| Hybrid electric vehicle(HEV)has the advantages of both electric vehicles and traditional vehicles,which can recover energy during braking thereby improving energy utilization,and has become a research hotspot at home and abroad in recent years.This paper takes a new type of hybrid electric vehicle as the research object.In a series of studies on its regenerative braking system,the coordinated distribution of braking force of front and rear axle and electromechanical braking force of the front axle of HEV during braking process is emphatically studied,and the influence of gear change of HEV on the power generation efficiency of the motor was further considered.The research work in this paper can provide a certain theoretical basis for the development of regenerative braking technology of hybrid electric vehicle,and has a certain research significance.Firstly,based on the powertrain of a new hybrid electric vehicle(HEV),this paper builds the model of the vehicle and its powertrain based on AMESim platform,which mainly includes sub-models such as driver,motor,power battery,engine and transmission system.The model was verified by the analysis and comparison of simulation calculation and vehicle test data.·Secondly,this paper proposes a multi-level regenerative braking control strategy for the purpose of improving energy recovery efficiency.The first layer distributes the braking force of the front and rear axles based on the total braking force demand.On the premise of vehicle braking safety,the braking mode of HEV is divided into three types according to the braking strength,and the braking force distribution of front and rear axles is carried out for each braking mode.The second layer redistributes the braking force on the front axle.By designing a fuzzy controller which takes the speed V,the braking intensity z and the power battery SOC as the input and the proportional coefficient of regenerative braking K as the output,so as to realize the coordinated control of mechanical braking force and motor braking force of the front axle.The third layer conducts research on shift control during braking.In this paper,the front axle regenerative braking torque and wheel speed are optimized variables,and the power generation of the motor is used as the optimization target.An optimal economical shift control strategy is proposed to further improve the energy recovery efficiency of hybrid electric vehicles.Finally,a co-simulation platform was built based on AMESim and Matlab/Simulink software.Different braking strength conditions were selected.Selecting different braking intensity conditions,based on the regenerative braking control strategy proposed in this paper,the distribution of front and rear axle mechanical braking force and regenerative braking force was studied.In order to further analyze the energy recovery effect of this multi-level regenerative braking control strategy,the regenerative braking control strategy was simulated based on NEDC and WLTC conditions.The results show that,compared with the ideal regenerative braking control strategy and the parallel regenerative braking control strategy,the multi-level regenerative braking control strategy proposed in this paper can achieve better braking energy recovery effect. |
