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

Evaluating the use of lithium sulphur batteries for a deep ocean pressure balanced AUV energy source

Lithium sulphur batteries offer a huge potential advantage over established AUV energy sources, such as Lithium polymer or Lithium ion batteries. The high energy density and low specific gravity make them an ideal choice for pressure balanced systems which could significantly improve AUV endurance. This paper aims to evaluate the current technology readiness for deployment in the AUV industry

RRS James Cook cruise JC166-167, 19 June – 6 July 2018. CLASS – Climate-linked Atlantic System Science Haig Fras Marine Conservation Zone AUV habitat monitoring, Equipment trials and staff training

Expedition JC166-167 combined a number of science and technical objectives in order to deliver a comprehensive programme for the UK marine science sector. The expedition supported the NERC National Capability programme CLASS (Climate-Linked Atlantic Sector Science, grant no NE/R015953/1), which aims to increase our understanding of the Atlantic Ocean system, in order to support evidence-based ocean management. More specifically, JC166-167 was part of the Fixed Point Observations Underpinning Activity, where repeated observations and surveys of Marine Protected Areas (MPAs) and their surroundings provide insight into the development and recovery of benthic ecosystems following natural and/or anthropogenic impacts. The target location for JC166-167 was the Greater Haig Fras Marine Conservation Zone (MCZ), west of Cornwall, which was surveyed by NOC, using Autosub AUVs, in 2012 and 2015. The 2018 expedition continued that time series, and expanded the study by also looking at differences in benthic community observed between day and night. Haig Fras is the only rocky reef on the Celtic Shelf, and was protected in 2016. In parallel with these science objectives, JC166-167 included an extensive series of equipment trials, combined with training for staff members of the Marine Autonomous and Robotic Systems group at NOC. The robotic and autonomous systems tested included the Isis ROV, HyBIS vehicle, the Autosub6000 AUV, a deep glider, a wave glider, a C-worker 4 USV and a drone. Some of the trials were carried out in the shallow waters around Haig Fras, while others required greater depths, for which we visited the Whittard Canyon system along the Celtic Margin. Wherever possible, trials and training were carried out in a way that the resulting data would help address CLASS science objectives, including objectives related to the sustained observations in the Canyons MCZ

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

AURORA, a multi-sensor dataset for robotic ocean exploration

The current maturity of autonomous underwater vehicles (AUVs) has made their deployment practical and cost-effective, such that many scientific, industrial and military applications now include AUV operations. However, the logistical difficulties and high costs of operating at sea are still critical limiting factors in further technology development, the benchmarking of new techniques and the reproducibility of research results. To overcome this problem, this paper presents a freely available dataset suitable to test control, navigation, sensor processing algorithms and others tasks. This dataset combines AUV navigation data, sidescan sonar, multibeam echosounder data and seafloor camera image data, and associated sensor acquisition metadata to provide a detailed characterisation of surveys carried out by the National Oceanography Centre (NOC) in the Greater Haig Fras Marine Conservation Zone (MCZ) of the U.K in 2015

Autosub Long Range 1500: A continuous 2000 km field trial

Long Range Autonomous Underwater Vehicles (LRAUVs) offer the potential to monitor the ocean at higher spatial and temporal resolutions compared to conventional ship-based techniques. The multi-week to multi-month endurance of LRAUVs enables them to operate independently of a support vessel, creating novel opportunities for ocean observation. The National Oceanography Centre’s Autosub Long Range is one of a small number of vehicles designed for a multi-month endurance. The latest iteration, Autosub Long Range 1500 (ALR1500), is a 1500 m depth-rated LRAUV developed for ocean science in coastal and shelf seas or in the epipelagic and meteorologic regions of the ocean. This paper presents the design of the ALR1500 and results from a five week continuous deployment from Plymouth, UK, to the continental shelf break and back again, a distance of approximately 2000km which consumed half of the installed energy. The LRAUV was unaccompanied throughout the mission and operated continuously beyond visual line of sight

The use of computational fluid dynamics to assess the hull resistance of concept autonomous underwater vehicles

Autonomous Underwater Vehicles (AUV’s) provide an important tool for collecting detailed scientific information from the oceans depths. The hull resistance of an AUV is an important factor in determining the powering requirements and range of the vehicle. This paper discusses the use of Computational Fluid Dynamics (CFD) to determine the hull resistance of three existing AUV’s, of differing shape and size. The predictions are compared with available experimental data and good agreement found. This work has demonstrated that with use of suitable shape parameterisation it is possible to carry out concept design evaluation using a RANS flow solver

Autosub6000: results of its engineering trials and first science missions

In September 2007 on RRS Discovery, the Autosub6000 Autonomous Underwater Vehicle (AUV) completed its first deep water engineering trials, and less than a year later, fitted with a multibeam bathymetric mapping sonar, carried out its first science missions, as part of a geology and geophysics science cruise onboard the RRS James Cook to investigate potential geo-hazards (such as tsunami generating landslides) on the European and North African margin. In the spirit of true AUV autonomy, while the AUV was deployed, we used the ship for seabed coring operations, and once the AUV was recovered, the high resolution bathymetry which it had obtained guided the next coring operations. In this paper we will describe how we are tackling the issues that specifically affect a deep diving AUV capable of operating with true autonomy, and independently of the mother ship: How to carry enough energy for long endurance and range? How to operate safely and efficiently with varying buoyancy? How to maintain accurate navigation throughout missions lasting up to several days

System identification of the hydrodynamic characteristics of underwater vehicles

Accurate physics based simulations of Autonomous Underwater Vehicles (AUVs) and submarines require precise knowledge of the physical loads on the vehicle. Of these loads the hydrodynamic component is the most challenging to determine. One common method of representing these loads is to use hydrodynamic coefficients. These coefficients are commonly determined from captive model testing, which is expensive. However, in theory these coefficients can be found from free swimming trials. This thesis documents research undertaken, in collaboration with QinetiQ, to determine whether the hydrodynamic coefficients in a set of non-linear submarine equations can be determined from free swimming trials data. Two coefficients identification procedures are described. The first, a non-linear approach attempts to find a set of coefficients reproduced the manoeuvring submarine’s path. The second, a linear approach recasts the identification task into a linear algebra problem which can be solved using standard techniques. When testing using simulated data both approaches indicated that accurate submarine track identification is not equivalent to correct submarine hydrodynamic co-efficient identification. This arises from two causes.  First, it was discovered that the coefficients were not unique, and thus there are an infinite number of different coefficient sets which produce the same manoeuvre. Secondly, it was found that the manoeuvre always identified an ill-conditioned set of coefficients; that is small deviations in the manoeuvre produced large deviations in the identified coefficient values. Due to these results, the results of the research suggest that it is not possible to determine the non-linear hydrodynamic coefficients of a submarine or AUV from free swimming manoeuvre data.</p

System, identification of the hydrodynamic characteristics of underwater vehicles

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