A control strategy to reduce torque variation for dual-mode power-split hybrid electric vechile during mode shift

The paper presents a mode shift control strategy of dual-mode power-split hybrid electric vehicle during the mode shift phase, intended to reduce the torque variation in the driveshaft and improve the shift quality. To evaluate the shift characteristics of this power-split hybrid electric vehicle, the detailed dynamic models are developed. Based on the dynamic models, a mode shift performance simulator is built using MATLAB/Simulink, and simulations are carried out. To analyze the shift characteristics during the mode shift phase, a bond-graph model for the transition state is constructed, and dynamic equations are derived. From the bond-graph model and dynamic equations, it is seen that the transition torque occurs because of the inertia torques of the first motor/generator and the second motor/generator. To avoid the unwanted transition torque, a mode shift control strategy that coordinates the motor-generator torque to compensate for the transition torque. It is found that the torque variation in the driveshaft during the mode shift phase is effectively reduced by the proposed control strategy.