Adaptive Stabilization for High-Order Fully Actuated Systems With Unknown Control Directions

This article focuses on the adaptive stabilization control of high-order strict-feedback systems (SFSs) with unknown control directions. It addresses the challenge of dealing with unknown control directions in the fully actuated theory. To overcome this challenge, the Nussbaum gain technique and tuning functions directly based on the high-order fully actuated system (FAS) method are proposed to deal with the unknown control directions and system uncertainties, while avoiding the phenomenon of overparameterization. Additionally, a relative threshold event-triggered strategy is utilized to effectively avoid continuous controller updates, which helps conserve network resources used for signal transmission. The proposed controller guarantees the convergence of all system state variables to zero and ensures that all signals within the closed-loop system remain bounded. To validate the effectiveness of this approach, a numerical simulation and a practical example using the Nomoto ship model are conducted. Overall, this study contributes to the FAS field by providing a solution for adaptive stabilization control in high-order SFSs with unknown control directions.