• International Journal of Aeronautical and Space Sciences
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• 제17권2호
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• pp.167-174
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• 2016

Even though the differential drag type machines of the vertical wind turbines are a bit less efficient than the lift type machines such as Darrieus type machines, they have an advantage of low starting torque. The flapping blade type wind turbine is a specific type of the differential drag machines, and it has no need for orientation as well as quite low starting torque. This work is to develop an innovative 5kW class flapping type vertical wind turbine system which will be applicable to a hybrid power generation system driven by the diesel engine and the wind turbine. The parametric study was carried out to decide an optimum aerodynamic configuration of the wind turbine blade. In order to evaluate the designed blade, the subscale wind tunnel test and the performance test were carried out, and their test results were compared with the analysis results.

• 항공우주시스템공학회지
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• 제14권2호
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• pp.44-49
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• 2020

This work is intended to develop a flapping-type vertical wind turbine system that will be applicable to diesel generators and wind turbine generator hybrid systems. In the aerodynamic design of the wind turbine blade, parametric studies were performed to determine an optimum aerodynamic configuration. After the aerodynamic design, the structural design of the blade was performed. The major structural components of the flapping-type wind turbine are the flapping blade, the connecting part, and the stopper. The primary focus of this work is the design and analysis of the connecting part. Structural tests were performed to evaluate the blade design, and the test results were compared with the results of the analysis.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1437-1440
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• 2008

This research describes about designing and manufacturing X-wing type flapping micro aerial vehicle which intends to improve the performance of one-pair wing flapping vehicle with innovated design. This design, X-wing as we call, was introduced for some time ago from many laboratories but still there hasn’t any reports dealing on its theoretical or numerical analysis. By manufacturing the X-wing with our own design and succeeding its flight test will give us the general idea on X-wing which may guide us to conduct the numerical and experimental analysis later on. We focused to design the X-wing and introduce some conceptual theories about its characteristics on this report.

• 대한기계학회논문집A
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• 제34권10호
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• pp.1385-1391
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• 2010

본 논문에서는 폰 카메라 응용을 위해 H 형 비틀림 스프링으로 지지된 한 쌍의 사다리꼴 셔터 블레이드를 이용하는 초소형, 저전력, 고속 전자기력 Flapping 셔터를 제안한다. 기존의 정전기력 Rolling 셔터와 Flapping 셔터는 폰 카메라 응용을 위해 큰 입력 전압이 필요하며, 기존의 전자기력 Rotating 셔터는 큰 부피로 인해 폰 카메라에 사용하기 어렵다. 본 논문에서 제안하는 전자기력 Flapping 셔터는 폰 카메라에 사용 가능한 작은 크기로 회전 구동을 위해 저강성 H 형 비틀림 스프링과 저관성 사다리꼴 블레이드로 설계하여 제작된다. 실험에서 전자기력 Flapping 셔터는 입력전류 60 mA 에서 자기장 0.15 T 와 0.30 T 에 대하여 각각 최대 오버슈트 회전각 $80.2{\pm}3.5^{\circ}$와 $90.0{\pm}1.0^{\circ}$와, 정상 상태 회전각 $48.8{\pm}1.4^{\circ}$와 $64.4{\pm}1.0^{\circ}$ 성능을 보인다. 응답 시간 성능에서는 셔터 개방의 경우, 1.0 ms/20.0 ms 의 상승/정착 시간을 보이며, 셔터 폐쇄의 경우는 1.7 ms/10.3 ms 의 하강/정착 시간을 보인다. 본 논문에서는 폰 카메라용 셔터 응용을 위해 제안하는 전자기력 Flapping 셔터의 초소형(${\sim}8{\times}8{\times}2\;mm^3$), 저전력(${\leq}60\;mA$), 고속(~1/370 s) 성능을 실험적으로 검증하였다.

• 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 $3{\sim|}4V$.

• International Journal of Naval Architecture and Ocean Engineering
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• 제11권1호
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• pp.225-232
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• 2019

In recent years, nonlinear dynamic models have been developed for flapping-type energy harvesting systems with a rigid wing, but not for those with a flexible wing. Thus, in this study, flexible wing designs of NACA0012 section are proposed and measurements of the forces of rigid cambered wings, which are used to estimate the performance of the designed wings, are conducted. Polar curves from the measured lift and drag coefficients show that JavaFoil estimation is much closer to the measured values than Eppler over the entire given range of angles of attack. As the camber of the rigid cambered wings is increased, both the lift and drag coefficients increase, in turn increasing the resultant forces. Moreover, the maximum resultant forces for all rigid cambered wings are achieved at the same angle of attack as the maximum lift coefficient, meaning that the lift coefficient is dominant in representations of the wing characteristics.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.723-726
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• 2005

The two major obstacles in the application of IPMC to flapping actuators operated in the air are solvent loss and actuation force. In this paper, solvent loss of various IPMCs made of Nafion$^{TM}$117(183$\mu$m thickness) has been experimentally investigated to find out the best combination of cation and solvent for minimal solvent loss in IPMCs and higher actuation force. For this purpose. experiments for the internal solvent loss measurement of IMPCs have been conducted for various combinations of cation and solvent. From the experiments, it was found that heavy water showed improvement in the operating time up to more than two minutes. in the tip force measurement of IPMCs, it was found that smaller and thicker IPMCs produced larger tip forces. However, the shorter IPMCs generated reduced actuation displacements and created flapping motion with decreased natural frequency. For the design of flapping device actuated by 5mm wide, 10mm long, 0.2mm thick IPMCs were used in the stacked form. Since the actuation force is a few gram-force, we stacked five IPMCs to improve actuation force. To amply the actuation force, rack-and-pin ion type hinge was used for the flapping device and insect (Cicadidae) wing was attached to the stacked IPMC actuator. In the flapping test, the device could generate flapping angle of 15$^{\circ}$ at 6Hz excitation by 2.5 voltage square wave input.

• 한국항공운항학회:학술대회논문집
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• 한국항공운항학회 2006년도 추계학술대회 논문집
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• pp.107-110
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• 2006

• 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.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1566-1569
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• 2008

The flow visualization is conducted in order to investigate an unsteady flight characteristic of a model dragonfly. The flapping wings are analyzed using smoke-wire and high speed camera. The results of this experiment show that three mechanisms and high incidence angle of the wings are responsible for the lift. The leading edge vortex, which is induced by the rapid acceleration of the wing at the beginning of a stroke, causes the lift enhancement. The delayed stall during the stroke and the fast supination and pronation of the wing near the end of each stroke are also responsible for the lift generation.