Computationally efficient driving cycle based design and optimisation for variable air gap axial flux machines

Axial flux permanent magnet machines provide a unique set of possibilities and challenges to electric machine designers when compared to their radial flux counterparts. By varying the air gap width between the rotor and stator a mechanical rotor flux linkage control is made possible. This paper introduces a computationally efficient method of evaluating axial flux machines with air gap variation. The investigated machine is designed as a traction drive for a student racing series. Two different design scenarios are presented, comparing optimisation results from a single operating point and static air gap model to a variable air gap, driving cycle based design. A validation design is chosen for an in-depth investigation and a prototype motor is built and tested at a range of air gaps. This experimental data is compared to FEA results to validate the model.