Research On Mode Switching Coordinated Control Strategy For P2 Hybrid Electric Vehicle

With the deterioration of energy and environment,new energy vehicles have become a research hotspot,among which hybrid electric vehicles have become a better choice because they effectively balance the advantages of pure electric vehicles and traditional fuel vehicles.P2 hybrid electric vehicle is a kind of parallel hybrid vehicles which has been researched and applied widely.However,the hybrid electric vehicle with this configuration has the problem of rough driving when the driving mode is switched.Therefore,based on the P2 hybrid electric vehicle,the research of this paper is to design the mode switching control strategy and coordinate the main components of the powertrain system at the aim of reducing the impact vibration in the mode switching process.In order to design a reasonable and effective coordinated engine-start control strategy,this paper studies the dynamic characteristics of different driving modes and establishes the kinetic equations.Meanwhile,considering the dynamic characteristics of motor,engine and clutch,the simulation model of the P2 hybrid electric vehicle is established.The engine resistant torque below idle speed is predicted by combining the experimental engine resistant torque above idle speed and the 1-D engine simulation model built in GT-suite.In order to accurately reflect the dynamic response characteristics of the separating clutch,the hydraulic system is established.In this paper,the control methods of motor,engine and clutch are proposed respectively.To change the speed and torque control objectives in the process of mode switching,the control mode signals are added in the control method of motor and engine to switch the control objectives.Based on the kinetic analysis and the control methods of main components,this paper designs a seven-phase coordinated engine-start control strategy to achieve coordinated torque control for meeting the dynamic performance and reducing the impact of engine-start process simultaneously.The motor power limited and unrestricted conditions are fully considered in the coordinated engine-start control strategy proposed in this paper,so that the strategy can play a good control role in both conditions.Furthermore,the main design parameters of the mode switching process,the maximum drag torque and the engine ignition speed,are optimized to obtain the parameter combination for the optimal equivalent fuel consumption.In order to verify the effectiveness of the designed engine-start control strategy,simulations and tests are carried out.Through the simulation results,it can be seen that whether the motor power is limited by the battery discharge power or not,the designed multi-phase engine-start coordinated control strategy can effectively limit the impact of the mode switching process within±10 m/s~3,which means it can satisfy the requirements of regulations,and also ensure the drivability.Test results also validate the effectiveness of the control strategy.