Author

Waldo Lizcano

Advisor

Pah I. Chen

Date of Award

7-23-1976

Document Type

Thesis

Degree Name

Master of Science (M.S.) in Applied Science

Department

Applied Science

Physical Description

1 online resource. Digitized photocopy of typescript, illustrations

Subjects

Offshore structures

DOI

10.15760/etd.2438

Abstract

A new technique for controlling the pitching motion of a floating platform is proposed in this study.

The floating platform is assumed to be a simplified model of the columnar type rectangular platform supported by buoyant force from four cylindrical legs. The control arrangement consists of water jet streams immerging horizontally from two points located some distance apart on each leg to form a restoring couple. The water jet streams can be shifted t0 opposite horizontal positions or to the vertical downward ,positions according to control requirements. They are governed by angle control criterion as well as velocity control criterion. The goal is to attain the platform stability within a desirable range of angles about the equilibrium position.

The mathematical model governing the motion of the floating platform consists of all pertinent forces along with a control variable. It is a second order nonlinear differential equation having no known exact solution. The state variable technique is employed to solve this equation numerically. The state transition equation is established and reduced to a sampled-data system. Two Fortran computer programs were written for the numerical process involved in the solution of this nonlinear equation.

This theoretical study shows that the platform motion under investigation is controllable by the proposed technique. The study also shows that major concern of this technique is the high energy consumption that would be required to maintain the stability of the structure.

Persistent Identifier

http://archives.pdx.edu/ds/psu/15828

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