A comparative MATLAB/Simulink framework for drive-cycle-based traction motor sizing in battery electric four-wheelers

Abstract

As more battery electric vehicles (BEVs) are being introduced, the need for accurate traction motor sizing to achieve optimal performance, energy efficiency, driving range and cost has become more important. The conventional analytical sizing methods are based on worst-case conditions and often result in over- or under-sizing a motor, with the resulting negative impact on system efficiency and economic viability. In this study, a MATLAB/Simulink model is developed which compares directly between analytical sizing and drive cycle-based simulation of a battery electric four-wheeler for a Maruti Zen passenger car. The equations of the vehicle dynamics with the four forces: rolling resistance, aerodynamic drag, acceleration, and gradient force approximate the tractive force, wheel torque, and motor power. The vehicle is tested in three standardised drive cycles (New European Driving Cycle (NEDC), Highway Fuel Economy Test (HWFET) and the Artemis Urban Drive Cycle (UDC)), and the results are compared to the analytical method. The analytical approach predicts a 23.23–67.99 kW power band for the road gradient range (0°–18°) analysed, while drive-cycle simulation suggests 15.29 kW (NEDC), 14.52 kW (HWFET) and 22.10 kW (UDC)—a 67.5–78.6% decrease from the analytical upper bound. The results show that drive-cycle-based sizing can provide a more accurate, application-specific assessment of traction-motor sizing and help to minimize the risk of over-sizing and increase efficiency. In addition to re-working known vehicle-dynamics equations, this work is novel in that the power gap between the two routes of analytical and drive-cycle sizing is benchmarked for a vehicle and set of parameters, and a low-cost, practical screening tool for selecting a traction motor appropriate for the operating environment and duty profile is provided to manufacturers and researchers.