Research On Decoupling Control Strategy Of New Energy Vehicle Equipped With Electro-mechanical Booster Braking System

New energy vehicles have become an important direction of automotive development in the current energy and environmental crisis.New energy vehicles have not only the advantage of emission reduction in the type of energy source,but also the potential to further improve the effect of energy conservation and emission reduction by new technology.Regenerative braking technology is one of the key technologies.However,the regenerative braking force produced in regenerative braking will affect the braking performance of the vehicle.Therefore,it is necessary to decouple the brake pedal,which means to cut off the coupling relationship between the brake pedal and the brake wheel cylinder.At present,many manufacturers and researchers have proposed various braking system design schemes and corresponding pedal decoupling strategies.Among them,the one using electro-mechanical booster can make the least change to the existing braking system,which has obvious advantages in promotion.This paper focuses on the research of pedal decoupling control strategy for electromechanical booster braking system.Firstly,the pedal decoupling schemes were designed.Secondly,the electro-mechanical booster braking system model and vehicle model were established.Then,the pedal decoupling strategy based on the new decoupling scheme was studied.Finally,the simulation and experimental studies were carried out.The research contents involved are as follows:(1)Pedal decoupling design and main component characteristic test.Firstly,the structure and working characteristics of vacuum booster,electro-mechanical booster,Eletronic Stability Program(ESP)and active accumulator were introduced.Then,three new pedal decoupling schemes were designed by using different combination of four decoupling elements.Next,the characteristic test bench was designed.Finally,hydraulic characteristic test,vacuum booster characteristic test,electro-mechanical booster characteristic test and ESP liquid storage characteristic test were conducted.(2)Electro-mechanical booster braking system and vehicle modeling.Firstly,the electromechanical booster braking system and the model frame of the vehicle were analyzed,the electro-mechanical booster braking system model includes electro-mechanical booster model and hydraulic braking system model.Then,the electro-mechanical booster model(including the motor model and the transmission model)and the hydraulic braking system model(including the brake master cylinder model,the ESP hydraulic control unit model and the brake wheel cylinder model)were established respectively.Finally,the vehicle model(including longitudinal dynamics model,driving motor model and battery model)was built.(3)Research on new pedal decoupling control strategy.Firstly,the braking force allocation constraints of the vehicle were analyzed,and the influence of regulations and other constraints on regenerative braking force was studied.Then,for the decoupling scheme based on electro-mechanical booster and ESP,electric-hydraulic braking force allocation strategy,pedal decoupling strategy and electro-mechanical booster motor control strategy were designed.Finally,for the decoupling scheme based on vacuum booster and active accumulator,the electric-hydraulic braking force allocation strategy and pedal decoupling strategy were designed.(4)Simulation and experimental verification of booster braking system.Firstly,the control strategy of Permanent Magnet Synchronous Motor(PMSM)for electro-mechanical booster was simulated and verified.Then,the simulation and experiment test were carried out to verify the decoupling strategy based on electro-mechanical booster and ESP,and the effectiveness and feasibility of the decoupling strategy were proved.Finally,the vehicle test was conducted to verify the effectiveness of the decoupling strategy based on the vacuum booster and active accumulator.