• 한국항공우주학회지
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• 제38권8호
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• pp.758-766
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• 2010

태양에너지 기반 무인기는 공급되는 전력량이 날개 면적에 영향을 받으므로 형상설계와 비행에 필요한 전력량이 동시에 고려되어야 하며 따라서 설계 과정이 복잡해진다. 복잡한 설계과정에 앞서 주어진 임무 요구를 만족시키는 태양에너지 기반의 무인기 제작 가능 여부와 제작 가능하다면 무인기의 대략적인 주요 치수를 구하는 방법론이 있다면 이를 활용함으로서 불필요한 설계 시행 오차 없이 무인기를 설계 할 수 있을 것이다. 본 논문에서는 주요 치수 결정 방법론으로 날개 면적을 가정하고 날개 면적과 임무 요구로부터 에어포일(양력계수, 항력계수), 무게를 결정한 후 필요 전력과 태양 전지 효율로부터 다시 날개 면적을 계산하는 것으로 제시하였는데, 이는 날개에서 생산되는 전력, 양력 및 항력이 날개 면적에 직접적으로 영향 받기 때문이다. 앞서 가정된 날개 면적 값과 계산된 날개 면적 값의 오차가 충분히 작아질 때 까지 반복적으로 가정된 날개 면적 값을 바꾸어가며 계산을 수행한다. 본 방법론을 실제 제작된 태양에너지 기반 무인기의 값을 이용해 검증하고, 태양에너지 기반 고고도 장기체공 무인기의 주요 치수를 결정해보았다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 추계학술대회 초록집
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• pp.55.2-55.2
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• 2011

This research aims to study the effects of the incidence angle and surface temperature on the power generation performance of a thin-film CIGS solar cell for solar powered unmanned aerial vehicles (UAVs). The test rig consists of a unit CIGS solar cell is installed on a table whose angle is controlled manually. A K-type thermocouple is attached to the solar cell surface for temperature measurements. A solar module analyzer measures the voltage and current generated from the test solar cell. The solar module analyzer also calculates the maximum solar power and efficiency of the solar cell. All test data are acquired in a PC. Test results show that the solar cell efficiency decreases significantly with increasing incidence angle and increasing surface temperature in general. As the incidence angle increases from 0 degree to 90 degree, the solar cell efficiency decreases by 60%. The solar cell efficiency decreases by 10% with increasing solar cell surface temperature from $20^{\circ}C$ to $30^{\circ}C$, for exmaple. The direct cooling method of the solar cell using dry ice decreases dramatically the solar cell surface temperature, thus increasing the solar cell efficiency by 15%.

• 한국항공운항학회지
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• 제19권2호
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• pp.1-9
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• 2011

Several studies on the development for solar powered uninhabited aerial vehicles(UAVs) are under way as the use of the renewable energy becomes more and more important these days. This paper is for the conceptual design by a discrete and iterative method. An initial design point with 1.5 meter wing span is determined in the global design, which deploys the mass and energy balances among each component of UAV including solar cells and airframe. Then, the iteration for subsystems is carried out with the help of Vortex Lattice Method(VLM) to optimize the aircraft configuration and the solar power system. It is demonstrated in simulations that the optimized design increases the flight time from 62 to 120 minutes when the solar power system is installed. Also, the associated dynamic analysis reveals that the designed small aircraft has the acceptable stability and controllability.

• 한국항행학회논문지
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• 제20권5호
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• pp.401-407
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• 2016

본 논문에서는 태양광 장기체공 무인기의 전력모델을 포함한 3차원 경로계획과 유도에 대하여 기술한다. 본 논문에서 사용한 Dubins curve는 계산속도가 빨라 경로계획에 곧바로 적용이 가능하다는 장점이 있다. 하지만 Dubins curve의 경로생성 문제는 2차원 평면에서 정의되기 때문에 실제 항공기의 경로계획을 위해 Randal W. Beard에 의해 수행된 비행 경로각의 한계를 고려하여, 고도 차이에 따라 선회경로를 추가하는 방식의 3차원 Dubins 경로생성 알고리즘을 활용하였다. 본 논문에서 사용한 항공기 모델은 Aileron이 없기 때문에 Rudder를 사용하여 횡축 방향 제어기를 설계하였으며, 비선형 경로추종 유도기법을 사용하여 경로추종 시뮬레이션을 수행하였다. 고도조건에 따른 예제를 생성하였으며, 시뮬레이션 결과 생성된 경로를 잘 추종하는 것을 확인하였다. 마지막으로 태양에너지 수율에 대한 계산식을 통해 태양광 장기체공 무인기의 전력 시스템을 모델링하여 48시간 연속비행 시뮬레이션을 실시하였고, 이에 대한 시뮬레이션 결과를 제시하였다.

• 한국추진공학회지
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• 제22권4호
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• pp.133-140
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• 2018

최근 친환경적인 항공용 추진시스템에 대한 관심과 필요성이 더욱 부각되면서 다양한 전력원을 조합하여 임무를 수행할 수 있는 무인기 및 추진시스템 개발에 많은 연구가 이루어지고 있다. 본 논문에서는 태양광발전을 기반으로 하는 무인기의 복합추진계통의 구성품을 하나의 시스템으로 통합하여 계통의 안정성 및 출력을 확인하는 시험과 실 기체에 탑재하여 지상에서 통합검증시험을 수행하였고, 이를 통해 비행시험 전 시스템의 기능 및 정상작동 여부를 확인하였다.

• 한국추진공학회지
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• 제14권3호
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• pp.79-86
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• 2010

현재 운용중인 UAV 추진기관의 종류 및 각각의 특징과 장단점들을 살펴보았다. 전기추진을 위한 에너지원과 내연기관 추진의 동력원을 상호 비교하였으며, 미래의 UAV에 적합한 추진기관들의 성능 요구 조건을 분석, 제시하였다.

• 한국태양에너지학회 논문집
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• 제34권4호
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• pp.17-22
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• 2014

The design of a fuel cells stack is important to get optimal output power. This study focuses on the evaluation of fuel cell system for unmaned aerial vehicles (UAVs). Low temperature proton exchange membrane (LTPEM) fuel cells are the most promising energy source for the robot applications because of their unique advantages such as high energy density, cold startup, and quick response during operation. In this paper, a 600 W open cathode LTPEM fuel cell was tested to evaluate the performance and to determine optimal operating conditions. The open cathode design reduces the overall size of the system to meet the requirement for robotic application. The cruise power requirement of 600 W was supported entirely by the fuel cell while the additional power requirements during takeoff was extended using a battery. A peak of power of 900 W is possible for 10 mins with a lithium polymer (LiPo) battery. The system was evaluated under various load cycles as well as start-stop cycles. The system response from no load to full load meets the robot platform requirement. The total weigh of the stack was 2 kg, while the overall system, including the fuel processing system and battery, was 4 kg.

• International Journal of Aeronautical and Space Sciences
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• 제16권2호
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• pp.311-324
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• 2015

This study presents computational analyses for low-drag aerodynamic design that are applied to modify a long-endurance UAV. EAV-2 is a test-bed for a hybrid electric power system (fuel cell and solar cell) that was developed by the Korean Aerospace Research Institute (KARI) for use in future long-endurance UAVs. The computational investigation focuses on designing a wing with a reduced drag since this is the main contributor of the aerodynamic drag. The airfoil and wing aspect ratio of the least drag are defined, the fuselage configuration is modified, and raked wingtips are implemented to further reduce the profile and induced drag of EAV-2. The results indicate that the total drag was reduced by 54% relative to EAV-1, which was a small-sized version that was previously developed. In addition, static stabilities can be achieved in the longitudinal and lateral-directional by this low-drag configuration. A long-endurance flight test of 22 hours proves that the low-drag design for EAV-2 is effective and that the average power consumption is lower than the objective cruise powerof 200 Watts.

• Journal of Electrochemical Science and Technology
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• 제7권1호
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• pp.41-51
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• 2016

In the stratosphere, the air is stable and a photovoltaic (PV) system can produce more solar energy compared to in the atmosphere. If unmanned aerial vehicles (UAVs) fly in the stratosphere, the flight stability and efficiency of the mission are improved. On the other hand, the weakened lift force of the UAV due to the rarefied atmosphere can require more power for lift according to the weight and/or wing area of the UAV. To solve this problem, it is necessary to minimize the weight of the aircraft and improve the performance of the power system. A regenerative fuel cell (RFC) consisting of a fuel cell (FC) and water electrolysis (WE) combined PV power system has been investigated as a good alterative because of its higher specific energy. The WE system produces hydrogen and oxygen, providing extra energy beyond the energy generated by the PV system in the daytime, and then saves the gases in tanks. The FC system supplies the required power to the UAV at night, so the additional fuel supply to the UAV is not needed anymore. The specific energy of RFC systems is higher than that of Li-ion battery systems, so they have less weight than batteries that supply the same energy to the UAV. In this paper, for a stratospheric long-endurance hybrid UAV based on an RFC system, three major design factors (UAV weight, wing area and performance of WE) affecting the ability of long-term flight were determined and a simulation-based feasibility study was performed. The effects of the three design factors were analyzed as the flight time increased, and acceptable values of the factors for long endurance were found. As a result, the long-endurance of the target UAV was possible when the values were under 350 kg, above 150 m² and under 80 kWh/kg H₂.