Adaptive control of underwater vehicles with unknown model parameters and unstructured uncertainties

Adaptive motion control of a general class of autonomous underwater vehicles (AUVs) in the presence of model uncertainties and environmental disturbances is addressed. The both parametric and unstructured uncertainties are incorporated into the mathematical model, due to the variations in hydrodynamic and damping coefficients. An adaptive-based control algorithm is first constructed to tackle the parametric model uncertainties. Then, a robustifying term is incorporated into the control law, ensuring the robustness of the method with respect to unstructured uncertainties and external disturbances. Without any pre-assumption on the periodicity and the upper bound of unknown parameters and disturbances, the robust stability is shown to be achieved, using the Lyapunov stability theorem. The proposed robust adaptive controller is then applied to a known AUV to evaluate the performance of the method.