Development of a Generalized Extended State Observer-Based Nonlinear Control Algorithm for Overactuated Autonomous Underwater Vehicle

Non-singular Fast Terminal Sliding Mode Control (NFTSMC) is a controller that complements the characteristic of sliding mode controller, one of the representative nonlinear controllers, which does not guarantee convergence within a finite time. It has no singularity problem and guarantees fast convergence. However, when the external disturbance is large, using a sliding mode controller requires a large control gain value, which increases chattering and reduces performance. Therefore, in this study, a Generalized Extended State Observer (GESO) was proposed to compensate for external disturbances and model uncertainty in the control system of Autonomous Underwater Vehicle (AUV). The stability analysis of the proposed NTFSMC and GESO was proven based on Lyapunov stability. Therefore, the simulation results show that the introduction of GESO improves the performance and robustness of the AUV controller.