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Indexed by:Journal Papers

Date of Publication:2020-01-02

Journal:SHIPS AND OFFSHORE STRUCTURES

Included Journals:EI、SCIE

Volume:15

Issue:1

Page Number:75-88

ISSN No.:1744-5302

Key Words:All-direction thruster; mean pitch angle; wind loads; dynamic positioning; thrust allocation; sandglass-type FDPSO

Abstract:Due to the special characteristics of the sandglass-type FDPSO (Floating, Drilling, Production, Storage, and Offloading unit), such as the inclined structure with external expansion and large deck area, obvious wind forces in the vertical plane can be excited in harsh sea condition. Combined with its small-waterplane-area and low metacentric height, obvious mean pitch angle can be induced, which may make the extremal pitch angle to exceed the positioning accuracy requirement. In this paper, regarding the mean pitch angle problem and the invalidity of conventional azimuth thrusters, a novel concept of all-direction thruster is proposed. With the proposed thruster, a new 5-DOF (degree-of-freedom) controller with feedforward wind moment in pitch (or roll) direction and an improved 5-DOF thrust allocation are presented. Comparing with two kinds of traditional thrusters, the proposed all-direction thruster with the improved 5-DOF controller is demonstrated to have better performances on positioning accuracy and power consumption.