An energy-casimir approach to underwater vehicle depth and heading regulation in short crested waves

Conventional underwater vehicle models neglect wave excitation forces and free surface effects, since the vessel is most often deeply submerged where these effects are negligible. For near-surface operations, wave excitation forces significantly affect vessel motion. This paper focuses on depth and heading regulation for a fully actuated underwater vehicle operating in the wave-affected zone. We first construct a non-canonical Hamiltonian model for the nominal system dynamics. We then employ the energy-Casimir method to construct a control law, together with a Lyapunov function, which renders the desired motion asymptotically stable. Finally, using a disturbance model developed in an earlier work, we study the effects of the Froude-Krylov excitation forces on the closed-loop system response.