A Method of Gear-shift in Parallel Hybrid Electric Vehicle using Motor Control

To alleviate vibration of power-train system in hybrid electric vehicle (HEV) is one of the most difficult obstacles that most of engineers would face. The vibration of gear-shifting would be hider by precise synchronization of applied members in gear-shifting process; however, improvement of the vibration by calibrating conventional hydraulic control was limited. To transcend the limitation of hydraulic method, we developed a combined gear-shifting method assisted by motor speed feedback control to synchronize an input speed of transmission with a target input speed exactly.

We divided a whole gear-shifting process into the following five phases to combined hydraulic control with motor speed control. In addition, to prevent the additional vibration, motor speed feedback control starts at the second phase and parameters of motor feedback control are categorized by each phases. By means of the method stated above, we can shorten the whole time of gear-shifting process and improve the feeling of gear-shift by reduction of shift vibration.