Date of Award

Winter 2003

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Mechanical Engineering

Committee Director

Jen-Kuang Huang

Committee Member

Sebastian Bawab

Committee Member

Keith M. Williamson

Committee Member

Cheng Lin

Abstract

This dissertation uses the Generalized Predictive Control (GPC) approach to design a control system for a ship rolling motion coupled with the sway and yaw using an activated flume tank. GPC is a strategy based on system output prediction over finite horizon known as the prediction horizon. GPC controller is designed from the coefficients of the Autoregressive model with exogenous input (ARX) that are computed directly from input and output data. It computes the future control input based on the cost function with weighted input and output. System identification approach is implemented on the system to find the ARX coefficients parameters.

A mathematical model of the anti-rolling flume tank and the ship coupling model are derived to be in the state space form. The time domain model of the ship motions has been extended to predict the coupling motions of sway, yaw and roll. Also, the disturbance model is generated as irregular waves. Analyses for the ship rolling and coupling models, with and without the anti-rolling flume tank, are presented.

A numerical simulation using the MATLAB program is implemented. The numerical simulation indicates that there are three factors that affect the ship motions: sea state conditions, wave attack angle and ship control system. The simulation result shows that the passive control system using an anti-rolling flume tank is able to reduce the ship rolling angle up to fifty percent.

In comparison, simulation result of the actively controlled system using GPC shows that the ship rolling angle can be mitigated up to eighty percents. The GPC approach is tested on the ship model in different weather conditions. The numerical simulation is implemented to evaluate the controller performance and investigate the benefit of the GPC in the ship coupling motions. The numerical results show that the coupling model of roll, sway and yaw can affect each other simultaneously. The roll motion can be affected by the sway force more than yaw moment. The effect and performance of the GPC in controlling the ship roll motion in different wave's disturbances and sea state conditions are discussed.

DOI

10.25777/5ag3-dc12

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