• 한국항공우주학회지
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• 제46권7호
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• pp.602-609
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• 2018

본 논문은 LTE 통신망 환경에서 군집 UAV의 비디오 영상 데이터를 고속으로 암호화하기 위한 하이브리드 암호시스템을 제안한다. 이 암호시스템은 ECC 공개키 알고리즘과 LEA 대칭키 알고리즘으로 구성된다. ECC는 RSA보다 빠르면서 동일한 보안성을 가지며, LEA는 동일한 키로 AES보다 빠른 국내 표준 알고리즘이다. 본 논문은 OpenSSL과 OpenCV를 활용하여 Socket 프로그램으로 8개의 군집 UAV 환경에서 하이브리드 암호시스템을 구성하여 구현하였다. 실험을 통하여 본 하이브리드 암호시스템이 실시간 환경에서 효율적으로 적용이 가능함을 보인다.

• 제어로봇시스템학회논문지
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• 제22권9호
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• pp.759-765
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• 2016

This paper presents the principle, dynamics modeling and control, hardware implementation, and flight test result of a hybrid-type unmanned aerial vehicle (UAV). The proposed UAV was designed to provide both hovering and fixed-wing type aerodynamic flight modes. The UAV's flight mode transition was achieved through the attitude transformation in pitch axis, which avoids a complex rotor tilt mechanism from a structural and control viewpoint. To achieve this, a different navigation coordinate was introduced that avoids the gimbal lock in pitch singularity point. Attitude and guidance control algorithms were developed for the flight control system. For flight test purposes, a quadrotor attached with a tailless fixed-wing structure was manufactured. An onboard flight control computer was designed to realize the navigation and control algorithms and the UAV's performance was verified through the outdoor flight tests.

• 한국시뮬레이션학회논문지
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• 제15권1호
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• pp.43-50
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• 2006

UAV(Unmanned Air Vehicle) 시스템은 새로운 알고리즘과 소프트웨어 디자인에 바탕을 두고 빠르게 발전하고 있다. 빠르게 발전하는 현대의 UAV 시스템은 상황에 따른 효과적이고 지능적인 제어를 요구한다. 이에 본 논문에서는 UAV 시스템의 효과적이고 지능적인 제어를 위하여 이산사건 시스템인 조종사 모델과의 연동 모델링을 제안한다. 비행기 모델은 연속시간 시스템으로 표현되며, 자세한 표현력을 바탕으로 정량적이고 정확한 비행기 모델을 표현할 수 있다. 또한, 조종사 모델은 이산사건 시스템으로 표현되며, 각 사건과 시스템의 상태에 따른 정성적인 행동제어를 가능하게 한다. 본 연구는 한국항공대학교에서 개발한 이산사건 시뮬레이터인 DEJAVA(DEVS Java)와 연속시간시뮬레이터인 MATLAB 시뮬레이터 환경을 바탕으로 NASA에서 개발된 HL20 비행시뮬레이터와 지능제어시스템을 이용한 조종사 모델을 사용하여 구현되었다.

• International Journal of Aeronautical and Space Sciences
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• 제17권4호
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• pp.631-640
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• 2016

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.

• 한국수소및신에너지학회논문집
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• 제25권4호
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• pp.405-418
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• 2014

Fuel cells are suitable for a power plant of a unmanned aerial vehicle (UAV) as it is not only environmentally friendly and quiet but also more efficient than an internal combustion engine. A fuel cell hybrid UAV has better performance in endurance than a fuel cell only or battery only UAV. One of the key purposes of making fuel cell hybrid UAVs is having long endurance and now maximum 26 hours of flight is possible. Because optimal design and control methods for fuel cell hybrid UAVs are absolutely needed for their long endurance we have to check the methods. The aircraft made by using application-integrated design method has less BOP mass and better performances. The optimal design and control methods are generally based on computer simulations or Hardware-In-The-Loop simulations by using dynamic models for their design and control. The Hardware-In-The-Loop simulation (HILS) is to use a hardware device like a fuel cell stack as well as a simulation program and it allows for making optimally designed applications. This paper introduce efficient methods of design, control and evaluation for the fuel cell hybrid UAVs.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권2호
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• pp.711-732
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• 2019

Many unmanned aerial vehicle (UAV) applications have been employed for performing data collection in facilitating tasks such as surveillance and monitoring objectives in remote and dangerous environments. In light of the fact that most of the existing UAV relaying applications operate in conventional half-duplex (HD) mode, a full-duplex (FD) based UAV relay aided wireless network is investigated, in which the UAV relay helps forwarding information from the source (S) node to the destination (D). Since the activated UAV relays are always floating and flying in the air, its channel state information (CSI) as well as channel capacity is a time-variant parameter. Considering decode-and-forward (DF) relaying protocol in UAV relays, the cooperative relaying channel capacity is constrained by the relatively weaker one (i.e. in terms of signal-to-noise ratio (SNR) or signal-to-interference-plus-noise ratio (SINR)) between S-to-relay and relay-to-D links. The channel capacity can be optimized by adaptively optimizing the transmit power of S and/or UAV relay. Furthermore, a hybrid HD/FD mode is enabled in the proposed UAV relays for adaptively optimizing the channel utilization subject to the instantaneous CSI and/or remaining self-interference (SI) levels. Numerical results show that the channel capacity of the proposed UAV relay aided wireless networks can be maximized by adaptively responding to the influence of various real-time factors.

• 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.

• 한국군사과학기술학회지
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• 제23권3호
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• pp.302-309
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• 2020

Early-detection and monitoring of toxic chemical gas cloud with chemical detector is essential for reducing the number of casualties. Conventional method for chemical detection and reconnaissance has the limitation in approaching to chemically contaminated site and prompt understanding for the situation. Stand-off detector can detect and identify the chemical gas at a long distance but it cannot know exact distance and position. Chemical detection UAV is an emerging platform for its high mobility and operation safety. In this study, we have conducted chemical gas cloud detection with the stand-off chemical detector and the chemical detection UAV. DMMP vapor was generated in the area where the cloud can be detected through the field of view(FOV) of stand-off chemical detector. Monitoring the vapor cloud with standoff detector, the chemical detection UAV moved back and forth at the area DMMP vapor being generated to detect the chemical contamination. The hybrid detection system with standoff cloud detection and point detection by chemical sensors with UAV seems to be very efficient as a new concept of chemical detection.

• 한국멀티미디어학회논문지
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• 제20권4호
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• pp.593-605
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• 2017

In applications which are covered wide range, it is possible that one or more number of Unmanned Aerial Vehicle(UAV) squadrons are used to perform a mission. In this case, it is most important to communicate seamlessly between the UAV squadrons. In this paper, we applied the modified OLSR(OSLR-Pds) which can prediction for state of the link for the communication in UAV squadron, and applied the modified AOMDV which can build multi-path for the communication between UAV Squadrons. The mobility of nodes are modeled using Gauss-Markov algorithm, and relative speed between nodes were calculated by derive equation of movement, and thereby we can predict link state for in a squadron and between squadrons. An experiment for comparing AODV, AOMDV and the proposed routing protocol was conducted by three factors such as packet delivery ratio, end to end delay, and routing overhead. In experiment result, we make sure that the proposed protocol performance are superior in these three factors. However, if the density of the nodes constituting FANET are too low, and if the moving speed of node is very slow, there is no difference to others protocols.

• 한국통신학회논문지
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• 제39C권12호
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• pp.1250-1260
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• 2014

본 논문에서는 허브 네트워크 기반의 장거리 공중 전술 통신을 위한 새로운 자원 스케줄링 기법을 제안한다. 최근 세계 각국에서는 네트워크 중심전 (NCW, Network Centric Warfare)으로 변화하는 현대전의 흐름에 맞추어 공용데이터링크 (CDL, Common Data Link)의 전송속도 및 네트워킹 기능을 향상시키기 위한 기술 개발에 주력하고 있으며, 우리 군도 자립적인 차세대 대용량 CDL 기술 개발에 박차를 가하고 있다. CDL의 대표적 운용 구조인 허브 네트워크에서는 제한된 주파수 대역 내에서 다수의 UAV (Unmanned Aerial Vehicle)들과 대용량의 영상 전술 정보를 동시 다발적으로 교환하기 위해, hybrid FDMA(Frequency Division Multiple Access)/TDMA(Time Division Multiple Access) 구조를 고려할 수 있다. 그러나 UAV 별 상이한 왕복 시간 지연 (RTT, Round-Trip Time) 및 트래픽 크기로 인해 동일 주파수 대역을 점유하는 UAV 간 유휴 시간 자원이 발생하거나 불필요한 패킷 전송 지연이 발생할 수 있으며, 이는 장거리 운용 시 허브 네트워크의 자원 효율을 저하시킨다. 따라서 본 논문에서는 UAV 별 발생하는 RTT와 트래픽 크기를 기반으로 하는 반복적 정렬 알고리즘을 통해 UAV의 시간/주파수 자원을 스케줄링하는 기법을 제안한다. 성능 평가를 통해 제안 기법이 낮은 복잡도로 데이터 처리율과 패킷 지연 측면의 성능 향상이 가능함을 입증하였다.