Large Autonomous Underwater Vehicles Research Articles

Оценка безопасности движения большого автономного необитаемого подводного аппарата

The problems of ensuring the safe motion of a large autonomous underwater vehicle (AUV) when it passes through sections with different environmental conditions are considered by the example of the development of the Northern Sea Route. An analysis was made of the influence of various environmental conditions - open and coastal water, fast ice and ice conditions - on the safety of the operation of a large AUV. An approach is proposed to assess the vehicle safety in various environments using a dynamic Bayesian network and conditional probability tables. To test the algorithms for controlling the the vehicle motion and the vehicle itself, a digital test site was developed in the form of a stand for simulating the functioning of the AUV. The development of digital twins in the form of software simulators of the vehicle devices and mechanisms made it possible to test control algorithms on the simulation stand both during normal operation of its systems and in the event of malfunctions due to functioning in various environments. The results obtained on a simulation stand for a large AUV operating on the farthest and most complicated part of the Northern Sea Route - the Vilkitski Strait, helped us to assess the safety of the vehicle operation and outline the ways to improve the safety by upgrading the algorithms for controlling the AUV motion in difficult environmental conditions.

Bubble Plume Tracking Using a Backseat Driver on an Autonomous Underwater Vehicle

Autonomous underwater vehicles (AUVs) have been applied in various scientific missions including oceanographic research, bathymetry studies, sea mine detection, and marine pollution tracking. We have designed and field-tested in the ocean a backseat driver autonomous system for a 5.5 m survey-class Explorer AUV to detect and track a mixed-phase oil plume. While the first driver is responsible for controlling and safely operating the vehicle; the second driver processes real-time data surrounding the vehicle based on in situ sensor measurements and adaptively modifies the mission details. This adaptive sensing and tracking method uses the Gaussian blur and occupancy grid method. Using a large bubble plume as a proxy, our approach enables real-time adaptive modifications to the AUV’s mission details, and field tests show successful plume detection and tracking. Our results provide for remote detection of underwater oil plumes and enhanced autonomy with these large AUVs.

An evaluation of key challenges of CO2 transportation with a novel Subsea Shuttle Tanker

Recently, a novel Subsea Shuttle Tanker (SST) concept has been proposed to transport carbon dioxide (CO2) from ports to offshore oil and gas fields for either permanent storage or enhanced oil recovery (EOR). SST is a large autonomous underwater vehicle that travels at a constant water depth away from waves. SST has some key advantages over subsea pipelines and tanker ships when employed at marginal fields. It enables carbon storage in marginal fields which do not have sufficient volumes to justify pipelines. Further, in contrast to ships, SST does not require the use of a permanently installed riser base. This paper will evaluate the key challenges of using such vessel for CO2 transportation. It discusses the most important properties such as thermodynamic properties, purity, and hydrate formation of CO2 at different vessel-transportation states in relation to cargo sizing, material selection, and energy consumption.

Requirements for Autonomous Underwater Vehicles (AUVs) for scientific data collection in the Laurentian Great Lakes: A questionnaire survey

Using mobile environmental monitoring can aid in gathering ecological data to meet fish community goals in the Great Lakes. One such approach is the use of large Autonomous Underwater Vehicles (AUVs) to gather data, or the potential use of AUV swarms, where multiple small AUVs work together with each having different data-gathering capabilities. To understand data needs that could be collected by mobile sensor networks to inform decision making, we surveyed Great Lakes professionals involved directly and indirectly in such decision making. Basic data that respondents chose as most important to collect were water temperature, dissolved oxygen, chlorophyll a, turbidity, and blue-green “algae”, which seems to align with variables affecting fish directly or indirectly (through identification of harmful algal blooms). Specialized data chosen as most important were mapping of habitat characteristics, sonar of groupings of fish, and images/video. The time of year to collect all data was chosen as all seasons by the majority of respondents, the frequency most chosen was once a season for mapping of habitat characteristics, once a week for sonar detection of groupings of fish, and once per day for images/video and water temperature. Results were very similar when respondents were asked where data should be collected in the Great Lakes (i.e., tributaries, nearshore areas, etc.) except respondents indicated that images/video should be collected most in fish spawning habitats. Understanding data important to inform decisions of resource professionals will help guide the design of mobile and stationary sensor networks in the Great Lakes.

Development of a High-Resolution Underwater Gravity Measurement System Installed on an Autonomous Underwater Vehicle

Recently, hydrothermal deposits below the seafloor are believed to be useful for human activity. Because the size of each deposit is much smaller than that of an offshore oil field, detailed exploration for the position and the estimated mass is needed. An underwater gravity survey just above seafloor can directly give localized mass distribution below the seafloor. Therefore, we have developed an underwater gravity measurement system onboard an autonomous underwater vehicle (AUV), which is suitable for wide area surveys close to the seafloor with high resolution. An improved gravimeter was mounted on a levelling platform and the system was contained in a spherical pressure vessel with a diameter of 50 cm. The gravimeter system was installed on a large AUV. All the power is supplied from the AUV and an acoustic communication system enables control and monitoring during observation. The first observation was carried out in September 2012 in Sagami Bay, Japan. The AUV was navigated at a constant speed and constant depth on the same profile. As a result, our system has a repeatability of 0.1 mGal. The developed underwater gravimeter has been used for mapping of gravity anomalies in seafloor deposits areas around Japan since 2013.

Automated Ballast Tank Control System for Autonomous Underwater Vehicles

Autonomous underwater vehicles (AUVs) are frequently used for deep-water ocean applications such as surveying and cable laying, where accurate control of vehicle depth and attitude is needed. The water level in the onboard ballast tanks is typically manually set for neutral buoyancy before each mission, while the vehicle is on the surface. The ballast tank contents are not normally adjusted to control vehicle depth and orientation while the AUV is in operation. As a result, vehicle trajectory and orientation is exclusively controlled using the vehicle's control surfaces during a mission. The challenges with controlling the depth and trim of an underwater vehicle include nonlinear hydrodynamic forces, as well as inherent time delays (latencies) associated with water tank level changes and valve adjustments. Furthermore, small changes in the location of the vehicle's center of gravity (i.e., due to the deployment of the AUV's payload equipment) can reduce the control authority of the AUV's control surfaces. To meet these challenges, this paper proposes two unique variable ballast system (VBS) control approaches. The first proposed VBS controller changes the weight of the AUV to help control vehicle depth and vertical (inertial) velocity. The second proposed VBS controller attempts to shift the center of gravity <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sup> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">G</i> along the body-fixed <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</i> -(longitudinal)-axis to reduce depth and pitch angle error while restoring control authority to the bowplane and sternplane deflection fins. The ballasting system consists of two water tanks positioned aft and forward of amidships. The ballast tanks are then automatically filled or emptied of ocean water as desired. Numerical simulations have been carried out on a 2-D underwater vehicle simulator to test and compare the performance of the proposed ballast and fin deflection control systems. The simulation results show that, for the assumptions and conditions tested, the proposed controllers are capable of achieving a setpoint depth and pitch angle with minimal error by effectively utilizing the ballast tanks and deflection fins. As a result, the work presented in this paper helps increase the autonomy of large AUVs on long-duration missions.

A low-cost testbed of underwater mobile sensing network

Comprised by a swarm of acoustically linked and cooperative autonomous underwater vehicles (AUVs) with onboard sensors, an underwater mobile sensing network (UMSN) will be a complementary means to fixed observatory networks, e.g. seafloor observatory networks and moored buoy arrays. It has obvious advantages over a single large AUV in higher efficiency due to parallel observation, stronger robustness to vehicle failures and lower cost. Although an UMSN can be viewed as a counterpart of wireless mobile sensing networks for air and terrestrial applications, it is much more challenging due to poor performance of underwater acoustic communication, poor performance of underwater positioning and high degree of uncertainty in vehicle dynamics and underwater environment. In order to verify key technologies involved in an UMSN, e.g. cooperation of multi-AUVs based on acoustic communication, a low cost testbed has been developed for experimental study. The design of both hardware and software is introduced. Also the results of a functional test for verification of the effectiveness of the testbed are presented.

Precision Hybrid Inertial/Acoustic Navigation System for a Long-Range Autonomous Underwater Vehicle

ABSTRACT: The Canadian Department of National Defence has developed an autonomous underwater vehicle (AUV) capable of performing long-range missions in ice-covered waters. Autonomous operations in such an extreme environment, where a priori knowledge of the bathymetry is frequently limited, requires a navigation system that is precise, reliable, and repeatable. A hybrid navigation system has been developed that provides precise navigation by combining data from two different types of sensors—inertial and acoustic. This navigation system has been integrated into a large AUV, and for mission lengths of up to 200 km has demonstrated horizontal navigational accuracies of better than 0.05 percent of distance traveled. This paper describes the AUV and its mission, the specific navigation sensors selected, and how the overall navigation solution is mechanized. It also describes the behavior of the navigation system during field experiments and during a successful long-range under-ice mission in the High Arctic.

Turbulence Measurement from an Autonomous Underwater Vehicle

Abstract Horizontal profiles of the microstructure of velocity and temperature were obtained with a large autonomous underwater vehicle (AUV) using two piezoelectric shear probes, an FP07 thermistor, and three orthogonal accelerometers mounted on a sting at the forward end of the vehicle. A winter field trial in Narragansett Bay provided a run in the midwater pycnocline at 8-m depth that contained a thermal front, an ascending profile to 3-m depth, and a run in the weakly stratified surface layer at this depth. Although shear spectra were strongly contaminated by narrowband vibrations produced by the motor and actuators, this contamination was highly coherent with the measured acceleration and was removed with standard signal processing techniques. The corrected spectra agreed well with the Nasmyth universal spectrum for wavenumbers up to 40 cpm. The estimated rate of dissipation of kinetic energy varied from 0.8 to 250 × 10−8 W kg−1 and was consistent with the rate of production of turbulence by surface ...