Vehicle Braking Stability Control With Variable Ratio Braking Forces Optimization Distribution During Cornering Braking Process

Abstract

During the vehicle cornering braking process, there is a complex coupling relationship between the longitudinal and lateral forces, and the auxiliary steering and braking systems are usually coordinated to achieve the vehicle braking stability and the lane keeping simultaneously. However, the auxiliary steering angle may change the trajectory of the vehicle. In order to simplify the control process and enhance the braking stability, a braking stability control strategy without the auxiliary steering system is proposed based on an adaptive sliding mode control algorithm with optimized braking forces distribution. The distribution ratio of the front and rear braking forces is optimized by considering the various braking strengths and compliance with ECE regulations. The adaptive sliding mode control algorithm is designed to obtain the additional yaw moment to control the steering process. A new convergence law is developed based on a constant rate convergence law and a power rate convergence law to accelerate the convergence process. The ultimate braking forces of each wheel are formed with the optimized front and rear braking forces and the additional braking forces obtained based on the steering characteristics of the vehicle and the additional yaw moment. Finally, the strategy's effectiveness and superiority are validated and compared with the fixed ratio strategy through hardware-in-loop experiments. The results demonstrate that the vehicle braking stability control strategy achieves smaller tracking errors for yaw rate and sideslip angle, reduced fluctuation in the sideslip angle curve, a smaller lateral deviation, a smaller phase plane trajectory area, and improved stability.