Abstract
As the water depth of offshore oil/gas development becomes deeper, cost reduction of installing various subsea facilities becomes more important. Using an existing installation vessel, a new method which is applicable to more precise installation of subsea modules should be developed. As for future resource development in the Japanese EEZ, the cost reduction of the development systems and their installation is essential. In this paper, I examine a possibility of a method which uses active control of a structure. The structure is suspended from an installation vessel and a thruster is attached to control the horizontal position relative to the vessel. The control force is LQR feedback based on the modeling of the linearized equations of motion. Several simulation results showed if the descending speed of the structure is higher the horizontal displacement becomes larger, which means there is a trade-off relation in saving time with accurate positioning. From the simulation, active control method has possibility to solve this trade-off issue and seems effective for precise installation to the deep sea and may reduce the total installation cost.
