Coordinated Mode Transition Control for a Novel Compound Power-Split Hybrid Electric Vehicle 2019-01-1306

Because of the direct connection between the compound power split hybrid transmission (CPSHT) and the engine in hybrid electric vehicle (HEV), engine ripple torque (ERT) can lead to obvious jerks when the mode transition from electric driving mode to hybrid driving mode occurs. In order to enhance the riding comfort, two additional wet clutches are mounted in this novel CPSHT and the relevant coordinated control strategy is developed. Firstly, after the description of the mechanical and hydraulic parts of the novel CPSHT, the dynamic plant model including driveline model, engine ripple torque and clutch torque is deduced. Secondly, the mode transition process in the original and current designs are compared and analyzed with the equivalent level diagram and the encountered problems are stated. Thirdly, a coordinated control strategy is designed to determine the target motor torque, clutch torque, engine torque, and the moment of fuel injection based on the second-order sliding mode control (SMC). A Kalman filter (KF) based estimator is deduced to estimate the clutch transmitted torque with the information of two electric motors. In addition, an active damping algorithm is applied further to suppress the oscillation during the mode transition. Finally, the effectiveness of this coordinated control strategy is validated in simulation. The results from simulation indicate that the proposed coordinated control strategy can indeed suppress vehicle jerk and improve the riding comfort during mode transition.