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Nonlinear coupled rotor-fuselage helicopter vibration studies with higher harmonic controlThis paper addresses the problem of vibration prediction and vibration reduction in helicopters by means of active control methodologies. The nonlinear equations of a coupled rotor/flexible-fuselage system have been derived using computer algebra, thus relegating this tedious task to the computer. In the solution procedure the trim state and vibratory response of the helicopter are obtained in a single pass by using a harmonic balance technique and simultaneously satisfying the trim and the vibratory response of the helicopter in all the rotor and fuselage degrees of freedom. Using this solution procedure, the influence of the fuselage flexibility on the vibratory response is studied. In addition, it is shown that the conventional single frequency HHC is capable of reducing either the hub loads or only the fuselage vibrations but not both simultaneously. A new scheme called MHHC, having multiple higher harmonic pitch inputs, was used to accomplish this task of simultaneously reducing both the vibratory hub loads and fuselage vibratory response. In addition, the uniqueness of this MHHC scheme is explained in detail.
Document ID
19910032607
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Friedmann, P. P.
(California Univ. Los Angeles, CA, United States)
Venkatesan, C.
(California, University Los Angeles, United States)
Papavassiliou, I.
(California Univ. Los Angeles, CA, United States)
Date Acquired
August 15, 2013
Publication Date
January 1, 1990
Subject Category
Aircraft Stability And Control
Meeting Information
Meeting: AHS, Annual Forum
Location: Washington, DC
Country: United States
Start Date: May 21, 1990
End Date: May 23, 1990
Accession Number
91A17230
Funding Number(s)
CONTRACT_GRANT: DAAL03-86-G-0109
CONTRACT_GRANT: NAG2-477
Distribution Limits
Public
Copyright
Other

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