Research on Factors to Influence Coasting Resistance for Electric Vehicles 2020-01-1068

The research on coasting resistance is vital to electric vehicles, since the smaller the coasting resistance, the longer the coast-down distance. Vehicle coast resistance consists of rolling resistance, vehicle inner resistance and the aerodynamic drag. The vehicle inner resistance is mainly caused by driveline’s friction loss and oil splash loss. The rolling resistance is decided by tire resistance coefficient, which is influenced by tires and road conditions. And the aerodynamic drag is affected by vehicle’s shape and air. In this paper, four factors including tire pressure, road surface condition, atmosphere temperature, and recirculation on or off are examined. Experimental tests have been conducted on three different vehicles: one subcompact sedan, one compact sedan and one subcompact SUV. Then experimental results have been imported to simulation model to investigate the corresponding influence on NEDC range. The outcome shows that, when the tire pressure is 20% less, the average coasting resistance is increased by 1% to 3% depending on vehicle types, which indicates a decrease in NEDC range by around 2%. And with atmosphere temperature in 6 to 32°C range, the resistance is decreased by 0.48% for every 1°C increased. On wet road surface, the average coasting resistance is increased by 10% - 20%, which could decrease the NEDC range by 6% to 12%. As for the recirculation on or off, one vehicle with inside air recirculation on experiences an average 6% coasting resistance reduction. Other two vehicles have similar coasting resistances whether the recirculation is on or off. The overall results give a better understanding on how the coasting resistance is influenced by various factors and can instruct future vehicle’s low coasting resistance development. More factors such as brake calipers, tire size, and other corresponding influences will be studied in future tests.