Date of Award

Winter 2003

Document Type


Degree Name

Doctor of Philosophy (PhD)


Mechanical Engineering

Committee Director

Jen-Kuang Huang

Committee Member

Sebastian Bawab

Committee Member

Gene Hou

Committee Member

Duc T. Nguyen


The primary influences of ship motion are roll motion. The purpose of this dissertation is to discuss a means to reduce the roll amplitude of ship motion in the case of zero forward speed using the roll mitigation device known as the flume tank, or U-tube, tank. Passive control and active control are studied. Optimal feedback control is the designated algorithm for activated roll mitigation device. The assumed model in this study is a submarine chaser. The linear coupled equation of swaying, rolling, and yawing motion of this assumed model is studied. The roll motion of this vessel is investigated under Sea State 3. The irregular wave, which attacked the ship hull, is studied with different encounter angles. The large roll amplitude is found when the wave encounters ship hull at Beam Sea (β = 90°). The simulation results of passive control demonstrate that the flume tank creates high damping system under various wave angle's attacks. This mitigation device can cancel the roll amplitudes over 50%. For an activated anti-rolling tank, the optimal feedback control (LQR) shows that the full-state-variables method results in a high-damped system as well as the suboptimal feedback control. Technically, the linear coupled equation of motion should improve to the nonlinear range in order to obtain higher accuracy of the ship's motion and online control algorithms should be developed.