Design considerations of outer-rotor permanent magnet synchronous machines for in-wheel electric drivetrain using particle swarm optimization

For the past decade, in-wheel electric motors have been widely promoted as an alternative propulsion system for future drivetrains. A key requirement for the in-wheel motor is high torque density with minimum torque ripple. The outer-rotor surface permanent magnet synchronous machine with the fractional-slot concentrated-winding configuration lends itself for the application. In this paper, the electromagnetic performance of the machine with various stator slot and rotor pole combinations is optimized by particle swarm algorithm based on finite element analysis (FEA). The optimised designs are comprehensively appraised by key performance metrics. The study shows that the particle swarm optimisation is superior to other tools in terms of simplicity and effectiveness in multi-objective parametric machine design.