STEERING CONTROL OF SHIPS IN WAVES

The stability and oscillatory motions of ships ( automatically steered and unsteered ) in the horizontal plane were examined on a digital computer for the case of regular following seas. Available hydrodynamic data for Series 60 hull forms were used. Analysis of directional stability was made for the case of zero encounter frequency ( i.e., the ship runs at high speeds equal to the wave celerity ). The ship ( which is hydrodynamically stable without automatic control in calm water ) is directionally unstable in following seas except for the small region near the ascending node of the waves. Addition of automatic control can give the ship directional stability when it is located in the wave trough, but not when it is located on the wave crest. At relatively high frequency ( i.e., at low speeds in following seas ), the rudder and control system are almost incapable of reducing oscillatory motion. Violent rudder activity in following seas can be decreased by reducing yaw-rate-gain control constant and by increasing rudder-response-time constant. ( Author )

• Supplemental Notes:
  • Department of Commerce Library number SIT-R-1205.
• Corporate Authors:

  Stevens Institute of Technology

  Davidson Laboratory, Castle Point Station
  Hoboken, NJ  United States  07030
• Authors:
  • Eda, H
• Publication Date: 1967-6

Media Info

• Pagination: 57 p.

Subject/Index Terms

• TRT Terms: Automatic steering control; Cargo ships; Rudders
• Old TRIS Terms: Course stability
• Subject Areas: Design; Marine Transportation; Vehicles and Equipment;

Filing Info

• Accession Number: 00007136
• Record Type: Publication
• Source Agency: Maritime Administration
• Report/Paper Numbers: SIT-DL-69-1205
• Contract Numbers: MA-2701
• Files: TRIS, USDOT
• Created Date: Dec 22 1974 12:00AM