Study On CVT Hybrid Electric Vehicle Regenerative Brake Control Strategy Under Overall Braking Condition

Regenerative braking is an important function of hybrid electric vehicle. Kinetic energy or potential energy of vehicle can be converted into electric energy by motor through utilization of regenerated braking under safety braking conditions. Meanwhile the braking force is produced. So regenerative braking can reduce engine fuel consumption, exhaust gas emission and brake wear efficiently. When hybrid electric vehicle brake, there are engine brake,motor brake,wheel brake and combined brake. Therefore, further study braking energy distribution strategy of different braking condition and obtain optical distribution law of motor brake engine brake and wheel brake that can improve fuel economy and ensure brake safe.The focus of this paper is on Chang An Hybrid Electric Vehicle with CVT. The braking energy distribution and control strategy is researched, and regenerative braking system is Modeled simulated and analysis. The main results include:(1) The braking forces distribution of CVT hybrid electric vehicle is analyzed, considering effects of the Engine braking,battery quick charging characteristic,the ISG motor generating with high efficiency,CVT speed ratio. A regenerative braking control strategy of overall braking(downhill,skidding and general brake) for hybrid electric vehicle is proposed.(2) Based on engine brake theoretical analysis, engine brake model is established by solving the calculation program. The engine brake torque as engine rotational speed is measured, which helps to building modes.(3) Based on braking dynamics analysis of downhill, the brake force distribution model and complete vehicle model of driving down slope road is established and simulated. The results show that the proposed control strategy. Vehicle speed can be transited From initial vehicle speed to target vehicle speed stability by the proposed control strategy, and Braking-Energy is efficient recovery.(4) Based on braking dynamics analysis of skidding and general brake, the brake force distribution model and complete vehicle model of skidding and general brake is established. The regenerative braking system models are simulated under skidding,the typical city driving cycles(1015,EUDC and UDDS) and the typical braking modes(z=0.45). The simulation results illustrate the correctness and effectiveness of the proposed control strategy, and has greater application value.