Pages 65-73
Recently various types of special vessel as like FPSO, shuttle tanker, and drill ship come to fore and are ordered from the European ship owner, because of the necessity of multi-purpose vessel and deep sea drilling rig. Traditionally mooring systems of offshore structures has been used to keep her position in relatively shallow water but nowadays Dynamic Positioning System is being used to keep her position in deep sea. In this study, DP simulation program is introduced. The program can predict the time varying motion of the ship with mooring and DP propulsion system in the horizontal plane. Motion equations used in this program considers the wind, waves, and current as the external forces and mooring line forces in addition to propulsion systems. To find the input variables of the positioning systems, PID and LQR processes are considered as the control system. Furthermore Kalman filter and digital filter are used to exclude the noise and high frequency components of motions in the calculation of input power. For the validation of this program, model test results of 125K shuttle tanker and 103K drill ship are used. The comparison between model tests results and sinulation results showed good agreements.
