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Publications (4)0 Total impact

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    ABSTRACT: Most existing propeller-driven, cruising AUVs operate with a support ship and have an endurance of about one day. However, many oceanographic processes evolve over days or weeks, requiring propeller-driven vehicles be attended by a ship for complete observation programs. The Monterey Bay Aquarium Research Institute (MBARI) developed the 105 kg propeller-driven Tethys AUV to conduct science missions over periods of weeks or even months without a ship [1]. Here we describe a three week deployment covering 1800 km at a speed of 1 m/s, supporting sensor power levels averaging 5 watts. Unlike buoyancy driven gliders, Tethys uses a propeller that allows level flight and a variable speed range of 0.5 - 1.2 m/s. The extended endurance enables operations in remote locations like under the ice, across ocean basins in addition to enabling continuous presence in smaller areas. Early success led to the construction of a second Tethys-class AUV with a third in planning. An AUV docking station that can be mated to a cabled observatory or standalone mooring is in development to further extend Tethys endurance.
    Autonomous Underwater Vehicles (AUV), 2012 IEEE/OES; 01/2012
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    ABSTRACT: Thermoclines play a key role in ocean circulation, marine ecology, and underwater acoustics. In oceanographic surveys, it is often desirable to detect the thermocline and track its spatio-temporal variation. Mobility of an autonomous underwater vehicle (AUV) makes it an efficient platform for thermocline tracking. In this paper, we present a fully autonomous algorithm for detecting and tracking the thermocline by an AUV. The key is detection of the peak gradient of temperature. We have tested the algorithm by post-processing data from a previous Dorado AUV survey over the northern Monterey Bay shelf. We are in preparation for field tests of the algorithm on the newly developed long-range AUV Tethys.
    OCEANS 2010; 10/2010
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    ABSTRACT: A scripting language for state configured layered control of a long range autonomous underwater vehicle (AUV) is introduced. The XML-based language has been designed to meet the complex requirements for long-term autonomous operation. It does not require that mission planners be programmers, yet allows them to have a high degree of certainty at deployment that the robot will do what they want it to do. The script is simple to execute on the vehicle, both to minimize CPU power usage and to minimize the chance of failure due to complexity. Users do not need a high-fidelity model of the AUV to plan a mission, as the robot may change in unexpected ways over the course of the mission. Those who wish to do more advanced programming of mission commands and behaviors can do so in the script and are not able to crash the vehicle's operating system. To address these needs, the “Tethys script” state-configured layered control language has been developed.
    OCEANS 2010; 10/2010
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    ABSTRACT: The Tethys autonomous underwater vehicle (AUV) is a 110 kg vehicle designed for long-range, high- endurance operations. Performance goals include supporting a payload power draw of 8 W for a range of 1000 km at 1 m/s, and a power draw of 1 W for 4000 km at 0.5 m/s. Achieving this performance requires minimizing drag and maximizing propulsion efficiency. In this paper, we present the design of the propulsion system, explore the issues of propeller-hull interactions, and present preliminary test results of power consumption and efficiency. In recent underwater experiments, the propulsion system's power consumptions were measured in both Bollard pull tests and during the vehicle's flights. Preliminary results of power consumptions and efficiency are shown to be close to the theoretical predictions.
    Autonomous Underwater Vehicles (AUV), 2010 IEEE/OES; 10/2010