Fixed-time control with prescribed performance for path following of underwater gliders

TL;DR

This paper introduces a fixed-time prescribed performance control method for underwater gliders, ensuring accurate, robust, and rapid 3D path following despite uncertainties and disturbances, suitable for challenging oceanic missions.

Contribution

It develops a novel fixed-time control scheme with prescribed performance bounds and a disturbance observer, improving robustness and convergence speed for underwater glider navigation.

Findings

Outperforms conventional controllers in tracking accuracy

Achieves convergence within fixed time regardless of initial conditions

Enhances robustness against environmental disturbances

Abstract

Underwater gliders are increasingly deployed in challenging missions - such as hurricane-season observations and long-endurance environmental monitoring - where strong currents and turbulence pose significant risks to navigation safety. To address these practical challenges, this paper presents a fixed-time prescribed performance control scheme for the 3D path following of underwater gliders subject to model uncertainties and environmental disturbances. The primary contribution is the integration of a finite-time performance function within a fixed-time control framework. This synthesis ensures that the tracking errors are constrained within prescribed performance bounds and converge to a compact set within a fixed time, independent of initial conditions. A second key contribution is the development of a fixed-time sliding mode disturbance observer that provides accurate finite-time estimation of lumped disturbances, enhancing the system's robustness. Integrated with an iLOS guidance law, the proposed controller enables precise and safe waypoint following. Numerical simulations demonstrate that the proposed method outperforms conventional sliding mode and prescribed performance controllers in tracking accuracy, convergence speed, and control effort smoothness, validating its efficacy for robust underwater navigation.