• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.2
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• pp.103-110
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• 2022

Degradation of handling qualities(HQs) due to bad weather or mechanical failure can pose a fatal risk to pilots unfamiliar with such situation. In particular, icing is an important issue to consider as it is a frequent cause of accidents. Most of the previous research works focuses on aerodynamic performance changes due to icing and the corresponding icing modeling or methods to prevent icing, whereas the present work attempts to actively compensate for HQ degradation due to icing on a full-scale helicopter through flight control law design. To this end, the present work first demonstrates HQ degradation due to icing using CONDUIT software, and subsequently presents a robust control design via the RS-LQR(Robust Servomechanism Linear Quadratic Regulation) procedure to compensate for the HQ degradation. Simulation results show that the proposed robust control maintains Level 1 HQ in the presence of icing.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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• pp.52-56
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• 2011

Recently, KARI(Korea Aerospace Research Institute) has been developing a modern 11.5m diameter four bladed bearingless main rotor system, and this rotor system can be used for 7,000lb class helicopter. Flexbeam and torque tube can be considered as the key structural components, and large elastic twist of flexbeam induced by pitch control motion of torque tube can influence the nonlinear aeroelastic behavior. In this paper, the dynamic characteristic analysis results of bearingless rotor system were presented. In order to construct a input model and validate the analysis procedures, calculated results using the comprehensive helicopter analysis program CAMRAD II were compared with the measured natural frequencies and lag damping data from small-scale wind tunnel test. Next, the analysis model was extended to a full-scale model, and the dynamic analysis results were presented.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.2
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• pp.187-192
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• 2012

Recently, KARI(Korea Aerospace Research Institute) has been developing a modern 11.5 m diameter four bladed bearingless main rotor system, and this rotor system can be used for 7,000 lb class helicopter. Flexbeam and torque tube can be considered as key structural components, and large elastic twist of flexbeam induced by pitch control motion of torque tube can influence the nonlinear aeroelastic behavior. In this paper, the dynamic characteristic analysis results of bearingless rotor system were presented. In order to construct a input model and validate the analysis procedures, calculated results using the comprehensive helicopter analysis program CAMRAD II were compared with the measured natural frequencies and lag damping data from small-scale wind tunnel test. Next, the analysis model was extended to a full-scale model, and the dynamic analysis results were presented.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.1
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• pp.54-60
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• 2009

In this paper, a precision landing approach is implemented based on real-time image processing. A full-scale landmark for automatic landing is used. canny edge detection method is applied to identify the outside quadrilateral while circular hough transform is used for the recognition of inside circle. Position information on the ground landmark is uplinked to the unmanned helicopter via ground control computer in real time so that the unmanned helicopter control the air vehicle for accurate landing approach. Ground test and a couple of flight tests for autonomous landing approach show that the image processing and automatic landing operation system have good performance for the landing approach phase at the altitude of $20m{\sim}1m$ above ground level.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.3
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• pp.213-219
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• 2021

In this paper, an incremental twisting compensator is proposed for improving the performance of helicopter control and tested on an in-house full-scale helicopter simulator. The proposed compensator has a merit in that an incremental control input (a second-order sliding mode control input or so-called twisting control input) is simply added to improve the performance of helicopter control, while the original flight control structure remains untouched. The proposed control technique has been shown to improve the transient and steady-state response of the in-house helicopter simulator.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2010.05a
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• pp.82-83
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• 2010

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.3
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• pp.50-57
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• 2003

In the paper, the design and evaluation of a helicopter trajectory tracking controller are presented. The control algorithm is implemented using the feedback linearization technique and the two time-scale separation architecture. In addition, and on-line adaptive architecture that employs a neural network compensating the model inversion error caused by the deficiency of full knowledge of helicopter dynamic is applied to augment the attitude control system. Trajectory tracking performance of the control system in evaluated using modified TMAN simulation program representing as Apache helicopter. It is show that the on-line neural network in an adaptive control architecture is very effective in dealing with the performance depreciation problem of the trajectory tracking control caused by insufficient information of dynamics.

• Aerospace Engineering and Technology
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• v.9 no.2
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• pp.1-7
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• 2010

Fatigue properties of composite materials are extremely important to design durable and reliable helicopter rotor blades. However, it is very difficult to apply conventional fatigue test loads in short period. Therefore, accelerating test speed and facilitating spectrum load realization are required. In this study, we have developed a fatigue testing method that uses a resonance of simply supported beam type blade specimen. This test consists in exciting the blade specimen with a frequency that corresponds to its natural frequency. In that case, the test specimen similar to a beam fixed between two pivot points starts vibrating and is significantly deformed. Resonant fatigue tests were performed by changing exciting vertical amplitude and frequency, and S-N curves of each composite materials were successfully obtained.

• New & Renewable Energy
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• v.3 no.3
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• pp.54-62
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• 2007

The present paper describes the scale effect correction methods for scaled NREL Phase VI wind turbines by using CFD[computational fluid dynamics). For the corrections of wind turbine scale effect, various researches on the helicopter rotor scale effect were investigated and the feasibility study of the methods was performed to correct wind turbine scale effect. The present paper also introduces scale effect correction methods based on two dimensional lift slope. In order to test the present method, performance analyses of NREL Phase VI wind turbines under various scale conditions were carried out and new correction method was applied. Granting that the new correction method is valid only above Reynolds No. 100,000, it showed reasonable agreement between model and full scale wind turbines in the linear torque region.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.2
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• pp.159-166
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• 2018

In this study, the internal structural design, dynamic characteristics and load analyses of the small scaled rotor blade required for LCH(Light Civil Helicopter) main rotor wind tunnel test were carried out. The test is performed to evaluate the aerodynamic performance and noise characteristics of the LCH main rotor system. Therefore, the Mach-scale technique was appled to design the small scaled blade to simulate the equivalent aerodynamic characteristics as the full scale rotor system. It is necessary to increase the rotor speed to maintain the same blade tip speed as the full scale blade. In addition, the blade weight, section stiffness, and natural frequency were scaled according to the Mach-type scaling factor(${\lambda}$). For the design of skin, spar, torsion box, which are the main components of the blade, carbon and glass fiber composite materials were adopted, and composite materials are prepreg types that can be supplied domestically. The KSec2D program was used to evaluate the section stiffness of the blade. Also, structural loads and dynamic characteristics of the Mach scale blade were investigated through the comprehensive rotorcraft analysis program CAMRADII.