Performance-guaranteed adaptive switching tracking control for steer-by-wire system with disturbance observer

Prescribed performance control has been widely proven to enable high-precision tracking in steer-by-wire system. However, the variable steering load and unknown initial conditions may lead to invalid control actions, potentially compromising vehicle safety. To address these challenges, this paper proposes an adaptive dynamic switching tracking control method for steer-by-wire system, which ensures strict adherence to prescribed performance. Considering that the steering load degrades tracking performance by acting as external disturbances, a rack force observer based on fourth-order system dynamics is introduced to indirectly estimate and compensate for unmeasurable disturbance. To eliminate the potential singularity issues and initial error constraints inherent in prescribed performance control, a performance-guaranteed nonlinear switching controller is developed by integrating a control barrier function with a finite-time prescribed performance control method, without sacrificing control performance or redesigning the original controller. The stability of the developed controller with switched nonlinear control policy is rigorously analyzed. Finally, hardware-in-loop experimental results under different standard test conditions show that the presented method significantly enhances both transient performance and tracking precision under road bumps and uncertain parameters while remaining computationally feasible for embedded implementation.