust controller is used to control the SMA actuators. The control design uses the sliding-mode approach and can compensate the nonlinearities associated with the SMA actuator. A proof-of-concept model is fabricated and its feedback control experiments show that the intake area can be precisely controlled using the SMA wire actuator and has the ability to reduce the area up to 25%. The experiments demonstrate the feasibility of engine intake area control using an SMA wire actuator under the proposed design.

• Smart Structures and Systems
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• 제21권3호
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• pp.257-262
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• 2018

Vibrational problems in the domestic Small Horizontal Axis Wind Turbines (SHAWT) are due to flap wise vibrations caused by varying wind velocities acting perpendicular to its blade surface. It has been reported that monitoring the structural health of the turbine blades requires special attention as they are key elements of a wind power generation, and account for 15-20% of the total turbine cost. If this vibration problem is taken care, the SHAWT can be made as commercial success. In this work, Shape Memory Alloy (SMA) wires made of Nitinol (Ni-Ti) alloys are embedded into the Glass Fibre Reinforced Polymer (GFRP) wind turbine blade in order to reduce the flapwise vibrations. Experimental study of Nitinol (Ni-Ti) wire characteristics has been done and relationship between different parameters like current, displacement, time and temperature has been established. When the wind turbine blades are subjected to varying wind velocity, flapwise vibration occurs which has to be controlled continuously, otherwise the blade will be damaged due to the resonance. Therefore, in order to control these flapwise vibrations actively, a non-linear current controller unit was developed and fabricated, which provides actuation force required for active vibration control in smart blade. Experimental analysis was performed on conventional GFRP and smart blade, depicted a 20% increase in natural frequency and 20% reduction in amplitude of vibration. With addition of active vibration control unit, the smart blade showed 61% reduction in amplitude of vibration.

• Journal of Electrical Engineering and Technology
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• 제5권2호
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• pp.337-341
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• 2010

In this paper, an extremely low voltage operated micro corner cube retroreflector (CCR) was fabricated for free-space optical communication applications by using bulk silicon micromachining technologies. The CCR was comprised of an orthogonal vertical mirror and a horizontal actuated mirror. For low voltage operation, the horizontal actuated mirror was designed with two PZT cantilever actuators, torsional bars, hinges, and a mirror plate with a size of $400{\mu}m{\times}400{\mu}m$. In particular, the torsional bars and hinges were carefully simulated and designed to secure the flatness of the mirror plate by using a finite element method (FEM) simulator. The measured tilting angle was approximately $2^{\circ}$ at the applied voltage of 5 V. An orthogonal vertical mirror with an extremely smooth surface texture was fabricated using KOH wet etching and a double-SOI (silicon-on-insulator) wafer with a (110) silicon wafer. The fabricated orthogonal vertical mirror was comprised of four pairs of two mutually orthogonal flat mirrors with $400{\mu}m4 (length) $\times400{\mu}m$ (height) $\times30{\mu}m$ (thickness). The cross angles and surface roughness of the orthogonal vertical mirror were orthogonal, almost $90^{\circ}$ and 3.523 nm rms, respectively. The proposed CCR was completed by combining the orthogonal vertical and horizontal actuated mirrors. Data transmission and modulation at a frequency of 10 Hz was successfully demonstrated using the fabricated CCR at a distance of approximately 50 cm.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 C
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• pp.1629-1630
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• 2006

This paper describes a micro total analysis system ($\mu$ TAS) for detecting and digesting the target protein which includes a bead based temperature controllable microchip and computer based controllers for temperature and valve actuation. We firstly combined the temperature control function with a bead based microchip and realized the on-chip sequential reactions using two kinds of beads. The PEG-grafted bead, on which RNA aptamer was immobilized, was used for capturing and releasing the target protein. The target protein can be chosen by the type of RNA aptamer. In this paper, we used the RNA aptamer of HCV replicase. The trypsin coated bead was used for digesting the released protein prior to the matrix assisted laser desorption ionization time of flight mass spectrometer (MALDI TOF MS). Heat is applied for release of the captured protein binding on the bead, thermal denaturation and trypsin digestion. PDMS microchannel and PDMS micro pneumatic valves were also combined for the small volume liquid handling. The entire procedures for the detection and the digestion of the target protein were successfully carried out on a microchip without any other chemical treatment or off-chip handling using $20\;{\mu}l$ protein mixture within 20 min. We could acquire six matched peaks (7% sequence coverage) of HCV replicase.

• 한국항공우주학회지
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• 제37권2호
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• pp.139-146
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• 2009

능동 비틀림 제어기법을 이용한 복합재료 로터 블레이드의 헬리콥터 진동억제에 대한 수치연구를 수행하였다. 허브에 작용하는 진동하중 억제를 위해 복합재료 블레이드의 탄성 연계와 함께 압전 소재의 전단변형 메커니즘을 이용하였다. 로터 블레이드는 표면에 압전 작동기를 부착한 박벽 상자형 단면을 갖는 복합재료 보로 모델링하였다. 회전익에 대한 지배 운동방정식은 Hamilton 원리를 이용하여 구성하였고, 공력하중은 자유후류모델을 포함하는 비정상 공력 이론을 이용하여 구했다. 다양한 탄성연계 적층과 능동 작동기를 부착한 복합재료 블레이드에 대해 허브진동 하중 특성을 고찰하였다. 수치해석 결과 최적 제어 알고리듬을 적용하여 $N_b$/rev 진동하중을 대폭 줄일 수 있음을 보였다.

• 한국항공우주학회지
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• 제37권3호
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• pp.307-313
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• 2009

우주 발사체의 비행 중에 파이로 충격은 일반적으로 여러 단 분리, 페어링 분리, 그리고 위성 분리 시 화약을 이용한 분리 장치의 작동에 의해 발생하게 된다. 이러한 분리 이벤트 시 고주파 영역까지 큰 가속도가 유발되는 천이 진동 현상이 유발되어 위성 또는 발사체의 전자 장비가 비정상적인 기능을 보일 수 있다. 본 논문에서는 이러한 파이로 충격 절연을 위해 형상기억합금 소재를 적용하여 두 종류의 메쉬 와셔 절연계를 소개하였다. 한 종류는 형상기억합금의 의탄성 효과를 주로 이용하였고 다른 한 종류는 형상기억효과를 주로 이용하였다. 형상기억합금 절연계의 기본적인 하중-변위 선도를 파악하기 위해 압축 시험을 수행하였고 그 결과로 절연 가능성을 확인하였다. 파이로 충격 절연 시험을 수행하여 형상기억합금 절연계의 절연 성능이 뛰어남을 확인하였으며 추가로 랜덤 진동 시험을 통해 각 절연계의 동특성을 살펴보았다.

• 한국항공우주학회지
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• 제35권4호
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• pp.302-307
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• 2007

본 연구에서는 이온성 폴리머-금속 복합재료 (IPMC) 작동기를 사용한 플랩 밸브 마이크로 펌프의 설계, 제작 및 실험적 특성 규명을 수행하였다. 나피온/실리케이트 층과 나피온/실리카 나노복합재료를 기반으로 한 다층형 IPMC를 마이크로 펌프의 작동층으로 사용하였다. 마이크로 펌프의 핵심 요소인 IPMC 다이아프램의 주위를 유연한 폴리디메틸실옥산(PDMS)을 사용하여 지지하도록 함으로써 상당히 큰 작동 변위를 내도록 설계하였다. 이렇게 개발된 마이크로 펌프의 크기는 $20{\times}20{\times}5$ ${mm}^3$ 이고, 최대 유량은 760 l/min, 최대 배압은 1.5 kPa이었다. 본 연구에서 개발한 마이크로 펌프는 간단하고 효율적인 설계를 수행하여 제작이 용이할 뿐 아니라, 동작 전압이 1-3V라는 장점이 있다.

• 한국안전학회지
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• 제15권3호
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• pp.115-123
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• 2000

공압구동기는 다양한 형태의 위험작업 환경하에서 사용되고 있다. 또한, 공압구동기를 적용한 공정은 일반적으로 환경친화적인 것으로 인식되고 있다. 대부분의 경우, 공압구동기는 point to point 제어에 사용된다. 그러나, 최근 공압구동기의 정밀 위치제어에 관한 많은 연구가 수행되고 있다. 본 연구에서는 비례밸브로 구성된 공압구동기의 추종위치제어에 관하여 논의한다. 제안되는 제어기는 압력제어 루프와 위치제어 루프로 구성된다. 공기의 압축성에 기인한 비선형성을 상쇄하기 위하여 되먹임선형화에 의한 PID제어기가 압력제어 루프에 사용된다. 위치제어에는 신경회로망을 사용하여 비선형성을 보상한 PID제어기가 사용된다. 실험결과에 의하면, 제안된 제어기는 공압구동기의 추종성능을 대폭 향상시킬 수 있는 것으로 나타났다.

• 한국정밀공학회지
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• 제29권7호
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• pp.717-722
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• 2012

This paper presents the design and dynamic model of the finger exoskeleton actuated by Ionic Polymer Metal Composites (IPMC) to assist a tip pinch task. Although this exoskeleton will be developed to assist 3 degree-of-freedom motion of each finger, it has been currently made to perform the tip pinch task using 1 degree-of-freedom mechanism as the first step. The six layers of IPMC were stacked in parallel to increase the low actuation force of IPMC. In addition, the finger dummy was manufactured to evaluate the performance of the finger exoskeleton. The pinch task experiments, which were performed on the finger dummy with the developed exoskeleton, showed that the pinch force close to the desired level was obtained. Moreover, the dynamic model of the exoskeleton and finger dummy was developed in order to perform the various analyses for the improvement of the exoskeleton.