Design and Modelling of a Semi-active Helicopter Seat Cushion Aerospace Engineering

118 Pages·2016·6.73 MB·English

by  Andre C. Marta

Design and Modelling of a Semi-active Helicopter Seat
Cushion
Nicole Tiago da Cruz
Thesis to obtain the Master of Science Degree in
Aerospace Engineering
Supervisors: Prof. Afzal Suleman
Eng. Amin Fereidooni
Examination Committee
Chairperson: Prof. Fernando José Parracho Lau
Supervisor: Prof. Afzal Suleman
Member of the Committee: Prof. Aurélio Lima Araújo
November 2016
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Tomyparents,fortheunconditionalsupport...
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Acknowledgments
Theconclusionofauniversitymasterdegreeisalongcommitmentinvolvingmanyobstaclesandchal-
lengesand,itsaccomplishmentinvolvesthehelpofmanydifferentpeoplethatIwanttomentionandto
whomIneedtoextendmygratitude.
This research work was accomplished at University of Victoria, in Canada, in collaboration with NRC
Canada,inOttawa.
Mymostsincerethanksto:
First my supervisor on such an innovative field Dr. Afzal Suleman for this great opportunity and
Dr. FernandoOliveirafortheirpatience,guidance,timespentandsupervisionduringmyworkand
supportthroughoutthisperiod;
University of Victoria (UVic) for having welcomed me in the best way and provided the use of its
facilitiesandresources;
NRC Canada for all the information available and the resulting partnership, in particular to Eng.
AminFereidooniandhisteam;
AspecialwordtoDr. LuisFalca˜odaLuz,AerospaceEngineer,forhisknowledgeaboutthesubject
andhisexperiencestepbystep;
CfAR team and former colleagues for all the help regarding technical adversities when using the
equipmentandsoftwareandproductivesuggestions;
Myfamilyandfriends, whomImissedalotduringmy6monthsstayinCanada, fortheirsupport,
encouragementandbelievinginmethroughallthese5years.
Without their valuable participation and input, this research thesis would have not been successfully
concluded.
Lisbon,Portugal
15/10/2016
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Resumo
Os helico´pteros esta˜o sujeitos a elevadas cargas vibrato´rias, o que leva a` reduc¸a˜o da qualidade do
voo. Temhavidoumcrescentenu´merodequeixasdefadiga,desconfortoedorporpartedatripulac¸a˜o
duranteexposic¸o˜esprolongadasa` vibrac¸a˜onesteaparelho.
Oprincipalobjectivoe´ ajudaraatenuarestetipodevibrac¸a˜oatrave´sdaavaliac¸a˜odeumnovoassento.
Esta investigac¸a˜o centra-se na utilizac¸a˜o de materiais magnetoreolo´gicos para uma melhor protecc¸a˜o
econfortodosocupantes,afimdeapresentarumsistemadeassentosemi-activo.
Os materiais magnetoreolo´gicos sa˜o uma das estrate´gias mais promissoras para esta finalidade. As
propriedades u´nicas destes materiais - a sua capacidade de responder mecanicamente a campos
magne´ticos e a sua na˜o-linearidade caracter´ıstica - fazem do desenvolvimento destas aplicac¸o˜es um
desafio.
Aalmofadadoassentomagnetoreolo´gicoconsistenautilizac¸a˜odematerialmagne´tico,va´riasbobinas
electromagne´ticasediferentesamostrasdefluidoouelasto´meromagnetoreolo´gico.
Doissoftwarecomerciais(COMSOL(cid:13)R eFEMM),capazesdemodelarproblemascomplexosemmate´ria
de ana´lise electromagne´tica e materiais na˜o-lineares, foram analisados e utilizados. Um estudo detal-
hado de cada material e´ levado a cabo, em termos de design e das suas aplicac¸o˜es, bem como a
definic¸a˜odageometria,propriedades,condic¸o˜esdefronteiraegerac¸a˜odamalha.
O sistema da almofada do assento demonstrou ser eficaz, apo´s o estudo de modelos teo´ricos do
desempenho do material magnetoreolo´gico e a criac¸a˜o de modelos de elementos finitos bem como
atrave´sdarespostadomaterial,emreduzirasvibrac¸o˜essentidaspelatripulac¸a˜o.
Para concluir, e´ proposta uma configurac¸a˜o final do design a produzir, assim como um diagrama de
blocos do Simulink(cid:13)R para representar a resposta da almofada e uma primeira proposta de controlo. E´
expecta´velque,nofuturo,estasejaasoluc¸a˜oaimplementarnestaproblema´tica.
OdesignpropostodoassentovaiserfabricadopeloNationalResearchCouncilCanada,comoqualfoi
poss´ıvelestacolaborac¸a˜o.
Palavras-chave:
assento de helico´ptero, materiais magnetoreolo´gicos, elementos finitos, cir-
cuitomagne´tico,design,controlo
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Abstract
Helicopters are susceptible to excessive vibratory loads that lead to poor flight ride quality. There have
been increasing complaints of fatigue, discomfort and pain by crew, during extended exposures to this
vibration.
Themaingoalofthethesisistohelpmitigatestructuralvibrationbydesigningandevaluatingthestruc-
turalperformanceofanovelseatcushion.
This solution focuses on the use of magnetorheological (MR) fluids and elastomers to dampen the
structuralresponseofthesemi-activeseatsystem,toenhanceoccupantprotectionandcomfort.
Magnetorheologicalmaterialspresentapromisingapproachforthispurpose. TheMRseatcushioncon-
sistsofadistributedmagneticmaterialembeddedinelastomersandvariouselectromagneticcoils. The
unique properties of magnetorheological materials - their ability to mechanically respond to magnetic
fieldsandtheircharacteristicmaterialnon-linearity-makedesigningtheseapplicationsachallenge.
Twocommercialsoftware(COMSOL(cid:13)R andFEMM),capableofmodellingcomplexelectromagneticprob-
lemsandnon-linearmaterials,havebeenevaluatedandused. Adetailedstudyofeachmaterialiscar-
riedout,intermsofdesignandresponseaswellasthedefinitionofthegeometry,properties,boundary
conditionsandmeshconvergence.
The study of analytical and computational models to quantify the performance of the MR material (re-
sponse output) has demonstrated that the proposed helicopter seat cushion system is effective in re-
ducingthevibrationfeltbythepilots.
Toconclude,aconceptualfinaldesignconfigurationisproposedaswellasSimulink(cid:13)R blockdiagramto
representthecushionresponseandaone-degreeoffreedomcontrolmodel. Thisisexpectedtobethe
mainsolutionadoptedinthefuture.
The thesis has been performed in collaboration with the National Research Council Canada and the
seatcushiondesignproposedisgoingtobemanufacturedandtested.
Keywords:
helicopterseatcushion,magnetorheologicalmaterial,finiteelementmethod,magnetic
circuit,design,control
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