Abstract
Tracking control for unmanned underwater vehicles is essential, both for autonomous operations and complex tasks where the vehicle is manually controlled by a pilot. Underwater vehicles are typically subjected to perturbations due to environmental effects such as ocean currents and waves. Moreover, obtaining an accurate model of the vehicle dynamics is highly challenging. This introduces a need for a model-free control system that is robust to such perturbations. In this paper, we propose the use of two higher-order sliding mode controllers, the generalized super-twisting algorithm (GSTA) and the adaptive GSTA, for 4 degree-of-freedom control of an underwater vehicle. The stability of the closed loop system is analyzed through Lyapunov theory and the performance of the controllers is evaluated in a set of full-scale field trials at an aquaculture facility. The results show that the controllers outperform classical PID control.