• 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.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.04a
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• pp.484-489
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• 2011

In this paper, it was described the current technology status of bearingless rotor hub system for helicopter which is one of major rotor hub system. Also, a conceptual study on the new bearingless rotor hub system of helicopter was described. First, the advantages and disadvantages of major helicopter rotor hub system are described in comparison to each other types of rotor hub system. The unique characteristics of bearingless rotor hub system are described compared to other types of rotor hub systems. Next, the main function, role and characteristics of the sub-components of bearingless rotor hub system are described. Recent helicopters which adopt this bearingless rotor hub system are described and introduced. This conceptual study shows that double-H sectional construction and rectangular construction of flexbeam are the most effective candidates of this new bearingless rotor system. This bearingless rotor hub system can be used for 7,000lbs class helicopter. Now, a further trade-off study will show.

• 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.

• Current Industrial and Technological Trends in Aerospace
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• v.8 no.1
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• pp.118-130
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• 2010

In this paper, it is described the current technology status of bearingless rotor hub system for helicopter which is one of major rotor hub system. First, the advantages and disadvantages of major helicopter rotor hub system are described and compared each other. The unique characteristics of bearingless rotor hub system are described compared to other types of rotor hub systems. Next, the main function, role and characteristics of the sub-components of bearingless rotor hub system are described. Furtherly, recent helicopters which adopt this bearingless rotor hub system are described and introduced.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.8
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• pp.784-790
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• 2012

This paper describes a stability and dynamic characteristics of bearingless helicopter main rotor in hover. Baseline rotor configuration is defined and modal analysis for the configuration is taken to verify the dynamic characteristics. The kinematic pitch-lag couplings through ways of pitch link installation are analyzed to know effects on loads, frequencies and stability. The effects of pitch link attachments in spanwise direction and chordwise direction as well as pitch link inclination on thrust, power, flpa-lag-pitch mode frequencies and inplane damping are examined. Pitch link at trailing edge location in chordwise direction has influence on aeroelastic stability of the rotor. Also, the pitch link with negative inclination angle makes inplane damping increase.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.394-399
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• 2012

This paper describes a stability and dynamic characteristics of bearingless helicopter main rotor in hover. Baseline rotor configuration is defined and modal analysis for the configuration is taken to verify the dynamic characteristics. The kinematic pitch-lag couplings through ways of pitch link installation are analyzed to know effects on loads, frequencies and stability. The effects of pitch link attachments in spanwise direction and chordwise direction as well as pitch link inclination on thrust, power, flpa-lag-pitch mode frequencies and inplane damping are examined. Pitch link at trailing edge location in chordwise direction has influence on aeroelastic stability of the rotor. Also, the pitch link with negative inclination angle makes inplane damping increase.

• 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 the Korean Society for Aeronautical & Space Sciences
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• v.44 no.5
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• pp.439-446
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• 2016

The characteristics of bearingless main rotor of helicopter are investigated through non-rotating tests and rotating tests. The stiffness and natural frequencies of rotor blades, flexbeam, and torque tube which are core components of baearingless rotor are measured to obtain input material properties for rotor analysis. The functional test on ground for assembly of one hub with damper, snubber, and no blade is carried out to check interfaces between components, kinematics of components, and pitch motion ranges under applied loads including centrifugal load. The 4-bladed bearingless rotor with 5.82m of rotor radius is tested on the whirl tower with rotation plane of 9.65m height. The thrust and power are measured to obtain hover performance and the frequencies and dampings of the rotor are obtained by excitation of cyclic pitch by hydraulic actuators.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.1
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• pp.57-64
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• 2010

In this paper, a novel Bearingless Switched Reluctance Motor(BLSRM) with the shoe rotor pole in order to minimize the torque ripple and the suspension force ripple at an overlap position is proposed. For reduction the torque ripple and the suspension force ripple at an overlap position, the fringing flux is used for the main flux. This configuration of the rotor pole results in more average torque with high suspension force. In addition, this paper is compared the transient characteristics using the inductance look-up table. The torque, radial force and flux density are analyzed by finite element method.