International Journal of Automotive Technology

, Volume 19, Issue 6, pp 1081–1089 | Cite as

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

  • Kihan Kwon
  • Minsik Seo
  • Seungjae MinEmail author


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.

Key Words

In-wheel motor vehicle Gear ratio Energy efficiency Probabilistic driver model Surrogate model 



equivalent inertia of vehicle at wheel, kgm2


rotational speed of wheel, rad/s


motor torque, Nm


resistance torque, Nm


gear ratio


mass of body, kg


inertia of wheels, kgm2


inertia of motors, kgm2


radius of tire, m


velocity of vehicle, m/s


coefficient of rolling resistance


gravity acceleration, m/s2


coefficient of air resistance


frontal area, m2


air density, kg/m3


maximum motor torque, Nm


motor speed, rad/s


maximum regenerative braking torque, Nm


capacity of braking torque, Nm


terminal voltage of battery, V


open circuit voltage, V


internal resistance, ohm


load current, A


initial SOC, %


nominal capacity of battery, As


motor efficiency


proportional gain


reaction time delay, s


neuromuscular lag, s V


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Copyright information

© The Korean Society of Automotive Engineers and Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Department of Automotive EngineeringHanyang UniversitySeoulKorea

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