Research On Brake-by-wire Technology Based On Semi-decoupled Electronic Brake Booster

With the rapid development of intelligence and electrification in automobile engineering field,the braking system of automobile is also upgrading at the same time.The early anti-lock braking system(ABS)evolve to the electronic stability system(ESC),then to the EHB with integrated master cylinder and hydraulic control unit,until now to the latest branch,electronic brake booster(eBooster).The integration of automotive dynamics stability control is getting higher and higher,and the involved aspects are getting wider and wider.This paper firstly studies the scheme based on electro-hydraulic servo valve of ESC to realize brake-by-wire,and then explores eBooster with higher integration of actuators.The research on brake-by-wire technology is closer to electrification and intelligence.Firstly,this paper introduces two strategies for brake-by-wire by means of ESC.They are based on PWM modulation with pressure sensor feedback and flow model control without pressure feedback.The closed-loop control based on PWM views HCU as a black box,which records the pressure rate during increase and decompression into two two-dimensional table.The PWM regulation parameters of plunger pump and pressure limiting valve will be calculated according to the closed-loop pressure feedback and looking up the table.The other is to establish the flow model of the valve and the plunger pump.During the period of active during the active pressure's increasing,the relationship between the electromagnetic force of the electro-hydraulic servo valve and the pressure difference between the master cylinder and wheel cylinder will be observed by the flow model of the hydraulic control unit(HCU).EBooster can be divided in principle as a semi-decoupled dry EHB,which is an extended extension of ESC brake-by-wire technology with shorter response time and longer service life than ESC.So it's of great research value.A new type of eBooster assembly is designed in next chapter,which uses a brushless DC motor as the power source and integrates mechanical structure,electrical components and software.A physical mathematical model of the assembly is established,which laid a theoretical foundation for eBooster to achieve its goal.The semi-decoupled electronic brake booster realizes the decoupling of the pedalforce and the wheel cylinder pressure,which lays a solid foundation for the electro-hydraulic coupling braking process of the electric vehicle.Based on the braking force distribution of the front and rear axles of the vehicle body,an electro-hydraulic coupling braking strategy based on the semi-decoupled braking system will be presented.Under the premise of ensuring the stability of the body during brake process,the brake energy recovery will be applied to the conditions with higher deceleration,and the driver's foot feel will be ensured not be changed.For testing hydraulic system circuit in the eBooster-ESC system,the test simulation platform including the test assembly and the hydraulic actuator has been established.The actual signal of the hydraulic circuit and the controller will be captured by sampling the sensor to verify the effect of the electro-hydraulic coupled braking strategy.Under the premise of ensuring that the driver's subjective driving feeling is acceptable,the electric vehicle's cruising ability will be improved.And then the eBooster is matched with the real vehicle platform in order to verify the brake-by-wire effect on the braking system of the platform car and the actual road working conditions.At last,The actual vehicle results verify the response speed and response accuracy of brake-by-wire technology based on eBooster.