Adaptive Fault-Tolerant Fixed-Time Sliding Mode Tracking Control for Steer-by-Wire System With Dual-Three-Phase PMSM

The steer-by-wire (SbW) system is regarded as the optimal steering solution for achieving autonomous driving and has garnered increasing attention in recent years. However, the intrinsic design of the system presents significant challenges for precise steering execution due to parameter uncertainties, external disturbances, and the substantial risk posed by actuator faults. To achieve exact, rapid, and robust tracking, this study utilizes a dual three-phase permanent magnet synchronous motor (DT-PMSM) to drive the SbW system and proposes a fault-tolerant tracking scheme integrating fixed-time sliding mode control (FT-SMC) with adaptive actuator fault compensation. Initially, we describe the structure of the DT-PMSM-driven SbW system and establish a mathematical model that accounts for actuator faults. Subsequently, utilizing dual-layer fixed-time sliding mode surfaces, we ensure that the tracking error converges within a fixed time. A novel adaptive control law, combined with FT-SMC, is introduced, guaranteeing fixed-time stability under normal and faulty conditions. Furthermore, a fixed-time extended disturbance observer (FEDO) is incorporated to suppress lumped disturbances, with its stabilization time being bounded and independent of the initial state. Real-vehicle experiments are conducted on high and low-adhesion road surfaces to validate the proposed controller's effectiveness. The experimental results demonstrate that the proposed scheme exhibits excellent transient and tracking performance under normal and fault conditions.