Research On Compound Baking Control Strategy Of Pure Electric Vehicle

Current regenerative braking technology is an important method to extend the driving range of pure electric vehicles.The braking system of pure electric vehicle includes motor braking and hydraulic braking.It is a composite braking system with dynamic transformation of braking force.The advantages and disadvantages of vehicle braking system have an important effect on braking energy recovery and braking safety.Therefore,it is necessary to study the electro-hydraulic compound braking control strategy of pure electric vehicle to coordinate the control of these two kinds of braking forces,which is of great significance to ensure the safety of vehicle braking,improve the recovery of braking energy and prolong the range of life.In this thesis,the compound braking control strategy suitable for pure electric vehicle is worked out.Firstly,the structure,principle and influence factors of the regenerative braking system of pure electric vehicles are analyzed.Based on the in-depth study of the braking mechanical characteristics,typical compound braking control strategy and braking regulations,the braking force allocation strategy of the maximum braking energy recovery is proposed,and the braking force distribution mode of the front and rear axles of the vehicle is determined.Secondly,based on the fuzzy logic control theory,a fuzzy control strategy is proposed to coordinate the distribution ratio between the power of the electrical mechanism and the power of the hydraulic suppression.A fuzzy controller with three inputs and one output is designed,and the proportion of the regenerated braking force in the compound braking is determined.Then,based on Cruise vehicle simulation software,a pure electric vehicle model is established,and the key components of the vehicle are theoretically analyzed and the parameters are set.In order to make the motor output torque closer to the actual and realize the smooth transition,the model of motor regenerative braking torque limit is established and the braking force correction factor is added.Then,the simulation model of compound braking control strategy is built in Matlab/Simulink software and simulated with Cruise model.The braking performance,acceleration performance and cycle condition of the vehicle are analyzed,and the superiority of the compound braking control strategy is verified.The simulation results show that the braking and accelerating performance of the vehicle is good,and the braking energy recovery rate and the range of life are obviously improved in the cycle working condition.Finally,the fuzzy control rules are optimized by genetic algorithm and the fuzzy controller is redesigned.The simulation results show that the optimized control strategy has a certain improvement in the battery SOC value and the continuous driving mileage than the pre-optimization control strategy,which proves the effectiveness of the genetic algorithm to optimize the fuzzy control.