Abstract: There are many driving modes existing in the hybrid electric vehicle (HEV), the torque coordination problem of related power sources during the transition of different modes is essential to vehicle’s power and drivability performance. Based on the four wheel drive hybrid electric car, focusing on the switching from pure electric mode to hybrid four wheel drive mode as well as considering the difference of dynamic characteristics between ICE and in-wheel motors, bumpless mode switching control strategy is designed in order to solve drivability issues caused by propulsion mode’s change during the vehicle running process. Forward simulation model of four wheel drive HEV is built on Matlab/Simulink/SimDriveline platform, simulation and real vehicle road test of mode switching control strategy are carried out. Results show that the designed control strategy can ensure a smooth power transfer during the mode switching process, and can effectively suppress the longitudinal impact caused by power coupling. Finally an enhanced drivability is achieved on condition of satisfying driver’s requirement on torque.

Key words: Drivability performance, Four wheel drive, Hybrid electric car, Mode switching control, Real vehicle road test