A novel combination between finite-time extended state observer and proportional-integral-derivative nonsingular fast terminal sliding mode controller for an autonomous underwater vehicle

This study investigates a novel finite-time extended state observer based on a proportional integral derivative-based nonsingular fast terminal sliding mode controller for an overactuated autonomous underwater vehicle. First, a finite-time extended state observer is designed to estimate the unknown lumped modeling uncertainties and high-frequency external disturbances. A new type of sliding surface—a proportional-integral-derivative nonsingular fast terminal sliding surface—is then proposed to guarantee the tracking performance of the system. Globally stable convergence in finite time is established via Lyapunov stability theory. Next, control allocation is utilized to distribute the forces and moments to the actuators. Finally, to verify our proposed approach, simulation results are provided to demonstrate its effectiveness. The results illustrate that the system performance is enhanced by at least \(8.6\%\) $8.6\%$ compared with existing methods.