Fixed‐Time Adaptive Tracking Control for Nonlinear Systems With Unmodeled Dynamics and Input Dead‐Zone and Saturation

ABSTRACT This study proposes a fixed‐time adaptive control strategy for a class of strict‐feedback nonlinear systems subject to unmodeled dynamics, input saturation, and dead‐zone nonlinearities. The key innovation lies in the introduction of a fixed‐time dynamic compensator that effectively handles unknown unmodeled dynamics within a fixed convergence time, independent of initial conditions. To overcome the non‐smooth characteristics of input saturation and dead‐zone, a smooth non‐affine approximation is employed and transformed into an affine form using the mean‐value theorem. A systematic control design is developed by integrating adaptive backstepping with fixed‐time Lyapunov theory, ensuring that all closed‐loop signals remain bounded and the tracking error converges to a small neighborhood of zero within a fixed time. The proposed method not only enhances robustness but also guarantees fast and predictable transient performance, which is critical for safety‐critical applications. The effectiveness and superiority of the approach are validated through two illustrative simulation examples.