Analysis of Regenerative Braking Effect for E-REV Bus According to Driving Cycle Based on Simulation

Abstract

Among eco-friendly vehicles, extended range electric vehicle (E-REV) is concept for electric vehicle that has light engine for extended range driving. One of the most important features of these vehicles based electricity is their ability to recover significant amounts of braking energy. Recovering the braking energy and reusing it can significantly improve the fuel economy of the vehicle which is subject to frequent braking events such as a city bus. To develop the E-REV bus, the regenerative braking effect should be checked in advance. However, because of many technical constraints, regenerative braking should consider some conditions like vehicle speed, accelerator pedal signal, brake pedal signal, battery voltage and so on. Hence, regenerative braking torque is assumed as 2D and 3D maps with these conditions based on simulation. Fuel economy simulations are conducted to analyze regenerative braking effect according to driving cycle. They consist of E-REV bus without regenerative braking and with regenerative braking torque maps. Fuel economy difference between two cases was calculated and driving cycles were analyzed. Among the characteristic analyzed, the aggressiveness means harshness of driving cycle. And the inclination between the aggressiveness and the fuel economy difference is verified. The smaller absolute value of the aggressiveness is, the smaller fuel economy difference is. In short, the aggressiveness and the regenerative braking effect have direct proportion. According to the obvious tendency, proper regenerative braking should be determined.