Dynamic Coordination Control Strategy of Dual-Planetary Power-Split Hydraulic Hybrid Vehicle

The ride comfort of driving has higher requirements for the double planetary row hybrid hydraulic hybrid system applied in the bus. However, compared with the electric hybrid system, the vibration problem of the hydraulic hybrid system is particularly prominent due to the different dynamic characteristics of the engine and the hydraulic pump/motor, as well as the structural characteristics of the multi clutch/brake system. In the process of driving mode switching and rear planetary transmission, the timing of state transition of power and executive part has a great influence on the output of the system torque, which leads to the impact of the whole vehicle. Firstly, considering the real-time response state of the power source and the driving demand torque analyzed by the driving operation, the “dynamic transition torque coordination control” function module is added to revise the demand torque for the second time, to solve the total output torque fluctuation caused by the change of control logic and torque distribution mode before and after the driving mode switching, so as to realize the system coordination control during the mode switching. Then, through the dynamic analysis of the rear planetary system, the approximate linear relationship between the system output torque and clutch/brake friction torque, pump/motor output torque is obtained, and the torque control law of pump/motor is obtained. At the same time, the coordination control logic between the power and the actuator in each stage is determined. Finally, the joint simulation results of Simulink and AMESim show that the ride comfort of the vehicle is greatly improved during the impact prone multi-mode switching and the upshift/downshift of the rear planetary row.