Study On Regenerative Braking System Of Hybrid Electric Vehicle

Hybrid Electric Vehicle(HEV: Hybrid Electric Vehicle) has been a new orientation for vehicle as it combines the two advantages of low emission and low fuel consumption. As a key technology to reduce energy consumption, more and more importance has been attached to regenerative braking,which has been extensively utilized by Hybrid Electric Vehicle manufactures. Regenerative braking is a technology to transform part of the vehicle's kinetic energy into other forms (such as electricity) or transfer this part of energy to other parts(such as Super High-speed Fly Wheel) to store so that the energy could be stored when it is braking. This part of the energy will be released when the vehicle drives or accelerates, so it can improve the vehicle's fuel economy effectively and prolong the mileage.Regenerative braking system and its calculation is the key point of regenerative braking. At present, the research on Hybrid Electric vehicle in our country is just at the beginning, most of them are in the pilot phase, so the study on it is relatively weak. Considering the braking energy recovery and braking stability, most HEV utilizes both hydraulic braking and regenerative system at the same time, that is, to reserve the intrinsic hydraulic braking system and introduce the motor into braking. How to make the hydraulic braking system cooperate with the regenerative braking system stably and to get the most recovery is the key technology to HEV. Currently there are many problems in the application of the regenerative braking system on HEV in our country, such as the hydraulic braking force is inaccurately controlled, and the limitations on reduced energy etc.. There is a gap between domestic and foreign regenerative braking system. Based on the achievement of our laboratory in the national"863"program—hybrid electric city vehicle, and also for the demand of developing the hybrid electric vehicle"CA7220E"in the"eleventh Five-Year plan", some researches have been made on regenerative braking system, by consulting both domestic and foreign literature.Firstly, the author rebuilt a set of regenerative braking system on the basis of"CA7220E"ABS braking system, which could meet the requirement of hybrid electric vehicle braking system in a variety of working conditions.After doing some analyses about the braking process of hybrid electric vehicle, the author consulted three typical braking force distribution control strategies, combining with the actual demand of the HEV, and finally the author proposed a braking force distribution control strategy, which could effectively improve fuel consumption on condition of the vehicle's braking stability. This strategy takes a variety of the factors into account. According to the energy recovery characters of electric motor, this strategy effectively improves energy recovery by applying a new greatest electric power system with the speed relationship.A dynamic vehicle model for regenerative braking system was built up under the environment of AMESim in this paper, which included some models for the key parts (the motor model, the battery model and the semi-empirical tire model and so on) of the HEV braking system, a ABS hydraulic control model and the whole dynamics simulation model. A braking force distribution control arithmetic model was built under the environment of Matlab/Simulink, based on the proposed braking force distribution control strategy. We can do a co-simulation with this arithmetic model and the dynamic vehicle model to assort the motor braking system with the ABS hydraulic braking system. A sub-model was also built for ABS hydraulic braking system to control the switch valves. Do simulation with the co-simulation model under different typical braking cycles. Adjust the parameters according to the simulation results. The results indicated that this HEV braking system could improve the regenerative recovery efficiently under new control strategy on the premise of the stability.Finally, based on dSPACE, the author built hardware in loop test platform for ABS hydraulic adjust organ. Under the circumstances, the author completed hardware in loop test of the ABS hydraulic adjust organ in typical braking condition, and finished control response test and control precision test. The results indicated that the model of hydraulic system is close to that of the real system. Also it is verified that ABS hydraulic adjust organ can be effectively controlled by regenerative braking system and ABS control strategy is able to prevent wheels from locking. With the co-ordination between the regenerative braking and hydraulic brake system, and braking energy recovery is highly raised and vehicle stability is ensured.As one of the key technology of HEV, the regenerative braking system plays an important role in HEV study and research on regenerative braking system and its control strategy. This paper will be quite significant for the further study of regenerative braking system on hybrid electric vehicle.