• Proceedings of the Korea Information Processing Society Conference
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• 2022.05a
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• pp.691-694
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• 2022

최근 고해상도 영상이 필요하게 되었으며, 저해상도 영상을 고해상도 영상으로 변환하는 딥러닝 기반의 초해상도 알고리즘에 대한 연구가 활발히 진행되고 있다. 그럼에도 불구하고 딥러닝 기반의 초해상도 알고리즘은 하드웨어의 한계로 인해 임베디드 시스템에서 실행시간이 느린 단점이 있다. 본 논문에서는 심층신경망 기반의 초해상도 알고리즘의 네트워크 구조를 제시하고 다양한 활성화 함수에 따른 화질 및 실행시간 성능을 분석한다. 실험 결과, 젯슨 나노보드의 다양한 활성화 함수 중 화질과 실행 시간의 관계에서 도출한 최적의 활성화 함수가 PReLU 함수임을 확인하였다.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.2
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• pp.269-276
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• 2023

In this research works, we propose a hybrid power generation system for drone capable of staying in the air for more than 1 hour. This power system converts the alternating current generated by the generator into direct current through a diode bridge circuit to charge the battery and uses a battery system having separated cells to obtain high controllability of the power system. The fuel efficiency and the power output for individual load were analyzed, and also the performance of a selected generator was studied in this paper. The drone which is equipped with the proposed hybrid power generation system calculated 0.82 ratio for weight vs power output, and flight time of drone showed 4,179 seconds.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.11
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• pp.940-947
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• 2012

The target system is a middle size UAV, which is a low-speed long-endurance UAV with a weight of 18 kg and wingspan of 6.4 m. Three electric power sources, i.e. solar cells, a fuel cell, and a battery, are considered. The optimal takeoff time is determined to maximize the endurance because the generated solar cell's energy is heavily dependent on it. Each power source is modeled in Matlab/Simulink, and the component models are verified with the component test data. The component models are integrated into a power system which is used for power simulations. When takeoff time is at 6 pm and 2 am, it can supply the power during 37.5 hrs and 27.6 hrs, respectively. In addition, the thermostat control simulation for fuel cell demonstrates that it yields more power supply and efficient power distribution.

• The Journal of the Korea institute of electronic communication sciences
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• v.17 no.3
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• pp.433-440
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• 2022

High Altitude Long Endurance(HALE) solar powered UAV is the vehicle that flies for a long time as solar power energy sources. It can be used to replace satellites or provide continuous service because it can perform long-term missions at high altitudes. Due to the property of the mission, it is very important for HALE solar powered UAV to have maximum flight time. It is required for mission performance to fly at high altitudes continuously except a return for temporary maintenance. Therefore mission availability time analysis is a critical factor in the commercialization of HALE solar powered UAV. In this paper, we presented an analytic model and logic for available time analysis based on the design parameters of HALE solar powered UAV. This model can be used to analyze the possibility of applying UAV according to the UAV's mission in concept design before the UAV detail design stage.

• Journal of the Institute of Convergence Signal Processing
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• v.24 no.4
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• pp.229-235
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• 2023

Recently, for drones to be used for agricultural applications, it is necessary to increase the payload and extending flight time. Currently, the payload and extending flight time are limited by the battery technology for solar paper drone. In addition, charging or replacing the batteries may be a practical solution at the field that requires near continuous operation. In this paper, the procedure to optimize the main power system of an electric hybrid drone that consists of a battery and electric motor is presented. As a result, the solar paper drone flied successfully for 2-3%. The developed solar paper drone consumes and average of 55W when cruising and can receive up to 25W of energy during the day, and its extending flight time was verified through flight tests.

• Proceedings of the Korean Society of Disaster Information Conference
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• 2022.10a
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• pp.369-370
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• 2022

4차 산업혁명이 도래함에 따라서 군사용으로 개발된 드론이 광범위하게 다양한 분야에 활용되어 가고 있다. 드론의 활용으로 이전에 사람이 접근하기 어려웠던 지역이나 현장을 원격탐사 및 데이터 취득이 가능하게 되면서, 도시문제 해결과 재난에 대응할 수 있다. 하지만 기존 드론의 동력원으로 사용하는 리튬폴리머(Li-Po)는 짧은 비행시간 때문에, 재난 현장의 드론 투입에 한계가 있다. 이러한 문제점을 보완하기 위하여 기존 드론 대비 4배 이상 향상된 비행시간을 통해 장기체공이 가능한 액화 수소 드론의 도입이 필요한 것으로 보인다. 늘어난 비행시간과 비가시 장거리 비행 능력을 통해 높은 효율을 낼 수 있는 액화 수소 드론의 활용으로 효과적인 재난 대응 활동에 대한 연구가 필요하다.

• Aerospace Engineering and Technology
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• v.12 no.1
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• pp.1-9
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• 2013

In order to increase endurance flight efficiency of long endurance electric powered UAV with solar cell, the light weight airframe design techniques are important. In this paper, the design of the main wing of electric powered UAV manufactured using Mylar film and fiber reinforced composite was conducted in order to achieve weight reduction and structural integrity of the structure. The shape of spar and size were determined using beam theory analysis. The finite element analysis of the wing was performed under various load condition derived from flight environment of EAV-2H. Finally, the static strength test of the main wing was conducted to verify structural integrity. It was found that the developed main wing weigh less than 42% than the previous EAV-2 and the main wing passed static strength test under ultimate load.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.8
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• pp.775-782
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• 2010

This study is performed to study the effect of the tray in the absorber of a flue-gas desulphurization (FGD) system by using a computational fluid dynamic (CFD) technique. Stagnant time of slurry and the pressure drop in the FGD absorber increase when a tray is used in the absorber. Stagnant time of slurry results in an increase in the desulfurization effect and a decrease in the power of the absorber recirculation pump; however, increased pressure drop requires more power of booster fan in the FGD system should be increased. The gas and slurry hydrodynamics inside the absorber is simulated using a commercial CFD code. The continuous gas phase has been modeled in an Eulerian framework, while the discrete liquid phase has been modeled by adopting a Lagrangian approach by tracking a large number of particles through the computational domain. It was observed that the power saved upon increasing the stagnant time of slurry was more than increased power with pressure drop.

• Journal of Institute of Convergence Technology
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• v.11 no.1
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• pp.33-37
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• 2021

The application of multicopters using a battery is limited by the short endurance due to the low energy density. A propeller is one of crucial components that determine the performance of the multicopter. In the present study, a systematic method for predicting the endurance of multicopters is described. Propeller performance database are constructed using the data from UIUC Propeller Data Site. Using the 'trendline' function of MS Excel software, the performance of the commercial propellers are represented as a function of polynomials. The multicopter's endurance is computed iteratively using Peukert's Law and considering the voltage drop effect. We evaluated the endurance of multicopters that use commercial propellers. The endurance of the multicopter was within the range of 28 min. to 36 min. It is expected that the present method can be utilized for optimal propeller selection for the given multicopters.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.2
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• pp.129-138
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• 2012

A MDO study of a midium-sized solar powered High Altitude Long Endurance (HALE) UAV has been performed, focused on energy balance. In the MDO process, Vortex Lattice Method(VLM) is employed for the aerodynamic modeling of the vehicle, of which structural weight is estimated with the modeling proposed by Cruz. Tail volume ratios have been set as constants, while the location of tail surfaces is determined from longitudinal static stability criterion. By balancing the available energy from solar cells, battery, and altitude, with the energy-requirement of the vehicle, the possibility of continuous flight over 24-hours has been investigated. The solar radiation level is set as that of summer at the latitude of $36^{\circ}$ north. During the daytime, the aircraft climbs using solar energy, accumulating potential energy, which supplements energy balance during the night. Optimizations have been sought in size of the vehicle, its weight distribution, and flight strategy.