Cicada (Tibicen linnei) steers by force vectoring

(整期优先)网络出版时间:2016-02-12
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Tochangeflightdirection,flyinganimalsmodulateaerodynamicforceeitherrelativetotheirbodiestogeneratetorqueaboutthecenterofmass,orrelativetotheflightpathtoproducecentripetalforcethatcurvesthetrajectory.Inemployingthelatter,thedirectionofaerodynamicforceremainsfixedinthebodyframeandrotationsofthebodyredirecttheforce.Whilebothaforementionedtechniquesareessentialforflight,itiscriticaltoinvestigatehowananimalbalancesthetwotoachieveaeriallocomotion.Here,wemeasuredwingandbodykinematicsofcicada(Tibicenlinnei)infreeflight,includingflightperiodsofbothlittleandsubstantialbodyreorientations.Itisfoundthatcicadasemployacommonforcevectoringtechniquetoexecutealltheseflights.Weshowthatthedirectionofthehalf-strokeaveragedaerodynamicforcerelativetothebodyisindependentofthebodyorientation,varyinginarangeofmerely20deg.Despitedirectionallimitationoftheaerodynamicforce,pitchandrolltorquearegeneratedbyalteringwingangleofattackanditsmeanpositionrelativetothecenterofmass.Thisresultsinbodyrotationswhichredirectthewingforceintheglobalframeandconsequentlychangetheflighttrajectory.