The project design for steering qualities of a new ship as well as the prediction and control of its behaviour when at sea may all be based on records of the motions of scale models of previous ships, or even on the observation of the particular ship in the immediate past. In recent years new techniques of stochastic system identification have appeared as alternatives to deterministic methods hitherto applied to the analysis of free-sailing experiments. The present report covers the initial results of co-operation on ship steering problems between the Swedish State Shipbuilding Experimental Tank (SSPA) and the Lund Institute of Technology, Department of Automatic Control (LTH), where the theory of the maximum likelihood parameter estimation has earlier been developed for a variety of dynamic processes. The role of system identification within ship steering analysis is discussed, the kinematics of ships are high-lighted and the mathematical models for the ship dynamics are reformulated. The system identification complex is introduced with special emphasis on parameter identifiability and estimation, and on the requirements to be placed on input-output models. A general program package developed for the computation of the maximum likelihood estimate of the parameters of either a continuous or a discrete model is described. A special subroutine containing three different types of ship models is included. A program for calculating the sway velocity from heading and Decca coordinates is put forth to use the special information from maneuvering tests. Finally several examples of estimations of the hydrodynamic coefficients and the components of the second order transfer function, relating the yaw rate to the rudder angle, are given.

  • Corporate Authors:

    Swedish State Shipbuilding Experimental Tank

    P.O. Box 24001
    S-40022 Goteborg 24,   Sweden 
  • Authors:
    • Astrom, K J
    • Kallstrom, C G
    • Norrbin, N H
    • Bystrom, L
  • Publication Date: 1975

Media Info

  • Features: References;
  • Pagination: 105 p.
  • Serial:
    • Issue Number: 75

Subject/Index Terms

Filing Info

  • Accession Number: 00153805
  • Record Type: Publication
  • Source Agency: Swedish State Shipbuilding Experimental Tank
  • Files: TRIS
  • Created Date: Jun 17 1977 12:00AM