Type of Document	Master's Thesis
Author	Nickell, Christopher Lee
Author's Email Address	cnickell@vt.edu
URN	etd-09122005-121951
Title	Modular Modification of a Buoyant AUV for Low-Speed Operation
Degree	Master of Science
Department	Aerospace and Ocean Engineering
Advisory Committee	Advisor Name Title Dr. Craig Woolsey Committee Chair Dr. Daniel Stilwell Committee Member Dr. Hanspeter Schaub Committee Member
Keywords	Autonomous Underwater Vehicle AUV Moving Mass Internal Actuation
Date of Defense	2005-09-09
Availability	unrestricted
Abstract Conventional streamlined autonomous underwater vehicles (AUVs) with a single thruster and stern planes are typically trimmed to be somewhat buoyant or heavy in water. To maintain depth, they must generate a constant hydrodynamic force which requires that they swim at a constant pitch angle. Although tail fins are the typical mechanism for generating this control moment, they become ineffective at low speeds. To enable an existing AUV to travel at lower speeds, one may easily incorporate a modular moving mass actuator. In some cases, it may also be advantageous to include a fixed wing. The equations of motion and equilibrium conditions to regulate depth are derived, and the effectiveness and low-speed efficiency of a fixed wing is evaluated. The effect of the vertical offset of the moving mass is analyzed to establish the relation between the control angle and the moving mass linear position. A description of the design of a one degree of freedom moving mass actuator module and preliminary experiments using the Virginia Tech Miniature AUV is provided. Data is presented for a series of fixed MMA position experiments as well as a dynamic position test. The results illustrate the effectiveness of a moving mass actuator at generating low-speed control moments. With the collected data, parameter identification is performed to get an estimate of the hydrodynamic parameters.
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