Fixed-time fault-tolerant control for electro-mechanical braking systems under input saturation and time-delay

This paper proposes a novel fault-tolerant control strategy for electro-mechanical brakes (EMB) subject to supply faults, input saturation, and time delays, aiming to enhance vehicle safety and align with the development of high-precision fault-tolerant anti-lock braking systems (ABS). The proposed strategy employs a fixed-time controller with a time-varying funnel constraint to maintain the slip ratio within its optimal range, thereby ensuring maximum braking efficiency and enabling the vehicle to achieve the shortest possible stopping distance during emergency braking. Furthermore, a fixed-time command filter is introduced to mitigate the derivative explosion problem, while a fractional-order compensation strategy with auxiliary compensation signals is developed to counteract filtering inaccuracies and input saturation effects. To improve robustness and fault tolerance against external disturbances, supply faults, and input delays, fixed-time extended state observers (FESO) are integrated, enabling the ABS to effectively handle lumped disturbances under various road conditions. The global fixed-time stability of the entire system is rigorously established using Lyapunov theory, and simulation results under dry, wet, and snowy road conditions-along with analyses of key performance indicators (KPIs)-demonstrate the effectiveness, robustness, and novelty of the proposed control strategy.