Abstract
The equation of steering motions of ships can be described by a differential equation of the 1st order as follows: [numerical formula] where T is a constant which represents the quick responsibility of ships, and K is a constant which represents the turning quality. The performance of the turning motion of ships is decided by these manoeuverability index T and K. These index can be obtained from a Z manoeuvering test or a turning test of ships. On the other hand, turning motion of ships is represented on the Phase Plane which has the coordinates of angular velocity (on the ordinate) and angular position (on the abscissa) of ships. To minimulize steering time, the principles of nonlinear Optimal Control system can be applied to the steering motion of ships. The optimum switching point, when ships are steered from port to starboard or from starboard to port, is decided on the Phase Plane by application of the nonlinear Optimal Control theory.
