NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
A study of coupled rotor-fuselage vibration with higher harmonic control using a symbolic computing facilityA fundamental study of vibration prediction and vibration reduction in helicopters using active controls was performed. The nonlinear equations of motion for a coupled rotor/flexible fuselage system have been derived using computer algebra on a special purpose symbolic computing facility. The details of the derivation using the MACSYMA program are described. The trim state and vibratory response of the helicopter are obtained in a single pass by applying the harmonic balance technique and simultaneously satisfying the trim and the vibratory response of the helicopter for all rotor and fuselage degrees of freedom. The influence of the fuselage flexibility on the vibratory response is studied. It is shown that the conventional single frequency higher harmonic control (HHC) capable of reducing either the hub loads or only the fuselage vibrations but not both simultaneously. It is demonstrated that for simultaneous reduction of hub shears and fuselage vibrations a new scheme called multiple higher harmonic control (MHHC) is required. The fundamental aspects of this scheme and its uniqueness are described in detail, providing new insight on vibration reduction in helicopters using HHC.
Document ID
19920053146
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Papavassiliou, I.
(NASA Ames Research Center Moffett Field, CA, United States)
Venkatesan, C.
(NASA Ames Research Center Moffett Field, CA, United States)
Friedmann, P. P.
(California, University Los Angeles, United States)
Date Acquired
August 15, 2013
Publication Date
September 1, 1990
Subject Category
Aircraft Stability And Control
Accession Number
92A35770
Funding Number(s)
CONTRACT_GRANT: DAAL03-86-G-0109
CONTRACT_GRANT: NAG2-477
Distribution Limits
Public
Copyright
Other

Available Downloads

There are no available downloads for this record.
No Preview Available