21,069 research outputs found
Exploring beneath the PIG Ice Shelf with the Autosub3 AUV
No full textOn 31st January 2009, two numbers: “range and
bearing” flashing up on a laptop screen, indicated that Autosub3
had returned from its last mission beneath the Pine Island Glacier
(PIG) Ice Shelf in the Western Antarctic. The Autosub technical
team from NOCS, Southampton, onboard the US ice breaker
Nathanial B Palmer breathed a collective sigh of relief. Any
significant technical failure would have resulted in total loss of the
multi million Euro Autonomous Underwater Vehicle with no hope
of recovery from 60 km into the ice shelf cavity. This was the last
of six successful missions to investigate the shape the ice shelf, the
sea bed bathymetry, the currents and the physical oceanography
within the ice cavity. Each are vital to understanding the
interaction between the sea water and the ice shelf, and
quantifying whether the melting rate is changing. During the
cruise, Autosub3 had run beneath the ice for almost 4 days and
for 510 km.
Autosub3 had been exploring the Pine Island Glacier, a floating
extension of the West Antarctic ice sheet, as part of an
international team effort lead by Dr Adrian Jenkins of the British
Antarctic Survey and Dr Stanley Jacobs of the Lamont-Doherty
Earth Observatory, New York. Autosub3 was launched from the
Nathaniel B Palmer, an American icebreaker, as part of the two
month cruise to investigate the oceanography, biology and
glaciology of the Southern Amundsen Sea.
This paper will concentrate on the technical aspects of the
Autosub3 vehicle and its missions under the PIG, and seek to
answer a number of questions: How did the AUV successfully
dead reckon navigate for over 24 hours, and return accurately to
the rendezvous point? How did we cope with the possibility of ice
bergs or sea ice drifting over the recovery position ? How did
Autosub3 (almost always) avoid collision with the jagged ice shelf
above, or the unknown depths of the seabed? How did we
communicate with the vehicle at the start and the end of missions?
How did we manage risk, and prior to the cruise, what
modifications and testing did we apply to the AUV to improve the
overall reliability? What measures did we take during the cruise
to further improve our chances of a successful outcome ?
The paper will outline the history of the use of AUVs for polar
science. Results from the recent cruise will be presented showing
the actual mission tracks, with the echo sounder isonified ice draft
and seabed. Not all went completely to plan: the paper will also
describe the events of Autosub’s close scrape on its 4th mission
under the PIG.
This work was fun
RRS Discovery Cruise 343, 27 Sep-15 Oct 2009. Deepwater trials of the Autosub6000 AUV, HyBIS, and telemetry systems
No full textThere were 3 main objectives for the trials cruise: Testing of the Autosub6000 AUV, the HyBIS system (both supported by personnel from the National Oceanography Centre, Southampton), and acoustic and satellite telemetry systems (Proudman Oceanographic Laboratory, Liverpool). Specifically, the Autosub6000 trials were to test: the AUV, its systems and control to as deep as possible up to 6000 m, a new collision avoidance system based on scanned sonar collision avoidance sensor, and recently installed sensors (dual CT, LSS EH probe, magnetometer, Multibeam sonar sensors). The objectives of the HyBIS trials were to test the video guided grab system to as deep as possible, and to gain further operational experience. The objectives of the telemetry systems trials were to develop and test remote measurement technologies, deep water communication systems and a compact version of the MYRTLE (multi-year return tide level equipment) long term deep water recoverable lander. The cruise began with initial tests of the Autosub6000 AUV in the Celtic deep, followed by deep tests of the AUV to 5600m on the Iberian Abyssal plain. The majority of the work for the Autosub6000, HyBIS and the POL telemetry tests were carried out further south over and around the Casablanca seamount. A high percentage of the tests were successful, with Autosub6000 reaching a depth of 5600m
Simulations of a self propelled autonomous underwater vehicle
No full textThe missions being proposed for autonomous underwater vehicles (AUVs), by both marine scientists and industry, are becoming increasingly complex and challenging. In order to meet these demands the next generation of AUVs will need to be faster, operate for longer and be more manoeuvrable than existing vehicles. It is therefore vital that the hydrodynamic forces and moments acting on a self propelled manoeuvring AUV can be predicted accurately at the initial design stage. The flow around a typical AUV is both turbulent and three dimensional with significant interactions between the hull, propeller and control surfaces. An unsteady computational fluid dynamics analysis based on the Reynolds Averaged Navier Stokes (RANS) equations is too expensive for AUV design. In order to capture the action of the propeller at an acceptable computational cost, a novel method of coupling a commercial RANS solver with a body force propeller model based on blade element momentum theory has been developed. This discretises the propeller plane into a series of radial and circumferential sectors. The local axial and tangential inflow conditions at each sector of the propeller plane can then be considered. This allows analysis of non-uniform propeller inflow conditions due to the interaction of hull, propeller and control surfaces. During a manoeuvre the hull boundary layer may separate due to the adverse pressure gradient, resulting in free vortex sheets which roll up to form a pair of body vortices. An adaptive mesh strategy is required to ensure a suitable mesh structure and density to capture these flow features. Modifications to a vortex capture algorithm (VORTFIND) are proposed, optimising it as a tool for identifying the path of vortex structures. This enables it to be used as part of an iterative meshing strategy, capturing vortical flow features more accurately and consequently their influence on the pressure loading experienced by the hull. To demonstrate the pertinence of the numerical methods developed in this work a series of case studies has been analysed. These include: determining the hydrodynamic derivatives of an AUV, propeller-rudder interaction studies, steady state manoeuvring performance of the self propelled KVLCC2, and in-service straight line performance prediction of Autosub 3. These highlight the roles of the numerical methodologies in the design process for future AUVs. The techniques developed in this work enable the designer to accurately predict the hydrodynamic loading acting on a self propelled manoeuvring AU
Deploying an AUV beneath the Sørsdal Ice Shelf: Recommendations from an expert-panel workshop
No full textTo support future scientific missions beneath Antarctic ice shelves, the Antarctic Gateway Partnership, a special research initiative of the Australian Research Council, is trialling its Autonomous Underwater Vehicle, nupiri muka, at the Sørsdal Glacier in East Antarctica. As history has shown, deploying an AUV beneath ice is both challenging and inherently risky. To support the planning and execution of this mission a panel of experts were invited to participate in a workshop to provide both peer-review of the readiness of the AUV and team, and, to establish a set of recommendations and best-practices to maximise the data return and minimise the risk. This panel consisted of those working in the area of AUVs, Polar operations, and those with relevant experience.Recommendations from this panel included strict definition of mission objectives, a risk analysis methodology, and plans for a dress rehearsal. In addition a staged approach was formulated to both validate the AUV performance and parametrise the environment to reduce uncertainty
Report of the inquiry into the loss of Autosub2 under the Fimbulisen
No full textThe Board of inquiry into the loss of Autosub2 under the Fimbulisen found that the loss was caused by a technical systems failure on the AUV. A comprehensive analysis was made of the technical reasons for the loss. However, because it was not possible to recover the AUV from under the ice shelf for direct examination, it was not possible to identify the actual cause of loss. Consequently an assessment was made of the likelihood of different failure modes causing the loss. The results of this analysis suggest that the loss was equally likely to have come about from an Abort Command (AC) as a Loss of Power (LP). A root cause analysis was performed which indicated that the source of the failure was most likely to have been a fault introduced during the manufacturing/assembly phase (52%), followed by Maintenance (25%). Design error was considered less likely (14%) while Operations (7%) and External factors (1%) were considered least likely.This analysis indicates that the greatest benefits to reliability improvements are most likely to come from attention to faults originating in the manufacturing and assembly stage, followed by attention to faults arising from maintenance activities. Due to the large numbers of connections and leakage paths, it is necessary to pay particular attention to the reliability of electrical connectors and harnesses. A high level of quality assurance in manufacture and assembly is required to achieve an acceptable level of system reliability.While it was accepted that the development team at NOC had adopted sound engineering practices in the development of the AUV and that reliability considerations had informed design decisions, the design team had no formally implemented reliability or technical risk assessment procedures to support design decision making. This was considered to be a major management weakness
Team perfectionism and team performance: A prospective study
No full textPerfectionism is a personality characteristic that has been found to predict sports performance in athletes. To date, however, research has exclusively examined this relationship at an individual level (i.e., athletes’ perfectionism predicting their personal performance). The current study extends this research to team sports by examining whether, when manifested at team level, perfectionism predicts team performance. A sample of 231 competitive rowers from 36 boats completed measures of self-oriented, team-oriented, and team-prescribed perfectionism prior to competing against one another in a 4-day rowing competition. Strong within-boat similarities in the levels of team members’ team-oriented perfectionism supported the existence of collective team-oriented perfectionism at the boat level. Two-level latent growth curve modeling of day-by-day boat performance showed that team-oriented perfectionism positively predicted the position of the boat in mid-competition and the linear improvement in position. The findings suggest that imposing perfectionistic standards on team members may drive teams to greater levels of performance
Report of an independent peer review of A forest management strategy for the proposed Coquille Forest submitted to the Coquille Indian Tribe by the Independent Scientific Advisory Team (ISAT)
No full text"[T]he [Coquille Indian] Tribe requested that the State of Oregon assemble a team of independent scientists to peer review the forest management strategy proposed by the ISAT. The purpose of the independent peer review would be to: 1) assess the degree to which the two major goals assigned by the Tribe are met by the proposed ISAT forest management strategy, 2) validate the scientific soundness of the proposed strategy, 3) identify any gaps in the strategy or components not adequately addressed, and 4) make recommendations to correct deficiencies or to make improvements in the strategy. In response to the Tribe's request, the Governor's Office of Natural Resources assembled a team of independent peer reviewers and structured the process by which the review would be accomplished. The results of the IPR were presented to the ISAT in a conference open to the public which was held on November 21, 1995 at the LaSells Stewart Center, Oregon State University. Following is a consolidated report of major conclusions and recommendations presented by the independent reviewers to the ISAT at the November 21 public forum. This information also reflects key points contained in written reports prepared by IPR team members"--Page 2.Introduction -- Presentation by Independent Peer Review Team to the ISAT -- Independent Peer Reviewers (IPR) -- Introduction to the IPR process -- The "nine questions" and their answers -- Does the review team generally support the strategy of the proposed Coquille Forest -- Does the strategy meet the goals of the Northwest Forest Plan (NFP)? -- Is the adaptive management approach described in the strategy adequate? -- Is the monitoring approach described in the strategy? -- Is the strategy generally consistent with scientific knowledge? -- Are Northern spotted owls and riparian species adequately considered? -- Are aquatic species adequately considered? -- Are future natural disturbances adequately planned for in the strategy? -- Does the strategy meet Tribal goals? -- Overall comments -- Preliminary response by ISAT -- Response by the Coquille Indian Tribe -- Individual Independent Peer Reviewer reports / submitted by Peter Bisson, Bernard Bormann, Larry Davis, Walt Knapp, Jim Rochelle -- November 21, 1995 conference brochure ; list of conference attendeessubmitted to the State of Oregon Governor's Office of Natural Resources by the Independent Peer Review TeamThis archived document is maintained by the State Library of Oregon as part of the Oregon Documents Depository Program. It is for informational purposes and may not be suitable for legal purposesElectronic reproduction Salem, Or. State Library of Oregon 2023 Electronic reproduction from print version OrMode of access: Internet from the Oregon Government Publications CollectionText in Englis
Underwater AUV communication
No full textKomunikacija s AUV
om tijekom misije može se odvijati putem akustičnog modema kada je
potopljen ili putem radio frekvencije (mobitel, WiFi, satelit) kada vozilo ispliva na površinu.
AUV tehnologija ima la je intenzivnu fazu istraživanja i r azvoja tijek om 1990 ih koju su
uglavnom financirale nacionalne obrambene agencije, a komercijalna vozila nisu bila ši roko
dostupna tek oko 2000. AUV i i ROV i sve se više koriste u oceanografiji jer omogućuju
prikuplja nje podataka ko ji se inače ne bi mogli dobiti. Razvoj autonomnih podvodnih vozila
(AUV) dopustio je automatizacij u mnogih zadataka koji su prvo bi tno postignuti vozilima s
posadom u podvodnom okruženju. Timovi AUV ova osmišljenih za rad u okviru zajedničke
misije otvaraju mogućnosti za nove i s loženije aplikacije. U podvodnom okruženju,
komunikacija, lokalizacija, i navigacija AUV a smatraju se izazovima zbog nemogućnosti
oslanjanja na radio komunikaciju i globalne sustav e pozicioniranja.Communication
s with the AUV during the mission can take place via an acoustic modem
when submerged or via a radio frequency (mobile phone, WiFi, satellite) when the vehicle
comes to the surface. AUV techno logy had an intensive phase of research and development
during the 1990s, mostly funded by national defense agencies, and commercial vehicles were
not widely available until around 2000. AUVs and ROVs are increasingly used in
oceanography because they allow the collection of data that otherwise they would not be able
to get it. The development of autonomous underwater vehicles (AUVs) has allowed the
automation of many of the tasks originally accomplished by manned vehicles in an underwater
environment. Team s of AUVs designed to work on joint missions open up opportunities for
new and more complex applications. In the underwater environment, AUV communication,
localization, and navigation are considered challenges due to the inability to weaken radio
communication and global positioning systems
Underwater AUV communication
No full textKomunikacija s AUV
om tijekom misije može se odvijati putem akustičnog modema kada je
potopljen ili putem radio frekvencije (mobitel, WiFi, satelit) kada vozilo ispliva na površinu.
AUV tehnologija ima la je intenzivnu fazu istraživanja i r azvoja tijek om 1990 ih koju su
uglavnom financirale nacionalne obrambene agencije, a komercijalna vozila nisu bila ši roko
dostupna tek oko 2000. AUV i i ROV i sve se više koriste u oceanografiji jer omogućuju
prikuplja nje podataka ko ji se inače ne bi mogli dobiti. Razvoj autonomnih podvodnih vozila
(AUV) dopustio je automatizacij u mnogih zadataka koji su prvo bi tno postignuti vozilima s
posadom u podvodnom okruženju. Timovi AUV ova osmišljenih za rad u okviru zajedničke
misije otvaraju mogućnosti za nove i s loženije aplikacije. U podvodnom okruženju,
komunikacija, lokalizacija, i navigacija AUV a smatraju se izazovima zbog nemogućnosti
oslanjanja na radio komunikaciju i globalne sustav e pozicioniranja.Communication
s with the AUV during the mission can take place via an acoustic modem
when submerged or via a radio frequency (mobile phone, WiFi, satellite) when the vehicle
comes to the surface. AUV techno logy had an intensive phase of research and development
during the 1990s, mostly funded by national defense agencies, and commercial vehicles were
not widely available until around 2000. AUVs and ROVs are increasingly used in
oceanography because they allow the collection of data that otherwise they would not be able
to get it. The development of autonomous underwater vehicles (AUVs) has allowed the
automation of many of the tasks originally accomplished by manned vehicles in an underwater
environment. Team s of AUVs designed to work on joint missions open up opportunities for
new and more complex applications. In the underwater environment, AUV communication,
localization, and navigation are considered challenges due to the inability to weaken radio
communication and global positioning systems
A Hybrid AUV design for shallow water reef navigation
No full textThe highly unstructured nature of coral reef environments makes them difficult for current robotic vehicles to efficiently navigate. Typical research and commercial platforms have limited autonomy within these environments and generally require tethers and significant external infrastructure. This paper outlines the development of a new robotic vehicle for underwater monitoring and surveying in highly unstructured environments and presents experimental results illustrating the vehicle’s performance. The hybrid AUV design developed by the CSIRO robotic reef monitoring team realises a compromise between endurance, manoeuvrability and functionality. The vehicle represents a new era in AUV design specifically focused at providing a truly low-cost research capability that will progress environmental monitoring through unaided navigation, cooperative robotics, sensor network distribution and data harvesting. \ud
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