As the basic function of the active safety configuration of a vehicle, the
anti-lock braking system will compromise the driving safety if it fails. Based
on the self-designed electro-hydraulic braking system, this article proposes an
anti-lock brake redundant control architecture. The electro-hydraulic braking
system is mainly composed of four parts: a brake pedal unit, a hydraulic drive
unit, a brake execution unit, and a control unit. The mechanical structure is
compact and exquisite, and the system has the function of precise and adjustable
hydraulic pressure. The control architecture adopts a hierarchical control
design, which is mainly composed of an upper wheel slip rate controller and a
lower hydraulic pressure controller. Both the upper and lower controllers use a
sliding mode variable structure control to improve the robustness and accuracy
of the control. The upper slip rate controller outputs the desired master
cylinder hydraulic pressure with the optimum slip rate of the rear wheels of the
vehicle as the control target. The lower hydraulic pressure controller outputs
the desired torque of the motor with the desired master cylinder hydraulic
pressure as the target and achieves hydraulic pressure regulation of the master
cylinder by controlling the motor motion. To verify the effectiveness of the
algorithm, co-simulation and a hardware-in-the-loop test platform are built.
Anti-lock braking tests are carried out under different typical working
conditions: low-adhesion road, high-adhesion road, butt road, and split road.
The results show that when the anti-lock braking system fails, the redundant
control algorithm can achieve effective slip rate control under different
driving road conditions and meets the anti-lock brake redundant control
requirements. This study provides a reference for the development of low-cost
anti-lock braking redundancy functions for vehicles equipped with
electro-hydraulic braking systems.
