• 한국정밀공학회지
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• 제27권3호
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• pp.73-79
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• 2010

A preliminary study on a length-variable rotor blade for a small unmanned helicopter has been conducted. After surveys on previous researches, and examining requirements for application to a small unmanned helicopter, a length-variable rotor blade was designed and manufactured to be driven by centrifugal force from rotor revolution with no mechanical actuator. The rotor blade was divided into a fixed inboard section and an outboard section sliding in span-wise direction. In order to determine the operating conditions of the length-variable rotor during revolution, and to derive the design variables of extension spring and rotor weight, a series of analyses from multi-body dynamics solution were conducted. The manufactured prototype was verified of its length-varying mechanism from a rotor stand, the results and required future improvements are discussed.

• 항공우주시스템공학회지
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• 제8권1호
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• pp.12-17
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• 2014

In this paper, optimal design of composite rotor blade cross-section to consider manufacturability was performed. Skin thickness, torsion box thickness and skin lay-up angle were adopted as discrete design variables and The position and width of a torsion box were considered as continuous variables. An object function of optimal design is to minimize the mass of a rotor blade, and various constraints such as failure index, center mass, shear center, natural frequency and blade minimum mass per unit length were adopted. Finally, design variables such as the thickness and lay-up angles of a skin, and the thickness, position and width of a torsion box were determined by using an in-house program developed for the optimal design of rotor blade cross-section.

• 한국항공우주학회지
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• 제39권5호
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• pp.458-465
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• 2011

무인지상차량을 통해 수직이착륙 무인항공기의 운반, 발사, 귀환 및 재충전 기능을 제공함으로서 두 체계의 단점을 보완할 수 있는 무인항공기-무인지상차량 합동운용 개념이 제시되었다. 합동운용 개념은 두 체계의 물리적 결합을 통해 무인지상차량의 감시정찰 범위를 확대하고, 수직이착륙 무인항공기의 운용능력을 확장할 수 있는 개념이다. 체계간의 유연하고 정확한 인터페이스를 제공하기 위해 구형 동체를 가지는 동축반전 회전익형 무인항공기의 형상이 제안되었다. 무인항공기의 정밀착륙을 위해 영상기반 목표추적 기법이 포함된 복합항법 기술이 검토되었고, 실험적 연구가 수행되었다. 또한, 탑재된 회전익형 비행체에 콤팩트한 형상을 제공하기 위한 길이-가변 로터의 구현 가능성에 대해서도 기술하였다.

• Smart Structures and Systems
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• 제18권4호
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• pp.683-705
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• 2016

A semi-active algorithm for edgewise vibration control of the spar-type floating offshore wind turbine (SFOWT) blades, nacelle and spar platform is developed in this paper. A tuned mass damper (TMD) is placed in each blade, in the nacelle and on the spar to control the vibrations for these components. A Short Time Fourier Transform algorithm is used for semi-active control of the TMDs. The mathematical formulation of the integrated SFOWT-TMDs system is derived by using Euler-Lagrangian equations. The theoretical model derived is a time-varying system considering the aerodynamic properties of the blade, variable mass and stiffness per unit length, gravity, the interactions among the blades, nacelle, spar, mooring system and the TMDs, the hydrodynamic effects, the restoring moment and the buoyancy force. The aerodynamic loads on the nacelle and the spar due to their coupling with the blades are also considered. The effectiveness of the semi-active TMDs is investigated in the numerical examples where the mooring cable tension, rotor speed and the blade stiffness are varying over time. Except for excessively large strokes of the nacelle TMD, the semi-active algorithm is considerably more effective than the passive one in all cases and its effectiveness is restricted by the low-frequency nature of the nacelle and the spar responses.