Abstract
In the steer-by-wire (SBW) system, the traditional mechanical link is replaced by the steering motor and the feedback motor, which can enhance steering performance. However, the existence of more electronic components could lead to the fault conditions in sensors and actuators that may degrade steering performance and cause instability. The reconstruction of faults becomes challenging where both actuator faults and sensor faults are involved. In this article, an active fault-tolerant control method is proposed for the SBW system. Firstly, a nonlinear fault model of the SBW system is established, by which the original front wheel subsystem is transformed into a primary system with actuator fault and a secondary system with sensor fault. Then, a dual observer structure is developed. An improved robust adaptive sliding mode observer is designed for actuator fault reconstruction in the primary system. A filter robust adaptive sliding mode observer is designed for sensor fault reconstruction in the secondary system. Secondly, the fuzzy adaptive fast fixed-time nonsingular terminal sliding mode based fault-tolerant controller is developed to compensate the actuator and sensor faults by using the fault reconstruction results and the fault model of the SBW system. The developed fault-tolerant controller can achieve the precise front wheel angle tracking in the presence of actuator and sensor faults, parametric uncertainties and external disturbances. Finally, the validity and performance of the proposed scheme are verified through simulation and real-time experimental results.