Optimisation-based motion control for AUVs under non-linear wave-current disturbances

With the increasing exploitation of marine resources, autonomous underwater vehicles (AUVs) are being applied more extensively in a variety of tasks, such as maritime search, rescue, and marine archaeology. The attitude stability of AUVs can be significantly disturbed by highly non-linear waves and currents near the sea surface, yet the influence of wave non-linearity on AUV motion and the associated control strategies remains insufficiently studied. In this work, the authors investigate an optimisation-based motion control problem for AUVs under combined current and non-linear wave disturbances. The wave fields induced by linear and non-linear waves in uniform current are obtained using linear wave theory and stream function wave theory, respectively. The Morison equation is adopted to compute forces of the wave field on the AUV. A comparative analysis has been conducted on the effects of linear against non-linear waves on the AUV trajectory and attitude in the presence of the uniform current. Furthermore, three optimisation-based control strategies are developed and their performance is evaluated.