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A new drive system for electric vehicles is presented. An axial flux disc motor is used. The stator of the machine is attached to tlie chassis whilst the rotor directly drives the wheel. This arrangement reduces the unsprung mass compared with a conventional wheel drive and also because of tlie machine geometry permits movement of the wheel as it is perturbed by the road. The motor is modelled using 2D and 3D finite element techniques and estimates are given for the reduction in torque and induced enif when tlie rotor disc and stator are misaligned. Keywords: electric vehicle, drive system, perinanent magnet, disc mottors.

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Traction drives used in electric vehicles can be divided into two categories, (i) single drive systems, and (ii) multi-drive systems. With multi-drive systems the motor controllers must additionally be configured to provide an electronic differential effect i.e. they must also perform a similar function as their mechanical differential counterpart. Thus the electronic differential must take account of the speed difference between the two wheels when cornering. This paper presents a design for an electronic differential utilising a sliding mode controller employing a 4-switch 3-phase inverter. This type of inverter is particularly suitable for this application as the supply batteries can be easily split into two separate battery strings. The system is evaluated on a test vehicle in which the rear wheels are directly driven by permanent magnet brushless motors. Results indicate that this arrangement can be successfully implemented into an electric vehicle drive train