Fault-Tolerant Vehicle Stability Control Based on Active Steering and Direct Yaw Moment With Finite-Time Constraint Performance Recovery

Vehicle lateral stability is of great importance for maintaining vehicle safety. Active front-wheel steering (AFS) is the typical actuator to realize lateral control. However, if a fault occurs on AFS, direct yaw rate control (DYC) can also be used to control lateral stability through differential braking, guaranteeing actuation redundancy. The paper proposes a practical active fault tolerant method for controlling the AFS to DYC process in case of a complete failure of AFS, whereby DYC is expected to take over the control after a certain duration. The proposed method has a distinctive feature in that it can keep the yaw rate tracking error within a predetermined boundary before the failure occurrence and recover the error back to the preset boundary within a desired time period after the DYC takes over. Specifically, the proposed method can guarantee a strict constraint of yaw rate tracking error before the fault occurs on AFS. Furthermore, the method can recover the error back to the desired error boundary in a finite time once the DYC starts to operate. The key points of the method are as follows: First, a tangent barrier Lyapunov function (TBLF) is used with a backstepping mechanism to strictly constrain the yaw rate tracking error in a desired error boundary. Second, the delayed switch from AFS to DYC, which may cause a violation of the preset error boundary, is considered. And a set of functions named reconfigurable transform functions (RTF) are carefully designed, using which the tracking error can recover to the preset boundary within the desired time. The effectiveness of the proposed method is validated and compared with two comparative methods through co-simulation between the High-fidelity vehicle simulation software CarSim $\circledR$ and Matlab/Simulink.