ABS automatic disturbance rejection control of automotive electronic mechanical braking system
Under the development trend of electrification and intelligence,the automobile braking system has ushered in revolutionary changes.Traditional hydraulic braking system typically has a slow response time.This delay is critical in emergency situations where immediate braking is required.The complexity of hydraulic system,which include numerous components such as master cylinders,brake lines,and calipers,makes them more challenging to maintain.It is necessary to perform regular maintenance in order to ensure that the system functions correctly.This can be a time-consuming and costly process.One of the most prevalent issues associated with hydraulic braking systems is fluid leaks.It is possible for brake fluid to leak from a number of different points within the system,including the master cylinder,brake lines,or calipers.Leaks may lead to a reduction in braking power,which increases the risk of accidents.Compared with the traditional vehicle hydraulic braking system,the Electro-Mechanical Braking (EMB)system completely eliminates the hydraulic device and is powered by an electric motor to generate the braking clamping force.The system has a simpler configuration,a faster response time,a smaller quality and volume,and represents an important development direction for future automotive brake-by-wire technology.Meanwhile,as the number of vehicles in China increases,the demand for safety performance continues to rise,leading to more passenger cars being equipped with electronic braking control systems,such as Anti-lock Braking System (ABS),to prevent wheel lock-up during braking and improve vehicle stability.The EMB system is fully electronic and easily integrated with the vehicle's electronic control system.This integration capability allows the ABS system to work better with other safety systems to provide more comprehensive control of vehicle dynamics.However,the EMB system also faces challenges such as strong nonlinearity,large load variations,and complex control.During emergency braking,the ABS is often disturbed by uncertainties in the system parameters due to changes in road conditions and shifts in front and rear axle loads.These potential issues may all affect the safety performance of actual vehicles.Therefore,this paper focuses on the ABS control strategy of automotive EMB system,and the main contents are as follows.Aiming at the slow response of the traditional hydraulic braking system,this paper designs an EMB actuator scheme of"planetary gear reduction mechanism+ball screw+piston",and establishes an EMB actuator model with complete structure and fast response.In order to make sure that the wheels are not locked when the vehicle is braking,the ABS active disturbance rejection controller is designed with the optimal slip ratio and the actual slip ratio as input.It consists of three parts:Tracking-Differentiator,Extended State Observer,and Nonlinear State Error Feedback.The controller enables the EMB system to regulate the braking force of each wheel with great precision and speed,facilitating the control of wheel slip rate and effectively meeting the requirements of ABS in the EMB system.At the same time,this paper verifies the response performance of the EMB actuator in Matlab/Simulink,and completes the emergency braking comparative simulation with fuzzy PID control under single road condition and docking road condition.The research results show that the designed EMB actuator can accurately track the initial target clamping force. When the clamping force signal changes,the actuator still has good responsiveness.In the case of ABS control,the active disturbance rejection control is more robust to internal and external system perturbations than the fuzzy PID control.The system ensures that the front and rear wheel slip rates of the vehicle are stabilised at the target slip rate more quickly,effectively reducing the braking time and braking distance of the vehicle and improving the safety of the vehicle during emergency braking.
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