Abstract
In order to clarify nonlinear effects on time optimal control for ship maneuvering motions, the authors make numerical simulation with respect to the optimal control input for course changing maneuver. Calculations of the optimal control are made for a tanker and a car-ferry ship. The simplified nonlinear equation developed by Nomoto, which describes directly ship's response to the rudder angle, is employed. This report deals with the effects of a hysterisis loop formed by the so-called r-δ curve and linearization of the nonlinear equation. From the results of numerical calculation, it is indicated that the nonlinearity has a considerable effect on the first execution time at which the rudder is deflected to the opposite side. However, significant difference in the terminal time is not found between the nonlinear system and the linearized system. As a result, it is pointed out that the optimal rudder behaviour through the bang-bang control is related to both turning quality and course-keeping quality of the ship.
