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이보화,권세진 한국항공우주학회 2016 International Journal of Aeronautical and Space Sc Vol.17 No.4
A dual-mode power management for a hybrid-electric UAV with a cruise power of 200W is proposed and empirically verified. The subject vehicle is a low-speed long-endurance UAV powered by a solar cell, a fuel cell, and a battery pack, which operate in the same voltage bounds. These power sources of different operational characteristics can be managed in two different methods: passive management and active management. This study proposes a new power management system named PMS2, which employs a bypass circuit to control the individual power sources. The PMS2 normally operates in active mode, and the bypass circuit converts the system into passive mode when necessary. The output characteristics of the hybrid system with the PMS2 are investigated under simulated failures in the power sources and the conversion of the power management methods. The investigation also provides quantitative comparisons of efficiencies of the system under the two distinct power management modes. In the case of the solar cell, the efficiency difference between the active and the passive management is shown to be 0.34% when the SOC of the battery is between 25~65%. However, if the SOC is out of this given range, i.e. when the SOC is at 90%, using active management displays an improved efficiency of 6.9%. In the case of the fuel cell, the efficiency of 55% is shown for both active and passive managements, indicating negligible differences.
Coherent Growth Behavior of an Orthorhombic (Ca,Sr)SnO3 Thin Film on a Cubic SrTiO3 (110) Substrate
이보화,정창욱 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.61 No.5
Ca1−xSrxSnO3 has an orthorhombic crystal structure, and thicker Ca1−xSrxSnO3 buffer layers having a relaxed growth behavior have been successfully used to control the growth orientation and the strain status of a SrRuO3 film on top of a SrTiO3 (110) substrate. In this work, we report the coherent growth behavior of Ca0.7Sr0.3SnO3 films having smaller thicknesses. The structural information obtained from X-ray diffraction (XRD) -2 scans and reciprocal-space mapping measurements showed that 1) the unit-cell volume was smaller for the films grown at higher temperatures and 2) the degree of coherent epitaxy of the films was better along the SrTiO3 [1-10] in-plane direction than along the SrTiO3 [001] in-plane direction. These were interpreted based on 1) the inherently lower lattice mismatch of the orthorhombic crystal along the cubic substrate’s [1-10] in-plane direction than along the cubic substrate’s [001] in-plane direction, 2) the higher efficiency of oxygen annealing at higher temperatures, and 3) the dynamic (kinetic) process during the film growth.
소형 무인기용 하이브리드 전기추진시스템 패시브 전력제어 시뮬레이션
이보화,박부민,양수석,안석민 한국항공우주학회 2011 한국항공우주학회 학술발표회 논문집 Vol.2011 No.4
본 연구에서 하이브리드 전기추진 시스템은 전력원으로써 연료전지, 태양전지, 배터리를 사용한다. 전기추진시스템의 출력에 대하여 능동적 제어로직이 적용된 전력제어 시뮬레이션으로 발전시켜나가기 위한 선행 연구로써, 각 전력원 및 시스템의 모델링 및 검증을 수행하였다. 시뮬레이션 결과, 각 전력원들의 성능은 적절히 모사됨을 확인 하였고, 이러한 전력원들을 결합하여 passive 전력제어 시스템을 구성하여 비행기의 요구동력 시나리오 대하여 시뮬레이션을 수행하여 각 전력원들의 출력 특성 변화를 알아보았다. In this paper, hybrid electric propulsion system use fuel cell, solar cell and battery as power source. The research activity is the precedent study for developing power management simulation applied active control logic to the outputs of electric propulsion system. All components and system have been modeled and verified. In result of simulation, it is revealed that the performance of the power sources are properly simulated. Also, simulations have been performed through constituting passive power management system at given power scenario. The variations of power characteristic are investigated.
Growth and Magnetic Characterization of Epitaxially Stabilized Fe-doped SrRuO_3 Thin Films
이보화,정창욱 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.2
We demonstrated the stabilization of Fe-doped SrRuO_3 single crystalline films by using epitaxial strain during thin film growth. X-ray diffraction (XRD) θ-2θ scans of Sr(Ru_(1−x)Fe_x)O_3 (SRFO) films (x = 0.1, 0.2, 0.3) showed strong peaks with a rocking-curve width of ∼0.04˚. Reciprocalspace mapping measurements showed that films grew epitaxially and coherently. We found that the magnetic and the transport properties of SrRuO_3 could be tuned by Fe doping and by using different substrate orientations; in addition, a transition from step flow growth in SrRuO_3 to layer-by-layer growth in Fe-doped SrRuO_3 is shown.
The flight test and power simulations of an UAV powered by solar cells, a fuel cell and batteries
이보화,박부민,김근배,권세진 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.1
The target mid-class UAV system used in this study consists of three types of power sources operating simultaneously. These powersources are designed and constructed to share the same operation voltage range and connect to the power bus without additional convertersor controllers. The flight test of the target UAV system was conducted for 22.13 hours after the take-off at 20:53 on June 21, 2012. The power sources successfully supplied the propulsion power required during the test flight. In addition, the power simulation was conductedand validated against the flight test results proving that the dynamic behavior of each power source can be properly predicted.
Power managements of a hybrid electric propulsion system for UAVs
이보화,박부민,김춘택,양수석,안석민 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.8
Power managements of a UAV’s hybrid electric propulsion systems are described. Three electric propulsion systems with different power sources, i.e. solar cells, fuel cells, and batteries are considered. Each power source is modeled in Matlab/Simulink and integrated into the power system. For fuel cells and batteries, the simulation process is verified via comparison between the simulation results and available flight test results of UAVs. Two types of power control logics are investigated: passive and active. The passive power management simulation shows that the behavior of each power source and its integrated system is adequate for the overall flight envelope. In addition, the active power management simulation demonstrates that active power management yields more efficient power distribution and better system safety than passive power management does. Also, a power simulation of a hybrid electric power system allows for estimation of the output behavior of the power source. Therefore, it can be a valuable tool for development of a power control logic that ensures efficient power distribution.
이보화,Chuntaek Kim,Inyoung Yang,Kyungjae Lee,Yangji Lee 한국항공우주학회 2019 International Journal of Aeronautical and Space Sc Vol.20 No.2
The Korea Aerospace Research Institute runs the ground-based Altitude Engine Test Facility (AETF) for simulating high-altitude environments. This facility is widely used to test the performance of gas turbine engines at ground level to high altitudes. When engine performance is tested in the AETF, total pressure and total temperature of airflow can be measured using rakes in a duct directly connected to the engine inlet. The total pressure and total temperature of airflow into an engine are the main factors affecting the thrust and specific fuel consumption rate of the engine. Furthermore, the total pressure and total temperature at the engine inlet are used as the main reference values when operating test equipment to determine the airflow rate and temperature corresponding to the performance test conditions of the engine. The performance evaluation of the rake used to measure this is crucial. Accordingly, in this study, to improve the accuracy of the total pressure and total temperature values measured using rakes, their total pressure coefficient and total temperature recovery factor are measured, and the measurement uncertainty of the total temperature recovery factor is evaluated.