Fuel-optimally guided navigation and tracking control of AUV under current interaction

Fuel-optimally guided navigation and tracking control of AUV under current interaction is presented. Existence of sea current should be one of the most important considerations for the navigation of AUV, since the speed of it is set low to reduce the fuel consumption as possible. This is because the replenishment during the mission is not possible for AUV, as it attains more motion freedom at the expense of umbilical cable. When an AUV is subjected to transfer between two pre-designated points in the region of sea current, ingenious guidance enables the AUV to reach the terminal position minimizing the fuel consumption. In this paper, fuel-optimal guidance law is derived and applied to the navigation of "R2D4", a newly developed AUV by IIS, the university of Tokyo. Optimal guidance law is formulated as a two-point boundary value problem on the basis of Euler-Lagrange equations. In this formulation, position vector relative to inertia! frame is qualified as the state vector, while the vehicle\´s heading as the input. Simulations of optimal guidance of R2D4 in arbitrarily defined current distributions show as the current distribution becomes more complicated and diverse, gains by optimal guidance become more apparent.