DESIGN OF A DISCRETE-TIME SHIP CONTROLLER FOR STATION-KEEPING DURING UNDERWAY REPLENISHMENT

Ship control requirements for the conning officer during the replenishment at sea (RAS) operation are discussed in detail. Equations of motion in four degrees of freedom are applied to a ship in the ship coordinate system based on five forces: rudder command, speed command, wind, seas, and venturi effect of two ships making way in close proximity. A mathematical model of ship motion is incorporated into a computer program so that ship motion in reaction to the above five forces can be simulated. Ship's head, surge and sway are then used to find a ship's geographical movement during the same time increment. Equations of motion are then linearized about the expected operation point of the ship. Control of lateral and longitudinal separations is assumed to be orthogonal, allowing separate discrete control matrices to be developed for use in the standard regulator problem for both lateral movement control and longitudinal movement control using the rudder and propulsion plant as control forces, respectively. Feedback gains are found based on the control matrices and required damping and settling time as discussed in the requirements for ship control. Feed-forward techniques are used to adjust rudder and propulsion plant commands to account for wind and sea disturbances. The linear control system is then incorporated into the nonlinear simulation of ship movement, and several simulations are run under a variety of possible conditions. The results of the simulations are then used to evaluate the ability of the controller to meet the ship control requirements previously met by the conning officer, helmsman and throttleman.

  • Supplemental Notes:
    • Report; Master's Thesis; DTIC distribution restrictions apply
  • Corporate Authors:

    Naval Postgraduate School

    1 University Circle
    Monterey, CA  United States  93943
  • Authors:
    • Clark, M J
  • Publication Date: 1989-12

Media Info

  • Features: References;
  • Pagination: 118 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00661055
  • Record Type: Publication
  • Source Agency: Maritime Technical Information Facility
  • Files: TRIS
  • Created Date: Jul 21 1994 12:00AM