Experimental and Analytical Investigation of the Vibration Characteristics of a Remotely Piloted Helicopter
NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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The Department of Aeronautics and Astronautics at the Naval Postgraduate School is involved in an ongoing program of Higher Harmonic Control HHC research using Remotely Piloted Helicopters RPH. To date a host RPH has been acquired and a preliminary HHC design study completed. This thesis reports the results of free vibration shake test conducted on the host RPH as well as efforts to construct a representative finite element model of the vehicle. Broadband noise was used to excite the structure both laterally and vertically from 10-200 Hz in and attempt to accurately document the airframe and rotor system dynamics. Primary airframe structural modes were identified in the tail boom and at frequencies well below the characteristic 4rev 78.3 Hz main rotor induced vibration frequency. These modes should not be of concern at normal operating rpm. Main rotor blade modes were documented under non-rotating conditions then extended to predict the modes at operating rpm. Finally, a finite element model of the structure was constructed. Difficulties in matching finite element predictions with experimental results, however, will require refinements to the computer model before is can become a useful design tool. HHC, Modal testing, Vibration, Finite element analysis, RPH, Shake testing.
- Pilotless Aircraft
- Theoretical Mathematics