Research On Torque Coordination Control Strategy Of Hybrid Electric Truck Power Transmission Process

Facing the aggravation of environmental pollution,the gradual lack of fuel resources and the increasingly stringent laws and regulations,electric vehicles are gradually popularized in society.Because of the heavy truck’s large demand for power and long driving distance,the use of pure electric power can not meet the demand for driving distance.Hybrid trucks can be used to maintain transport capacity,reduce emissions and save energy at the same time.Medium and heavy hybrid electric trucks have a large demand for torque.If the output torque of power source is not coordinated controlled,the transmission system will be impacted,the service life of components will be reduced,the driving comfort will be worse,and even the power structure will be damaged.This paper studies the coordinated control of the torque transfer process of a hybrid heavy truck,and designs the torque control strategy for it.The main research contents are as follows:(1)The power system structure of hybrid truck is analyzed,and the parallel hybrid power structure with single clutch is selected.AMESim is used to model the power components and systems of hybrid electric trucks.(2)According to the working state of power system and the characteristics of power demand,the vehicle model is divided into seven modes.The state of engine and motor in each mode is analyzed,and the mode division and threshold selection are completed.The evaluation index of the torque coordination strategy and the whole vehicle’s torque control are analyzed.The two processes of the maximum change of the vehicle’s torque are mainly controlled: the switching and shifting process between the single drive mode of the motor and the dual power source mode.In order to optimize the shift process,a torque dynamic control strategy without clutch is designed.The active control strategy of engine and motor is designed,and the clutch speed control strategy is adjusted at the same time to reduce the impact,reduce the engagement time and sliding work;the synchronizer engagement control strategy after the motor active speed control is designed;and the motor speed control fuzzy PI controller and the clutch engagement fuzzy PID controller are designed.(3)Aiming at the shift control strategy with clutch,Simulink is used to model the shift control strategy,and the function model used in each step and the important parameters and control methods of model control are elaborated.The shift control process of clutch-free shift control strategy and single motor mode switching with dual power source mode is modeled.(4)The joint simulation of three cases is carried out,and the simulation results are analyzed.The time of synchronizer engagement after motor active speed regulation is 0.093 s shorter than that without motor speed regulation,and the impact is 25.94 m/s3 lower.Fuzzy PI controller for motor speed regulation can shorten the time of speed regulation by 0.045 s compared with ordinary PI controller.Fuzzy PID control with clutch engagement reduces 0.013 s of control time,19.24 m/s 3 of impact and 0.02 J of sliding work compared with ordinary PID control.The shift time without clutch is 0.342 s shorter than that with clutch.