Robust global stabilization of an underactuated marine vehicle on a linear course by smooth time-invariant feedback

The stabilization of an underactuated marine vehicle on a linear course is considered. In spite of being controllable and that Brocketts Theorem does not prevent the existence of a smooth pure feedback control solution, standard tools of nonlinear control as feedback linearization cannot be applied. A smooth, time invariant, globally converging control solution is designed on the basis of a simple and novel idea to derive motion control laws for underactuated systems. Robustness with respect to model parameter uncertainty and state measurement errors is discussed both analytically and through simulations.