Page - 12 - in Emerging Technologies for Electric and Hybrid Vehicles

Energies 2017,10, 1217 useful toprovidebetter traction inslipperyconditions, theycanalsouse torquevectoringforbetter corneringperformanceandhandling. AWDconfigurationcanalsobe realized for in-wheelmotor systems. It canprovequiteuseful for city cars like theHirikoFold (Figure14)whichhas steering actuator, suspension,brakesandamotorall integrated ineachwheel. Sucharrangementscanprovide efficientallwheeldriving,allwheel steeringalongwitheaseofparkingandcornering. Figure13.TeslaModelS,all-wheeldriveconfiguration[24]. (Reprintwithpermission[24];2017,Tesla.) Figure14.HirikoFold—avehicleemploying in-wheelmotors. In-wheelmotorconfigurationsarequiteconvenient inthesensethat theyreducetheweightof the drive trainbyremovingthecentralmotor, relatedtransmission,differential,universal jointsanddrive shaft [25]. Theyalsoprovidemorecontrol, better turningcapabilitiesandmorespace forbatteries, fuelcellsorcargo,but in thiscase themotor isconnectedto thepowerandcontrol systemsthrough wires thatcangetdamagedbecauseof theharshenvironment,vibrationandacceleration, thuscausing serious trouble. Satoetal.,proposedawireless in-wheelmotorsystem(W-IWM)in[26]whichthey hadimplemented inanexperimentalvehicle (showninFigure15). Simplyput, thewiresarereplaced bytwocoilswhichareable to transferpower in-betweenthem.Becauseofvibrationscausedbyroad conditions, themotorandthevehiclecanbemisalignedandcancausevariation in thesecondaryside voltage. In-wheelmotorconfigurationsareshowninFigure16,whereas theefficienciesatdifferent stagesofsuchasystemareshowninFigure17. Inconditions like this,magnetic resonancecoupling ispreferred forwirelesspower transfer [27] as it canovercome theproblemsassociatedwith such 12