• 한국항공우주학회지
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• 제33권9호
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• pp.9-15
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• 2005

국방과학연구소 풍동실험실에서는 회전익 항공기 개발에 소요되는 관련 풍동시험 기법의 확립과 형상연구 관련 시험자료의 확보를 위한 실험적 연구를 수행하였다. 본 연구는 회전익 항공기 동체구성품의 형상조합에 따른 항력증분과 안정성 평가를 위한 공기역학적 특성의 추출을 목적으로 하였으며, 풍동시험에는 모듈화된 1:8 축척의 회전익 항공기 동체형상과 500 rpm으로 회전하는 로터허브의 부분모형이 사용되었다. 시험결과들을 기존의 유사 항공기 시험결과들과 비교하였으며, 기존 연구결과들과 잘 부합됨을 확인하였다.

• 항공우주산업기술동향
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• 제9권1호
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• pp.77-89
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• 2011

헬리콥터는회전하는구동시스템에의해추력및비행제어력을발생하기때문에회전체에서기체로전달되는 진동 및 소음을 줄이는 것이 아주 중요하다. 과거에는 수동적 방법으로 특정주파수에 해당하는 진동 및 소음을 줄였지만, 기술이 발달함에 따라 주파수를 변동시킬 수 있는 장치를 적용할 수 있는 능동적 진동 및 소음 제어방법이 개발되었다. 본 논문에서는 이러한 헬리콥터 진동 및 소음을 제어하는 능동적 방법에 대한 세계적인 기술동향 및 사례를 기술하였다. 서론에서는 헬리콥터 진동 및 소음을 제어하는 일반적인 방법론을 소개하고, 본론에서는 능동적으로 제어하는 사례 및 동향을 중심으로 기술하였다. 현재 가장 활발하게 진행되고 있는 능동적 플랩구동장치 및 비틀림장치 등을 중심으로 소개하였다.

• Journal of Biosystems Engineering
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• 제34권2호
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• pp.89-94
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• 2009

Aerial application using an agricultural unmanned helicopter was suggested for an alternative against current pesticide application methods. Centrifugal clutches play important roles in the performance and safety of the helicopter operation. A previous study analyzed and verified the power transfer theory of the guide type centrifugal clutch. Based on the clutch theory, optimal designs of the clutch became possible and feasible using a simulation method. Design criteria of the clutch were the power transfer capacity of 24.66 kW(33.5 PS) at the rated engine speed and the engaging range speed of 3,000${\sim}$3,500 rpm. Various designs were accomplished using the simulation. An optimal clutch was simulated by determining the values of spring constant and mass of friction sector, which were 94,700 N/m and 123.7 g, respectively. The design performed the power capacity of 24.86 kW(33.8 PS) and engagement speed of 3,069 rpm, meeting the design criteria. Using the designed clutch, an efficient transfer of the power would be possible for the unmanned agricultural helicopter.

• Advances in aircraft and spacecraft science
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• 제3권3호
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• pp.271-298
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• 2016

In this paper, we study a problem of passive suppression of helicopter Ground Resonance (GR) using a single degree freedom Nonlinear Energy Sink (NES), GR is a dynamic instability involving the coupling of the blades motion in the rotational plane (i.e. the lag motion) and the helicopter fuselage motion. A reduced linear system reproducing GR instability is used. It is obtained using successively Coleman transformation and binormal transformation. The analysis of the steadystate responses of this model is performed when a NES is attached on the helicopter fuselage. The NES involves an essential cubic restoring force and a linear damping force. The analysis is achieved applying complexification-averaging method. The resulting slow-flow model is finally analyzed using multiple scale approach. Four steady-state responses corresponding to complete suppression, partial suppression through strongly modulated response, partial suppression through periodic response and no suppression of the GR are highlighted. An algorithm based on simple criterions is developed to predict these steady-state response regimes. Numerical simulations of the complete system confirm this analysis of the slow-flow dynamics. A parametric analysis of the influence of the NES damping coefficient and the rotor speed on the response regime is finally proposed.

• Advances in aircraft and spacecraft science
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• 제6권1호
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• pp.31-49
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• 2019

Flutter is a dangerous phenomenon encountered in flexible structures subjected to aerodynamic forces. This includes aircraft, helicopter blades, engine rotors, buildings and bridges. Flutter occurs as a result of interactions between aerodynamic, stiffness and inertia forces on a structure. The conventional method for designing a rotor blade to be free from flutter instability throughout the helicopter's flight regime is to design the blade so that the aerodynamic center (AC), elastic axis (EA) and center of gravity (CG) are coincident and located at the quarter-chord. While this assures freedom from flutter, it adds constraints on rotor blade design which are not usually followed in fixed wing design. Periodic Structures have been in the focus of research for their useful characteristics and ability to attenuate vibration in frequency bands called "stop-bands". A periodic structure consists of cells which differ in material or geometry. As vibration waves travel along the structure and face the cell boundaries, some waves pass and some are reflected back, which may cause destructive interference with the succeeding waves. In this work, we analyze the flutter characteristics of a helicopter blades with a periodic change in their sandwich material using a finite element structural model. Results shows great improvements in the flutter forward speed of the rotating blade obtained by using periodic design and increasing the number of periodic cells.

• 항공우주시스템공학회지
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• 제13권3호
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• pp.70-77
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• 2019

본 논문에서는 헬리콥터의 유입류 모델에 따라 헬리콥터에서 발사되는 로켓의 궤적에 대한 영향성을 비행역학 해석을 통해 검토하였다. 무장형상의 비선형 비행역학 해석모델은 UH-60 헬리콥터 형상으로 구성하고 헬리콥터에서 발사되는 발사체의 궤적예측에는 HYDRA 70 로켓을 이용하였다. 다양한 로터 유입류 모델을 사용하여 각각의 모델에 따라 로켓 발사궤적에 미치는 영향을 검토하였다. 또한 헬리콥터의 다양한 비행조건에 대해 로켓 발사 시뮬레이션 해석을 수행하고 로켓이 로터 디스크 면과 근접하는 위험한 로켓발사 비행영역을 검토하였다.

• Journal of Electrical Engineering and Technology
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• 제12권4호
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• pp.1649-1656
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• 2017

This paper addresses the control problem of a laboratory-level 2 degree-of-freedom helicopter. The exact fuzzy model in a Takagi - Sugeno form is constructed by the sector nonlinearity technique, and is then represented as a set of uncertain linear systems. Output-tracking controller is designed in terms of linear matrix inequalities and the closed-loop stability is rigorously analyzed. Experimental evaluation shows that the proposed method is of benefit to many real industrial plants.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1991년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 22-24 Oct. 1991
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• pp.889-893
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• 1991

This paper describe the mathematical model of helicopter rotor, which is suitable for the calculation of trim condition to develop the stability and control. The mathematical model is a nonlinear, total force and moment model of a single main rotor helicopter. The effects of fuselage, tail rotor, horizontal tail, and vertical tail are included. The phase angle and stick displacement are obtained and compared at the trim condition.

• 한국화재소방학회:학술대회논문집
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• 한국화재소방학회 2008년도 추계학술논문발표회 논문집
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• pp.105-110
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• 2008

Unmanned helicopter has several abilities such as vertical take off, hovering, low speed flight at a specific altitude. Such vehicles are becoming popular in actual applications such as search and rescue, aerial reconnaissance and surveillance in the case of a large size disaster and forest fire. In this paper, a flight control system was designed for an unmanned helicopter. This paper was concentrated on describing the systematic design, electronic equipments and their interconnections for realizing the autonomous flight and aerial monitoring. A study on the autonomous waypoint navigation and altitude control performance were performed and tested on a test unmanned helicopter and the performance and the feasibility were represented.

• 한국측량학회:학술대회논문집
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• 한국측량학회 2007년도 춘계학술발표회 논문집
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• pp.157-160
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• 2007

In this study, the method of extracting DEM is presented using RC Helicopter Photogrammetry System. From the result of reference points and checkpoints using Total Station which is conventional type of survey, the errors turned out to $-0.194{\sim}0.224m$ on the X-axis, $-0.088{\sim}0.180m$ on the Y-axis and $-0.286{\sim}0.283m$ on the Z-axis when RC Helicopter Photogrammetry System utilized. Through this RC Helicopter Photogrammetry System, they can provide efficient update of digital map on toparchy area or access is not easy area.