• 한국산학기술학회논문지
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• 제17권1호
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• pp.597-604
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• 2016

본 논문에서는 항공 방제 시 균일 방제를 통하여 병해충에 의한 농산물 생산량 저하 및 농약이 과도 살포된 농작물 생산을 방지하고자 하였다. 항공 방제가 실시되는 비행 고도 3m와 속도 15km/h를 유지하는 것은 사용자의 조종 습관 및 방법, 바람의 변화 같은 환경적 요인이 작용하여 대단히 어렵다. 따라서 무인 헬리콥터로부터 비행 데이터를 전송받아 비행속도 및 고도의 변화에 따라 붐의 각도와 DC 펌프의 제어가 가능하도록 살포 장치 및 제어기를 설계 및 제작하였고 무성항공사의 무인 헬리콥터 Rmax에 탑재하여 살포 성능을 검증했다. 실험은 가로 10m, 세로 50m의 농지에서 감수지를 한 열에 1.25m 간격으로 9장씩 5열을 5m의 위치에서부터 10m 간격으로 배치하고, 방제 실험 시 제작된 항공 살포 시스템을 이용하여 살포하였다. 무인 헬리콥터는 최저속도 7.2km/h부터 최고속도 17.6km/h, 최저높이 2.32m부터 최고 3.47m까지 최고 10.4km/h의 속도 변화와 1.15m 고도 변화를 보이며 비행하였고, 각 열이 평균 46423개의 입자개수의 분포로 7.5m의 유효 살포 영역을 형성함을 보여 제안된 항공 살포시스템이 균일 방제에 효과가 있음을 증명한다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2009년도 추계학술대회 논문집
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• pp.335-336
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• 2009

• International Journal of Aeronautical and Space Sciences
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• 제17권1호
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• pp.120-131
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• 2016

The full results of troubleshooting process related to the flight control system of a tilt-rotor type UAV in the flight tests are described. Flight tests were conducted in helicopter, conversion, and airplane modes. The vehicle was flown using automatic functions, which include speed-hold, altitude-hold, heading-hold, guidance modes, as well as automatic take-off and landing. Many unexpected problems occurred during the envelope expansion tests which were mostly under those automatic functions. The anomalies in helicopter mode include vortex ring state (VRS), long delay in the automatic take-off, and the initial overshoot in the automatic landing. In contrast, the anomalies in conversion mode are untrimmed AOS oscillation and the calibration errors of the air data sensors. The problems of low damping in rotor speed and roll rate responses are found in airplane mode. Once all of the known problems had been solved, the vehicle in airplane mode gradually reached the maximum design speed of 440km/h at the operation altitude of 3km. This paper also presents a comprehensive detailing of the control systems of the tilt-rotor unmanned air vehicle (UAV).

• 제어로봇시스템학회논문지
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• 제14권6호
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• pp.608-614
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• 2008

This paper describes a location tracking system to guide landing process of an Unmanned Helicopter(UMH) exploiting MIT Cricket nodes. For automatic landing of a UMH, a precise positioning system is indispensable. However, GPS(Global Positioning System) is inadequate for tracking the three dimensional position of a UMH because of large positioning errors. The Cricket systems use Time-Difference-of-Arrival(TDoA) method with ultrasonic and RF(Radio Frequency) signals to measure distances. They operate in passive mode in that a listener attached to a moving device receives distance signals from several beacons located at fixed points on ground. Inevitably, this passive type of implementation causes large disturbances in measuring distances between beacons and the listener due to wind blow from propeller and turbulence of UMH body. To cope with this problem, we proposed active type of implementation for positioning a UMH. In this implementation, a beacon is set up at UMH body and four listeners are located at ground area at least where the UMH will land. A pair of Ultrasonic and RF signals from the beacon arrives at several listeners to calculate the position of the UMH. The distance signals among listeners are synchronized with a counter value appended to each distance signals from the beacon.

• 항공우주시스템공학회지
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• 제4권1호
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• pp.15-18
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• 2010

In the hot summer manual spray work for plants would be the hardest one among the agricultural field works. Besides the physical load the possible toxication would strongly ask a way to do the job on behalf of human. Although an aircraft with sprayer could be a good candidate, the manned airplanes do not play proper roles in our country because of field geometry. Today, unmanned helicopter as expensive as 200,000 dollars can do the job with high risk of control. Therefore safe and cheap air vehicle with sprayer, if developed, could be a great help to agriculture.

• Journal of Biosystems Engineering
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• 제31권4호
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• pp.342-348
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• 2006

Aerial application using an unmanned agricultural helicopter became necessary for both labor saving and timely spraying. In the previous paper, a rotor system was developed and lift capability was evaluated. The experimental results were compared with simulated predictions using the CFD-ACE program. From the simulation, the relative velocity on the top surface of the blade airfoil increased, resulting in the pressure drop. The CFD analyses were revealed that a drag resistance on the leading edge of the airfoil, a wake at the trailing edge, and a positive pressure underneath the bottom surface were observed. As the results of the simulation, total lifts of 56.8, 74.4 and $95.0kg_f$ were obtained at the 6, 8 and $10^{\circ}$ of AAT (angle of attack), respectively. The simulation results agreed reasonably up to $10^{\circ}$ of AAT. However, at a greater AAT $(<12^{\circ})$ the simulated total lift continuously increased to $105kg_f$, comparing with a decreasing experimental total lift due to the lack of engine power. At a stiff angle of $18^{\circ}$ AAT, a wake was observed at the trailing edge of the airfoil. A rated operating condition determined from the previous paper was also verified through the simulation.

• 한국정밀공학회지
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• 제27권12호
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• pp.41-47
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• 2010

There are many unbalanced models such as helicopter's rotor blades, small-sized precision motor in industrial applications. In the real products, their gravity center usually does not accord with the desired gravity center. If the deviation is large between them, it can be a major cause of vibration and noise as the part of model rotate. Therefore the gravity center in the rotational parts should be controlled properly because of static and dynamic balancing of the parts. In the research, the rotor blade of unmanned helicopter has been selected to obtain the high quality of balancing. In order to achieve the purpose, measuring system has been developed. In the system applied principle is three point weighting method, which is one of the Multiple-point Weighting Method. It has circle fitting for compensation of machining error, after measuring the values. From this study, the results showed that the proposed measurement procedure gives reliable and precise gravity center.

• 한국군사과학기술학회지
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• 제23권4호
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• pp.311-318
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• 2020

This study investigates the performance and blade airloads for a rigid coaxial rotor of high-speed compound unmanned rotorcrafts. The present compound unmanned rotorcraft uses not only a rigid coaxial rotor, but also wings and propellers for high-speed flights. For the rigid coaxial rotor in this work, CAMRAD II, a rotorcraft comprehensive analysis code, is used to study the performance at a flight speed of up to 250 knots and blade section lift forces at 230 knots. As the flight speed increases, the rotor power decreases; however, the power of propellers increases to overcome the drag force of a rotorcraft in high-speed flight. The effective lift-to-drag ratio of a rotor has the maximum value of about 11.6 which is much higher than the value of the conventional helicopter. The blade section lift forces of the upper and lower rotors at 230 knots show the similar variation trends for one rotor revolution, and the impulses because of the aerodynamic interaction between both rotors are observed.

• International Journal of Aeronautical and Space Sciences
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• 제16권4호
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• pp.614-623
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• 2015

When the speed of a coaxial rotor helicopter in forward flight increases, the wake skew angle of the rotor increases and consequently the position of the vena contracta of the upper rotor with respect to the lower rotor changes. Considering ambient air and the effect of the upper rotor, this study proposes a nonuniform inflow model for the lower rotor of a coaxial rotor helicopter in forward flight. The total required power of the coaxial rotor system was compared against Dingeldein's experimental data, and the results of the proposed model were well matched. A plant model was also developed from first principles for flight simulation, unknown parameter estimation and control analysis. The coaxial rotor helicopter used for this study was manufactured for surveillance and reconnaissance and does not have any stabilizer bar. Therefore, a feedback controller was included during flight test and parameter estimation to overcome unstable situations. Predicted responses of parameter estimation and validation show good agreement with experimental data. Therefore, the methodology described in this paper can be used to develop numerical plant model, study non-uniform inflow model, conduct performance analysis and parameter estimation of coaxial rotor as well as other rotorcrafts in forward flight.

• 항공우주기술
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• 제12권1호
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• pp.10-21
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• 2013

오늘날 헬리콥터 기술의 발전과 더불어 함상에서 헬리콥터를 운용하는 것은 당연한 것으로 여겨지고 있다. 육상과 달리 해상에서 항공기를 운용하기 위해서는 육상보다 심한 바람과 파도와 배의 이동에 의한 착륙장의 운동과 염분에 의한 장비의 부식이 고려되어야하며 안전한 운용을 위한 운용절차가 요구된다. 본 논문에서는 수직이착륙 항공기의 함상운용 사례분석을 통하여 함상운용에 요구되는 항공기와 선박의 고려사항과 운용절차를 알아보고 이를 기반으로 틸트로터 무인기의 함상운용 기술개발 방안을 제시한다.