• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.4
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• pp.352-357
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• 2012

The ground resonance instability of a helicopter with bearingless main rotor hub were investigated. The ground resonance instability is caused by an interaction between the blade lag motion and hub inplane motion. This instability occurs when the helicopter is on the ground and is important for soft-inplane rotors where the rotating lag mode frequency is less than the rotor rotational speed. For the analysis, the bearingless rotor was composed of blades, flexbeam, torque tube, damper, shear restrainer, and pitch links. The fuselage was modeled as a mass-damper-spring system having natural frequencies in roll and pitch motions. The rotor-fuselage coupling equations are derived in non-rotating frame to consider the rotor and fuselage equations in the same frame. The ground resonance instabilities for three cases where are without lead-lag damper and fuselage damping, with lead-lag damper and without fuselage damping, and finally with lead-lag damper and fuselage damping. There is no ground resonance instability in the only rotor-fuselage configuration with lead-lag damper and fuselage damping.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.1
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• pp.22-28
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• 2018

In case of developing a combined system by a number of distributed resources with storage device, a number of application suggests a huge capacity can derive operational flexibility both power supply issues or when unexpected situation imposed. However, it is important to determine a resonable energy capacity because the device have many controversial cost issues in current power system industry. An ESS application which focusing essentially required points can induce appropriate storage capacity that required in economic operation. In this paper, a curtailment supporting algorithm based on storage device is introduced, and applied in the capacity calculation method. The main algorithm pursues handling minor exceeding quantities which can cause mechanical load at blade; This paper tries to include it for configuring hybrid algorithm with pitch control. Several fluctuating conditions are utilized in simulation to reflect critical situation. The analyzing process focuses on the control feasibility with applied capacity and control method.

• International Journal of Aeronautical and Space Sciences
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• v.9 no.1
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• pp.76-84
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• 2008

This paper is mainly concerned with the vision-based attitude stabilization of a quad-rotor UAV. The methods for attitude control rely on computing the roll and pitch angles of the vehicle from a two-camera vision system. One camera is attached to the body-fixed x-axis and the other to the body-fixed y-axis. The attitude computation for the quad-rotor UAV is performed by image processing consisting of Canny edge and Hough line detection. A proportional and integral controller is employed for the attitude hold autopilot. In this paper, the quad-rotor UAV is modeled by 6-DOF nonlinear equations of motion that includes rotor aerodynamics with blade element theory. The performance of the proposed method is evaluated through 3D environmental numerical simulations.

• Proceedings of the KIEE Conference
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• 2003.04a
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• pp.365-368
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• 2003

전북 부안군에 설치된 30kW급 Dual-rotor 풍력발전기의 Main rotor blade를 대상으로 공기역학적 모델링을 수행한 후 각종 바람 상황과 풍속에 따라 변화하는 RPM 상황을 고려하여 전산모의 실험을 수행하였다. 또한 출력성능을 향상시키기 위하여 최대 출력을 계산하고 이를 추종하도록 하는 직접 출력 제어 알고리즘을 제안하였다.

• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.236-239
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• 2011

This paper introduces the design concepts and characteristics of WinDS3000$^{TM}$(TC IIa) which is a trade name of Doosan's 3MW offshore/onshore wind turbine. WinDS3000$^{TM}$(TC IIa) has been designed in consideration of high Reliability, Availability, Maintainability and Serviceability (RAMS) and low cost of electricity (CDE) for the TC IIa condition based on GL guideline. An integrated drive-train design with an innovative three-stage gearbox has been introduced to minimize nacelle weight of the wind turbine and to enhance a high reliability for transmission. A permanent magnet generator with full converter system has been introduced to get higher efficiency in partial load operation and grid-friendly system for both 50 Hz and 60 Hz. A pitch-regulated variable speed control system has been introduced to control wind turbine power while generator reaction torque can be adjusted almost instantaneously by the associated power electronics. The wind turbine has been also equipped with condition monitoring and diagnostic systems in order to meet maintainability requirements.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.6
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• pp.691-698
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• 2014

This paper describes the manufacturing processes for a flexbeam and torque tube made of composite materials, along with the procedures for testing their basic properties. A flexbeam and torque tube can be considered to be key structural components of a bearingless rotor hub system. A hinge offset effect can be realized by a large elastic deformation and twist of the flexbeam, and the blade pitch control forces are transferred by the rotation of the torque tube. The basic property tests included bending and twist tests to determine the flap stiffness, lag stiffness, and torsion stiffness of the flexbeam, torque tube, and blade, and these tests were performed prior to starting the whirl tower test. In addition, the estimated results were compared with experimental data, and the calculations were found to be a good match for the analysis results and had a similar tendency. Through these results, we could confirm that a flexbeam and torque tube made of composite materials satisfied the structural stiffness requirements.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.7
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• pp.731-738
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• 2012

In this study, the evaluation of the aerodynamic characteristics of the NREL Phase VI Rotor System has been performed, for the 7 m/s upwind case using commercial FEA and CFD tools which are ANSYS Mechanical 12.1 and CFX 12.1. The initial operating conditions of the rotor blade include a $3^{\circ}$ tip pitch angle. A numerical simulation was carried out on only the rotor parts, excluding the tower structure based on the equivalent stiffness model, to consider the aeroelastic effect for the numerical simulation using the loosely coupled 2-way fluid-structure interaction method. The blade root bending moment was monitored in real time to obtain reasonable results. To verify the analysis results, the numerical simulation results were compared with the measurements in the form of the root bending moment and the pressure distributions of the NREL/NASA Ames wind tunnel test.

• Journal of Aerospace System Engineering
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• v.17 no.2
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• pp.45-55
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• 2023

This study conducted aeromechanics modeling and structural load analyses of Tilt Rotor Aeroacoustic Model (TRAM), a 25% scaled V-22 tiltrotor model used in wind tunnel tests. A rotorcraft comprehensive analysis code, CAMRAD II, was used. Analysis results of this study in low-speed forward flights were compared with DNW test and previous analysis results. Blade flap bending moments were in good agreement with measured data. Mean values and oscillatory loads for lead-lag bending and torsion moments were slightly different from measured data. However, when mean values were removed, results of structural loads for one rotor revolution were moderately compared with wind tunnel tests and previous analyses. Total forces and half peak-to-peak forces of the pitch link reasonably well matched with previous analysis results and measured data. Finally, harmonic magnitudes of blade structural loads were investigated.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.158-163
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• 2005

In this paper the aeroacoustic characteristics of a tilt-rotor system is measured by using a sealed model tilt-rotor. With a microphone array system and the do-dopplerization algorithm, the location and the characteristics of rotor noise are successfully measured. The most of high frequency noise (4kHz) is found to be located at rotor blade tips, but the low frequency tonal noise is dominant on the middle of the rotor blades. The measured tonal noise characteristics are compared to the results of theoretical calculation. At 0.5m distance from the rotor plane, measured and calculated data are relatively well matched regardless of rotating speed and collective pitch angie for the azimuthal angles between $0^{\circ}\;and\;60^{\circ}$. However, the data on the azimuthal angles between $70^{\circ}\;and\;90^{\circ}$ are not quite comparable. In addition, the compared data for far-field case (1.5m) are quite different. This is probably due to the unsteady effect which if not included in the theoretical calculation.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.62 no.3
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• pp.117-126
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• 2013

This paper is written for the development and application of boiler furnace pressure control algorithm and distributed control system of coal-fired power plant by the steps of design, coding, simulation test, site installation and site commissioning test. The control algorithms were designed in the shape of cascade control for two parts of furnace pressure control and induced draft fan pitch blade by standard function blocks. This control algorithms were coded to the control programs of distributed control systems. The simulator for coal-fired power plant was used in the test step and automatic control, sequence control and emergency stop tests were performed successfully like the tests of the actual power plant. The reliability was obtained enough to be installed at the actual power plant and all of distributed control systems had been installed at power plant and all signals were connected mutually. Tests for reliability and safety of plant operation were completed successfully and power plant is being operated commercially. It is expected that the project result will contribute to the safe operation of domestic new and retrofit power plants, the self-reliance of coal-fired power plant control technique and overseas business for power plant.