Research on Accurate Adjustment of Braking Force and Vehicle Yaw Stability Control Strategy Based on New Electro-hydraulic Brake System

Abstract

A new electro-hydraulic brake system with the structural characteristics of dual master cylinders is presented in this paper and considering the disadvantage of functional backup of the conventional vehicle stability control system, three vehicle yaw stability control strategy are presented. Firstly, the three-closed-loop pressure following PI control algorithm of the new electro-hydraulic brake system is studied to make it quickly follow the target pressure value; Secondly, based on analyzing the two-degree-of-freedom(2-DOF) vehicle dynamic model, the upper-layer, lower-layer controller were designed respectively using the hierarchical control strategy. The upper-layer controller adopted PID, Fuzzy and PID + Fuzzy three controls for the front wheel, rear wheel and front wheel + rear wheel of the vehicle respectively to calculate the additional yaw moment; Then the additional yaw moment is distributed to the single action wheel by lower-layer controller, and then motor control command is calculated by the target braking torque value to ensure that the additional yaw moment generated by the brake actuator tracks the desired yaw moment value of the upper-layer controller in real time. Finally, in order to verify the feasibility of the control strategy and the effectiveness of the algorithm, a co-simulation experiment of CarSim and MATLAB/Simulink is established. The results show that the control algorithm can match the characteristics of the electro-hydraulic brake system and has a good failure backup function and yaw stability control efficiency.