Study On Gear-Shifting Mechanism And Cooperative Control Strategy Of Single-Shaft Parallel Hybrid Electric Powertrain System

Depending on National High-tech R&D Programs(863 Program)Evaluation and Research on Typical Electric Vehicle(Commercial Vehicle Powertrain)and Technical Research on Industrialization on Foton Ou Hui Medium Hybrid Electric Vehicle,the thesis mainly focuses on the research of shift process quality control for AMT which applied on single axle parallel hybrid powertrain system.The major theme of this paper is to improve the system's comprehensive performance.Aiming at some typical problems of AMT such as difficult gear-shift and shift failure that still exist after the completion of speed synchronization of the synchronizer's driving and driven parts during the AMT's shifting process without clutch's disengagement,theoretical analysis and experimental research are carried out from the areas of modeling of rigid-flexible coupled system,torque estimation and closed-loop control,cooperative control of motor assist torque and shifting force,and so on.The ultimate goals are to improve the reliability of gear shifting,to reduce the whole shifting time,and to restrain jerk of shifting.Firstly,rigid-flexible coupled and decoupled dynamical models of single shaft hybrid powertrain system are established by mechanism method and experimental method and the correctness of the model is validated through vehicle's experimental data.The reason and character of torsional vibration generated by shifting process of driveline are analyzed.At the same time,this paper reveals the driveline's coupling dynamic characteristics and law of vibration,which provides the theoretical foundation for the control strategy of the unloading stage of the gear shifting process.Secondly,a powertrain system's torque estimator is designed based on Extended Kalman filter algorithm to accurately estimate the torque of the vehicle's driveline.According to the accurate estimation of the transmitted torque,a torque tracking closed-loop controller for the powertrain system in the stage of gear shifting process is designed.Simulation results show that this algorithm also has good robustness in the case of system model's uncertain or uncertain of the external load.Compared with the traditional open-loop control,the closed-loop control based on torque transmitted in driveline system can better damp the speed resonance of gearbox's output shaft and restrain vehicle's jerk after picking neutral gear.Besides,the mathematical model of engine-motor-transmission direct connection system is established based on multi body dynamics theory.The shifting characteristics of hybrid automated mechanical transmission are deep analyzed.And then the failure reasons while shifting under the circumstances of synchronizer's speed synchronization are summarized.In this paper,a cooperative control method of motor's assisted synchronization and actuator's force is proposed.This method raises reliability of successful shift,and guarantees good shifting quality as well.According to the specific phase relationship among synchronizer's sleeve,block ring,cone gear in particular speed condition during the engaging process of the synchronizer,a coordinated control strategy of motor's assisted synchronization and shifting force is proposed based on the shifting displacement,the speed feedback of driving and driven part of the synchronizer to improve the quickness and reliability of the engagement process of the synchronizer.At last,the shifting quality control strategy of hybrid powertrain system based on torque closed loop algorithm is validated by bench test and vehicle test.The experimental results show that quick and smooth unload process can be achieved by sliding mode control of driving shaft's zero torque tracking with the constraint of the maximum jerk at different gears.At the same time,the output shaft's speed oscillation can be damped after picking neutral gear to guarantee better driving comfort.Another conclusion can be obtained is that the reliability of shifting process can be increased through the cooperative method of motor's assisted synchronization and shifting force cooperative control depended on the feedback of shifting displacement and speed information of driving and driven parts of the synchronizer during the shifting process.