Ahmadian, Hossein and Arefi, Mohammad Mehdi and Khayatian, Alireza and Montazeri, Allahyar (2024) An improved L 1 adaptive high-gain observer with guaranteed performance and stability robustness for uncertain Euler–Lagrange systems. Ocean Engineering, 311: 118684. ISSN 0029-8018
Full text not available from this repository.Abstract
One of the main challenges in designing adaptive controllers for the robotic applications is the inability to measure the system states and respecting the physical constraints of the robot. To address this issue, a modified L 1 adaptive controller is proposed in this paper by integrating the controller with an adaptive high-gain observers ( HGO ) and Barrier Lyapunov Function ( BLF ). In addition to addressing the unavailability of the system states, the proposed method provides a way to compromise between robust performance and fast adaptation in the presence of time delay and uncertainties. For this purpose, the observer gain is designed to be adaptive to keep the output estimation error within a previously known range and the BLF is used to constrain the system outputs. A rigorous stability analysis of the whole closed-loop system in the presence of observer, system uncertainties, and disturbances is provided and guarantees that the closed loop system is semi-globally uniformly ultimately bounded ( SGUUB ). As the next step, the stability of the closed loop system in the presence of input delay is analyzed and the performance of the proposed observer-based controller is evaluated on an uncertain 6- DOF remotely operated underwater vehicle ( ROV ). The detailed numerical results confirm that the integral absolute tracking and estimation errors of the system using the proposed controller outperforms other adaptive controllers for this application. Moreover, the results confirm the ability of the proposed method in rejecting time-varying disturbances and uncertainties, and demonstrates a satisfying tracking performance when the system dynamics is uncertain.