AUVAC

Exploring the oceans – 20,000 colleagues under the sea

January 9, 2013
Exploring the oceans 20,000 colleagues under the sea, The Economist, Jan 9, 2013

SAILING the seven seas is old hat. The latest trick is to glide them. Sea gliders are small unmanned vessels which are now cruising the briny by the hundred. They use a minuscule amount of power, so they can stay out for months. And, being submarines, they are rarely troubled by the vicissitudes of weather at the surface. Their only known enemies are sharks (several have come back covered in tooth marks) and fishing nets.

Sea gliders are propelled by buoyancy engines. These are devices that pump oil in and out of an external bladder which, because it deflates when it is empty, means that the craft’s density changes as well. This causes the glider to ascend or sink accordingly, but because it has wings some of that vertical force is translated into horizontal movement. Such movement is slow (the top speed of most gliders is about half a knot), but the process is extremely efficient.

That means gliders can be sent on long missions. In 2009, for example, a glider called Scarlet Knight, operated by Rutgers University, in New Jersey, crossed the Atlantic on a single battery charge, though it took seven months to do so.

Since that crossing, gliders have been deployed on many previously unthinkable missions. In 2010 teams from the American navy, the Scripps Institution of Oceanography and iRobot, a robot-maker based in Bedford, Massachusetts, used them to track the underwater effects of the Deepwater Horizon oil spill in the Gulf of Mexico. That same year a glider owned by Oregon State University watched an underwater volcano erupting in the Lau basin near Tonga. In 2011 a glider made by another firm, Teledyne Webb of East Falmouth, also in Massachusetts, tracked seaborne radiation leaked from the tsunami-damaged reactors in Fukushima, Japan. And the University of Newfoundland is planning to use gliders equipped with sonar to inspect icebergs, to work out whether they are a threat to underwater cables and other seabed infrastructure.

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Glacier expedition a success for NUWC Division Newport and NASAGlacier expedition a success for NUWC Division Newport and NASA

October 1, 2012
Farley S, Glacier expedition a success for NUWC Division Newport and NASA [PART 2], NUWC Newport, Oct 1 2012

The mission: determining the utility of AUVs for collecting data on the rapidly receding Helheim Glacier.

They needed to determine [1] how an underwater vehicle could reach the glacier, [2] find a sonar system that would work with both glacial and arctic ice, and [3] understand the operational challenges inherent in such an isolated environment. The team also needed to assess operational logistics for future AUV operations through the deployment of glider AUVs for oceanography and an assessment is also needed for a multi-narrow beam sonar for iceberg profiling and for the creation of future obstacle avoidance algorithms.

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360°: A Glider Testbed That Rolls Over

July 3, 2012
Woolsey C, 360°: A Glider Testbed That Rolls Over, VaCAS, July 3 2012

When VaCAS researchers were unable to find an underwater glider that could test their different designs and control algorithms, they decided to build one. Now working on their second version of the testbed, the researchers, led by aerospace and ocean engineering faculty members Craig Woolsey and Leigh McCue, are developing an underwater glider that is very different from its peers.

A 360 ROLL CAPABILITY
The Virginia Tech testbed glider shares the general design elements and capabilities of other underwater gliders; however, it has a creative buoyancy actuation system and it can roll over. With this rollover capability, researchers can test more efficient turning schemes and control algorithms.

Most underwater gliders use symmetric airfoils to achieve high efficiency whether sinking or rising. The ability to roll over means that this glider does not need symmetric airfoils, and can therefore use more efficient, curved (“cambered”) airfoils — like the ones used for gliders in the air.

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Slocum Glider Expanding the Capabilities

August 22, 2011
Jones C, Webb D, Slocum Glider Expanding the Capabilities, UUST 17, Aug 2011

Architecture: A significant change is that instead of providing shallow and deep gliders, the G2 is pressure tolerant to 1000 meters depth operation and, building on the modular concept, can be outfitted with interchangeable front pump sections that are optimized for the operational depths. Pump combinations include 30, 100, 200, 350, and 1000 meters. Carrying the additional structure to handle a greater pressure tolerance and still have acceptable payload performance in the shallow water regime is made possible by utilizing our patented composite hulls sections that are significantly lighter than aluminum and additionally are tuned to match the compressibility of water – saving buoyancy drive energy during ascent and descent.

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Steady three dimensional gliding motion of an underwater glider

May 26, 2011
S. Zhang, J. Yu, A. Zhang, and Fumin Zhang, “Steady Three Dimensional Gliding Motion of an Underwater Glider,” in Proc. 2011 IEEE Conference on Robotics and Automation (ICRA 2011), 2011.

Abstract

Underwater Gliders have found broad applications in ocean sampling. In this paper, the nonlinear dynamic model of the glider developed by the Shenyang Institute of Automation, Chinese Academy of Sciences, is established. Based on this model, we solve for the parameters that characterize steady state spiraling motions of the glider. A set of nonlinear equations are simplified so that a recursive algorithm can be used to find the solutions.

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Dynamic Modeling and Motion Simulation for A Winged Hybrid-Driven Underwater Glider

October 26, 2010
WANG Yan-hui, WU Jian-guo, and WANG Xiao-ming, Dynamic Modeling and Motion Simulation for A Winged Hybrid-Driven Underwater Glider, China Ocean Eng., Vol. 25, No. 1, pp. 97 – 112

ABSTRACT
PETREL, a winged hybrid-driven underwater glider is a novel and practical marine survey platform which combines the features of legacy underwater glider and conventional AUV (autonomous underwater vehicle). It can be treated as a multi-rigid-body system with a floating base and a particular hydrodynamic profile. In this paper, theorems on linear and angular momentum are used to establish the dynamic equations of motion of each rigid body and the effect of translational and rotational motion of internal masses on the attitude control are taken into consideration. In addition, due to the unique external shape with fixed wings and deflectable rudders and the dual-drive operation in thrust and glide modes, the approaches of building dynamic model of conventional AUV and hydrodynamic model of submarine are introduced, and the tailored dynamic equations of the hybrid glider are formulated. Moreover, the behaviors of motion in glide and thrust operation are analyzed based on the simulation and the feasibility of the dynamic model is validated by data from lake field trials.

Key words: hybrid-driven; underwater glider; autonomous underwater vehicle; dynamic modeling; momentum theorem

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A new world of velocity measurements for gliders

October 31, 2009
Seigle E, A new world of velocity measurements for gliders, Marine Technology Reporter, Oct 2009

Why current profiling from gliders?

There are really good reasons for making current velocity measurements on a glider. Simply using profiles of current velocity structure and shear as a reference to interpret contour plots of other physical variables is reason enough for many researchers. Measuring higher velocity in  one location compared to another could provide evidence of upwelling. Observing variation in the velocity shear at different locations can provide insight to the formation and dissipation of phytoplankton thin layers. Or simply use the acoustic backscatter to map and quantify zooplankton in an effort to understand zooplankton in a effort to understand zooplankton distribution, dynamics, and relationship to whale or fish feeding.

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Autonomous observations of the ocean biological carbon pump.

June 30, 2009
Bishop, J.K.B. 2009. Autonomous observations of the ocean biological carbon pump. Oceanography 22(2):182–193, doi:10.5670/oceanog.2009.48.

Abstract.

Prediction of the substantial biologically mediated carbon flows in a rapidly changing and acidifying ocean requires model simulations informed by observations of key carbon cycle processes on the appropriate spatial and temporal scales. From 2000 to 2004, the National Oceanographic Partnership Program (NOPP) supported the development of the first low-cost, fully autonomous ocean profiling Carbon Explorers, which demonstrated that year-round, real-time observations of particulate organic carbon (POC) concentration and sedimentation could be achieved in the world’s ocean. NOPP also initiated the development of a particulate inorganic carbon (PIC) sensor suitable for operational deployment across all oceanographic platforms. As a result, PIC profile characterization that once required shipboard sample collection and shipboard or shore-based laboratory analysis is now possible to full ocean depth in real time using a 0.2-W sensor operating at 24 Hz. NOPP developments further spawned US Department of Energy support to develop the Carbon Flux Explorer, a free vehicle capable of following hourly variations of PIC and POC sedimentation from the near surface to kilometer depths for seasons to years and capable of relaying contemporaneous observations via satellite. We have demonstrated the feasibility of real-time, low-cost carbon observations that are of fundamental value to carbon prediction and that, when further developed, will lead to a fully enhanced global carbon observatory capable of real-time assessment of the ocean carbon sink, a needed constraint for assessment of carbon management
policies on a global scale.

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Autonomous Underwater Gliders

December 31, 2008
Wood S, Autonomous Underwater Gliders, Intech, Dec 2008

Over the past few decades, a range of strategies and techniques has been used to monitor the sea. More recently, the role of monitoring has been expanded to include the use of autonomous underwater vehicles to perform ocean surveys. With these vehicles it is now possible for the scientist to make complex studies on topics such as the effect of metals, pesticides and nutrients on fish abundance, reproductive success and ability to feed, or on contaminants such as chemicals or biological toxins that are transported in particulate form and become incorporated into living organisms (plankton, bivalves, fishes) or become deposited in bottom sediments. The scientist or environmentalist may desire to detect hazardous substances in the ocean such as chemicals from an underwater vent or toxic algae such as red tide. Additionally, the military’s detection of mines, biological, chemical or radioactive threats are also very important in the monitoring of the seas.

These considerations explain today’s development of new types of autonomous underwater vehicles with integrated sampling equipment that is able to perform a wide-range of fully automated monitoring surveys over extended periods of time. These vehicles survey and monitor the sea environment in a cost-effective manner combining survey capabilities, simultaneous water sampling and environmental data gathering capacities. Included in these types are autonomous underwater gliders that have the ability to glide for long distances and are in some cases able to travel under power. There are currently four classes of underwater gliders: 1) those that use mechanical or electrical means of changing their buoyancy (i.e., drop weights, or electrical power from batteries), 2) those that use the thermal gradient of the ocean to harness the energy to change the vehicle’s buoyancy, 3) those that are able to use other means of power such as ocean wave energy, and 4) hybrid vehicles that use standard propulsion systems and glider systems.

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Slocum Gliders – Advancing Oceanography

August 19, 2007
Jones C, Webb D, Slocum Gliders – Advancing Oceanography, AUSI Aug 19 2007

Rutgers University Coastal Ocean Observation Lab (RU-COOL) and Webb Research Corporation (WRC) continue to apply the autonomous underwater Slocum gliders in field operations spanning the globe. Our goal is to share the operational experience that we have had with this class of vehicle in the past years and to show the unique data sets acquired.

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Underwater Gliders for Ocean Research

December 1, 2004
Rudnick, Davis, Eriksen, Frantantoni, Perry, “Underwater Gliders for Ocean Research,” Marine Technology Journal, vol. 38, no. 1, Dec., pp. 48-59, 2004.

Abstract
Underwater gliders are autonomous vehicles that profile vertically by controlling buoyancy and move horizontally on wings. Gliders are reviewed, from their conception by Henry Stommel as an extension of autonomous profiling floats, through their development in three models, and including their first deployments singly and in numbers. The basics of glider function are discussed as implemented by University of Washington in Seaglider, Scripps Institution of Oceanography in Spray, and Webb Research in Slocum. Gliders sample in the archetypical modes of sections and of “virtual moorings.” Preliminary results are presented from a recent demonstration project that used a network of gliders off Monterey. A wide range of sensors has already been deployed on gliders, with many under current development, and an even wider range of future possibilities. Glider networks appear to be one of the best approaches to achieving subsurface spatial resolution necessary for ocean research.

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Seaglider: A Long-Range Autonomous Underwater Vehicle for Oceanographic Research

October 1, 2001
Eriksen C. Osse T. Light R. Wen T. Lehman T. Peter L. Sabin P. Ballard J. and Chiodi A. Seaglider: A Long-Range Autonomous Underwater Vehicle for Oceanographic Research, IEEE JOURNAL OF OCEANIC ENGINEERING, VOL. 26, NO. 4, OCTOBER 2001

Seagliders are small, reusable autonomous underwater vehicles designed to glide from the ocean surface to a programmed depth and back while measuring temperature, salinity, depth-averaged current, and other quantities along a sawtooth trajectory through the water. Their low hydrodynamic drag and wide pitch control range allows glide slopes in the range 0.2 to 3. They are designed for missions in range of several thousand kilometers and durations of many months. Seagliders are commanded remotely and report their measurements in near real time via wireless telemetry. The development and operation of Seagliders and the results of field trials in Puget Sound are reported.

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