• 한국항공우주학회지
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• 제33권12호
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• pp.48-53
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• 2005

본 논문에서 LIPCA(Lightweight Piezoceramic Composite Actuator)를 이용한 날갯짓(flapping) 기구의 개발에 관한 최근의 연구진척 사항을 제시하였다. 날갯짓 기구는 여러 개의 연결막대를 이용하여 LIPCA의 제한된 작동변위를 커다란 날갯짓 각(flapping angle)이 발생하도록 증폭시켰으며, 패더링 메커니즘(feathering mechanism)을 적용하여 날갯짓과 동시에 날개에 비틀림이 발생하도록 설계되었다. 이 날갯짓 기구의 고유 날갯짓 주파수는 약 9Hz로, 이때 최대의 날갯짓 각이 발생하였다. 제작된 날갯짓 기구의 작동성능을 평가하기 위하여 날갯짓 주파수를 4Hz에서 15Hz까지 변화시키면서 발생되는 양력과 추력을 측정하였으며, 최대 양력과 최대 추력은 고유 날갯짓 주파수 부근에서 계측되었다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.719-722
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• 2005

In this paper, we present out recent progress in the LIPCA (Lightweight Piezo-Composite Actuator) application for actuation of a flapping wing device. The flapping device uses linkage system that can amplify the actuation displacement of LIPCA. The feathering mechanism is also designed and implemented such that the wing can rotate during flapping. The natural flapping-frequency of the device was about 9 Hz, where the maximum flapping angle was achieved. The flapping test under 5 Hz to 15 Hz flapping frequency was performed to investigate the flapping performance by measuring the produced lift and thrust. Maximum lift and thrust were produced when the flapping device was actuated at about the natural flapping-frequency.

• 로봇학회논문지
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• 제11권4호
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• pp.256-261
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• 2016

An insect-like flapping-wing flying-robot should be able to produce flight forces and control moments at the same time only by flapping wings, because there is no control surface at tail just like an insect. In this paper, design principles for the flapping mechanism and control moment generator are briefly explained, characteristics measured force and moment generations of the robot are presented, and finally controlled flight of the flying robot is demonstrated. The present insect-like robot comprises a lightweight flapping mechanism that can produce a flapping angle larger than $180^{\circ}$ and a control moment generator that produces pitch, roll, and yaw moments by adjusting location of the trailing edges at the wing roots. The measured force and moment data show that the control input angles less than $9^{\circ}$ would not significantly reduce the vertical force generation. It is also observed that the pitch, roll, and yaw control moments are produced only by the corresponding control input. The simple PID control theory is used for the controlled flight of the flying robot, controlling pitch, roll, and yaw motions. The flying robot successfully demonstrated controlled flight for about 40 seconds.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.759-764
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• 2003

Numerical simulations are conducted to investigate the mechanism of hovering flight by single flapping wing, and to examine the effect of the phase difference between the fore- and hindwings in hovering flight by two flapping wings. The numerical method used is based on an immersed boundary method in Cartesian coordinates. The Reynolds number considered is Re=150 based on the maximum translational velocity and chord length of the wing. For single flapping wing, the stroke plane angles are $0^{\circ}$, $30^{\circ}$, $60^{\circ}$, $75^{\circ}$ and $90^{\circ}$ and the downstroke angles of attack are varied for each stroke angle. Results show that for each stroke plane angle, there is an optimal angle of attack to maximize the vertical force. Below the stroke angle of $60^{\circ}$, wake capturing reduces the negative vertical force during the upstroke. For two flapping wings, The phase lags of the hindwing are $0^{\circ}$, $90^{\circ}$, $180^{\circ}$ and $270^{\circ}$. The amplitudes of the stroke are 2.5 and 4.0 times the chord length at each phase lag. The results show that maximum vertical force is generated when the phase lag is zero, and the amplitude of the vertical force is minimum at the phase lag of $180^{\circ}$.

• 한국전산유체공학회지
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• 제8권2호
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• pp.24-32
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• 2003

In this work, we propose a new idea of flapping airfoil design for optimal aerodynamic performance from detailed computational investigations of flow physics. Generally, flapping motion which is combined with pitching and plunging motion of airfoil, leads to complex flow features such as leading edge separation and vortex street. As it is well known, the mechanism of thrust generation of flapping airfoil is based on inverse Karman-vortex street. This vortex street induces jet-like flow field at the rear region of trailing edge and then generates thrust. The leading edge separation vortex can also play an important role with its aerodynamic performances. The flapping airfoil introduces an alternative propulsive way instead of the current inefficient propulsive system such as a propeller in the low Reynolds number flow. Thrust coefficient and propulsive efficiency are the two major parameters in the design of flapping airfoil as propulsive system. Through numerous computations, we found the specific physical flow phenomenon which governed the aerodynamic characteristics in flapping airfoil. Based on this physical insight, we could come up with a new kind of airfoil of tadpole-shaped and more enhanced aerodynamic performance.

• Composites Research
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• 제22권6호
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• pp.7-12
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• 2009

본 연구는 압전 작동기 기반 초소형 날갯짓 비행체의 날갯짓 운동을 위해, 압전 작동기의 펌핑 운동을 효과적으로 날갯짓 운동으로 변환하는 힌지 메커니즘 제작 기법에 대해 다루었다. 경량화를 위해 탄소섬유/에폭시(Graphite/Epoxy) 프리프레그를 사용하고, 반복적인 제작이 용이하도록 레이저 절단기를 활용하였으며, 힌지부는 얇은 캡톤 필름을 이용해 컴플라이언트(compliant) 메커니즘으로 구성하였다. 제작된 힌지 메커니즘을 압전 유니모프 작동기 PUMPS에 연결하여 동작시켜 본결과, 300V 170Hz 인가 전압에서 $173^{\circ}$의 큰 날갯짓 각을 가짐을 확인하였다.

• International Journal of Control, Automation, and Systems
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• 제4권6호
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• pp.748-755
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• 2006

In this paper, a trade-off design and fabrication of IPMC(Ionic Polymer Metal Composites) as an actuator for a flapping device have been described. Experiments for the internal solvent loss of IPMCs have been conducted for various combinations of cation and solvent in order to find out the best combination of cation and solvent for minimal solvent loss and higher actuation force. From the experiments, it was found that IPMCs with heavy water as their solvent could operate longer. Relations between length/thickness and tip force of IPMCs were also quantitatively identified for the actuator design from the tip force measurement of 200, 400, 640, and $800{\mu}m$ thick IPMCs. All IPMCs thicker than $200{\mu}m$ were processed by casting $Nafion^{TM}$ solution. The shorter and thicker IPMCs tended to generate higher actuation force but lower actuation displacement. To improve surface conductivity and to minimize solvent evaporation due to electrically heated electrodes, gold was sputtered on both surfaces of the cast IPMCs by the Physical Vapor Deposition(PVD) process. For amplification of a short IPMC's small actuation displacement to a large flapping motion, a rack-and-pinion type hinge was used in the flapping device. An insect wing was attached to the IPMC flapping mechanism for its flapping test. In this test, the wing flapping device using the $800{\mu}m$ thick IPMC. could create around $10^{\circ}{\sim}85^{\circ}$ flapping angles and $0.5{\sim}15Hz$ flapping frequencies by applying $3{\sim|}4V$.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2003년도 The Fifth Asian Computational Fluid Dynamics Conference
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• pp.291-293
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• 2003

This paper deals with a thrust generation of flapping-airfoil by dynamic stall. From many other previous research results, phase angle $ between pitching and plunging mode of flapping motion must be 90 deg. to satisfy maximum propulsive efficiency. In this case, leading edge vortex is relatively small. This phenomenon is related dynamic stall. So preventing leading edge vortex induced by dynamic stall guarantees maximum propulsive efficiency. But, in this paper we insist the leading edge vortex yields quite a positive influence on thrust generation and propulsive efficiency. In order to certify our opinion, pitching and plunging motions were calculated with the parameter of amplitude and frequency by using the unsteady, incompressible Navier-Stokes flow solver with a two-equation turbulence model. For more efficient computation, it is parallelized by MPI programming method.

• 한국전산구조공학회논문집
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• 제30권4호
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• pp.289-296
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• 2017

본 논문에서는 곤충 모방 날갯짓 초소형 비행체에 적용될 끈을 이용한 날갯짓 구동 장치의 구동 원리와 그 최적화 과정이 소개된다. 이 날갯짓 구동 장치는 끈을 이용하여 구조의 경량화와 관성력 감소로 인한 에너지 효율 상승을 목적으로 설계되었다. 먼저 장력만 전달할 수 있는 끈의 특성을 고려하여 운동학적인 수식이 정립되었으며, 이를 통해 구동 장치의 거동 특성을 파악할 수 있었다. 이 수식들은 수정된 패턴 검색 최적화 과정에 포함되어 메커니즘의 운동학적 최적화를 가능하게 만들었다. 최적화된 형상으로 제작된 시제품은 설계의 구동 원리에 맞게 운동하였으며, 그 날갯짓 폭은 목표한 날갯짓 폭을 만족시켰다. 수치적 시뮬레이션과 실험 결과는 잘 일치하여 제시된 구동 장치가 실제로 활용될 수 있음을 보였다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2007년도 제29회 추계학술대회논문집
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• pp.311-314
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• 2007

곤충의 날개짓을 모방한 공력특성 연구가 초소형 비행체의 설계 파라미터를 구하기 위하여 수행되었다. 한 쌍의 날개 모델은 초파리(rosophila) 날개짓을 모방하기 위하여 200배 확대하였으며, 두 쌍의 공간 4절 링크를 적용하였다. Weis-Fogh 메커니즘을 검증하기 위해 한 쌍의 날개모델은 후행회전(Delayed Rotation)의 움직임을 가지도록 설계되었다. 또한 양력 및 항력은 날개 끝 속도 기준 레이놀즈수 약 1200, 최대 받음각 $40^{\circ}$에서 측정되었다. 모델의 관성력은 99.98%의 진공 챔버로 측정되고 공기속에서 측정된 데이터에서 제거되었다. 본 연구에서 Weis-Fogh 메커니즘의 고양력 효과는 날개의 업스트로크 과정에서 나타났다.