A concept design for an ultra-long-range survey class AUV

Gliders and flight-style Autonomous Underwater Vehicles (AUVs) are used to perform perform autonomous surveys of large areas of open ocean. Glider missions are characterized by their profiling flight pattern, slow speed, long range (1000s of km) and many month mission duration. Flight-style AUV missions are faster, of shorter range (100s of km) and multi day duration. An AUV combining many aspects of both vehicle classes would be of considerable value.This paper investigates the factors that affect the range of a traditional flight-style AUVs. A generic range model is outlined which factors in the effects of buoyancy on the range. The model shows that to create a very long range AUV it is necessary to reduce the hotel load on the AUV to the order of 1W and to add wings to overcome the vehicle’s positive buoyancy whilst travelling at the reduced speed required for long range.Using this model a concept long range AUV is outlined that is capable of travelling up to 5000km. The practical issues associated with achieving this range are also discussed

Control of an AUV from thruster actuated hover to control surface actuated flight

An autonomous underwater vehicle (AUV) capable of both low speed hovering and high speed flight-style operation is introduced. To have this capability the AUV is over-actuated with a rear propeller, four control surfaces and four through-body tunnel thrusters. In this work the actuators are modelled and the non-linearities and uncertainties are identified and discussed with specific regard to operation at different speeds. A thruster-actuated depth control algorithm and a flight-style control-surface actuated depth controller are presented. These controllers are then coupled using model reference feedback to enable transition between the two controllers to enable vehicle stability throughout the speed range. Results from 3 degrees-of-freedom simulations of the AUV using the new controller are presented, showing that the controller works well to smoothly transition between controllers. The performance of the depth controller appears asymmetric with better performance whilst diving than ascendin

Exploring beneath the PIG Ice Shelf with the Autosub3 AUV

On 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

Optimization of the hydrodynamic performance of an in-service AUV

The AUV, AUTOSUB, developed by the Ocean Engineering Department of the Southampton Oceanography Centre is a versatile vehicle for the collection of scientific data. It has been used successfully worldwide for a range of missions over recent years including two beneath the Antarctic ice-shelf. In parallel with its in-service programme there is ongoing research to monitor and improve its performance. In particular means to increase mission range and versatility are sought This paper describes. methods for improving the hydrodynamic performance of in-service AUV's.</p