Study On The Torque Coordination Algorithm For Driving Mode-transition Of Parallel Hybrid Electric Bus

Hybrid electric bus (HEB) contains more than two kinds of energy sources. Engine andmotor can participate in work or not based on working conditions in order to improve theperformance of fuel saving and emission reduction. Hybrid electric vehicle has manyworking mode based on the two energy sources working or not, so the mode can changefrom one to others. Because the dynamic torque response characteristics of motor andengine are different, the coupling torque of engine and motor may fluctuate largely whichhas a bad influence on the feeling of driver. In order to reduce the interruption andfluctuation of coupling torque, the problem of torque coordination between engine andmotor should be studied.Due to the difference between dynamic torque response characteristics of motor andengine, hybrid control system and input redundant control system with bumpless transfercontrol have been used in HEB mode-transition for improving vehicle power performanceand ride comfort during mode transition based on the biaxial parallel hybrid electric buswhich is the study object of the actual project. The main contents are as follows:(1) Analyze the operating mode of HEB and mode-transition from one to others. Themode-transition can be classified into two types: mode-transition with clutch operation andmode-transition without clutch operation. Analyze the process of two kinds of the mode-transition, and analyze the vehicle dynamic when mode-transition and obtain the jerk ofeach mode-transition which is the evaluation indicator. The factors which can have aninfluence on jerk are the torque dynamic response characteristics of motor and engine.Study the torque dynamic response characteristics of motor and engine based on realvehicle test, which laid a solid foundation for the study control strategy and modeling HEB. (2) Hierarchical control structure is used in the control strategy of HEB in this paper.Firstly, the required torque by HEB is allocated between engine and motor based on thelogic threshold control strategy which can improve the fuel economy performance;secondly, hybrid control system and input redundant control system with bumpless transfercontrol have been used in HEB mode-transition for improving vehicle power performanceand ride comfort during mode transition;(3) Theoretical modeling and experimental modeling method are combined in thispaper to model the HEB, and the model can be used to simulate the control strategy.Themodel mainly contains engine, motor, battery, AMT, etc.In order to reflect the dynamicprocess of mode-transition, the moment of inertia of every parts is simplified reasonably.To verify the torque coordination algorithm for driving mode-transition of parallel hybridelectric bus, the model of control strategy is set up and is integrated with HEB parts.(4) Verify the torque coordination algorithm for driving mode-transition formode-transition with clutch operation and mode-transition without clutch operation bysimulation. Compare the simulation result of dynamic coordination with the simulationresult with no dynamic coordination. The results show that the dynamic coordinationalgorithm when mode-transition can improve the vehicle power performance and ridecomfort.