Design of an adaptive nonlinear controller for an autonomous underwater vehicle

The paper addresses the problem of trajectory tracking control of underactuated underwater vehicles in the presence of parametric uncertainty. Based on back-stepping design approach, an adaptive control law for 6 DOF model is derived for the trajectory tracking problem. The desired trajectory does not need to be of a particular type and in fact can be any sufficiently smooth bounded curve parameterized by time. The reference yaw velocity has not to satisfy various kinds of persistently exciting conditions which is often needed in previous works. It is assumed that system parameters are unknown and have to be estimated accurately. The stability analysis is carried out using the Lyapunov theorem. The effectiveness of the proposed control method is demonstrated through numerical simulations.