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Open Access Publications from the University of California

Control and optimization of wave-induced motion of ramp- interconnected craft for cargo transfer

Abstract

A two vessel interconnected by a ramp system was modeled using SimMechanics toolbox in Simulink. Both vessels were modeled as half cylinders and the ramp as a rectangular solid. Although the equations of motion for the system were derived, the SimMechanics model proved to be more efficient to implement certain control and optimization techniques and is emphasized throughout the thesis. This thesis documents different attempts to control and optimize the various motions of the system using passive and active methods. The passive methods include extremum seeking tuning of two parameters namely the ramp length and wave heading angle to reduce the pitch angle amplitude at the joint connecting the ramp and T-Craft. The second method employed mimics automotive shock absorbers to reduce relative motion between each vessel and ramp to reduce overall ramp motions. In both methods the results concur with the goal of the problem statement of stabilizing ramp/vessel motions. Applying the ES algorithm to tune the ramp length and wave heading angle reduced the pitch amplitude by 67% (from approx. 15 to 5 degrees) and applying the shock absorbers in the pitch joint case of the system reduced the pitch angle amplitude by two orders of magnitude (from approx. 10 to 0.1 degrees). The active method explored is installing a control moment gyroscope on the T-Craft to stabilize its roll motion. The results show that roll motion is decreased to lie within the stability region of one degree in amplitude and have a feasible size and weight requirement

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