School of Transportation and Vehicle Engineering, Shandong University of Technology
To achieve higher economy of the original driving scheme with single motor and settled gear ratio, new configurations with different powertrain systems in front and rear axle were designed. Firstly, according to the power and torque required by a micro electric vehicle (mEV) in various drive cycles, the parameters of a small and high power motor were determined. Secondly, for schemeⅠwith dual motor and one-speed gearbox, based on genetic algorithm (GA), theoptimal transmission and torque distribution were confirmed. Owing to the use of single-motor-drive mode (SMDM), the simulated energy consumption decreases by 4.01% compared with the original scheme, but the motor efficiency is still relatively low under low-speed conditions (0-1000r/min) due to the fixed transmission. Then, to solve this problem, scheme using two-speed gearbox to substitute the original one in rear axle was proposed. For this scheme, first of all, the explicit relation of energy consumption and the two-speed ratios was established based on response surface methodology (RSM); then hill climbing method was used to search the best ratios. ّFinally, economy performances of different schemes were discussed in simulation model and energy consumption of this scheme decreases by 7.55% compared with the original one.