Latest developments in direct EV wheel drives

Traditionally electric vehicles used an electric motor which simply replaced the combustion engine, and all the mechanical components were kept. Direct wheel drives in electric vehicles are advantageous because the gearbox, mechanical transmission and differential can be eliminated. Usually, the drive motor is mounted in the road wheel of the vehicle. However this results in the increase of the unsprung mass of the vehicle due to the weight of the drive motor. This can be overcome by using a double sided axial field machine with a central rotor. The stators of the machine can be attached to the chassis of the car whilst the rotor directly drives the road wheel. This paper investigates problems associated with this novel drive and proposes control techniques which can be employed in order to ensure safe operation of the vehicle