Page 24: of Maritime Reporter Magazine (April 2, 2010)

24 Maritime Reporter & Engineering News

COLUMN EYE ON DESIGN

Over the past years, MARIN’s activi- ties with multi-body hydrodynamics and in particular, multi-body Dynamic Posi- tioning (DP) have increased significantly.

This article focuses on DP, its growth and its potential. MARIN’s techniques and the way DP applications are used for a variety of projects are also highlighted.

At the end of the 1980s, MARIN per- formed the first DP model tests on drill- ships and semi-submersibles. The amount of DP model tests has increased ever since and the number of applications has grown. For steering the models dur- ing model tests, MARIN uses a home- grown software package called

DP-interactive. This software computes the required control settings for free sail- ing models online. The models are mov- ing as a consequence of the propulsors and the new position of the model forms the input for the DP controller. Hence, it becomes a closed-loop system. In relative

DP, the ship is trying to follow another ship. This is technically achieved by hav- ing a master ship and a slave ship. The master ship does its thing, while the slave ship reacts at a mutual distance between the master and the slave. The slave ship is steered in such a way that a point of the slave ship accurately follows the position of a point on the master ship.

Mimicking the real world with a

DP controller

MARIN performs these tests in the

Seakeeping and Maneuevring Basin and in the Offshore Basin, using actual ship

DP applications extended to relative DP

Dynamic Positioning in Spotlight

About the Author

Frans Quadvlieg is senior project manager Maneuver- ing & Seakeeping at MARIN, the Maritime Research Insti- tute Netherlands.

For more information, Email: [email protected]

Figure 1:

DP controller for absolute and relative DP as used in the model basin.