Underwater glider

An underwater glider is a type of autonomous underwater vehicle (AUV) that employs variable-buoyancy propulsion instead of traditional propellers or thrusters. It employs variable buoyancy in a similar way to a profiling float, but unlike a float, which can only move up and down, an underwater glider is fitted with hydrofoils (underwater wings) that allow it to glide forward while descending through the water. At a certain depth, the glider switches to positive buoyancy to climb back up, and the cycle is then repeated.

While not as fast as conventional AUVs, gliders offer significantly greater range and endurance compared to traditional AUVs, extending ocean sampling missions from hours to weeks or months, and to thousands of kilometers of range.[1]

The typical up-and-down, sawtooth-like profile followed by a glider can provide data on temporal and spatial scales unattainable by ordinary AUVs and much more costly to sample using traditional shipboard techniques. A wide variety of glider designs are in use by navies and ocean research organizations and typically cost around US$100,000.[1][2]

RU02 flying in Sargasso Sea
A Rutgers Slocum RU02 underwater glider deployed


A University of Washington Seaglider being prepared for deployment
A Seaglider at the surface between dives

The concept of an underwater glider was first explored in the early 1960s with a prototype swimmer delivery vehicle named Concept Whisper.[3] The sawtooth glide pattern, stealth properties and the idea of a buoyancy engine powered by the swimmer-passenger was described by Ewan Fallon in his Hydroglider patent submitted in 1960.[4] In 1992, the University of Tokyo conducted tests on ALBAC, a drop weight glider with no buoyancy control and only one glide cycle.[1] The DARPA SBIR program received a proposal for a temperature gradient glider in 1988. DARPA was aware at that time of similar research projects underway in the USSR.[5] This idea, a glider with a buoyancy engine powered by a heat exchanger, was introduced to the oceanographic community by Henry Stommel in a 1989 article in Oceanography, when he proposed a glider concept called Slocum, developed with research engineer Doug Webb. They named the glider after Joshua Slocum, who made the first solo circumnavigation of the globe by sailboat. They proposed harnessing energy from the thermal gradient between deep ocean water (2-4 °C) and surface water (near atmospheric temperature) to achieve globe-circling range, constrained only by battery power on board for communications, sensors, and navigational computers.[3]

By 2003, not only had a working thermal-powered glider (Slocum Thermal) been demonstrated by Webb Research (founded by Doug Webb), but they and other institutions had introduced battery-powered gliders with impressive duration and efficiency, far exceeding that of traditional survey-class AUVs.[6] These vehicles have been widely deployed in the years since then. The University of Washington Seaglider, Scripps Institution of Oceanography Spray, and Teledyne Webb Research Slocum vehicles have performed feats such as completing a transatlantic journey[7] and conducting sustained, multi-vehicle collaborative monitoring of oceanographic variables.[1]

In 2011, the first wingless glider, SeaExplorer was released with a large payload capacity, dedicating the first third of the vehicle to interchangeable payloads, in addition to typical CTD sensors. The vehicle achieves 1 knot speeds, is equipped with externally rechargeable Li-Ion batteries and its torpedo shape is able to glide relying on two pairs of small static rear fins for stability.

Functional description

Slocum-Glider-Auvpicture 5
NOAA personnel launch a Slocum glider

Gliders typically make measurements such as temperature, conductivity (to calculate salinity), currents, chlorophyll fluorescence, optical backscatter, bottom depth, and (occasionally) acoustic backscatter. They navigate with the help of periodic surface GPS fixes, pressure sensors, tilt sensors, and magnetic compasses. Vehicle pitch is controllable by movable internal ballast (usually battery packs), and steering is accomplished either with a rudder (as in Slocum) or by moving internal ballast to control roll (as in SeaExplorer, Spray and Seaglider). Buoyancy is adjusted either by using a piston to flood/evacuate a compartment with seawater (Slocum) or by moving oil in/out of an external bladder (SeaExplorer, Seaglider, Spray, and Slocum Thermal). Commands and data are relayed between gliders and shore by satellite.[3]

Gliders vary in the pressure they are able to withstand. The Slocum model is rated for 200 meter or 1000 meter depths. Spray can operate to 1500 meters, Seaglider to 1000 meters, SeaExplorer to 700, and Slocum Thermal to 1200. In August 2010, a Deep Glider variant of the Seaglider achieved a repeated 6000-meter operating depth.[1] Similar depths have been reached by a Chinese glider in 2016. [8]

Liberdade class flying wings

In 2004, the US Navy Office of Naval Research began developing the world's largest gliders, the Liberdade class flying wing gliders, which uses a blended wing body hullform to achieve hydrodynamic efficiency. They were initially designed to quietly track diesel electric submarines in littoral waters, remaining on station for up to 6 months. The current model is known as the ZRay and is designed to track and identify marine mammals for extended periods of time.[9] It uses water jets for fine attitude control as well as propulsion on the surface.[9][10]

See also


  1. ^ a b c d e Wood, Stephen (2009). "26. Autonomous Underwater Gliders". Underwater vehicles (pdf). IntechOpen. p. 499. doi:10.5772/107. ISBN 978-953-7619-49-7. Retrieved 23 May 2019.
  2. ^ US patent 7987674, Jack A. Jones; Yi Chao & Thomas I. Valdez, "Phase Change Material Thermal Power Generator", issued 2011-08-02
  3. ^ a b c Jenkins, Scott A.; Humphreys, Douglas E; Sherman, Jeff; Osse, Jim; Jones, Clayton; Leonard, Naomi (May 6, 2003), Underwater Glider System Study, Scripps Institution of Oceanography, Report No. 53, retrieved May 26, 2012
  4. ^ US patent 3204596, Ewan S. Fallon, "Hydroglider", issued 1965-09-07
  5. ^ "Perpetual Autonomus Survey Submersible". Tony Bigras. Retrieved 2009-07-03.
  6. ^ Autonomous buoyancy-driven underwater gliders
  7. ^ Kirk Moore, "Rutgers undersea glider makes trans-Atlantic crossing," Daily Record, December 6, 2009 "Archived copy". Archived from the original on 2013-01-21. Retrieved 2009-12-16.CS1 maint: archived copy as title (link)
  8. ^ "PLA Navy eyes China's deep-sea underwater glider after successful test shows it rivals US vessel". South China Morning Post. Retrieved 2017-05-16.
  9. ^ a b D'Spain, Gerald L., XRay/ZRay Flying Wing Gliders, Scripps Institution of Oceanography, retrieved May 25, 2012
  10. ^ Liberdade XRay Advanced Underwater Glider, Office of Naval Research, April 19, 2006, retrieved May 25, 2012

External links

Autonomous logistics

Autonomous logistics describes systems that provide unmanned, autonomous transfer of equipment, baggage, people, information or resources from point-to-point with minimal human intervention. Autonomous logistics is a new area being researched and currently there are few papers on the topic, with even fewer systems developed or deployed. With web enabled cloud software there are companies focused on developing and deploying such systems which will begin coming online in 2018.

Autonomous underwater vehicle

An autonomous underwater vehicle (AUV) is a robot that travels underwater without requiring input from an operator. AUVs constitute part of a larger group of undersea systems known as unmanned underwater vehicles, a classification that includes non-autonomous remotely operated underwater vehicles (ROVs) – controlled and powered from the surface by an operator/pilot via an umbilical or using remote control. In military applications an AUV is more often referred to as an unmanned undersea vehicle (UUV). Underwater gliders are a subclass of AUVs.

Cargo spacecraft

Cargo spacecraft are robotic spacecraft that are designed to carry cargo, possibly to support space stations' operation by transporting food, propellant and other supplies. This is different from space probes, whose missions are to conduct scientific investigations.

Automated cargo spacecraft have been used since 1978 and have serviced Salyut 6, Salyut 7, Mir, the International Space Station and Tiangong space laboratory.

Hexapod (robotics)

A six-legged walking robot should not be confused with a Stewart platform, a kind of parallel manipulator used in robotics applications.

A hexapod robot is a mechanical vehicle that walks on six legs. Since a robot can be statically stable on three or more legs, a hexapod robot has a great deal of flexibility in how it can move. If legs become disabled, the robot may still be able to walk. Furthermore, not all of the robot's legs are needed for stability; other legs are free to reach new foot placements or manipulate a payload.

Many hexapod robots are biologically inspired by Hexapoda locomotion. Hexapods may be used to test biological theories about insect locomotion, motor control, and neurobiology.

Intervention AUV

Intervention AUV or I-AUV is a type of autonomous underwater vehicle. Its characteristic feature is that it is capable of autonomous interventions on the subsea installations, a task usually carried out by remotely operated underwater vehicles (ROVs) or human divers.

Legged robot

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Liberdade class underwater glider

Liberdade class blended wing bodies are autonomous underwater gliders developed by the US Navy Office of Naval Research which use a blended wing body hullform to achieve hydrodynamic efficiency. It is an experimental class whose models were originally intended to track quiet diesel electric submarines in littoral waters, move at 1–3 knots and remain on station for up to six months. The "Liberdade" (Portuguese for "Liberty") was the name of a ship cobbled together by Joshua Slocum prior to the one he single-handedly piloted around the world.

Members of the Liberdade class are the world's largest known underwater gliders and were developed as part of the US Navy's Persistent Littoral Undersea Surveillance Network (PlusNet) system of unmanned surveillance vehicles. The gliders can be deployed covertly with the capability of monitoring over 1000 km of ocean. The glider is designed to be difficult to detect using passive acoustic sensing.The Marine Physical Lab at Scripps Institution of Oceanography, and the Applied Physics Lab at the University of Washington are the primary developers of the Liberdade class. The hull of the latest model was constructed by Legnos Boat, and consists of an ABS outer shell over a titanium frame. First major field tests of the Liberdade XRay took place in 2006 in Monterey Bay, California. Also participating in the development of the Liberdade class wings were:

University of Texas at Austin’s Applied Research Lab

Applied Research Lab at Penn State University

Massachusetts Institute of Technology

Woods Hole Oceanographic Institution


Bluefin RoboticsIn 2007, XRay 2 was completed and demonstrated a 20 to 1 lift-to-drag ratio. In 2008, 55 field tests were conducted. In 2010, the latest generation "ZRay" model was completed and includes a 27 channel hydrophone array. Its goal is to track and automatically identify marine mammals. ZRay has a 35 to 1 lift-to-drag ratio, and has water jets for fine attitude control, as well as propulsion on the surface.

List of hexapod robots

This is a list of hexapod robots.

Medical robot

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OpenROV (open-source remotely operated vehicle) is a low-cost telerobotic submarine/underwater drone built with the goal of making underwater exploration and education affordable.

Pacific Research Laboratories

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The company also works in product development and design, including quick-turnaround projects using urethanes, silicones, glass/carbon fibers, braided fiberglass, thermoplastics, electronics, hydraulics, and pneumatics; the creation of prototypes, master patterns, and tooling; reverse engineering; laser scanning; and manufacturing using 3D printing, 3-axis CNC router, 4-axis CNC machining, and a triaxial fiberglass braider.

In December 2010, Pacific Research Laboratories became employee owned under an employee stock ownership plan (ESOP).

Paravane (weapon)

The paravane , a form of towed underwater "glider" with a warhead that was used in anti-submarine warfare, was developed from 1914–16 by Commander Usborne and Lieutenant C. Dennistoun Burney, funded by Sir George White, founder of the Bristol Aeroplane Company. It was used against naval mines and submarines.

Petrel HUG

Petrel hybrid underwater glider (HUG) is a Chinese autonomous underwater vehicle (AUV)/autonomous underwater glider (AUG)/remotely operated underwater vehicle (ROUV) developed by Tianjin University. After the initial Petrel, a follow-on Petrel II has also been fielded by the same developer.

The need of Petrel HUG is due to the inherent problem of AUG, namely, its speed. Typical speed of traditional AUG is less than 0.5 kt and although at this speed, the endurance of the AUG can last several months, this presents a problem when the speed of the oceanic current is greater than that of the AUG, where it would impossible for the AUG to successfully accomplish its mission. A high speed AUG is therefore needed for prolonged missions in the high speed oceanic currents environment. Petrel AUG is the Chinese answer to this problem. Petrel HUG is designed to combine the advantage of both AUV and AUG, and can act in either role by automatically switching between the two modes based on command or environmental conditions. There is also a manual override mode to operate Petrel HUG as ROUV via remote control. Petrel HUG is designed by a design team consisting three members of Tianjin University: Professor Wang Shu-Xin (王树新), Associate Professor Wang Yan-Hui, (王延辉, unrelated to Wang Shu-Xin) and PhD graduate student Liu Fang.

Remote control vehicle

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Unmanned vehicle

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Wave base

The wave base, in physical oceanography, is the maximum depth at which a water wave's passage causes significant water motion. For water depths deeper than the wave base, bottom sediments and the seafloor are no longer stirred by the wave motion above.

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