A multivariable low speed controller for a ship autopilot with experimental results

The paper presents the structure of the multivariable control system for the ship moving on the water surface at low speeds in three degrees of freedom. The speed controller determines the multidimensional force, i.e. the longitudinal, lateral and angular momentum, which should be applied to the hull of the ship. These forces are applied by actuators installed on the ship. The ship control system use three propellers: the bow tunnel thruster, the stern tunnel thruster, and the main propeller of the ship. Power distribution between the propellers is made by the thruster allocation system. The designed system was run on a training ship Blue Lady at Ship Handling Training Center on the lake Silm near Ilawa. No speed measurements were performed on the ship, and the measured quantities only included the position coordinates, measured by the DGPS system, and the ship heading, measured by the gyrocompass. The results of these measurements made the basis for estimating the surge, sway and yaw rates by the Kalman filter.