S. Gair

A new 2D FEM analysis of a disc machine with offset rotor

The paper presents a new 2-D finite element method (2D FEM) analysis of a double-sided axial field, permanent magnet excited brushless DC motor. The rotor of the machine is free to move in a direction perpendicular to the axis of the shaft. Computed 2D results are compared with 3D FEM analysis and the new analysis method is shown to give close agreement.

Disc motor with reduced unsprung mass for direct EV wheel drive

A new drive system for electric vehicles is presented. An axial flux disc motor is used. The stator of the machine is attached to the chassis whilst the rotor directly drives the wheel. This arrangement reduces the unsprung mass compared with a conventional wheel drive and also, because of the 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 EMF when the rotor disc and stator are misaligned.

Elimination of torque pulsations in a direct drive EV wheel motor

Double sided axial field machines are attractive for direct wheel drives in electric vehicles. This is due to the fact that stator/rotor misalignments can be accommodated. In this case the stator of the machine is envisaged mounted on the chassis of the car whilst the rotor directly drives the road wheel. Since the wheel is perturbed by the road surface the rotor will move vertically between the outside stator assemblies and thus give rise to torque pulsations. A vector control scheme has been implemented whereby the torque pulsations are eliminated by (i) calculation of the flux variation due to the rotor perturbation and (ii) using this signal for the modulation of the motor input current.

EFFECTS OF SLOT CLOSURE BY SOFT MAGNETIC POWDER WEDGE MATERIAL IN AXIAL-FIELD PERMANENT MAGNET BRUSHLESS MACHINES

The article reports on a study of the effects of slot closure in axial‐field permanent magnet brushless machines by a two‐dimensional finite element method (2D FEM) of analysis. The closure of the slots is made by using soft magnetic powder wedge material. Parameter values and machine performance for the open and closed slot configuration are computed. In order to test the 2D FEM model, calculated results are compared with measurements and favorable agreement is shown.

Control of torque fluctuations in a PM disc motor

Direct wheel drives in electric vehicles are advantageous because the gearbox, mechanical transmission and differential can be eliminated. Two opportunities then arise: (i) mount the drive motor in the road wheel of the vehicle; or (ii) mount the drive motor inboard on the vehicle chassis. The major drawback associated with (i) is the resultant increase in the unsprung mass of the vehicle, whilst the second option introduces a degree of complexity in the mechanical coupling to the road wheel. However the difficulties associated with (i) 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. Perturbation of the rotor while the vehicle is moving will however cause torque fluctuations in the machine. This paper shows that these torque pulsations can be eliminated by the modulation of the input motor current using a signal obtained from the identification of the flux.

Application of neural networks to a disc motor with offset rotor

Axial field permanent magnet disc machines are attractive for direct wheel drives in electric vehicles because the stators can be mounted on the vehicle body whilst the rotor can be directly coupled to the driven wheel. However, this arrangement gives rise to torque pulsations in the drive due to the perturbation of the wheel by the road surface effects. It is shown here that torque pulsations due to the rotor perturbation can be eliminated by modulation of the input motor current based on flux identification determined by a neural network.

Torque control of a BDC axial field drive motor with open and closed slot configuration

This paper examines the model for a brushless DC, permanent magnet disc motor suitable for light electric vehicle traction application. Subsequently a torque control scheme is proposed. Finally the model of the motor and the control are simulated in order to verify the behaviour of the drive motor with open and closed slots in the machine.