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Nonlinear dynamics of autonomous underwater vehicles in ocean currents
Title
Nonlinear dynamics of autonomous underwater vehicles in ocean currents.
Creator
Li, Bo, Su, Tsung-Chow, Graduate College
Abstract/Description
Ocean is human’s last frontier on Earth with most of its space inaccessible to human and remains largely unexplored. For the protection of our ocean and its sound development, unmanned autonomous underwater vehicle AUV, plays an increasingly important role. However, today’s AUV can’t function in a strong current environment. Propeller-driven AUVs typically move at speeds of up to 1.5-2.0 m/s, and thus strong ocean currents could push AUVs way from the planned paths. And their control surfaces...
Show moreOcean is human’s last frontier on Earth with most of its space inaccessible to human and remains largely unexplored. For the protection of our ocean and its sound development, unmanned autonomous underwater vehicle AUV, plays an increasingly important role. However, today’s AUV can’t function in a strong current environment. Propeller-driven AUVs typically move at speeds of up to 1.5-2.0 m/s, and thus strong ocean currents could push AUVs way from the planned paths. And their control surfaces may not work properly, especially when AUVs are maneuvering. Extra thrusters may be added to improve the maneuverability, yet the endurances of the vehicles will be shortened since extra thrusters consume more power. On the other hand, buoyancy-driven underwater gliders, using internal actuators, are characterized by long endurance. However, gliders typically move at horizontal speeds of about 0.3 m/s, which make gliders unsuitable for the missions in strong ocean currents. In the present research, a hybrid AUV design will be studied which combines the capabilities of both AUVs and underwater gliders. The proposed AUV will be propeller-driven yet the maneuverability of the vehicle in both horizontal and vertical planes will be achieved by using internal actuators instead of control surfaces and extra thrusters. The research will mainly focus on the control strategy of an AUV in a horizontal plane by using internal actuators to exploit the vehicle’s coupling effect of the roll motion on horizontal motions to maneuver AUV in a strong current environment.
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Date Issued
2015
PURL
http://purl.flvc.org/fau/fd/FA00005895
Format
Document (PDF)
Fluid Structure Interaction and Morphing Ocean Structure Deployment
Title
Fluid Structure Interaction and Morphing Ocean Structure Deployment.
Creator
Li, Yanjun, Su, Tsung-Chow, Graduate College
Abstract/Description
As human explore deeper into ocean, more and more subsea structures need to be installed. Deployable structures, a folded package which could be drop from surface and at destination morphing into its final structure form have significant advantages like its counterpart in space structures. More recently, many space missions have proposed large inflatable structure for different proposes. In lieu of the difference between outer space and underwater environment, it is necessary to include the...
Show moreAs human explore deeper into ocean, more and more subsea structures need to be installed. Deployable structures, a folded package which could be drop from surface and at destination morphing into its final structure form have significant advantages like its counterpart in space structures. More recently, many space missions have proposed large inflatable structure for different proposes. In lieu of the difference between outer space and underwater environment, it is necessary to include the fluid structure interaction in underwater deployable inflatable structures application to study the effect of dense liquid environment on the inflating dynamics of ocean structures. The purpose for the present research is to demonstrate, through a numerical simulation and a small scale water tank test, a Deployable Structure for Intervention on Oil Seeps DISIOS, which could form an underwater dome and collect lower density chemicals from oil seep. DISIOS prototype are formed by membranes and inflatable tubes, where tubes act as framework to support the membranes to construct a dome. The study begin with simulate water injection into flatted structures to verify the ability of LS-Dyna software. Deflection and velocity of membranes are recorded to compare with experiment data. Then we turned to inflate process of folded structure by different folded methods. From unfolding process simulation, we could determine which type of fold method works best for our predesign shape of tube. We are now conducting the dynamic analysis of inflatable tube, which is the elementary component of DISIOS framework.
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Date Issued
2015
PURL
http://purl.flvc.org/fau/fd/FA00005896
Format
Document (PDF)