ADAPTIVE CONTROL OF THRUSTER MODULATION FOR A DYNAMICALLY POSITIONED DRILLSHIP

A primary tradeoff in the design of a vessel dynamic positioning system is tightness of control versus the modulation levels of the automatically controlled propulsion units due to wave motion and noise. An algorithm is described whereby the parameters of the digital controller are adjusted to achieve the desired compromise between control stiffness and thruster modulation, while maintaining the vessel stability margins at their design values. The algorithm is currently implemented in the DP system of a new North Sea drillship, Nordic Offshore's Havdrill. The basic algorighm is applicable to any existing vessel dynamic positioning system while utilizes a digital computer of control. Different degrees of automation are achievable to meet operator requirements for monitor and adjustment of control stiffness or thruster modulation. Analytical results have been verified through simulation. These study results, including computer data, are presented in the paper.

• Supplemental Notes:
  • Presented at the 6th Annual Offshore Technology Conference, Houston, Texas, May 6-8, 1974. Requests for this document should be directed to David L. Riley.
• Corporate Authors:

  Offshore Technology Conference

  6200 North Central Expressway
  Dallas, TX  United States  45206
• Authors:
  • Sargent, J S
  • Eldred, J J
• Conference:
  • Presented at the 6th Offshore Technology Conference
  • Location: Houston Texas
  • Date: 1974-5-6 to 1974-5-8
• Publication Date: 1974-5

Media Info

• Features: References;
• Pagination: p. 9-16
• Serial:
  • Volume: 2

Subject/Index Terms

• TRT Terms: Drilling ships; Dynamic positioning; Offshore platforms; Thrusters
• Subject Areas: Bridges and other structures; Marine Transportation; Vehicles and Equipment;

Filing Info

• Accession Number: 00072922
• Record Type: Publication
• Source Agency: Engineering Index
• Report/Paper Numbers: OTC #2036
• Files: TRIS
• Created Date: Apr 22 1975 12:00AM