Multi-objective optimization of in-wheel motor powertrain and validation using vehicle simulator

A method based on multi-objective optimization (MOO) is employed for the concept design of electric powertrain with in-wheel motor (IWM). The inherent challenges of IWM vehicles are powertrain packaging, increased unsprung mass, and motor cooling. Elimination of hub-reduction gearbox and adaption of high torque and low power electric motor can mitigate these challenges, but it degrades high speed gradeability. Simultaneous optimization of motor power, battery size and drivability parameters to size the powertrain components (electric motor and gearbox) is important for the effective design of powertrain layout. In this study, motor torque, base speed, and gear-ratio are taken as design variables to minimize the motor peak power and the battery size, while maximizing the drivability performance. AC induction machines and Li-ion batteries are considered for the discussion, but the same approach can be applied for other motor and battery types. The results are validated virtually using a high-fidelity vehicle simulator, which confirms the findings of MOO. The optimal powertrain layout includes a high torque (600Nm) and low speed motor without gearbox.