Automatic Tug Assistance

Abstract

Usually in the harbour area, a big ship with single rudder-single propeller often requires a set of adequate thrust device or tug assistance which exactly takes into account the surge, sway and yaw rate to execute such crabbing motion. The number of tugs involved in each operation depends on the size of the ship as well as existing wind disturbances. The effect of wind varies with its relative direction and the speed of the ship. Therefore, the tug operators must be aware of the disturbances effect and adjust the tow or pulling forces by seeing the response of the ship. The same task, i.e. the adjustment the thrust values, could be done in an automated way which will eliminate the possibilities of human errors and thus ensure proper safety in tug operation. This paper discusses about a controller that can calculate the required tug forces by observing the ship response and then adjust the forces to finally align the ship with the pier with a minimum sway velocity under reasonable wind disturbances.