Research On Torque Coordination Control Of Power And Transmission For Coaxial Parallel HEV Driving-mode-switch

In recent years,the issues of energy shortages and environmental pollution are highlighted,so that the automotive industry energy efficiency,environmental protection requirements are increased.Thus the development of new energy vehicles is accelerated.Hybrid cars have the advantages of pure electric vehicles and traditional cars,which is favored by many domestic and foreign research institutions and companies.In this dissertation,the coaxial parallel hybrid bus is researched,which uses automatic clutch as the power coupling mechanism of engine and motor.A variety of work modes are formed through the clutch combination,which will bring the mutation of output torque and speed,affecting the stability of vehicle power output and vehicle driving performance.Thus this paper studies the coordinated control between the dynamic torque(engine,motor torque)and transmission torque(clutch torque)in the mode switching process,in which the clutch engages or separates.Firstly,the dynamic system layout structure of the coaxial parallel hybrid bus is analyzed.The coaxial parallel hybrid system model is established on the MATLAB/Simulink platform,which includes the engine model,the motor model,the diaphragm spring clutch model,the clutch actuator model,AMT model and so on.The nonlinear manipulative characteristic model of clutch torque is studied emphatically.Based on the dynamic programming theory,an improved dynamic programming algorithm is proposed to reduce the computational burden of the computer and to avoid the inaccurate boundary calculation results.The improved dynamic programming algorithm is used to study the mode switching process including the clutch engagement and separation action.The sliding friction and impact are used as assessment criteria,and the engine torque,the motor torque and the clutch friction torque are optimized by the algorithm.On the basis of torque optimization,the dynamic and transmission torque following control strategy in the mode switching process is studied.According to the knowledge of hierarchical control of hybrid system,this paper carries out hierarchical control to the torque coordinated follow in mode switching process.The torque of the engine,the motor and the clutch are optimized as the target torque.The digital PID controls the engine,the motor and the clutch to follow the target torque.Considering that the clutch torque response is slower than the response of the engine and the motor,this paper proposes the control strategy of motor and engine torque compensating clutch torque variation.Based on the MATLAB/Simulink simulation platform,a coaxial parallel HEV mode switching control model is established on the basis of the torque coordination and torque control of the hybrid bus.Simulation analyses are carried out for two typical mode switching processes involving clutch engagement and for one model switching process involving clutch separation action.The proposed dynamic coordination algorithm and the effect of control strategy are verified.