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Comparing Different Approaches for Modeling the Vertical Motion of the EC 135

Seher-Weiß, Susanne (2014) Comparing Different Approaches for Modeling the Vertical Motion of the EC 135. In: European Rotorcraft Forum 2014. Royal Aeronautical Society. 40th European Rotorcraft Forum 2014, 2.-5. Sep. 2014, Southampton, Großbritannien.

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Helicopters like the EC 135 with its bearingless main rotor design feature large equivalent hinge offsets of about 10 %, significantly higher than conventional rotor designs and leading to improved maneuverability and agility. For such a helicopter, the fuselage and rotor responses become fully coupled and the quasi-steady assumption using a 6-DoF rigid-body model state space description and approximating the neglected rotor degrees of freedom by equivalent time delays is not suitable. Depending on the intended use of the model, the accurate mathematical description of the vertical motion for these configurations requires an extended model structure that includes inflow and coning dynamics. The paper first presents different modeling approaches and their relationship. Next, identification results for the DLR EC 135 are presented for a model that only describes the vertical motion excluding coupling to the other axes. Here, the differences between the modeling approaches and the respective deficits are explained. Next, the modelling approach most widely used in the rotorcraft identification literature is extended to account for hinge offset. In addition, some model parameters are estimated instead of fixing them at their theoretical predictions which leads to a very good match with EC 135 flight test data. Results for a complete model of the EC 135 including flapping, coning/inflow, and regressive lead-lag are shown as a final result.

Item URL in elib:https://elib.dlr.de/89743/
Document Type:Conference or Workshop Item (Speech)
Title:Comparing Different Approaches for Modeling the Vertical Motion of the EC 135
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Date:3 September 2014
Journal or Publication Title:European Rotorcraft Forum 2014
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In ISI Web of Science:No
Publisher:Royal Aeronautical Society
Keywords:rotorcraft, vertical motion, modeling, system identification
Event Title:40th European Rotorcraft Forum 2014
Event Location:Southampton, Großbritannien
Event Type:international Conference
Event Dates:2.-5. Sep. 2014
Organizer:Royal Aeronautical Society
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Aeronautics
HGF - Program Themes:rotorcraft
DLR - Research area:Aeronautics
DLR - Program:L RR - Rotorcraft Research
DLR - Research theme (Project):L - The Innovative Rotorcraft (old)
Location: Braunschweig
Institutes and Institutions:Institute of Flight Systems > Rotorcraft
Deposited By: Seher-Weiß, Susanne
Deposited On:07 Oct 2014 16:04
Last Modified:13 Nov 2014 15:25

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