Double-loop predictive control scheme of hydraulic braking system for all braking conditions

To improve the adaptability of vehicle under the all braking (non-emergency/emergency braking) conditions, a double-loop predictive control scheme is developed for the hydraulic braking system. The proposed control system consists of the first predictive loop, front/rear axle braking force distribution unit,and second predictive loop. First, several state variables are transformed into differential equations in accordance with the minimum phase system and some infinitely small-sized items are added in the cost function to meet the working conditions of the optimal control strategy, then the first predictive loop is applied to solve drawbacks that the general approach fails to evaluate the ideal total braking force in accordance with the driver's braking command under the time-varying influences of air and tire rolling resistances. Second, the front/rear axle braking force distribution unit is applied to distribute the braking forces with consideration of both the identified road adhesion conditions and the load transfer between the front and rear axles. Finally, the second predictive loop is presented to track the ideal slip ratio of wheel by using the full information optimal sliding mode control method, which can be used to predict the braking torque accurately. The effectiveness of the proposed control system under different braking conditions is validated by numerical dynamic simulations based on the Matlab/Simulink software. The results show that the double-loop predictive control method can not only accurately track the required objective braking deceleration under the non-emergency braking condition, but also achieve an outstanding anti-locked control effect to obtain the maximum braking force under the emergency braking condition. So, the proposed double-loop predictive control scheme is with a better adaptability. © 2020, Jilin University Press. All right reserved.