A Study of Dynamic Ship Positioning System

• Main Authors: Ton Gen Pan, 潘同晉
• Other Authors: Y. Z. Kehr
• Format: Others
• Language: zh-TW
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/12565416675823835181

碩士 === 國立海洋大學 === 系統工程暨造船學系 === 89 === This work is concerned with the design of a dynamic ship positioning(D.P.) system controller via the Linear Quadratic Gaussian (LQG) method to maintain the vessel within a prescribed region by using the limited thruster power . A three-degree-of-freedom linear surge-sway-yaw model accompanied by the wind , current and wave disturbances are considered. The LQG method is essentially composed of the Linear Quadratic Regulator (LQR) and the Kalman Filter (K.F.). Specifically the K.F. is used to separate the high frequency components of the vessel motion due to wave oscillatory forces from the low frequency ship motions caused by the wind and currents. Only the low frequency ship motion components are fedback into the feedback loop to be compensated by the limited thruster power. This will avoid constantly fighting against the high frequency wave induced oscillatory motions in vain. With proper selection of the weighting matrices in the performance index to be minimized, the vessel can be maintained within 7 meters accuracy without causing thruster saturation. An optimization technique is used to distribute the required thruster forces among the six thrusters on board the vessel in an optimal way.