The Active Wheel-Corner (AWC) integrates driving, braking, steering, and
suspension systems into the wheel end, forming a fully drive-by-wire, four-wheel
independent steering and four-wheel independent driving (4WIS&4WID) vehicle
platform. While improving vehicle control performance, the full by-wire
architecture also places higher demands on system reliability and fault
tolerance. The steer-by-wire system has electrical, communication, and software
failure risks, which may cause the vehicle to lose steering capability and
trigger severe traffic accidents. This article proposes a hierarchical active
fault-tolerant control strategy based on fault information reconstruction
(FAST-FTC), enabling fault diagnosis and active fault-tolerant control when the
steer-by-wire system fails, effectively ensuring the steering maneuverability
and lateral stability of the vehicle under fault conditions. First, the strategy
designs an adaptive observer combined with the Dugoff tire model to estimate
nonlinear tire forces, while introducing a fault factor to achieve quantitative
grading of steering system faults. Second, a hierarchical controller is designed
for steering system faults. The upper-level controller, based on Adaptive
Super-Twisting Sliding Mode Control (AST-SMC), determines the generalized forces
required to track the desired trajectory under different fault conditions. The
lower-level controller, based on the Fault-Aware Model Predictive Control
(FA-MPC) strategy, dynamically adjusts weight matrices according to the fault
factor and tire reconstructed stiffness, coordinating the allocation of
four-wheel driving and the steering of healthy wheels to ensure lateral
stability. Finally, the effectiveness of the proposed active fault-tolerant
control strategy is validated through Hardware-in-the-Loop (HIL) simulation and
real-vehicle tests.
