Optimization of Gear Ratio of In-Wheel Motor Vehicle Considering Probabilistic Driver Model

A reduction gear of an in-wheel motor vehicle is mounted between a traction motor and wheel, to increase the wheel torque and decrease the rotational speed. To improve the energy efficiency of a vehicle, the determination of the optimal gear ratio is an important factor in the design of the reduction gear. This paper presents an optimization procedure to obtain the optimal gear ratio of an in-wheel motor vehicle that minimizes the electric energy consumption. Using a model-based design, a dynamic simulation model of a vehicle was developed for an analysis of the energy efficiency. Owing to a variation in energy efficiency across drivers, a probabilistic driver model that includes driver characteristics is employed. To reduce excessive calculations, a surrogate model was constructed for the optimization. The optimal gear ratio for saving energy was obtained, and the usefulness of the proposed optimization procedure was shown through a comparison of the results of the optimal gear ratio and the energy efficiency achieved between deterministic and probabilistic approaches.