Research On Coordinated Control Of Hybrid Power Mode Switching Based On Analysis Of Electromechanical Torque Coupling Characteristics

In the context of the upgrading and transformation of the automobile industry,the focus of automobile research and development has gradually tilted towards energy conservation and emission reduction.However,due to the limitation of the mileage of pure electric vehicles,there is still greater resistance in the development process.Based on the National Key R&D Program"New Energy Vehicles"special sub-project,the National Natural Science Foundation of China Jiangsu Province six talent peak projects,to study a power split the mode switching process of a hybrid electric vehicle.Hybrid electric vehicles will switch modes as the load changes during driving,but the switching process is a dynamic process involving the switching of the torque of the two power sources.The torque output by the power system will fluctuate greatly,which will produce shocks and affect the smoothness of the car.In order to reduce fluctuations and reduce the dynamic impact during the mode switching process,this article mainly focuses on the following contents:（1）Based on a power split hybrid electric vehicle,the structure of its power coupling system is analyzed.The torque and speed balance equation of the transmission system is established,and the relationship between the torque and speed of the engine and the two motors is discussed.And according to the load changes during driving,the work mode is divided,and then the two main driving modes of the vehicle are analyzed,the electric mode and the hybrid driving mode,and the energy flow and torque speed characteristics of these two modes are analyzed.（2）Establish the vehicle dynamics model of hybrid electric vehicle.According to the direction of energy flow in the model and the direction of signal transmission,a forward simulation model of the entire vehicle is established.According to the coupling characteristics of the planetary gears,a pure torsional dynamics model of the planetary gears is established.According to the coupling characteristics of the pure electric mode and the hybrid drive mode,the corresponding dimensionless form of the electromechanical coupled torsional vibration equation is derived for the following torsional vibration analysis.And the determination of the chaos threshold.（3）Optimization of hybrid electric vehicle working area based on electromechanical coupling analysis.The working modes of hybrid electric vehicles are different,and there is also a big gap in the electromechanical coupling characteristics of the transmission system.The two driving modes involved in the driving process of power split hybrid electric vehicles are studied:pure electric and hybrid driving modes.Establish the electromechanical coupling nonlinear dynamic equation in the corresponding working mode,and conduct torsional vibration analysis;study the influence of load,engine mechanical input excitation and motor electromagnetic excitation on the electromechanical coupling torsional vibration of the transmission system.Multi-scale method is used to solve the dynamic equation,and the amplitude-frequency response curve is drawn.According to the curve,the influence of load,engine mechanical input excitation and motor electromagnetic excitation on the electromechanical coupling torsional vibration of the transmission system is studied.Solve and analyze the equilibrium point of the non-disturbance Hamilton system.After adding the disturbance term to the Hamilton system,the chaos threshold in pure electric mode and hybrid driving mode is solved by Melnikov method,so as to obtain the working range of engine and motor in the two driving modes Optimization scheme:When the vehicle is running in pure electric mode,the motor MG2provides the torque to drive the vehicle,and the torque of the control motor MG2 is T_MG2≤74N·M.When the vehicle is running in the hybrid drive mode,the motor MG2 and the engine provide driving torque at the same time,the torque provided by the control motor T_MG2≤63N·M,and the rest of the driving torque is provided by the engine.The engine should be controlled to ensure that the system does not appear chaotic.The speed range is1500rpm≤n_E≤4237rpm.Make the system stable under the given distribution plan.（4）According to the proposed work domain optimization scheme,the mode switching process is coordinated and controlled.Aiming at the problem of engine dynamic response lag,a real-time engine torque estimator is designed,and the torque fluctuation at the power coupling output end is reduced through motor torque compensation.Using Matlab/Simulink software platform for simulation verification,the simulation results show that the entire switching process is basically controlled in about 0.4 second and the switching process can be completed quickly.Although the vehicle speed difference during the mode switching process before and after the control can be within a reasonable range,the vehicle speed tracking error fluctuates less during the mode switching process after the control,and the vehicle speed tracking situation is better.Moreover,the proposed torque compensation control strategy can effectively reduce the impact of the mode switching process.Finally,the rapid prototype of the control strategy is developed based on the D2P platform to verify the effectiveness of the control strategy.Due to the participation of the coordinated control strategy,the smoothness of the entire mode switching process is greatly enhanced,and the generated torque can be better controlled during the sudden torque change The magnitude of the impact,the maximum positive impact of the vehicle is reduced from 10.16m/s³ to 4.46 m/s³,and the maximum negative impact is reduced from-20.05m/s to-6.08 m/s³,and the impact duration and fluctuation range are greatly reduced.The fluctuation range is reduced from 36.21m/s³ to 10.81 m/s³,which greatly reduces the maximum longitudinal impact during the switching process.