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Detection and control of ground resonance using phase of fuselage attitude rates
Salini S. Nair,
Published in Association Aeronautique et Astronautique de France
2016
Volume: 2
   
Pages: 1401 - 1411
Abstract
Ground resonance is a type of aeromechanical instability that occurs when the helicopter is in contact with the ground. It may occur due to coalescence between frequencies of two modes of the system if damping is insufficient. In this paper, we analyze the phase relations between the fuselage states corresponding to the least damped mode (regressive lag mode) and its correlation with frequency coalescence. The phase of fuselage states (attitude or attitude rates), which are easily measurable, is observed to exhibit certain trends with variation in parameters like rotor speed and landing gear stiffness. The phase data can aid in the design of a stability augmentation system for ground resonance. It can serve as a parameter to detect the possibility of instability and in systems with uncertainties in parameters, like landing gear stiffness, it can aid in selecting the appropriate feedback gain for stabilization. The model we have primarily considered has isotropic rotor and anisotropic hub, hence multiblade coordinate transformation is used and the stability analysis is done in fixed frame. The analysis is further extended to incorporate dynamic inflow effects and anisotropy in rotor blades, where Floquet method is used for stability analysis. Air resonance instability is also investigated on similar lines and the proposed method is found to be good for its detection.
About the journal
Journal42nd European Rotorcraft Forum 2016
PublisherAssociation Aeronautique et Astronautique de France
Open AccessNo
Concepts (17)
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    Anisotropy
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    Fuselages
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    Gears
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    Landing
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    Landing gear (aircraft)
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    Resonance
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    ROTORS
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    Stiffness
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    AEROMECHANICAL
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    Co-ordinate transformation
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    DETECTION AND CONTROLS
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    DYNAMIC INFLOW
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    FLOQUET METHOD
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    GEAR STIFFNESS
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    GROUND RESONANCE
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    Stability analysis
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    Stability