mobile robot vehicles

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1、MobileRobotVehiclesThischapterdiscusseshowarobotplatformmoves,thatis,howitsposechangeswithtimeasafunctionofitscontrolinputs.Therearemanydifferenttypesofrobotplatformasshownonpages61–63butinthischapterwewillconsideronlytwowhichareimportantexemplars.Th

2、efirstisawheeledvehiclelikeacarwhichoperatesina2-dimensionalworld.Itcanbepropelledforwardsorbackwardsanditsheadingdirectioncontrolledbychangingtheangleofitssteeredwheels.Thesecondplatformisaquadcopter,aflyingvehicle,whichisanexampleofarobotthatmovesi

3、n3-dimensionalspace.Quadcoptersarebecomingincreasingpopularasarobotplatformsincetheycanbequiteeasilymodeledandcontrolled.Howeverbeforewestarttodiscussthesetworobotplatformsitwillbehelpfultoconsidersomegeneral,butimportant,conceptsregardingmobility.We

4、havealreadytouchedonthediversityofmobilerobotsandtheirmodesoflocomotion.Inthissectionwewilldiscussmobilitywhichisconcernedwithhowavehiclemovesinspace.Wefirstconsiderthesimpleexampleofatrain.Thetrainmovesalongrailsanditspositionisdescribedbyitsdistanc

5、ealongtherailfromsomedatum.Theconfigurationofthetraincanbecompletelydescribedbyascalarparameterqwhichiscalleditsgeneralizedcoordinate.Thesetofallpossibleconfigurationsistheconfigurationspace,orC-space,denotedbyCandq∈C.InthiscaseC⊂R.Wealsosaythatthetr

6、ainhasonedegreeoffreedomsinceqisascalar.Thetrainalsohasoneactuator(motor)thatpropelsitforwardsorbackwardsalongtherail.Withonemotorandonedegreeoffreedomthetrainisfullyactuatedandcanachieveanydesiredconfiguration,thatis,anypositionalongtherail.Anotheri

7、mportantconceptistaskspacewhichisthesetofallpossibleposesξofthevehicleandξ∈T.Thetaskspacedependsontheapplicationortask.IfourtaskwasmotionalongtherailthenT⊂R.IfwecaredonlyaboutthepositionofthetraininaplanethenT⊂R2.Ifweconsidereda3-dimensionalworldthen

8、T⊂SE(3),anditsheightchangesasitmovesupanddownhillsanditsorientationchangesasitmovesaroundcurves.Clearlyfortheselasttwocasesthedimensionsofthetaskspaceexceedthedimensionsoftheconfigurationspaceandthetraincannotattainanarbitraryposesinceitisconstrained