Page - 326 - in Emerging Technologies for Electric and Hybrid Vehicles

Energies 2017,10, 315 strategic locationsalongthehighway, theEVdrivingrangecanbeextended,allowingowners todrive longerdistanceswithout theanxietyofhavingtoworryaboutEVrange[7]. However, theonemaindisadvantageof thisDWCschemeis thereduction inreceivedpowerand efficiency thatoccurswhen there is a lateralmisalignmentof thevehicle’s loadcoil and thesource coil embeddedunder theroad. Thevehiclemustbealignedwithinacertainrangeof thesourcecoil toachievehighpower in the loadcoil [8],whichalsomaximizes thedrivingdistanceof thevehicle. Keeping the load coil of avehicle alignedat all timeswith the source coilwhile inmotion is very difficult, evenforanexperienceddriver. Inaddition,attemptingtokeepthevehiclealignedwith the sourcecoilmaydistract thedriver fromoncomingtrafficorobstaclesandeventually leadtoserious trafficaccidents. Tominimize theproblemwith transferringpower to the loadcoildue to lateralmisalignment inWPT,manymethods have been proposed tomaximize lateralmisalignment tolerance. Some proposedmethodsincludechangingthegeometryofthecoil [9],placingmultiplecoils inanorthogonal configuration [10]oranoverlappingconfiguration [11], andevencombiningmultiplecoilsofdifferent geometry intooneunit [12]. Anotherpopularmethod is theutilizationof ferromagneticmaterials, whereE-shapeorU-shapeferritecores [13,14]areutilizedat the load/sourcecoils.Othermethodsalso includeactivecoil resonancefrequencytuningcircuits tomaximize lateral tolerance [15,16].All the proposedmethodsdescribedaboveareconstructive,buttheir implementationinvehicularapplications canbevery limited,dueto thevehicle’s limited installationspace,weightconstraints,aswellas the dynamic driving environment. Even assuming that the proposedmethodswere implemented in thevehicle,misalignmentwouldstill beunavoidableas longasaperson is controlling thevehicle. Inaddition, evenaDWC-equippedEVwithahigh lateralmisalignment tolerance (45cm)will still haveregionsonahighwaylanewithoutwirelesspowerdelivery,asshowninFigure1.Andwithinthe tolerancerange, lossofpowerwill still inevitablyoccurwhenever the lateralmisalignment increases. Figure1.Powertransfercoverageareaona3.6mwidthhighwaylane(basedonFHWAstandards[17]) foraWPTsystemwitha45cmlateralmisalignment tolerance. Equippedonastandardsizedvehicle witha2mtrackwidth. Avehicle trackingandautonomousguidancesystemusingmagnetic sensingcanalsobeapplied toreduce theDWCpower transferproblem.Thesystemconcept is showninFigure2. Figure2.Conceptofautonomousvehicle trackingandguidance toreducedegradedpower transfer in aDWCsystem. 326