Rolling Resistance Effect of Tire Road Contact in Electric Vehicle Systems

The increasing demand of energy use in transportation systems combined with the limited supply of fossil hydrocarbons to support conventional engines has led to a strong resurgence in interest for electric vehicles (EVs). Although EVs offer the possibility of decoupling the issue of energy source from the primary torque generator in an automobile, the current technology is yet to match the well-developed internal combustion (IC) systems, especially in terms of energy capacity and travel range. In this study, the influence of rolling-resistance on the energy efficiency and road holding of electric vehicles is investigated. Rolling resistance is taken in the context of energy loss (e.g. the mechanical energy converted into other sources of energy) for a unit distance traveled by the tire. Considering that the primary factors that affect rolling resistance are pavement features (e.g. texture, stiffness and profile) together with temperature, vehicle speed and tire inflation pressure, a comprehensive simulation study has been conducted utilizing a vehicle model representing chassis dynamics with a battery electric powertrain and a specified tire model to account for rolling-resistance effects. A series of simulations are performed on given urban and highway drive cycles which are determined based on the standard assumption that the vehicle has to be equipped with drive motors that have a combined power of 30 kW in order to overcome the road load during normal driving and based on the assumption that a specific motor output of approximately 1 kW/kg can be considered to be an appropriate guideline for generic electric motors. At the end, the results are analyzed for estimating the amount of energy that can be saved by reducing such losses and the extended travel range in comparison to available examples of similar results for commercial vehicles in public domain.