GUIDE TO DYNAMIC POSITIONING OF VESSELS

The fundamental purpose of the DPS of any ship is the automatic control of the heading and position of the vessel. A more sophisticated definition is to maintain the variations in ship's position and heading within acceptable limits, while achieving minimum thruster activity. 

This is the dynamics of a free floating vessel in an offshore marine environment. Then, the control system is covered, providing a review of the control loop of force and moments: sensing: counteraction to force. Generally, forces acting on the vessel and associated moments are environmental plus task related i.e. pipe tension; Operational modes.

Each vessel is supplied with several different modes of operation, with the difference between the modes being the level of control available and how the position, heading speed and set points are generated. The combination of modes provided for a vessel mainly depends upon its role. Thus, a cable laying vessel will need Auto Track mode, which would commonly not be required for in case of a drilling platform...