Research On AEB System Of Four Wheel Drive Electric Vehicle

In recent years,with the rapid development of automobile technology and the rapid increase of automobiles,the number of deaths caused by traffic accidents keeps high,and the problem of active and passive safety of automobiles is attracting attention from all walks of life.In fact,the development of passive safety of automobiles has been very mature,while the research on active safety has just started.Therefore,the problem of active safety has become a hot topic in current automotive industry research.On the basis of the traditional AEB anti-collision system,this paper studies in combination with electric vehicles driven by four wheels with double-motor in front and rear axis,recovers the kinetic energy in the braking process in the form of regenerative braking,which is of great significance to improve the safety and endurance of electric vehicles.Starting from the function of AEB system of electric vehicles driven by four wheels,this paper carries out the overall design of the system,divides the functions of the system according to different modules and makes clear the relationship between different functions.And then this paper analyzes the braking process of vehicles,leads to the braking distance model containing reaction time of driver,derives a longitudinal safety distance model containing one warning distance,two warning distances and a minimum safe distance according to different functions of AEB anti-collision system and different driving conditions of vehicles in front or rear,builds the radar ranging coordinate system with the location of radar vehicle as the coordinate origin,the straight line paralleling to the ground,passing through the origin and paralleling to the longitudinal axis of the vehicle as x axis,the straight line paralleling to the ground,passing through the origin and vertically pointing to the left side of the driver as y axis,processes the information collected by the radar sensor,calculates the position information of the target vehicle in front relative to the lateral radar vehicle under the radar ranging coordinate system and builds the lateral safety model.Meanwhile,this paper confirms parameters needed in the longitudinal safety distance model and the lateral safety distance,and develops the control strategy of AEB system of electric vehicles.Then targeted at the characteristics of electric vehicles driven by four wheels,electric vehicles driven by four wheels with double-motor in front and rear axis are simplified,and a rotational three degree of freedom model that the body of the vehicle rotates around its rotating center,the wheels of the front axis vibrates vertically and the wheels of the rear axis vibrates vertically are established.In the breaking process of wheels,the braking force of front axis and rear axis in braking process is distributed with the wheel cylinder pressure demanded by wheels of front axis and rear axis as guidance,and the frictional braking force and regenerative braking force between axes are distributed.In order to ensure that vehicles can stop completely at low speed or the charge of the battery can not be overcharged after reaching a certain state,the influence factors of motor speed and battery energy storage system are introduced in the process of frictional braking force and regenerative braking force distribution between axes,meanwhile,the control strategy of regenerative braking system of electric vehicles is developed.In the end,Matlab/Simulink software and CarSim software are used to combine the vehicle operating environment and experimental conditions specified in C-NCAP to do the verification of joint simulation.The simulation results show that the AEB control system designed in this paper can meet the requirements of emergency braking well,can achieve the recovery of braking energy in regenerative braking,and can effectively improve the economy and endurance of vehicles.