The Engine Clutch Engagement Control for Hybrid Electric Vehicles

In this paper, an engine clutch engagement control for hybrid electric vehicles (HEVs) with a transmission mounted electric device (TMED) will be dealt with. In general, the engine of the HEVs repeatedly turns on and off in even one driving cycle, and when the engine turns on, the fast synchronization of the engine speed and the motor speed which is equal to the transmission input speed is very important to transfer the engine power to the driving wheel without a shock during the engagement for better fuel economy and drivability feeling. A hybrid starter generator (HSG) at HEVs is connected into the engine by a pulley, and the engine speed can be controlled by the HSG. When the engine starts to turn on, the engine torque is very unstable, and unpredictable and then the control of the engine speed by HSG is very difficult. The suggested method consists of a disturbance observer and a tracking controller which is composed of a feedback control and a feedforward control. The disturbance observer estimates and compensates a model uncertainty and disturbances such as an engine torque, a friction torque, and so on. The feedback and feedforward control are used for the engine speed to follow a target speed. Then the suggested method is very robust to the model uncertainty, and the disturbances, and then the fast engagement of the engine clutch without a shock is possible. For the effectiveness of the suggested method, the experimental results by TMED HEVs are shown.