Application of novel all-direction thruster for dynamic positioning of 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.

KEYWORDS:

• All-direction thruster
• mean pitch angle
• wind loads
• dynamic positioning
• thrust allocation
• sandglass-type FDPSO

Additional information

Funding

The authors are grateful to all organisations that funded the research in this paper, which was financially supported by the National Innovation Team Foundation [grant number 51221961] (China); the National Natural Science Foundation of China (General Program) [grant number. 51679034]; the National Natural Science Foundation of China [grant number 11202047]; the Fundamental Research Funds for the Central Universities [grant number DUT16TD11]; and Natural Science Foundation of Liaoning Province [grant number 2015020157] (China), Collaborative Innoration Center of Major Machine Manufacturing in Liaoning Province.