Research On The Compound Brake Control System Of Electric Vehicle With Four-wheel Independent Drive In-wheel Motors

With the rapid increase in the number of traditional cars,the world is facing more and more serious environmental problems.Therefore,vigorously developing new energy vehicles has become the trend of great potential for automobile industry.As one of the best solution for new energy vehicles,battery electric vehicle have not been widely used.The main reason is that its driving range is not far.As one of the battery electric vehicles,the four-wheel independent drive in-wheel motor electric vehicle is one of the most promising form.It's also gradually becoming one of the research hotspots to use the electro-mechanical composite brake system of electric vehicle to achieve the goal of recovering the braking energy and increasing the driving range.This thesis is applied to four-wheel independent drive in-wheel motor electric vehicle's composite braking system.In order to ensure effective braking energy recovery under full working condition with the premise of stable braking,the research is mainly divided into two parts of driving state estimation and braking force control.The main research contents include:Analysis electric vehicle composite braking system and modeling,and vehicle dynamics model are established.In the composite braking system,the model of in-wheel motor,hydraulic braking actuator and power battery are established.In order to feedback the state of control demanded in the car's braking,combined with the structural characteristics of composite braking system,the control architecture based on state estimation is put forward by this thesis.Based on Kalman filter theory,the longitudinal speed observer is designed,and the surface state modular identifier is designed by using fuzzy theory.The speed estimated by the vehicle speed observer can be used for speed following control feedback.Moreover,the identifier can estimate the road friction coefficient and the optimum slip ratio of road,so as to realize the judging of working condition and anti-lock control of regenerative braking.The combined simulation results of CarSim and Simulink indicate that the driving state observer has good estimate accuracy and stability.The controller of composite braking system is designed by hierarchical control,where in the upper controller is used for working condition judgment,vehicle speed follow-up control and anti-lock braking control,while the lower controller is used for optimal distribution of four-wheel braking moment and the distribution of regenerative braking force and hydraulic braking force.The combined simulation results of CarSim and Simulink can realize the recovery of braking energy maximization while following the braking speed under normal working conditions.In case of emergency condition,braking energy recovery can be guaranteed,and at the same time,the braking efficiency is fully guaranteed,which verified the feasibility and effectiveness of the controller under full working conditions to recovery more braking energy.Real-time simulation experiment based on dSPACE indicates that the control strategy meets the real-time requirement.