C. L. Siow

Underwater Target Tracking of Offshore Crane System in Subsea Operations

Accurate underwater target tracking during subsea lowering is a complex technological problem in offshore installation and deep ocean mining. It involves the real-time motion compensation of both combined effects from flow-induced vibration on the cable-payload and wave-induced motions on the host vessel. A target tracking mechanism for a planar motion was theoretically derived and simulated in this paper under both regular and irregular wave motions. The simulation results have shown that the proposed target tracking system, by using PID controller integrated with hydrodynamic effects of both surface vessel and subsea payload, has followed the movable subsea target with small vicinity. The findings of this paper can be further implemented in the development of automatizing the subsea operations of the offshore crane system.

TLP Motion Effect on Semisubmersible Motion

Floating structures play an important role in exploring the oil and gas from the sea. In loading and offloading, motion responses of offshore floating, structures are affected through hydrodynamic interaction. Large motions between floating bodies would cause the damage of moorings, offloading system and may colloid to each other. This research discussed on the hydrodynamic interaction between Tension Leg Platform (TLP) and Semisubmersible (Tender Assisted Drilling (TAD)) in regular waves with the scenario of 6-DOF both TLP and semisubmersible. The experiment is carried out in the Universiti Teknologi Malaysia (UTM) Towing Tank using semisubmersible GVA 4000 type. As primarily study, the experiment was conducted without Tension Leg. The wave height in full-scale ranges from 5.8 m - 11 m and separation distance of the models is 21.7 m. The results shows that surge, heave and pitch responses amplitude located at frequency 0.3 rad/s and 0.9 rad/s.