A fault estimation and fault-tolerant operation scheme design under simultaneous actuator and sensor faults for steer-by-wire system

In steer-by-wire (SBW) systems, actuator and sensor faults exhibit similar characteristics, making it challenging to accurately estimate one while being influenced by the other. Inaccurate fault estimation can significantly degrade the performance of fault-tolerant control, compromising vehicle reliability and safety. To address this issue, a fault estimation and fault-tolerant operation scheme under simultaneous actuator and sensor faults for the SBW system is proposed. Firstly, an SBW model considering both actuator and sensor faults is established. Secondly, an adaptive unknown input observer (AUIO) is designed to achieve simultaneous estimation of the sensor and actuator faults, with a fast fault estimation law improving fault estimation speed. Thirdly, a fault-tolerant operation scheme is proposed, where sensor signals are corrected through reconstruction, and a sliding mode fault-tolerant controller compensates for actuator faults. Finally, HIL and vehicle experiments validate the proposed scheme. The results demonstrate that the AUIO improves actuator and sensor fault estimation accuracy by 67.4% and 86.5%, respectively, compared to the H∞ observer. Additionally, the fault-tolerant scheme enhances front-wheel steering accuracy by 26.5% and 74.6% in HIL experiments under different failure conditions compared to the feedback-based fault-tolerant operation scheme.