Research On The No Power Interruption Switching Process For Two Motors Hybrid Electric Vehicle

The explosive growth of car ownership has led to huge resources and environmental pressure.An effective solution to this problem is developing Energy saving and new energy vehicles which including the pure electrical vehicles(PEVs),the hybrid electric vehicles(HEVs)and the fuel cell vehicles(FCVs).Overall considering the cost,driving range and safety,the HEVs have attracted widely attention from vehicle companies and research institutions who have put a large amount of resources into the research of HEVs.The current HEVs coupling mechanism mainly consists of fixed shaft gears and planetary gears.The planetary gears could switch the working modes of power sources rapidly.However,the complex construction reduces the transfer efficiency of the planetary gears.Many vehicle companies add motors to the driveline of traditional vehicles,and the transmissions are remained to increase the range of power system output torque and speed.To solve the power interruption during gear shifting in traditional HEVs with Automatic Mechanical Transmissions(AMT),the following research work is carried out in this paper:A HEV power system which mainly consists of one engine,two motors and a transmission with four gear ratios is proposed.Firstly the construction and working principle of the system are introduced,and the status of clutches and synchronizers in every working mode are analyzed.Based on dynamic theory and vehicle operating characteristics,the starting process and gear shifting process are analyzed,and the dynamic formulations of every stage are built.The parameters matching of power system is conducted targeting a B class car C70 from the BAIC,and the energy management strategy and torque allocation strategy are designed according to the efficiency characteristics of power sources and transmission ratios.The engine and motors working areas are divided,and the output torque of engine and motors are determined aimed at getting highest system efficiency.Vehicle model is built with the AMESim software,and hierarchical control strategy which includes the shifting process control and system components control in each period is built with the Matlab/Simulink software.The motors and engine speed control strategy,the clutches and synchronizers position control strategy and the torque coordinated control strategy constitute the main parts of components control strategy.The starting up process and gear shifting process are simulated with these models.The simulation results show that coordinating control the output torque of the engine and the motors could significantly reduce the vehicle jerk during starting process,which means improvement of driving comfort.The HEV system proposed could ensure the smooth change of output torque without power interruption during gear shifting,and the vehicle jerk is restricted in reasonable range.