Forward Modeling And Simulation For Regenerative Braking System Of CVT Hybrid Vehicle

Regenerative braking (energy recovery braking) is one of key advantages of HEV, which has a direct impact on fuel economy, emission and vehicle security. When HEV is braking, regenerative braking system will make the motor become a generator for generating electricity through the power train system and supplying the whole braking forces or partial braking forces at the same time. Finally, electric energy is saved into the battery pack. Regenerative braking not only realizes the braking and deceleration, but also recovers the kinetic energy.CVT hybrid electric vehicle can automatically change the speed ratio continuously. When HEV is in braking situation, it can be made the motor work on the most efficient region by adjusting the ratio of CVT to adapt to the rotate speed of motor, thereby reclaims energy mostly.Focus on CVT Hybrid Electric Vehicle with ISG, the deeply theoretical researching, system simulation and experiment performance evaluation have been completed in this paper. 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 and clamping force control during braking, a regenerative braking control strategy for hybrid electric vehicle is proposed.2. According to the battery quick charging characteristic and ISG motor generating with high efficiency, the changing rules of motor generating and battery charging efficiency are analyzed, an generating optimal working line with high efficiency combined battery with motor is drawn, and CVT ratio and clamping force control strategy are proposed based the optimal working line during braking.3. Based on the analysis of modeling method of driver model, a method built model for the vehicle deviation system in the driver model, adopting PID control and fuzzy logic control respectively; the modeling methods are simulated and the simulation results are analyzed and compared in detail. The results show that the accuracy of the driver model with fuzzy logic control is better.4. Based on forward modeling idea, according to bench experiment data of the engine,ISG motor and NiMH battery, combined with numeric modeling and theory modeling, forward simulation model for regenerative braking system of CVT hybrid electric vehicle is built.5. The evaluation indexes for regenerative braking system simulation are proposed, and the regenerative braking system models are simulated under the typical braking modes(30km/h,40km/h and 50km/h) and the typical city driving cycles(EUDC,ECE+EUDC,1015 and UDDS),the models are simulated in the condition of combined battery with motor working together with high efficiency and motor working lonely with high efficiency. The simulation results are analyzed to proof whether the braking distribution control strategy in this paper can satisfy with the requirement of vehicle braking safely or not and the accuracy of the energy recovery and the built HEV simulation models.6. Considering the configuration and parameters of CVT hybrid electric vehicle with ISG, a Hardware In the Loop Simulation (HILS) platform for the regenerative braking system is built, CVT ratio control,ISG motor braking torque control and regenerative braking hydraulic system control blocks are built under dSPACE. According to different velocity and braking severity, the regenerative braking experiment is done on the test bench. Test results show that the proposed regenerative braking control strategy in this paper can improve recovery rate effectively.