Research On The Shift Strategy Of AMT With Gear Shift Assistant Mechanism

The development of energy-saving vehicles,namely hybrid electric vehicles,is an important way for China to fulfill its carbon emission commitment and improve residents’ quality of life at the present stage.Hybrid electric vehicles have greater power,higher fuel economy and lower exhaust emissions than traditional fuel vehicles,so they have great market potential.Mechanical automatic transmission(AMT)has the advantages of high efficiency,wide torque range and long service life,which is suitable for the power transmission of commercial vehicle hybrid electric system.The AMT with gear shift assistant is a new hybrid gearbox,which can effectively improve the power interruption during the shift process of AMT.Aiming at the optimization problem of AMT with gear shift assistant for gear shift strategy,this thesis takes the hybrid electric truck with AMT with gear shift assistant as the research model,designs the gear shift strategy and carries out simulation verification.The main research contents are as follows:Firstly,the research model is determined to be a parallel hybrid electric truck,and its structure,working principle and five common working modes are analyzed.Then,through the way of comparative analysis,the various parts of the model are selected,the dynamic performance indicators of the vehicle are established,and the dynamic parameter matching of the various parts is completed.Finally,the dynamic performance simulation of the parameters matched in this thesis is carried out by using the Advisor model.Secondly,the characteristics of each shift law and the solving method of the shift law are analyzed,the control parameters of the shift strategy designed in this thesis are determined,and the analytical method derived from the formula is selected as the solving method of the shift law in this thesis.Finally,a two-parameter dynamic shift strategy considering shift impact degree,an optimal economic shift strategy considering fuel consumption and a comprehensive shift strategy considering both are designed,which provides a new idea for scholars to carry out related research in the future.Thirdly,the driver model and the simulation model of each part of the transmission system are established in the simulation modeling software Simulink,and the structure and working principle of AMT with gear shift assistant are analyzed emphatically.On this basis,the vehicle model in each state and the logic model of the state shift based on the gear shift strategy are established.Fourthly,the existing divergent two-parameter shift strategy based on throttle opening degree,the dynamic shift strategy,the economic shift strategy and the comprehensive shift strategy considering the shift impact degree designed in this thesis are simulated in Model-Inthe-Loop(MIL).The simulation results under FTP 75 condition show that,The gear shifting strategy designed in this thesis can significantly reduce the fuel consumption of vehicles,and the vehicle gear selection under this strategy is more reasonable,and the gear shifting process is more stable.The simulation results not only verify the rationality of the proposed PID control driver model and the effectiveness of the shift assisted AMT structure,but also focus on the superiority of the designed shift strategy.