Vehicle Longitudinal Dynamical Control Base On Electro-Mechanical Booster Braking

Intelligentization and e-tron are the main trends of the vehicle development.As an important part of intelligent vehicles,longitudinal dynamical control including adaptive cruise control(ACC)and automatic emergency braking(AEB)has been a research hotspot.And adaptive cruise control includes constant speed cruise control and following vehicle control.Intelligent vehicles require the braking system to have the function of active braking.At the same time,in order to increase the cruising range of electric vehicles,the braking system needs to have the ability to regenerate braking energy.The electro-mechanical booster system can achieve rapid fluid pressure buildup during active braking through a servo motor.In addition,it can also decouple the brake pedal force while ensuring the brake pedal feel,providing technical support for the realization of regenerative braking.So the electro-mechanical booster braking system well meets the development needs of automotive intelligence and e-tron.This article relies on the National Natural Science Foundation of China(51575225): Research on key technologies of multi-source intelligent tire information system for vehicle dynamics control to design the vehicle longitudinal dynamical control algorithm based on the electro-mechanical booster braking system.The main research contents are :(1)Upper controller design for vehicle longitudinal dynamics.Firstly,the switching criteria for the upper dynamics control of longitudinal dynamics is designed;then the cruise control and AEB control strategies to reasonably arrange the expected step speed and step target acceleration transition are designed;Finally,the safety clearance model under the conditions of following the front car is set up and the MPC control algorithm is designed for the car-following conditions.(2)Lower controller design for longitudinal dynamics.First longitudinal dynamic force analysis is performed and the feedforward compensator is designed;then PID control algorithm id designed to form a closed-loop control system of feedforward compensation and feedback correction;then an inverse model of the actuators to obtain the expected input of the actuators is build up;finally,in order to avoid frequent switching between braking and driving,the switching strategies between actuators is designed.(3)Active boost control strategy design for electro-mechanical booster braking system.Firstly,the mathematical model of the electro-mechanical booster braking system is established;then the ADRC is designed for the pressure loop control of the electro-mechanical booster braking system;finally the position control strategy of the electro-mechanical booster braking system is designed.When designing a position control strategy,the outer loop is the position loop and the inner loop is the current loop.The position loop adopts sliding mode structure control(SMC)to obtain the desired current of the motor.The current loop uses a linear matrix inequality(LMI)based control strategy to obtain the voltage required for space vector modulation.In order to prevent the current controller from entering saturation and losing its regulating effect when the motor speed increases rapidly,a field weakening control strategy is designed to modify the target current.(4)Simulation and experimental verification.Firstly,a rapid prototype experimental bench based on dSPACE is built to experimentally verify the active braking algorithm of the electro-mechanical booster braking system;then four typical operating conditions are designed to simulate and verify the longitudinal dynamical control strategy;finally,a real vehicle platform is used to verify the lower controller of the longitudinal dynamics based on the electro-mechanical booster braking system.