Regenerative Braking Of Estimated Braking Efficiency Research On Fuzzy Control Strategy

To solve the problem of environmental pollution and energy crisis,new energy vehicles are developing rapidly in China.However,now is the initial stage of the traditional car to the new energy vehicle transition,and a large number of new energy vehicle technical problems need to be resolved.Electric vehicle is one of the representatives of new energy vehicles,its current development bottleneck is the power battery technology.The key factor affecting people’s car is recharge mileage of electric vehicles,which is closely related to power battery technology.The application of regenerative braking technology can improve the energy efficiency and is an important research direction under the premise that the power battery technology can not achieve the breakthrough progress.When the best energy recovery rate is obtained,the regenerative braking control strategy is the key to whether the whole system can guarantee the safety of the brake and the driver’s good brake pedal feel.In the previous research,most of the regenerative braking strategies only considered the stability on the braking direction and ignored the braking efficiency constancy,thus these researches may have defect under the ideal braking condition.Based on the summary of the advantages and disadvantages of the current regenerative braking control strategy,a front driving electric vehicle is studied and the newly designed regenerative braking control strategy is put forward.The research results include the following aspects:(1)Based on the understanding of the advantages and disadvantages of the string and parallel control strategy,combined with the previous research on the front and rear axle braking force distribution strategy and the coordinated allocation strategy of electric and liquid braking force,the regenerative braking control strategy is designed that combines the initial distribution of the maximum front axle braking force with estimated mechanical braking efficiency fuzzy control.(2)During the braking process,the dynamic friction coefficient between the friction pairs is estimated by the friction brake pressure of the hydraulic braking system and the initial braking speed,and the corresponding three-dimensional spatial distribution is obtained.Using Matlab software to design the mechanical brake performance factor estimated model into simulink model.(3)Based on the Mamdani system,a regenerative braking fuzzy controller is designed.The controller structure is three inputs of the braking strength,the dynamic battery SOC and the estimated mechanical braking efficiency factor and an output of regenerative braking force distribution coefficients.Then through the multi-factor input fuzzy control,this can achieve the precise control of distribution ratio of electric and liquid braking force.(4)Based on ADVISOR brake control model,the initial distribution model of the maximum front axle braking force and electric,liquid braking force redistribution model are created,then the feasibility of the new model is verified.(5)The results of off-line simulation of frequent and constant braking condition and urban road condition show that:First,the front and rear axle braking force distribution adopts the strategy of the maximum front axle braking force to ensure the braking direction stability and the higher ratio of the front axle braking force.This creates the opportunity for the regenerative braking force of front driving test vehicle to achieve higher value.Second,the estimated mechanical brake efficiency factor is introduced into the fuzzy controller to ensure that the front axle friction braking force and the regenerative braking force are reasonably distributed according to the mechanical braking performance attenuation.Compared with the contrast test scheme,the efficiency of the whole braking system is improved to a great extent,and the energy recovery rate is improved.