Coordinated Control Strategy in Engine Starting Process for a Novel Compound Power-Split Hybrid Electric Vehicle

Due to the direct connection between the engine and the compound power split hybrid transmission (CPSHT) in hybrid electric vehicle (HEV), engine ripple torque (ERT) can result in obvious jerks in engine starting process (ESP). In order to improve the riding comfort, two wet clutches are mounted in this novel CPSHT. This research developed a new coordinated control strategy and its effectiveness was verified in simulation. Firstly, the mechanical and hydraulic parts of the CPSHT were introduced, and the riding comfort problem during ESP in primary design was illustrated. Secondly, the dynamic plant model including ERT, driveline model and clutch torque was deduced. Thirdly, a coordinated control strategy was designed to determine the target engine torque, motor torque, clutch torque and the moment of fuel injection. A Kalman filter based clutch torque estimator was applied with the help of electric motors information. The simulation result indicates that proposed coordinated control strategy can indeed suppress vehicle jerk and improve the riding comfort in ESP.