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An analytic modeling and system identification study of rotor/fuselage dynamics at hoverA combination of analytic modeling and system identification methods have been used to develop an improved dynamic model describing the response of articulated rotor helicopters to control inputs. A high-order linearized model of coupled rotor/body dynamics including flap and lag degrees of freedom and inflow dynamics with literal coefficients is compared to flight test data from single rotor helicopters in the near hover trim condition. The identification problem was formulated using the maximum likelihood function in the time domain. The dynamic model with literal coefficients was used to generate the model states, and the model was parametrized in terms of physical constants of the aircraft rather than the stability derivatives, resulting in a significant reduction in the number of quantities to be identified. The likelihood function was optimized using the genetic algorithm approach. This method proved highly effective in producing an estimated model from flight test data which included coupled fuselage/rotor dynamics. Using this approach it has been shown that blade flexibility is a significant contributing factor to the discrepancies between theory and experiment shown in previous studies. Addition of flexible modes, properly incorporating the constraint due to the lag dampers, results in excellent agreement between flight test and theory, especially in the high frequency range.
Document ID
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Hong, Steven W.
(United Technologies Research Center East Hartford, CT, United States)
Curtiss, H. C., Jr.
(Princeton Univ. NJ., United States)
Date Acquired
September 6, 2013
Publication Date
July 1, 1993
Publication Information
Publication: NASA. Ames Research Center, Piloting Vertical Flight Aircraft: A Conference on Flying Qualities and Human Factors
Subject Category
Aircraft Stability And Control
Accession Number
Distribution Limits
Work of the US Gov. Public Use Permitted.
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