Research On The Key Technology Of Braking Energy Recovery For Front-drive Pure Electric Vehicles

Compared with traditional fuel vehicle,pure electric vehicle has become the trend of automobile development because of its advantages of high energy efficiency,zero pollution in use process and relatively simple structure.However,due to a series of bottlenecks in the development of battery technology,the insufficient range has become a key factor restricting the rapid development of pure electric vehicles.The braking energy recovery technology of pure electric vehicle can convert part of the kinetic energy of the vehicle into electric energy to charge the battery when braking,thus extending the range of the electric vehicle.Therefore,it is of great significance to study the key technologies of braking energy recovery for pure electric vehicles.This paper takes the braking energy recovery control strategy of a front-wheel drive pure electric vehicle as the research object,aiming at recovering braking energy as much as possible under the premise of ensuring vehicle braking safety,so as to improve the driving range of the vehicle efficiently and increase the economic performance of the vehicle.The research results of this paper will further enrich the braking energy recovery control strategy of pure electric vehicles,and provide some methods and ideas for vehicle design and development.Specific research work is as follows:(1)on the basis of reviewing the background and research status of pure electric vehicle and its braking energy recovery technology,this paper expounds the principle of braking energy recovery technology for pure electric vehicle,analyses the key factors affecting braking energy recovery,and designs the structural scheme of braking energy recovery system for whole vehicle,which lays a theoretical foundation for the research of braking energy recovery control technology.(2)according to the relevant parameters of the electric vehicle,considering the power and economy requirements of the vehicle,the main components of the traditional power system of the vehicle are selected and matched.Then,the whole vehicle model is built by using CRUISE simulation software,and the power and economy simulation analysis is carried out according to the national standards.The simulation results meet the design objectives,verify the correctness of the vehicle model,and provide a vehicle platform for further joint simulation.(3)a three-input single-output braking energy recovery fuzzy control strategy is proposed.Firstly,based on I curve and ECE regulation,the distribution of braking moment of front and rear axles i5 eompleted,and the distribution of braking force of front axle is maximized.Secondly,a fuzzy controller is designed,which takes demand braking force,battery SOC and vehicle speed as input variables and motor braking force distribution coefficient as output variables to realize the distribution of braking energy recovery share.Then the proposed control strategy is modeled and embedded in the vehicle model by using MATLAB/Simulink.(4)based on the established vehicle model and the control strategy model of braking energy recovery,a joint simulation is earied out.Two urban cycle conditions,NEDC and FTP72,are selected to evaluate the coordination of electro-hydraulic braking in the braking process of the vehicle model,and the driving mileage with or without braking energy recovery is compared.The simulation results show that the motor braking intervention is reasonable and the vehicle driving mileage is obviously improved.The reliability and effectiveness of the control strategy designed in this paper are verified,and the economy of the whole vehicle is obviously improved.(5)the actual vehicle test is earied out to study the influence factors of motor braking participation in the process of energy recovery.By setting different single braking condition tests,the proportion of motor braking participation time and motor maximum braking moment are compared and analyzed under different initial braking speed under fixed pedal depth and different pedal depth under fixed initial braking speed.The test results show that the initial braking speed and pedal depth have an impact on the participation of motor braking when braking energy is recovered,which indirectly verifies the rationality and feasibility of the selection of input variables of the fuzzy controller in this paper.