Research On Braking System C Ontrol Of Distributed Drive Electric Vehicle Based On Driver’s Braking Intention Identification

When the distributed drive electric vehicle(DDEV)is braking,the driver’s braking intention identification system first identifies the braking intention accordin g to the driver’s input information,then the brake control system controls the electric vacuum power assisted braking system to provide braking assistance according to the driver’s braking intention,and controls the operation of the braking energy recove ry system and the anti-lock braking system(ABS)to turn on and off according to the driver’s braking intention and the wheel slip rate.The accuracy of driver’s braking intention identification not only affects the vacuum assist effect,regenerative brakin g force distribution and ABS control effect of DDEV,but also is the key factor to ensure the braking efficiency and safety of DDEV.Based on this,driver intention identification and corresponding braking control system of DDEV are studied:(1)Taking the driver intention identification system of DDEV as the research object,aiming at the problem of poor identification accuracy of driver’s pedal speed and braking strength in emergency braking,the sampling period of pedal displacement,the calculation method of pedal speed and the recognition metho d of braking strength under different braking intentions are proposed,and the identification parameters and algorithms of driver’s braking intention and driver’s brak ing strength are selected,Based on MATLAB/Simulink,the identification model of driver’s braking intention and braking strength is built,and the identification accuracy of driver’s braking strength is verified under various braking strength simulation conditions of different vehicle speeds.The setting pedal displacement sampling period according to driver’s braking intention can improve the identification accuracy of driver’s pedal speed and braking strength in emergency braking.(2)Taking the electric vacuum power assisted braking system of DDEV as the research object,the matching calculation of the electric vacuum power assisted braking system is completed according to the vehicle parameters and performance indicators,and the matching calculation of the power source of the electric vacuum pump is completed based on the assist characteristic curve of the electric vacuum pump.Considering the influence of the driver’s braking intention on the energy consumption of the electric vacuum assist system,a control strategy of the electric vacuum pump with the driver’s braking intention as the threshold value is proposed.Under three typical braking conditions and FTP-75 conditions,the effectiveness and economy of the electric vacuum power assisted braking system are verified,which can me et the braking power demand of DDEV brake assist,and can turn off the electric vacuum pump in light braking,reduce the working time of the electric vacuum pump,reduce the energy consumption of the vacuum power assisted system,and has a certain economy.(3)Taking the braking energy recovery system of DDEV as the research object,aiming at improving the efficiency of braking energy recovery and braking stability in the process of braking energy recovery on open road,considering the influence of braking strength on the recovery efficiency of brake energy and the influence on the braking stability of open circuit,the DDEV braking energy recovery control strategy with braking strength and road adhesion coefficient as the threshold is prop osed.Using MATLAB/Simulink to build the model of braking energy recovery system,the effectiveness and braking stability of the braking energy recovery control strategy are verified under FTP-75 working condition and split road working condition respect ively.The braking energy recovery control strategy based on braking strength and road adhesion coefficient can provide braking force only by two front in-wheel motors in low intensity braking,and four in-wheel motors can provide braking force together in medium intensity braking,which can effectively improve the braking energy recovery rate;it can reduce the braking force of high adhesion coefficient side wheels on the opposite road surface,reduce the ground braking force difference between the two sides of wheels,reduce the vehicle yaw moment,and effectively improve the braking stability of braking energy recovery under the open road surface.(4)Taking the DDEV ABS as the research object,in order to ensure the braking performance on the road with different adhesion coefficients,the ABS control strategy is designed according to the driver’s braking intention and road adhesion conditions,and the upper and lower controllers are set up to control the opening of ABS according to the driver’s braking intention.The upper controller controls the opening and closing of ABS according to the driver’s braking intention,and determines the target slip rate under different road adhesion conditions according to the road adhesion coefficient slip rate relationship curve.The optimal combination of threshold values of wheel angular acceleration and angular deceleration under different road conditions is determined by orthogonal test,and the lower controller uses logic threshold control algorithm to control the wheel braking force.Using MATLAB/Simulink to build the ABS model,the effectiveness of ABS control strategy is verified under various braking strength simulation conditions of different adhesion coefficient road.The ABS control strategy based on braking intention and road adhesion coefficient can control the opening and closing of ABS according to the driver’s braking intention,determine the target slip rate according to the road adhesion coefficient,reduce the tendency of wheel locking on the road with low adhesion coefficient,and shorten the braking distance and braking time of vehicles,and effectively improve the braking performance and braking stability of DDEV.