Title:
Stability and control issues associated with lightly loaded rotors autorotating in high advance ratio flight

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dc.contributor.advisor Prasad, Jonnalagadda V. R.
dc.contributor.author Rigsby, James Michael en_US
dc.contributor.committeeMember Schrage, Daniel P.
dc.contributor.committeeMember Peters, David A.
dc.contributor.committeeMember Hodges, Dewey H.
dc.contributor.committeeMember Sankar, Lakshmi N.
dc.contributor.department Aerospace Engineering en_US
dc.date.accessioned 2009-01-22T15:43:56Z
dc.date.available 2009-01-22T15:43:56Z
dc.date.issued 2008-10-22 en_US
dc.description.abstract Interest in high speed rotorcraft has directed attention toward the slowed-rotor, high advance ratio compound autogyro concept. The behavior of partially unloaded rotors, autorotating at high advance ratio is not well understood and numerous technical issues must be resolved before the vehicle can be realized. The necessity for a reduction in rotor speed with increasing flight speed results in high advance ratio operation. Further, rotor speed changes also affect the rotor dynamics and the associated hub moments generated by cyclic flapping. The result is rotor characteristics that vary widely depending on advance ratio. In the present work, rotor behavior is characterized in terms of issues relevant to the control system conceptual design and the rotor impact on the intrinsic vehicle flight dynamics characteristics. In this research, non-linear models, including the rotor speed degree of freedom, were created and analyzed with FLIGHTLABTM rotorcraft modeling software. Performance analysis for rotors trimmed to autorotate with zero average hub pitching and rolling moments indicates reduced rotor thrust is achieved primarily through rotor speed reduction at lower shaft incidence angle, and imposing hub moment trim constraints results in a thrust increment sign reversal with collective pitch angle above advance ratio . Swashplate control perturbations from trim indicate an increase in control sensitivities with advance ratio, and advance ratio dependent control cross coupling. Rotor speed response to swashplate control perturbations from trim results in non-linear behavior that is advance ratio dependent, and which stems from cyclic flapping behavior at high advance ratio. Rotor control strategies were developed including the use of variable shaft incidence to achieve rotor speed control with hub moment suppression achieved through cyclic control. Flight dynamics characteristics resulting from the coupling of the rotor and airframe were predicted in flight using a baseline airframe with conventional fixed-wing controls. Results predicted by linearization of the non-linear models were compared with system identification results using the non-linear simulation as surrogate flight test data. Low frequency rotor response is shown to couple with the vehicle motion for short period and roll mode response to airframe control inputs. The rotor speed mode is shown to couple with short period and long period vehicle modes as the rotor torque balance is sensitive to vehicle speed and attitude changes. en_US
dc.description.degree Ph.D. en_US
dc.identifier.uri http://hdl.handle.net/1853/26536
dc.publisher Georgia Institute of Technology en_US
dc.subject Autorotation rotorcraft autogyro stability control en_US
dc.subject.lcsh Rotors
dc.subject.lcsh Rotors (Autogiros)
dc.subject.lcsh Rotors Dynamics
dc.subject.lcsh Aerodynamics
dc.title Stability and control issues associated with lightly loaded rotors autorotating in high advance ratio flight en_US
dc.type Text
dc.type.genre Dissertation
dspace.entity.type Publication
local.contributor.advisor Prasad, Jonnalagadda V. R.
local.contributor.corporatename College of Engineering
local.contributor.corporatename Daniel Guggenheim School of Aerospace Engineering
local.relation.ispartofseries Doctor of Philosophy with a Major in Aerospace Engineering
relation.isAdvisorOfPublication 933b7ff4-7a2e-4eab-9618-bc6303890af3
relation.isOrgUnitOfPublication 7c022d60-21d5-497c-b552-95e489a06569
relation.isOrgUnitOfPublication a348b767-ea7e-4789-af1f-1f1d5925fb65
relation.isSeriesOfPublication f6a932db-1cde-43b5-bcab-bf573da55ed6
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