Capability-Based Hierarchical Fault-Tolerant Control Scheme for Four-Wheel-Independent-Drive Electric Vehicles under Actuator Faults

For four-wheel-independent-drive electric vehicles (4WID-EVs), the increasing number of actuators and electronic components raises the risk of actuator failure for the vehicle, potentially threatening driving safety. When actuator faults occur, the faulty actuator introduces disturbances to the vehicle system, making the coordinated control of actuators under fault conditions more difficult. To solve this problem, a capability-based hierarchical fault-tolerant control (FTC) scheme is proposed for 4WID-EVs. Firstly, the vehicle dynamics model under fault conditions is established. Secondly, in the upper layer of the control scheme, a nonsingular fast terminal sliding mode controller with nonlinear disturbance observer (NDOB) is designed to track the reference vehicle states under the impact of disturbances. In the lower layer, the driving capability and steering capability of faulty vehicles are assessed. Subsequently, a capability-based fault-tolerant coordinated distribution approach using fuzzy logic is introduced to dynamically distribute control commands to actuators. Finally, comparative works are conducted through both simulation and experiment. The results demonstrate that, compared with the sliding mode FTC scheme, the proposed scheme reduces RMSE, reflecting an improvement in tracking accuracy by 75% in simulation and 18.6% in experiment. The proposed scheme may serve as a theoretical reference for fault-tolerant control in 4WID-EVs.