Abstract
Since there exists more or less sea current in most of underwater environments, ingenious guidance can lead an AUV to reach the terminal position with reduced consumption of fuel. This paper addresses the development of fuel-optimal guidance law and tracking control of AUV when it transfers between two pre-designated points in the sea region of environmental flow disturbances. Strategy of fuel-optimal guidance is applied to the navigation of an AUV "R-One", developed by IIS, university of Tokyo. In the formulation of this guidance problem, position vector of the vehicle relative to inertial frame is qualified as the state vector, while the vehicle's heading as the input. Total amount of fuel consumption to reach the terminal position is considered as the performance index. Optimal guidance law is formulated by the calculus of variations using the state-space model of system dynamics and performance index mentioned previously. Solution of the formulated problem is obtained by satisfying the necessary conditions called Euler-Lagrange equations, the solution of which minimizes performance index keeping the imposed constraints. Since the Euler-Lagrange equations leads to the two-point boundary value problem which is extremely difficult to solve, authors propose a numerical algorithm named "AREN" which always achieves the fuel-optimally guided navigation within a given current distribution. AREN detects the correct initial condition to draw out the numerical solution of optimal guidance problem, irrespective of the detailed profile of disturbance distribution. Simulations of optimal guidance of R-One in arbitrarily defined current distributions show as the current distributions become more complicated and diverse, gains by optimal guidance become more apparent.
