Research On Intelligent Brake System Of Distributed Drive Electric Vehicle Based On Brake-by-wire System

The development of the new four modernizations of the automobile has undoubtedly brought a profound change to the automobile industry.Intelligent new energy vehicle is the direction of development,which needs more intelligent active drive,active braking and active steering system.Distributed drive electric vehicle(DDEV)has the characteristics of compact structure,high transmission efficiency,high energy recovery efficiency,independent control of each wheel drive and braking torque and so on.Distributed drive electric vehicle has the ability of regenerative braking,which can meet the braking needs of general driving conditions,but regenerative braking can not meet the braking requirements under emergency braking conditions,so additional braking pressure is needed.The brake system of intelligent distributed vehicle should also be a kind of intelligent braking system.Through full environmental awareness,it can provide appropriate braking force and ensure the safety of the vehicle when the driver participates and the driver does not participate.In order to meet the demand of intelligent distributed drive vehicle braking system,this paper carries out the design of intelligent braking system and control strategy.First of all,analyze the force of the vehicle,build the vehicle dynamics model,design and analyze an electronic hydraulic brake(EHB)system with fully decoupled between pedal and pressure booster,build its mathematical model,verify the correctness of the mathematical model through simulation,and clarify the problem of insufficient regenerative braking torque.In order to accurately execute the expected brake force of the wire-controlled EHB system,a closed-loop pressure control strategy of the wire-controlled EHB system is proposed,which includes feedforward loop,feedback loop and dead-zone compensation loop,and a cooperative braking strategy with priority effect of regenerative braking is proposed to make the wire-controlled EHB system cooperate with the hub motor regenerative braking system.The effectiveness of the proposed control strategy is verified by simulation.Secondly,the process of obstacle avoidance is analyzed,and a two-stage early warning improved safety distance model based on empirical data optimization is proposed,and compared with four common safety distance models,the effectiveness is verified by simulation;the time to collision deduced and the threshold is selected under different working conditions.In this paper,an obstacle avoidance decision based on extension method is proposed.By selecting the primary and secondary characteristics,calculating the correlation function,dividing different control domains,determining the obstacle avoidance mode under different control regions,and the expected braking deceleration during longitudinal active obstacle avoidance.Multi-case active obstacle avoidance simulation is carried out by Matlab/Simulink software to verify the effectiveness of the active obstacle avoidance system.Finally,on the hardware-in-the-loop test bench of the designed wire-controlled EHB system,the EHB pressure control test,cooperative braking test and active obstacle avoidance test are carried out respectively to further verify the effectiveness of the proposed distributed drive vehicle intelligent braking system.