Secure Tracking Control Under DoS Attacks Without Resilient Conditions: An Adaptive High‐Gain FAOB Approach

ABSTRACT This paper proposes a novel adaptive high‐gain fully actuated observer (FAOB)‐based secure tracking control scheme for second‐order strict‐feedback nonlinear systems under denial‐of‐service (DoS) attacks. To address the challenge of state unavailability induced by DoS attacks, an adaptive high‐gain FAOB is designed to directly estimate the system states within the second‐order framework. Second, unlike existing resilient control methods that rely on explicit attack frequency and duration parameters to derive resilient conditions, our approach incorporates an adaptive gain mechanism that dynamically adjusts the observer feedback strength to tolerate DoS attacks without using these parameters. We thoroughly analyze three cases of the convergence of the adaptive mechanism. In addition, to overcome the explosion of complexity in high‐order backstepping, we develop a derivative estimator that accurately approximates the high‐order derivatives of virtual control signals, ensuring computational tractability. Then, a high‐order fully actuated controller is constructed. Lyapunov analysis shows that all closed‐loop signals are semiglobally uniformly ultimately bounded under DoS attacks, and the tracking error converges to an adjustable residual neighborhood of the origin. Finally, the effectiveness of the proposed control scheme is validated through a numerical simulation.