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Automatic berthing control of underactuated surface ships in restricted waters based on nonlinear adaptive control method

This paper addresses the berthing control problem for an underactuated surface ships steering in restricted waters using nonlinear adaptive control method. For the berthing path along the given restricted waters, therefore, the following control law, which steers the ships along the path, and convergence, control law, which moors the ships to in its allotted place, are designed separately. Firstly, under realistic assumptions, we show that there exists a change of coordinates that transform the nonholonomic system into a cascade nonlinear system, and then a nonlinear control law can steer the ships follow the berthing path. Secondly, the convergence control law is got based on robust nonlinear method. Aimed at the unknown dynamics of the ships, environmental disturbances and measurement noise, etc., stable adaptive neural network algorithm is used to estimates the uncertainties. The stability of the closed-loop system is analyzed by using Lyapunov theory. Finally, numerical simulation results illustrate the effectiveness of the proposed control scheme.