Coordinated Control Approach for Brake Actuator Failures: A Fault-Tolerant Strategy Using Braking Systems and Steering

In this study, a fault-tolerant control system is proposed for brake actuators in a vehicle. A degradation in deceleration performance and lateral stability caused by brake actuator failure can cause serious safety issues. The integration of braking system with either the drive or steering actuators has performance limitations, and previously studied fully integrated braking, driving, and steering systems have complex structures. Therefore, a coordinated control approach for fault-tolerant control of brake actuators was proposed herein to achieve a coordinated control of the drive, brake, and steering actuators. The drive and brake controller performed optimal torque allocation of the desired longitudinal force and yaw moment, and a constraint was set to ensure that the yaw moment error did not exceed the allowable limit. The unachieved yaw moment in the the drive and brake controllers was compensated by the front and rear wheel feedforward steering angles of the steering controller. This structure improved deceleration performance and lateral stability by allowing a certain amount of imbalance in braking force and compensating for it with the steering control. The fault-tolerant control system was verified via simulations and experiments, demonstrating that additional control of driving and steering improved the deceleration performance and lateral stability, respectively. Simulation results revealed that the proposed strategy considerably improved lateral stability compared to independent control strategy using the same actuators. The experiments further verified the applicability of the proposed strategy to vehicles and confirmed that yaw rate errors were reduced under both single and dual brake actuator failure conditions.