Active roll control for ships
Publication Date: 2015-Apr-08
The IP.com Prior Art Database
There are provided small size thrusters on both sides of the ship for compensating ship movement in waves. The thrusters may point 90 degrees outwards, for example. The thrusters can be arranged to turn under the vessel when needed. The thrusters may be located substantially at the middle of the ship in longitudinal direction.
Page 01 of 3
Page 1 of 2
ACTIVE ROLL CONTROL FOR VESSELS
The present disclosure relates to active roll control of ships. Roll control refers here to side-to-side motion of the ship around a horizontal line passing through the centre of gravity of the ship parallel to the waterline.
In contrast to active roll control, also passive roll control can be applied. In one known solution, water bags are thrown outboard of the vessel. Bag has a big opening in top and a smaller one in bottom. Some weight is mounted to the bottom of the bag to keep it in correct position. When the ship starts to roll, a bag on one side of the vessel creates resistance due to the mass of the water inside the bag. The bag on the other side sinks when the rope carrying the bag gets loose. Multiple bags can be installed on both sides of the ship.
Active roll motion of the ship can be difficult for some vessel types. It is especially difficult to control the ship when it does not have any speed, working on dynamic position (DP) condition or similar.
Fin stabilizers are common in passenger vessels to control roll motion of the ship while the ship is moving. However, such devices are not provided to control ship movement when not driving ahead.
In this disclosure it is proposed that relatively small size thrusters whose rotation is enabled with low force, are located on both sides of the ship, directing substantially 90 degrees outwards, for example. The thruster can be an azimuthing propulsion unit, such as Azipod® (registered trademark of the ABB Group) propulsion unit.
By controlling thrus...