Research On Mode Switching Coordinated Control Of A Hybrid Electric Vehicle

Hybrid electric vehicles contain multiple power sources and various working modes.When the vehicle switches its working modes,there will be insufficient power or excessive output torque ripple in mode switching process due to different dynamic responses between power sources or unsuitable control strategy.The impact degree caused by this and the influence of power coupling mechanism dynamic characteristics on the vibration and noise characteristics of vehicle in mode switching process will affect the riding comfort.Therefore,it is very necessary to develop a suitable coordinated control strategy for the mode switching process.This paper takes a hybrid electric vehicle as research object,the dynamic model was set up,the dynamic coordination control strategy of mode switching was established,and the effectiveness of the control strategy was verified by the joint simulation.In addition,the rigid flexible coupling dynamic model of power coupling system was established,the multi-body dynamics simulation was carried out in order to observe the dynamic characteristics of the power coupling system during the process of mode switching.The specific work of the paper is as follows:1.Problem posing and vehicle modeling.The vibration characteristics test of a hybrid vehicle was carried out in the mode switching process.It is found that there is a longitudinal impact degree in the mode switching process,so a coordinated control strategy is needed for it.The structure characteristics and working characteristics of the hybrid electric vehicle were analyzed.The single degree of freedom vehicle model,the power source models and the transmission model were discussed and analyzed,and the dynamic model of the whole vehicle was established in the AMESim.2.Engine torque estimation.The BP neural network based on genetic algorithm optimization was used to estimate engine torque.With the weight and threshold of BP neural network optimized by genetic algorithm,the engine torque estimation model was established by it based on the experimental data of engine.3.Dynamic coordinated control strategy formulation and verification.The dynamic characteristics of engine and motor were analyzed.In view of the process of “engine starting or stopping”,the corresponding dynamic coordinated control algorithm was studied.An engine start coordination control algorithm from pure electric mode to combined driving mode was designed,and an engine stopping coordination control algorithm from combined driving mode to pure electric mode was designed by the principle of motor torque compensation.The evaluation index of the coordination of mode switching with the impact degree was proposed.To verify the effectiveness of the strategy,the vehicle control strategy and dynamic coordination control strategy were established in Matlab/Simulink,and the joint simulation analysis was carried out with vehicle model in AMESim.It is verified that the proposed dynamic coordination control strategy can greatly improve the ride comfort of mode switching.4.Dynamic simulation.The three-dimensional solid model of the double planetary gear power coupling mechanism was established in ADAMS,and the rigid flexible coupling multi-body dynamic model of the power coupling system was established with ANSYS.The dynamic characteristics of the power coupling system in mode switching process were simulated and analyzed with the engine starting as an example.The results showed that the time-frequency characteristics are all good,and the mode switching process works smoothly,which is beneficial to improve the vibration and noise level of vehicle.