• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.04a
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• pp.213-216
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• 2005

This paper describes the design, analysis and manufacture procedure of the composite blade for hingeless rotor system of unmanned helicopters. Helicopter rotor system is the key structural unit that produces thrust and control forces for intended flight conditions. In this work, a hingeless rotor system is adopted, and base on the design requirements for rotor system, composite blade section design and calculation of material properties were performed. In order to avoid the unstable state such as resonance, vibration characteristics of rotor system were analyzed. Finally, this paper describes simply the forming and manufacture of composite blade.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.904-910
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• 2014

The Helicopter noise analysis code was developed using Farassat's Formular 1A based on Ffowcs-Williams and Hawkings equation and Lowson's Formula which contains single loading noise source concept. HART-II(Higher harmonic control Aeroacoustic Rotor Test), STAR(Smart-Twisting Active Rotor) and Active-tab Rotor were computed and analyzed by using developed noise code. The results of these rotor noise prediction are explained and its applicability would be mentioned in this paper.

• Journal of the Korea Institute of Military Science and Technology
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• v.8 no.3 s.22
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• pp.33-41
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• 2005

This paper describes the conceptual design of medium size helicopter rotor system. Based on assumed design requirements, trade-off study for rotor configuration has been conducted in terms of rotor tip speed, disk loading, blade area, solidity, etc for estimated primary mission gross weight. For the main rotor, four-blade and five-blade rotors are studied with the conventional tail rotor. The performance analysis for baseline configuration is conducted using a helicopter performance analysis program. The analysis shows design results satisfy the design requirements.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.20 no.4
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• pp.50-56
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• 2012

Rotor system is a very important part which produce lift, thrust and control force in helicopter. Component of rotor system must have structural integrity for applied load. The estimation of structural integrity is regarded greatly as important in aerospace field. In this study, the process of structural analysis performed for bearingless main rotor system of helicopter. The composite flexbeam and torque tube of bearingless main rotor are very thick, so 3D layered soild elements of MSC.PATRAN were used to get the finite element analysis results. To estimate structural integrity, non-linear static analysis considering geometric non-linearity is performed. In addition, detailed finete element analysis and non-linear static analysis are performed to consider the stress concentration for fitting effect and contact surface. The estimation process of structural integrity for bearingless main rotor system of helicopter may help the design.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10a
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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.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.6_spc
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• pp.736-743
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• 2016

This study describes optimization methods for adjustment of helicopter main rotor tracking and balancing (RTB). RTB is a essential process for helicopter operation and maintenance. Linear and non-linear models were developed with past RTB test results for estimation of RTB adjustment. Then global and sequential optimization methods were applied to the each of models. Utilization of the individual optimization method with each model is hard to fulfill the RTB requirements because of different characteristics of each blade. Therefore an ensemble model was used to integrate every estimated adjustment result, and an adaptive method was also applied to adjustment values of the linear model to update for next estimations. The goal of this developed RTB adjustment optimization program is to achieve the requirements within 2 run. Additional tests for comparison of weight factor of the ensemble model are however necessary.

• Journal of Institute of Control, Robotics and Systems
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• v.21 no.7
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• pp.677-683
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• 2015

This paper proposes a helicopter direction adjustment system using barycenter shift. Most conventional methods for direction adjustment of uniaxial helicopters rely on the angle of inclination of the main rotor. However, the inherent burden of the bearing of the main rotor and serious abrasion of the helicopter using the above methods may results in loss of balance. To decrease abrasion and enhance the barycenter stability, the proposed method was used to shift the barycenter of the helicopter instead of the main rotor for direction adjustment. We set a biaxial ARM on a uniaxial helicopter to adjust the direction of ARM pointing as well as to realize stable direction control when the helicopter loses its balance. The method may enhance the landing safety of helicopters in emergencies. Uniaxial helicopters can be controlled under any environment by adjusting the motor parameters of the ARM which is dependent on the center of mass using neural network. The experiment results show that the helicopter can return to the starting position quickly under the external disturbance.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.15 no.3
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• pp.15-23
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• 2007

In this paper, we deducted the missions with respect to Korea utility helicopter (KUH) and consist of the scenarios which describe proper purpose of KUH. And so developed fatigue load spectrum of KUH by applying Helix that is fatigue load spectrum for blade of articulated helicopter rotor system. The developed load spectrum is applied to fatigue analysis of blade by modeled finite element with stress-life method (S-N). And we compared the result of fatigue analysis to prior to Helix for the sake of verifying the load spectrum that we generated.

• International Journal of Aeronautical and Space Sciences
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• v.16 no.4
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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.

• Journal of Biosystems Engineering
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• v.33 no.5
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• pp.289-295
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• 2008

The task of chemical spraying has been seriously considered as an irritating and annoying job for Korean rice farmers. An agricultural unmanned helicopter was suggested to solve this problem so as the farmers to have more decent farming condition. The objectives of this study were to analyze the adoptability of an experimental rotor blade (SW05) using the CFD simulation and also to compare the simulation results with experimental results. The simulation results showed that the induced power of this rotor reached to $57{\sim}63%$ of total power and the profile power was about $37{\sim}43%$ of total power. Therefore it can be concluded that this rotor's performance characteristics were not so efficient for the size of unmanned helicopter due to the low induced power and high profile power relatively compared with ones of conventional rotors. The comparison with experimental results showed that the tested lifts were less than 70% of simulated ones at the grip pitch of $12^{\circ}$ and decreased to 40% at the $18^{\circ}$ grip pitch. Therefore, it can be concluded that the rotor was too oversized to be used for a 15.4 kW (21 PS) engine.