Multi-objective optimal design and current waveforms control of axial-flux brushless DC wheel motors for electric vehicles

A multi-objective optimal design of a brushless dc disc-type axial-flux wheel motor and its optimal current waveforms are presented in this paper. This dedicated motor is modeled in magnetic circuits, and designed to meet the specifications of an optimization scheme, subject to constraints, such as limited space, current density, flux saturation and driving voltage. The torque-oriented optimization is then performed to obtain the optimal current waveform subject to various constraints for the independent winding structure. The best optimal waveform with maximized torque and confined ohmic loss is found to be proportional to the magnetic flux variation in the air-gap between the stator and the rotor, which is verified the same shape as the back emf.