Ship Path Following Control via Output Redefinition Method in Restricted Waters

Abstract

Due to the advances in shipbuilding technology and the needs in the shipping industry, the ship dimensions have kept increasing, and so is the traffic in the ports, approach channels, and harbors. Increase in ship dimensions and traffic in restricted waterways results in challenges in waterway transportation safety. Safe maneuver of ships of overtaking and encounter is one of them. This paper addresses the problem of the path control of ships in parallel motion in restricted waters accounting for the hydrodynamic effects, in which, the path control with nonminimum phase zero dynamics is a major concern. A new output redefinition method has been developed to solve the nonminimum phase zero dynamics. With the assumption of low-frequency ship motion in restricted waters and the use of the output redefinition method, a new ship response equation is proposed. Based on the new ship response equation, a feedforward + PID control law has been developed to control ship parallel motion in restricted waters. Simulation results show good control effect in medium hydrodynamic interaction, the control law and ship response equation can enhance the safety of ships moving in restricted waters.