Secure Cooperation of Autonomous Mobile Sensors Using an Underwater Acoustic Network

Directory of Open Access Journals (Sweden)

Gianluca Dini

2012-02-01

Full Text Available Methodologies and algorithms are presented for the secure cooperation of a team of autonomous mobile underwater sensors, connected through an acoustic communication network, within surveillance and patrolling applications. In particular, the work proposes a cooperative algorithm in which the mobile underwater sensors (installed on Autonomous Underwater Vehicles—AUVs respond to simple local rules based on the available information to perform the mission and maintain the communication link with the network (behavioral approach. The algorithm is intrinsically robust: with loss of communication among the vehicles the coverage performance (i.e., the mission goal is degraded but not lost. The ensuing form of graceful degradation provides also a reactive measure against Denial of Service. The cooperative algorithm relies on the fact that the available information from the other sensors, though not necessarily complete, is trustworthy. To ensure trustworthiness, a security suite has been designed, specifically oriented to the underwater scenario, and in particular with the goal of reducing the communication overhead introduced by security in terms of number and size of messages. The paper gives implementation details on the integration between the security suite and the cooperative algorithm and provides statistics on the performance of the system as collected during the UAN project sea trial held in Trondheim, Norway, in May 2011.

Autonomous Planning and Replanning for Mine-Sweeping Unmanned Underwater Vehicles

Science.gov (United States)

Gaines, Daniel M.

2010-01-01

This software generates high-quality plans for carrying out mine-sweeping activities under resource constraints. The autonomous planning and replanning system for unmanned underwater vehicles (UUVs) takes as input a set of prioritized mine-sweep regions, and a specification of available UUV resources including available battery energy, data storage, and time available for accomplishing the mission. Mine-sweep areas vary in location, size of area to be swept, and importance of the region. The planner also works with a model of the UUV, as well as a model of the power consumption of the vehicle when idle and when moving.

A Framework for Evaluating Advanced Search Concepts for Multiple Autonomous Underwater Vehicle (AUV) Mine Countermeasures (MCM)

National Research Council Canada - National Science Library

Gooding, Trent

2001-01-01

.... In recent years, autonomous underwater vehicles (AUV) have emerged as a viable technology for conducting underwater search, survey, and clearance operations in support of the mine countermeasures (MCM) mission...

Autonomous Navigation for Autonomous Underwater Vehicles Based on Information Filters and Active Sensing

Directory of Open Access Journals (Sweden)

Tianhong Yan

2011-11-01

Full Text Available This paper addresses an autonomous navigation method for the autonomous underwater vehicle (AUV C-Ranger applying information-filter-based simultaneous localization and mapping (SLAM, and its sea trial experiments in Tuandao Bay (Shangdong Province, P.R. China. Weak links in the information matrix in an extended information filter (EIF can be pruned to achieve an efficient approach-sparse EIF algorithm (SEIF-SLAM. All the basic update formulae can be implemented in constant time irrespective of the size of the map; hence the computational complexity is significantly reduced. The mechanical scanning imaging sonar is chosen as the active sensing device for the underwater vehicle, and a compensation method based on feedback of the AUV pose is presented to overcome distortion of the acoustic images due to the vehicle motion. In order to verify the feasibility of the navigation methods proposed for the C-Ranger, a sea trial was conducted in Tuandao Bay. Experimental results and analysis show that the proposed navigation approach based on SEIF-SLAM improves the accuracy of the navigation compared with conventional method; moreover the algorithm has a low computational cost when compared with EKF-SLAM.

Autonomous navigation for autonomous underwater vehicles based on information filters and active sensing.

Science.gov (United States)

He, Bo; Zhang, Hongjin; Li, Chao; Zhang, Shujing; Liang, Yan; Yan, Tianhong

2011-01-01

This paper addresses an autonomous navigation method for the autonomous underwater vehicle (AUV) C-Ranger applying information-filter-based simultaneous localization and mapping (SLAM), and its sea trial experiments in Tuandao Bay (Shangdong Province, P.R. China). Weak links in the information matrix in an extended information filter (EIF) can be pruned to achieve an efficient approach-sparse EIF algorithm (SEIF-SLAM). All the basic update formulae can be implemented in constant time irrespective of the size of the map; hence the computational complexity is significantly reduced. The mechanical scanning imaging sonar is chosen as the active sensing device for the underwater vehicle, and a compensation method based on feedback of the AUV pose is presented to overcome distortion of the acoustic images due to the vehicle motion. In order to verify the feasibility of the navigation methods proposed for the C-Ranger, a sea trial was conducted in Tuandao Bay. Experimental results and analysis show that the proposed navigation approach based on SEIF-SLAM improves the accuracy of the navigation compared with conventional method; moreover the algorithm has a low computational cost when compared with EKF-SLAM.

Task Allocation and Path Planning for Collaborative Autonomous Underwater Vehicles Operating through an Underwater Acoustic Network

Directory of Open Access Journals (Sweden)

Yueyue Deng

2013-01-01

Full Text Available Dynamic and unstructured multiple cooperative autonomous underwater vehicle (AUV missions are highly complex operations, and task allocation and path planning are made significantly more challenging under realistic underwater acoustic communication constraints. This paper presents a solution for the task allocation and path planning for multiple AUVs under marginal acoustic communication conditions: a location-aided task allocation framework (LAAF algorithm for multitarget task assignment and the grid-based multiobjective optimal programming (GMOOP mathematical model for finding an optimal vehicle command decision given a set of objectives and constraints. Both the LAAF and GMOOP algorithms are well suited in poor acoustic network condition and dynamic environment. Our research is based on an existing mobile ad hoc network underwater acoustic simulator and blind flooding routing protocol. Simulation results demonstrate that the location-aided auction strategy performs significantly better than the well-accepted auction algorithm developed by Bertsekas in terms of task-allocation time and network bandwidth consumption. We also demonstrate that the GMOOP path-planning technique provides an efficient method for executing multiobjective tasks by cooperative agents with limited communication capabilities. This is in contrast to existing multiobjective action selection methods that are limited to networks where constant, reliable communication is assumed to be available.

Construction Method of the Topographical Features Model for Underwater Terrain Navigation

Directory of Open Access Journals (Sweden)

Wang Lihui

2015-09-01

Full Text Available Terrain database is the reference basic for autonomous underwater vehicle (AUV to implement underwater terrain navigation (UTN functions, and is the important part of building topographical features model for UTN. To investigate the feasibility and correlation of a variety of terrain parameters as terrain navigation information metrics, this paper described and analyzed the underwater terrain features and topography parameters calculation method. Proposing a comprehensive evaluation method for terrain navigation information, and constructing an underwater navigation information analysis model, which is associated with topographic features. Simulation results show that the underwater terrain features, are associated with UTN information directly or indirectly, also affect the terrain matching capture probability and the positioning accuracy directly.

Biogeography-based combinatorial strategy for efficient autonomous underwater vehicle motion planning and task-time management

Science.gov (United States)

Zadeh, S. M.; Powers, D. M. W.; Sammut, K.; Yazdani, A. M.

2016-12-01

Autonomous Underwater Vehicles (AUVs) are capable of spending long periods of time for carrying out various underwater missions and marine tasks. In this paper, a novel conflict-free motion planning framework is introduced to enhance underwater vehicle's mission performance by completing maximum number of highest priority tasks in a limited time through a large scale waypoint cluttered operating field, and ensuring safe deployment during the mission. The proposed combinatorial route-path planner model takes the advantages of the Biogeography-Based Optimization (BBO) algorithm toward satisfying objectives of both higher-lower level motion planners and guarantees maximization of the mission productivity for a single vehicle operation. The performance of the model is investigated under different scenarios including the particular cost constraints in time-varying operating fields. To show the reliability of the proposed model, performance of each motion planner assessed separately and then statistical analysis is undertaken to evaluate the total performance of the entire model. The simulation results indicate the stability of the contributed model and its feasible application for real experiments.

Computing energy-optimal trajectories for an autonomous underwater vehicle using direct shooting

Directory of Open Access Journals (Sweden)

Inge Spangelo

1992-07-01

Full Text Available Energy-optimal trajectories for an autonomous underwater vehicle can be computed using a numerical solution of the optimal control problem. The vehicle is modeled with the six dimensional nonlinear and coupled equations of motion, controlled with DC-motors in all degrees of freedom. The actuators are modeled and controlled with velocity loops. The dissipated energy is expressed in terms of the control variables as a nonquadratic function. Direct shooting methods, including control vector parameterization (CVP arc used in this study. Numerical calculations are performed and good results are achieved.

Underwater robots

CERN Document Server

Antonelli, Gianluca

2014-01-01

This book, now at the third edition, addresses the main control aspects in underwater manipulation tasks. The mathematical model with significant impact on the control strategy is discussed. The problem of controlling a 6-degrees-of-freedoms autonomous underwater vehicle is deeply investigated and a survey of fault detection/tolerant strategies for unmanned underwater vehicles is provided. Inverse kinematics, dynamic and interaction control for underwater vehicle-manipulator systems are then discussed. The code used to generate most of the numerical simulations is made available and briefly discussed.       

Coordinated Formation Control of Multiple Autonomous Underwater Vehicles for Pipeline Inspection

Directory of Open Access Journals (Sweden)

Xianbo Xiang

2010-02-01

Full Text Available This paper addresses the control problem of inspecting underwater pipeline on the seabed, with coordinated multiple autonomous underwater vehicles in a formation. Based on the leader-follower strategy, the dedicated nonlinear path following controller is rigorously built on Lyapunov-based design, driving a fleet of vehicles onto assigned parallel paths elevated and offset from the underwater pipeline, while keeping a triangle formation to capture complete 3D images for inspection. Due to the spatial-temporal decoupling characteristics of individual path following controller, the velocities of the followers can be adapted in the coordinated control level, only relying on the information of generalized along-path length from the leader, in order to build the desired formation. Thus, the communication variable broadcast from the leader is kept to a minimum, which is feasible under the severely constraints of acoustic communication bandwidth. Simulation results illustrate the efficiency of coordinated formation controller proposed for underwater pipeline inspection.

Autonomous underwater vehicle motion tracking using a Kalman Filter for sensor fusion

CSIR Research Space (South Africa)

Holtzhausen, S

2008-01-01

Full Text Available AUVs are ideal platforms for search and rescue operations. They can also be used for inspection of underwater terrains. These vehicles need to be autonomous and robust to cope with unpredictable current and high pressures. In this paper...

DEPSCOR: Research on ARL's Intelligent Control Architecture: Hierarchical Hybrid-Model Based Design, Verification, Simulation, and Synthesis of Mission Control for Autonomous Underwater Vehicles

National Research Council Canada - National Science Library

Kumar, Ratnesh; Holloway, Lawrence E

2007-01-01

... modeling, verification, simulation and automated synthesis of coordinators has lead to research in this area. We have worked and are working on these issues with Applied Research Laboratory (ARL) at Pennsylvania State University (PSU) who have designed autonomous underwater vehicles for over 50 years primarily under the support of the U.S. Navy through the Office of Naval Research (ONR).

Acoustic inversion with self noise of an autonomous underwater vehicle to measure sound speed in marine sediments

NARCIS (Netherlands)

van Leijen, A.V.; Rothkranz, L.J.M.; Groen, F.C.A.

2009-01-01

This work reports on an experiment from the Maritime Rapid Environmental Assessment sea trials in 2007, where autonomous underwater vehicles were deployed for environmental assessment. Even though these underwater vehicles are very quiet platforms, this work investigates the potential of vehicle

Correction of Navigational Information Supplied to Biomimetic Autonomous Underwater Vehicle

Directory of Open Access Journals (Sweden)

Praczyk Tomasz

2018-03-01

Full Text Available In order to autonomously transfer from one point of the environment to the other, Autonomous Underwater Vehicles (AUV need a navigational system. While navigating underwater the vehicles usually use a dead reckoning method which calculates vehicle movement on the basis of the information about velocity (sometimes also acceleration and course (heading provided by on-board devicesl ike Doppler Velocity Logs and Fibre Optical Gyroscopes. Due to inaccuracies of the devices and the influence of environmental forces, the position generated by the dead reckoning navigational system (DRNS is not free from errors, moreover the errors grow exponentially in time. The problem becomes even more serious when we deal with small AUVs which do not have any speedometer on board and whose course measurement device is inaccurate. To improve indications of the DRNS the vehicle can emerge onto the surface from time to time, record its GPS position, and measure position error which can be further used to estimate environmental influence and inaccuracies caused by mechanisms of the vehicle. This paper reports simulation tests which were performed to determine the most effective method for correction of DRNS designed for a real Biomimetic AUV.

An autonomous underwater vehicle "Maya", for monitoring coastal waters, estuaries, rivers and dams

Digital Repository Service at National Institute of Oceanography (India)

Mascarenhas, A.A; Navelkar, G.S.; Madhan, R.; Dabholkar, N.A; Prabhudesai, S.P.; Maurya, P.K.; Desa, E.; Afzulpurkar, S.; Suresh, T.; Matondkar, S.G.P.; Mahalunkar, A

This article demonstrates the use of Maya, Autonomous Underwater Vehicle (AUV) for monitoring coastal waters, estuaries, rivers and dams. Maya is a mono hull structure with detachable nose and tail cones. The nose cone is mission specific...

A Game-theoretical Approach for Distributed Cooperative Control of Autonomous Underwater Vehicles

KAUST Repository

Lu, Yimeng

2018-05-01

This thesis explores a game-theoretical approach for underwater environmental monitoring applications. We first apply game-theoretical algorithm to multi-agent resource coverage problem in drifting environments. Furthermore, existing utility design and learning process of the algorithm are modified to fit specific constraints of underwater exploration/monitoring tasks. The revised approach can take the real scenario of underwater monitoring applications such as the effect of sea current, previous knowledge of the resource and occasional communications between agents into account, and adapt to them to reach better performance. As the motivation of this thesis is from real applications, in this work we emphasize highly on implementation phase. A ROS-Gazebo simulation environment was created for preparation of actual tests. The algorithms are implemented in simulating both the dynamics of vehicles and the environment. After that, a multi-agent underwater autonomous robotic system was developed for hardware test in real settings with local controllers to make their own decisions. These systems are used for testing above mentioned algorithms and future development of other underwater projects. After that, other works related to robotics during this thesis will be briefly mentioned, including contributions in MBZIRC robotics competition and distributed control of UAVs in an adversarial environment.

Consensus of multiple autonomous underwater vehicles with double independent Markovian switching topologies and timevarying delays

International Nuclear Information System (INIS)

Yan Zhe-Ping; Liu Yi-Bo; Zhou Jia-Jia; Zhang Wei; Wang Lu

2017-01-01

A new method in which the consensus algorithm is used to solve the coordinate control problems of leaderless multiple autonomous underwater vehicles (multi-AUVs) with double independent Markovian switching communication topologies and time-varying delays among the underwater sensors is investigated. This is accomplished by first dividing the communication topology into two different switching parts, i.e., velocity and position, to reduce the data capacity per data package sent between the multi-AUVs in the ocean. Then, the state feedback linearization is used to simplify and rewrite the complex nonlinear and coupled mathematical model of the AUVs into a double-integrator dynamic model. Consequently, coordinate control of the multi-AUVs is regarded as an approximating consensus problem with various time-varying delays and velocity and position topologies. Considering these factors, sufficient conditions of consensus control are proposed and analyzed and the stability of the multi-AUVs is proven by Lyapunov–Krasovskii theorem. Finally, simulation results that validate the theoretical results are presented. (paper)

Point features extraction: towards slam for an autonomous underwater vehicle

CSIR Research Space (South Africa)

Matsebe, O

2010-07-01

Full Text Available and Control. Available: http://www.robots.ox.ac.uk/~pnewman/papers/Robotica.pdf, date accessed: [2009, 05/20] [7] Williams, S.B., Newman, P., Rosenblatt, J., Dissanayake, G. & Whyte, H.D., Autonomous Underwater Simultaneous and Localisation and Map Building.... Available: http://www.robots.ox.ac.uk/~pnewman/papers/Robotica.pdf., date accessed: [2009, 05/20] [8]http://www.tritech.co.uk/products/products-micron_sonar.htm, date accessed: [10/01/10] [9] Tena, I., Petillot, Y., Lane, D.M.,Salson. Feature Extraction...

Reactor Power for Large Displacement Autonomous Underwater Vehicles

International Nuclear Information System (INIS)

McClure, Patrick Ray; Reid, Robert Stowers; Poston, David Irvin; Dasari, Venkateswara Rao

2016-01-01

This is a PentaChart on reactor power for large displacement autonomous underwater vehicles. Currently AUVs use batteries or combinations of batteries and fuel cells for power. Battery/fuel cell technology is limited by duration. Batteries and cell fuels are a good match for some missions, but other missions could benefit greatly by a longer duration. The goal is the following: to design nuclear systems to power an AUV and meet design constraints including non-proliferation issues, power level, size constraints, and power conversion limitations. The action plan is to continue development of a range of systems for terrestrial systems and focus on a system for Titan Moon as alternative to Pu-238 for NASA.

Autonomous Underwater Vehicle Data Management and Metadata Interoperability for Coastal Ocean Studies

Science.gov (United States)

McCann, M. P.; Ryan, J. P.; Chavez, F. P.; Rienecker, E.

2004-12-01

Data from over 1000 km of Autonomous Underwater Vehicle (AUV) surveys of Monterey Bay have been collected and cataloged in an ocean observatory data management system. The Monterey Bay Aquarium Institute's AUV is equipped with a suite of instruments that include a conductivity, temperature, depth (CTD) instrument, transmissometers, a fluorometer, a nitrate sensor, and an inertial navigation system. Data are logged on the vehicle and upon completion of a survey XML descriptions of the data are submitted to the Shore Side Data System (SSDS). Instrument data are then processed on shore to apply calibrations and produce scientifically useful data products. The SSDS employs a data model that tracks data from the instrument that created it through all the consuming processes that generate derived products. SSDS employs OPeNDAP and netCDF to provide data set interoperability at the data level. The core of SSDS is the metadata that is the catalog of these data sets and their relation to all other relevant data. The metadata is managed in a relational database and governed by a Enterprise Java Bean (EJB) server application. Cross-platform Java applications have been written to manage and visualize these data. A Java Swing application - the Hierarchical Ocean Observatory Visualization and Editing System (HOOVES) - has been developed to provide visualization of data set pedigree and data set variables. Because the SSDS data model is generalized according to "Data Producers" and "Data Containers" many different types of data can be represented in SSDS allowing for interoperability at a metadata level. Comparisons of appropriate data sets, whether they are from an autonomous underwater vehicle or from a fixed mooring are easily made using SSDS. The authors will present the SSDS data model and show examples of how the model helps organize data set metadata allowing for data discovery and interoperability. With improved discovery and interoperability the system is helping us

Flow around an autonomous underwater vehicle with bio-inspired coating

Science.gov (United States)

Watkins, Scott; Montoya-Segnini, Jose; Bocanegra Evans, Humberto; Curet, Oscar; Gorumlu, Serdar; Aksak, Burak; Kazemi, Amirkhosro; Chamorro, Leonardo; Castillo, Luciano

2017-11-01

Flow separation plays a major factor in the form drag of a moving object. In particular, suppressing or reducing flow separation is critical in the energy expenditure of autonomous underwater vehicles. Previous research suggests that bio-inspired micro-fibrillar structures are capable of reducing the boundary layer separation in a turbulent flow. Here, we present laboratory measurements using PIV near the wall and in the wake of two submersible vessel models; one had a coating composed of ordered fibers, and the other had smooth walls. Flow characterization with planar PIV included the presence or absence of a tail fin at multiple angles of attack of the vessels. Preliminary results reveal changes of the flow in the wake of the vessel with coating resulting in lower or similar velocity deficit in the wake compared to the smooth vessel.

Ocean outfall plume characterization using an Autonomous Underwater Vehicle.

Science.gov (United States)

Rogowski, Peter; Terrill, Eric; Otero, Mark; Hazard, Lisa; Middleton, William

2013-01-01

A monitoring mission to map and characterize the Point Loma Ocean Outfall (PLOO) wastewater plume using an Autonomous Underwater Vehicle (AUV) was performed on 3 March 2011. The mobility of an AUV provides a significant advantage in surveying discharge plumes over traditional cast-based methods, and when combined with optical and oceanographic sensors, provides a capability for both detecting plumes and assessing their mixing in the near and far-fields. Unique to this study is the measurement of Colored Dissolved Organic Matter (CDOM) in the discharge plume and its application for quantitative estimates of the plume's dilution. AUV mission planning methodologies for discharge plume sampling, plume characterization using onboard optical sensors, and comparison of observational data to model results are presented. The results suggest that even under variable oceanic conditions, properly planned missions for AUVs equipped with an optical CDOM sensor in addition to traditional oceanographic sensors, can accurately characterize and track ocean outfall plumes at higher resolutions than cast-based techniques.

Efficient Multivariable Generalized Predictive Control for Autonomous Underwater Vehicle in Vertical Plane

OpenAIRE

Yao, Xuliang; Yang, Guangyi

2016-01-01

This paper presents the design and simulation validation of a multivariable GPC (generalized predictive control) for AUV (autonomous underwater vehicle) in vertical plane. This control approach has been designed in the case of AUV navigating with low speed near water surface, in order to restrain wave disturbance effectively and improve pitch and heave motion stability. The proposed controller guarantees compliance with rudder manipulation, AUV output constraints, and driving energy consumpti...

Aspect-dependent radiated noise analysis of an underway autonomous underwater vehicle.

Science.gov (United States)

Gebbie, John; Siderius, Martin; Allen, John S

2012-11-01

This paper presents an analysis of the acoustic emissions emitted by an underway REMUS-100 autonomous underwater vehicle (AUV) that were obtained near Honolulu Harbor, HI using a fixed, bottom-mounted horizontal line array (HLA). Spectral analysis, beamforming, and cross-correlation facilitate identification of independent sources of noise originating from the AUV. Fusion of navigational records from the AUV with acoustic data from the HLA allows for an aspect-dependent presentation of calculated source levels of the strongest propulsion tone.

Data-based depth estimation of an incoming autonomous underwater vehicle.

Science.gov (United States)

Yang, T C; Xu, Wen

2016-10-01

The data-based method for estimating the depth of a moving source is demonstrated experimentally for an incoming autonomous underwater vehicle traveling toward a vertical line array (VLA) of receivers at constant speed/depth. The method assumes no information on the sound-speed and bottom profile. Performing a wavenumber analysis of a narrowband signal for each hydrophone, the energy of the (modal) spectral peaks as a function of the receiver depth is used to estimate the depth of the source, traveling within the depth span of the VLA. This paper reviews the theory, discusses practical implementation issues, and presents the data analysis results.

Accuracy of Positioning Autonomous Biomimetic Underwater Vehicle Using Additional Measurement of Distances

Directory of Open Access Journals (Sweden)

Naus Krzysztof

2016-12-01

Full Text Available The article describes a study of problem of estimating the position coordinates of Autonomous Biomimetic Underwater Vehicle (ABUV using two methods: dead reckoning (DR and extended Kalman filter (EKF. In the first part of the paper, navigation system of ABUV is described and scientific problem with underwater positioning is formulated. The main part describes a way of estimating the position coordinates using DR and EKF and a numerical experiment involving motion of ABUV along the predetermined test distance. The final part of the paper contains a comparative statistical analysis of the results, carried out for assessing the accuracy of estimation of the position coordinates using DR and EKF methods. It presents the generalized conclusions from the research and the problems relating to the proper placement of the components of the system measuring distances.

A mission executor for an autonomous underwater vehicle

Science.gov (United States)

Lee, Yuh-Jeng; Wilkinson, Paul

1991-01-01

The Naval Postgraduate School has been conducting research into the design and testing of an Autonomous Underwater Vehicle (AUV). One facet of this research is to incrementally design a software architecture and implement it in an advanced testbed, the AUV II. As part of the high level architecture, a Mission Executor is being constructed using CLIPS (C Language Integrated Production System) version 5.0. The Mission Executor is an expert system designed to oversee progress from the AUV launch point to a goal area and back to the origin. It is expected that the executor will make informed decisions about the mission, taking into account the navigational path, the vehicle subsystem health, and the sea environment, as well as the specific mission profile which is downloaded from an offboard mission planner. Heuristics for maneuvering, avoidance of uncharted obstacles, waypoint navigation, and reaction to emergencies (essentially the expert knowledge of a submarine captain) are required. Many of the vehicle subsystems are modeled as objects using the CLIPS Object Oriented Language (COOL) embedded in CLIPS 5.0. Also, truth maintenance is applied to the knowledge base to keep configurations updated.

High spatial resolution mapping of water quality and bathymetry with an autonomous underwater vehicle

Science.gov (United States)

Pampalone, Vincenzo; Milici, Barbara

2015-12-01

The drone Ecomapper AUV (Autonomous Underwater Vehicle) is a rare example of highly technological instrument in the environmental coastal monitoring field. The YSI EcoMapper is a one-man deployable, Autonomous Underwater Vehicle (AUV) designed to collect bathymetry and water quality data. The submarine-like vehicle follows a programmed course and employs sensors mounted in the nose to record pertinent information. Once the vehicle has started its mission, it operates independently of the user and utilizes GPS waypoints navigation to complete its programmed course. Throughout the course, the vehicle constantly steers toward the line drawn in the mission planning software (VectorMap), essentially following a more accurate road of coordinates instead of transversing waypoint-to-waypoint. It has been equipped with a Doppler Velocity Log (DVL) to increase its underwater navigation accuracy. Potential EcoMapper applications include baseline environmental mapping in freshwater, estuarine or near-coastal environments, bathymetric mapping, dissolved oxygen studies, event monitoring (algal blooms, storm impacts, low dissolved oxygen), non-point source studies, point-source dispersion mapping, security, search & rescue, inspection, shallow water mapping, thermal dissipation mapping of cooling outfalls, trace-dye studies. The AUV is used in the coastal area of the Augusta Bay (Italy), located in the eastern part of Sicily. Due to the heavy contamination generated by the several chemical and petrochemical industries active in the zone, the harbour was declared a Contaminated Site of National Interest. The ecomapper allows for a simultaneous data collection of water quality and bathymetric data providing a complete environmental mapping system of the Harbour.

The Design of an Autonomous Underwater Vehicle for Water Quality Monitoring

Science.gov (United States)

Li, Yulong; Liu, Rong; Liu, Shujin

2018-01-01

This paper describes the development of a civilian-used autonomous underwater vehicle (AUV) for water quality monitoring at reservoirs and watercourses that can obtain realtime visual and locational information. The mechanical design was completed with CAD software Solidworks. Four thrusters—two horizontal and two vertical—on board enable the vehicle to surge, heave, yaw, and pitch. A specialized water sample collection compartment is designed to perform water collection at target locations. The vehicle has a central controller—STM32—and a sub-coordinate controller—Arduino MEGA 2560—that coordinates multiple sensors including an inertial sensor, ultrasonic sensors, etc. Global Navigation Satellite System (GNSS) and the inertial sensor enable the vehicle’s localization. Remote operators monitor and control the vehicle via a host computer system. Operators choose either semi-autonomous mode in which they set target locations or manual mode. The experimental results show that the vehicle is able to perform well in either mode.

Safety aspects for underwater vehicles

Digital Repository Service at National Institute of Oceanography (India)

Madhan, R.; Navelkar, G.S.; Desa, E.S.; Afzulpurkar, S.; Prabhudesai, S.P.; Dabholkar, N.; Mascarenhas, A.A.M.Q.; Maurya, P.

instrumentation is intelligent small Autonomous Underwater Vehicles (AUV’s), autonomous profilers, gliders [1], etc. The ultimate aim in all autonomous platforms research and development is to reach the stage of unescorted missions with minimum failures...

Robust Design of Docking Hoop for Recovery of Autonomous Underwater Vehicle with Experimental Results

Directory of Open Access Journals (Sweden)

Wei Peng Lin

2015-12-01

Full Text Available Control systems prototyping is usually constrained by model complexity, embedded system configurations, and interface testing. The proposed control system prototyping of a remotely-operated vehicle (ROV with a docking hoop (DH to recover an autonomous underwater vehicle (AUV named AUVDH using a combination of software tools allows the prototyping process to be unified. This process provides systematic design from mechanical, hydrodynamics, dynamics modelling, control system design, and simulation to testing in water. As shown in a three-dimensional simulation of an AUVDH model using MATLAB™/Simulink™ during the launch and recovery process, the control simulation of a sliding mode controller is able to control the positions and velocities under the external wave, current, and tether forces. In the water test using the proposed Python-based GUI platform, it shows that the AUVDH is capable to perform station-keeping under the external disturbances.

Using Autonomous Underwater Vehicles as Sensor Platforms for Ice-Monitoring

Directory of Open Access Journals (Sweden)

Petter Norgren

2014-10-01

Full Text Available Due to the receding sea-ice extent in the Arctic, and the potentially large undiscovered petroleum resources present north of the Arctic circle, offshore activities in ice-infested waters are increasing. Due to the presence of drifting sea-ice and icebergs, ice management (IM becomes an important part of the offshore operation, and an important part of an IM system is the ability to reliably monitor the ice conditions. An autonomous underwater vehicle (AUV has a unique capability of high underwater spatial and temporal coverage, making it suitable for monitoring applications. Since the first Arctic AUV deployment in 1972, AUV technology has matured and has been used in complex under-ice operations. This paper motivates the use of AUVs as an ice-monitoring sensor platform. It discusses relevant sensor capabilities and challenges related to communication and navigation. This paper also presents experiences from a field campaign that took place in Ny-Aalesund at Svalbard in January 2014, where a REMUS 100 AUV was used for sea-floor mapping and collection of oceanographic parameters. Based on this, we discuss the experiences related to using AUVs for ice-monitoring. We conclude that AUVs are highly applicable for ice-monitoring, but further research is needed.

Onboard assessment of XRF spectra using genetic algorithms for decision making on an autonomous underwater vehicle

International Nuclear Information System (INIS)

Breen, Jeremy; Souza, P. de; Timms, G.P.; Ollington, R.

2011-01-01

In order to optimise use of the limited resources (time, power) of an autonomous underwater vehicle (AUV) with a miniaturised X-ray fluorescence (XRF) spectrometer on board to carry out in situ autonomous chemical mapping of the surface of sediments with desired resolution, a genetic algorithm for rapid curve fitting is reported in this paper. This method quickly converges and provides an accurate in situ assessment of metals present, which helps the control system of the AUV to decide on future sampling locations. More thorough analysis of the available data could be performed once the AUV has returned to the base (laboratory).

Comparing autonomous underwater vehicle (AUV) and vessel-based tracking performance for locating acoustically tagged fish

OpenAIRE

Eiler, John H.; Grothues, Thomas M.; Dobarro, Joseph A.; Masuda, Michele M.

2013-01-01

Autonomous underwater vehicles (AUV’s) are increasingly used to collect physical, chemical, and biological information in the marine environment. Recent efforts include merging AUV technology with acoustic telemetry to provide information on the distribution and movements of marine fish. We compared surface vessel and AUV tracking capabilities under rigorous conditions in coastal waters near Juneau, Alaska. Tracking surveys were conducted with a REMUS 100 AUV equipped with an integrated acous...

Hydrodynamic Modeling for Autonomous Underwater Vehicles Using Computational and Semi-Empirical Methods

OpenAIRE

Geisbert, Jesse Stuart

2007-01-01

Buoyancy driven underwater gliders, which locomote by modulating their buoyancy and their attitude with moving mass actuators and inflatable bladders, are proving their worth as efficient long-distance, long-duration ocean sampling platforms. Gliders have the capability to travel thousands of kilometers without a need to stop or recharge. There is a need for the development of methods for hydrodynamic modeling. This thesis aims to determine the hydrodynamic parameters for the governing equat...

Risk analysis for autonomous underwater vehicle operations in extreme environments.

Science.gov (United States)

Brito, Mario Paulo; Griffiths, Gwyn; Challenor, Peter

2010-12-01

Autonomous underwater vehicles (AUVs) are used increasingly to explore hazardous marine environments. Risk assessment for such complex systems is based on subjective judgment and expert knowledge as much as on hard statistics. Here, we describe the use of a risk management process tailored to AUV operations, the implementation of which requires the elicitation of expert judgment. We conducted a formal judgment elicitation process where eight world experts in AUV design and operation were asked to assign a probability of AUV loss given the emergence of each fault or incident from the vehicle's life history of 63 faults and incidents. After discussing methods of aggregation and analysis, we show how the aggregated risk estimates obtained from the expert judgments were used to create a risk model. To estimate AUV survival with mission distance, we adopted a statistical survival function based on the nonparametric Kaplan-Meier estimator. We present theoretical formulations for the estimator, its variance, and confidence limits. We also present a numerical example where the approach is applied to estimate the probability that the Autosub3 AUV would survive a set of missions under Pine Island Glacier, Antarctica in January-March 2009. © 2010 Society for Risk Analysis.

Liveness-Based RRT Algorithm for Autonomous Underwater Vehicles Motion Planning

Directory of Open Access Journals (Sweden)

Yang Li

2017-01-01

Full Text Available Motion planning is a crucial, basic issue in robotics, which aims at driving vehicles or robots towards to a given destination with various constraints, such as obstacles and limited resource. This paper presents a new version of rapidly exploring random trees (RRT, that is, liveness-based RRT (Li-RRT, to address autonomous underwater vehicles (AUVs motion problem. Different from typical RRT, we define an index of each node in the random searching tree, called “liveness” in this paper, to describe the potential effectiveness during the expanding process. We show that Li-RRT is provably probabilistic completeness as original RRT. In addition, the expected time of returning a valid path with Li-RRT is obviously reduced. To verify the efficiency of our algorithm, numerical experiments are carried out in this paper.

3D Laser Scanner for Underwater Manipulation.

Science.gov (United States)

Palomer, Albert; Ridao, Pere; Youakim, Dina; Ribas, David; Forest, Josep; Petillot, Yvan

2018-04-04

Nowadays, research in autonomous underwater manipulation has demonstrated simple applications like picking an object from the sea floor, turning a valve or plugging and unplugging a connector. These are fairly simple tasks compared with those already demonstrated by the mobile robotics community, which include, among others, safe arm motion within areas populated with a priori unknown obstacles or the recognition and location of objects based on their 3D model to grasp them. Kinect-like 3D sensors have contributed significantly to the advance of mobile manipulation providing 3D sensing capabilities in real-time at low cost. Unfortunately, the underwater robotics community is lacking a 3D sensor with similar capabilities to provide rich 3D information of the work space. In this paper, we present a new underwater 3D laser scanner and demonstrate its capabilities for underwater manipulation. In order to use this sensor in conjunction with manipulators, a calibration method to find the relative position between the manipulator and the 3D laser scanner is presented. Then, two different advanced underwater manipulation tasks beyond the state of the art are demonstrated using two different manipulation systems. First, an eight Degrees of Freedom (DoF) fixed-base manipulator system is used to demonstrate arm motion within a work space populated with a priori unknown fixed obstacles. Next, an eight DoF free floating Underwater Vehicle-Manipulator System (UVMS) is used to autonomously grasp an object from the bottom of a water tank.

Fish and chips: implementation of a neural network model into computer chips to maximize swimming efficiency in autonomous underwater vehicles.

Science.gov (United States)

Blake, R W; Ng, H; Chan, K H S; Li, J

2008-09-01

Recent developments in the design and propulsion of biomimetic autonomous underwater vehicles (AUVs) have focused on boxfish as models (e.g. Deng and Avadhanula 2005 Biomimetic micro underwater vehicle with oscillating fin propulsion: system design and force measurement Proc. 2005 IEEE Int. Conf. Robot. Auto. (Barcelona, Spain) pp 3312-7). Whilst such vehicles have many potential advantages in operating in complex environments (e.g. high manoeuvrability and stability), limited battery life and payload capacity are likely functional disadvantages. Boxfish employ undulatory median and paired fins during routine swimming which are characterized by high hydromechanical Froude efficiencies (approximately 0.9) at low forward speeds. Current boxfish-inspired vehicles are propelled by a low aspect ratio, 'plate-like' caudal fin (ostraciiform tail) which can be shown to operate at a relatively low maximum Froude efficiency (approximately 0.5) and is mainly employed as a rudder for steering and in rapid swimming bouts (e.g. escape responses). Given this and the fact that bioinspired engineering designs are not obligated to wholly duplicate a biological model, computer chips were developed using a multilayer perception neural network model of undulatory fin propulsion in the knifefish Xenomystus nigri that would potentially allow an AUV to achieve high optimum values of propulsive efficiency at any given forward velocity, giving a minimum energy drain on the battery. We envisage that externally monitored information on flow velocity (sensory system) would be conveyed to the chips residing in the vehicle's control unit, which in turn would signal the locomotor unit to adopt kinematics (e.g. fin frequency, amplitude) associated with optimal propulsion efficiency. Power savings could protract vehicle operational life and/or provide more power to other functions (e.g. communications).

Enabling Persistent Autonomy for Underwater Gliders with Ocean Model Predictions and Terrain Based Navigation

Directory of Open Access Journals (Sweden)

Andrew eStuntz

2016-04-01

Full Text Available Effective study of ocean processes requires sampling over the duration of long (weeks to months oscillation patterns. Such sampling requires persistent, autonomous underwater vehicles, that have a similarly long deployment duration. The spatiotemporal dynamics of the ocean environment, coupled with limited communication capabilities, make navigation and localization difficult, especially in coastal regions where the majority of interesting phenomena occur. In this paper, we consider the combination of two methods for reducing navigation and localization error; a predictive approach based on ocean model predictions and a prior information approach derived from terrain-based navigation. The motivation for this work is not only for real-time state estimation, but also for accurately reconstructing the actual path that the vehicle traversed to contextualize the gathered data, with respect to the science question at hand. We present an application for the practical use of priors and predictions for large-scale ocean sampling. This combined approach builds upon previous works by the authors, and accurately localizes the traversed path of an underwater glider over long-duration, ocean deployments. The proposed method takes advantage of the reliable, short-term predictions of an ocean model, and the utility of priors used in terrain-based navigation over areas of significant bathymetric relief to bound uncertainty error in dead-reckoning navigation. This method improves upon our previously published works by 1 demonstrating the utility of our terrain-based navigation method with multiple field trials, and 2 presenting a hybrid algorithm that combines both approaches to bound navigational error and uncertainty for long-term deployments of underwater vehicles. We demonstrate the approach by examining data from actual field trials with autonomous underwater gliders, and demonstrate an ability to estimate geographical location of an underwater glider to 2

Terrain aided navigation for autonomous underwater vehicles with coarse maps

International Nuclear Information System (INIS)

Zhou, Ling; Cheng, Xianghong; Zhu, Yixian

2016-01-01

Terrain aided navigation (TAN) is a form of geophysical localization technique for autonomous underwater vehicles (AUVs) operating in GPS-denied environments. TAN performance on sensor-rich AUVs has been evaluated in sea trials. However, many challenges remain before TAN can be successfully implemented on sensor-limited AUVs, especially with coarse maps. To improve TAN performance over coarse maps, a Gaussian process (GP) is proposed for the modeling of bathymetric terrain and integrated into the particle filter (GP-PF). GP is applied to provide not only the bathymetric value prediction through learning a set of bathymetric data from coarse maps but also the variance of the prediction. As a measurement update, calculated on bathymetric deviation is performed through the PF to obtain absolute and bounded positioning accuracy. Through the analysis of TAN performance on experimental data for two different terrains with map resolutions of 10–50 m, both the ability of the proposed model to represent the actual bathymetric terrain with accuracy and the effect of the GP-PF for TAN on sensor-limited systems in suited terrain are demonstrated. The experiment results further verify that there is an inverse relationship between the coarseness of the map and the overall TAN accuracy in rough terrains, but there is hardly any relationship between them in relatively flat terrains. (paper)

High–Level Control System for Biomimetic Autonomous Under-water Vehicle

Directory of Open Access Journals (Sweden)

Praczyk Tomasz

2017-01-01

Full Text Available Usually, a rough software architecture designed for a robot can be can be shortly presented in the form of layers. The lowest layer is responsible for direct control of the hardware, i.e. engines, energy system, sensors, navigation devices, etc. A next layer is a low–level control which knows how to use the hardware in order to achieve a desired state of the robot, e.g. to stay on a desired course. And the last layer, the layer which is the nearest to the human–operator, is a high–level control which decides how to use the low–level control and sometimes also individual pieces of the hardware to achieve predefined objectives. The paper describes architecture, tasks and operation of the high–level control system (HLCS designed for Biomimetic Autonomous Underwater Vehicle (BAUV.

Intelligent Navigation for a Solar Powered Unmanned Underwater Vehicle

Directory of Open Access Journals (Sweden)

Francisco García-Córdova

2013-04-01

Full Text Available In this paper, an intelligent navigation system for an unmanned underwater vehicle powered by renewable energy and designed for shadow water inspection in missions of a long duration is proposed. The system is composed of an underwater vehicle, which tows a surface vehicle. The surface vehicle is a small boat with photovoltaic panels, a methanol fuel cell and communication equipment, which provides energy and communication to the underwater vehicle. The underwater vehicle has sensors to monitor the underwater environment such as sidescan sonar and a video camera in a flexible configuration and sensors to measure the physical and chemical parameters of water quality on predefined paths for long distances. The underwater vehicle implements a biologically inspired neural architecture for autonomous intelligent navigation. Navigation is carried out by integrating a kinematic adaptive neuro-controller for trajectory tracking and an obstacle avoidance adaptive neuro- controller. The autonomous underwater vehicle is capable of operating during long periods of observation and monitoring. This autonomous vehicle is a good tool for observing large areas of sea, since it operates for long periods of time due to the contribution of renewable energy. It correlates all sensor data for time and geodetic position. This vehicle has been used for monitoring the Mar Menor lagoon.

3D Laser Scanner for Underwater Manipulation

Directory of Open Access Journals (Sweden)

Albert Palomer

2018-04-01

Full Text Available Nowadays, research in autonomous underwater manipulation has demonstrated simple applications like picking an object from the sea floor, turning a valve or plugging and unplugging a connector. These are fairly simple tasks compared with those already demonstrated by the mobile robotics community, which include, among others, safe arm motion within areas populated with a priori unknown obstacles or the recognition and location of objects based on their 3D model to grasp them. Kinect-like 3D sensors have contributed significantly to the advance of mobile manipulation providing 3D sensing capabilities in real-time at low cost. Unfortunately, the underwater robotics community is lacking a 3D sensor with similar capabilities to provide rich 3D information of the work space. In this paper, we present a new underwater 3D laser scanner and demonstrate its capabilities for underwater manipulation. In order to use this sensor in conjunction with manipulators, a calibration method to find the relative position between the manipulator and the 3D laser scanner is presented. Then, two different advanced underwater manipulation tasks beyond the state of the art are demonstrated using two different manipulation systems. First, an eight Degrees of Freedom (DoF fixed-base manipulator system is used to demonstrate arm motion within a work space populated with a priori unknown fixed obstacles. Next, an eight DoF free floating Underwater Vehicle-Manipulator System (UVMS is used to autonomously grasp an object from the bottom of a water tank.

Containment control of networked autonomous underwater vehicles: A predictor-based neural DSC design.

Science.gov (United States)

Peng, Zhouhua; Wang, Dan; Wang, Wei; Liu, Lu

2015-11-01

This paper investigates the containment control problem of networked autonomous underwater vehicles in the presence of model uncertainty and unknown ocean disturbances. A predictor-based neural dynamic surface control design method is presented to develop the distributed adaptive containment controllers, under which the trajectories of follower vehicles nearly converge to the dynamic convex hull spanned by multiple reference trajectories over a directed network. Prediction errors, rather than tracking errors, are used to update the neural adaptation laws, which are independent of the tracking error dynamics, resulting in two time-scales to govern the entire system. The stability property of the closed-loop network is established via Lyapunov analysis, and transient property is quantified in terms of L2 norms of the derivatives of neural weights, which are shown to be smaller than the classical neural dynamic surface control approach. Comparative studies are given to show the substantial improvements of the proposed new method. Copyright © 2015 ISA. Published by Elsevier Ltd. All rights reserved.

Underwater Gliders by Dr. Kevin Smith [video

OpenAIRE

Naval Postgraduate School Physics

2015-01-01

NPS Physics NPS Physics Research Projects Underwater glider research is currently underway in the physics department at the naval postgraduate in Monterey Ca. Dr. Kevin Smith is a specialist in underwater acoustics and sonar systems. He and his team are currently focused on autonomous underwater gliders and developing systems capable of detecting parameters in the ocean and listening for various sources of sound.

Lagrangian coherent structure assisted path planning for transoceanic autonomous underwater vehicle missions.

Science.gov (United States)

Ramos, A G; García-Garrido, V J; Mancho, A M; Wiggins, S; Coca, J; Glenn, S; Schofield, O; Kohut, J; Aragon, D; Kerfoot, J; Haskins, T; Miles, T; Haldeman, C; Strandskov, N; Allsup, B; Jones, C; Shapiro, J

2018-03-15

Transoceanic Gliders are Autonomous Underwater Vehicles (AUVs) for which there is a developing and expanding range of applications in open-seas research, technology and underwater clean transport. Mature glider autonomy, operating depth (0-1000 meters) and low energy consumption without a CO 2 footprint enable evolutionary access across ocean basins. Pursuant to the first successful transatlantic glider crossing in December 2009, the Challenger Mission has opened the door to long-term, long-distance routine transoceanic AUV missions. These vehicles, which glide through the water column between 0 and 1000 meters depth, are highly sensitive to the ocean current field. Consequently, it is essential to exploit the complex space-time structure of the ocean current field in order to plan a path that optimizes scientific payoff and navigation efficiency. This letter demonstrates the capability of dynamical system theory for achieving this goal by realizing the real-time navigation strategy for the transoceanic AUV named Silbo, which is a Slocum deep-glider (0-1000 m), that crossed the North Atlantic from April 2016 to March 2017. Path planning in real time based on this approach has facilitated an impressive speed up of the AUV to unprecedented velocities resulting in major battery savings on the mission, offering the potential for routine transoceanic long duration missions.

ROV90 - A prototype autonomous inspection vehicle

Energy Technology Data Exchange (ETDEWEB)

Roedseth, Oe.J.; Hallset, J.O.

1991-04-01

Simple autonomous inspection vehicles are suitable for operations where the cost, danger to humans, or area of operation prohibits the use of conventional underwater technology. Autonomous vehicles are, however, in their infancy and few such vehicles are available. There are still some problems to be overcome before this technology becomes useful in commercial applications. We have built ROV90 to investigate these problems. It is a test bed for experimenting with the different parts of an autonomous underwater vehicle. ROV90 will be able to autonomously follow prominent features in the real world, man made or natural. Examples are pipelines or walls in tunnels. ROV90 is tethered, but we are planning to use experience and results from ROV90 to develop av ''real'' autonomous underwater vehicle (AUV) called PISCIS. 11 refs., 8 figs.

Human Factors Issues When Operating Underwater Remotely Operated Vehicles and Autonomous Underwater Vehicles

Science.gov (United States)

2011-03-01

etiquette (Parasuraman & Miller, 2004). Through natural and intuitive communication, Johnson et al., (2007) hope that this interface will instill greater...and etiquette in high criticality automated systems. Communications of the ACM, 47(4), 51-55. Parasuraman, R., & Riley, V. (1997). Humans and... protocols for underwater wireless communications. IEEE Communications Magazine, pp. 97-102. Quazi, A. H., & Konrad, W. L. (1982, March 1982). Underwater

Sewage outfall plume dispersion observations with an autonomous underwater vehicle.

Science.gov (United States)

Ramos, P; Cunha, S R; Neves, M V; Pereira, F L; Quintaneiro, I

2005-01-01

This work represents one of the first successful applications of Autonomous Underwater Vehicles (AUVs) for interdisciplinary coastal research. A monitoring mission to study the shape and estimate the initial dilution of the S. Jacinto sewage outfall plume using an AUV was performed on July 2002. An efficient sampling strategy enabling greater improvements in spatial and temporal range of detection demonstrated that the sewage effluent plume can be clearly traced using naturally occurring tracers in the wastewater. The outfall plume was found at the surface highly influenced by the weak stratification and low currents. Dilution varying with distance downstream was estimated from the plume rise over the outfall diffuser until a nearly constant value of 130:1, 60 m from the diffuser, indicating the near field end. Our results demonstrate that AUVs can provide high-quality measurements of physical properties of effluent plumes in a very effective manner and valuable considerations about the initial mixing processes under real oceanic conditions can be further investigated.

Underwater wireless communication system

International Nuclear Information System (INIS)

Goh, J H; Shaw, A; Al-Shamma'a, A I

2009-01-01

Underwater communication has a range of applications including remotely operated vehicle (ROV) and autonomous underwater vehicle (AUV) communication and docking in the offshore industry. Current underwater transmission techniques is primarily utilise sound waves for large distance at lower frequencies and the velocity of sound in water is approximately 1500m/s the resultant communications have problems with multi-path propagation and low bandwidth problems. The use of electromagnetic (EM) techniques underwater has largely been overlooked because of the attenuation due to the conductivity of seawater. However, for short range applications, the higher frequencies and much higher velocity can prove advantageous. This paper will outline a project which will utilise recent investigations that demonstrate EM wave propagation up to the MHz frequency range is possible in seawater.

Stability analysis of hybrid-driven underwater glider

Science.gov (United States)

Niu, Wen-dong; Wang, Shu-xin; Wang, Yan-hui; Song, Yang; Zhu, Ya-qiang

2017-10-01

Hybrid-driven underwater glider is a new type of unmanned underwater vehicle, which combines the advantages of autonomous underwater vehicles and traditional underwater gliders. The autonomous underwater vehicles have good maneuverability and can travel with a high speed, while the traditional underwater gliders are highlighted by low power consumption, long voyage, long endurance and good stealth characteristics. The hybrid-driven underwater gliders can realize variable motion profiles by their own buoyancy-driven and propeller propulsion systems. Stability of the mechanical system determines the performance of the system. In this paper, the Petrel-II hybrid-driven underwater glider developed by Tianjin University is selected as the research object and the stability of hybrid-driven underwater glider unitedly controlled by buoyancy and propeller has been targeted and evidenced. The dimensionless equations of the hybrid-driven underwater glider are obtained when the propeller is working. Then, the steady speed and steady glide path angle under steady-state motion have also been achieved. The steady-state operating conditions can be calculated when the hybrid-driven underwater glider reaches the desired steady-state motion. And the steadystate operating conditions are relatively conservative at the lower bound of the velocity range compared with the range of the velocity derived from the method of the composite Lyapunov function. By calculating the hydrodynamic coefficients of the Petrel-II hybrid-driven underwater glider, the simulation analysis has been conducted. In addition, the results of the field trials conducted in the South China Sea and the Danjiangkou Reservoir of China have been presented to illustrate the validity of the analysis and simulation, and to show the feasibility of the method of the composite Lyapunov function which verifies the stability of the Petrel-II hybrid-driven underwater glider.

A Bayesian approach for predicting risk of autonomous underwater vehicle loss during their missions

International Nuclear Information System (INIS)

Brito, Mario; Griffiths, Gwyn

2016-01-01

Autonomous Underwater Vehicles (AUVs) are effective platforms for science research and monitoring, and for military and commercial data-gathering purposes. However, there is an inevitable risk of loss during any mission. Quantifying the risk of loss is complex, due to the combination of vehicle reliability and environmental factors, and cannot be determined through analytical means alone. An alternative approach – formal expert judgment – is a time-consuming process; consequently a method is needed to broaden the applicability of judgments beyond the narrow confines of an elicitation for a defined environment. We propose and explore a solution founded on a Bayesian Belief Network (BBN), where the results of the expert judgment elicitation are taken as the initial prior probability of loss due to failure. The network topology captures the causal effects of the environment separately on the vehicle and on the support platform, and combines these to produce an updated probability of loss due to failure. An extended version of the Kaplan–Meier estimator is then used to update the mission risk profile with travelled distance. Sensitivity analysis of the BBN is presented and a case study of Autosub3 AUV deployment in the Amundsen Sea is discussed in detail. - Highlights: • Novel method to estimate risk of autonomous vehicle loss in uncertain environments. • A framework to integrate frequentist and subjective probability modelling. • A Bayesian belief updating method for capturing variation in operating environment. • Graphical approach for sensitivity analysis, applicable to any BBN model validation. • Pragmatic case studies showing the application of the proposed framework.

Contribution à la coordination de flottille de véhicules sous-marins autonomes

OpenAIRE

Spiewak , Jean-Mathias

2007-01-01

Our researches are related to coordination of torpedo-shaped autonomous underwater vehicles flotilla. The cooperation of such vehicles can generate a gain of time, energy, data and exploring area. Indeed, we study the modelling and the control, based on classic sliding mode, of a torpedo-shaped autonomous underwater vehicle. We also present a new high order sliding mode control law in order to limit chattering phenomenon acting on actuators. Finally, we propose a new control strategy to coord...

Survivability design for a hybrid underwater vehicle

Energy Technology Data Exchange (ETDEWEB)

Wang, Biao; Wu, Chao; Li, Xiang; Zhao, Qingkai; Ge, Tong [State Key Lab of Ocean Engineering, School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China)

2015-03-10

A novel hybrid underwater robotic vehicle (HROV) capable of working to the full ocean depth has been developed. The battery powered vehicle operates in two modes: operate as an untethered autonomous vehicle in autonomous underwater vehicle (AUV) mode and operate under remote control connected to the surface vessel by a lightweight, fiber optic tether in remotely operated vehicle (ROV) mode. Considering the hazardous underwater environment at the limiting depth and the hybrid operating modes, survivability has been placed on an equal level with the other design attributes of the HROV since the beginning of the project. This paper reports the survivability design elements for the HROV including basic vehicle design of integrated navigation and integrated communication, emergency recovery strategy, distributed architecture, redundant bus, dual battery package, emergency jettison system and self-repairing control system.

Survivability design for a hybrid underwater vehicle

International Nuclear Information System (INIS)

Wang, Biao; Wu, Chao; Li, Xiang; Zhao, Qingkai; Ge, Tong

2015-01-01

A novel hybrid underwater robotic vehicle (HROV) capable of working to the full ocean depth has been developed. The battery powered vehicle operates in two modes: operate as an untethered autonomous vehicle in autonomous underwater vehicle (AUV) mode and operate under remote control connected to the surface vessel by a lightweight, fiber optic tether in remotely operated vehicle (ROV) mode. Considering the hazardous underwater environment at the limiting depth and the hybrid operating modes, survivability has been placed on an equal level with the other design attributes of the HROV since the beginning of the project. This paper reports the survivability design elements for the HROV including basic vehicle design of integrated navigation and integrated communication, emergency recovery strategy, distributed architecture, redundant bus, dual battery package, emergency jettison system and self-repairing control system

Centralised versus Decentralised Control Reconfiguration for Collaborating Underwater Robots

DEFF Research Database (Denmark)

Furno, Lidia; Nielsen, Mikkel Cornelius; Blanke, Mogens

2015-01-01

The present paper introduces an approach to fault-tolerant reconfiguration for collaborating underwater robots. Fault-tolerant reconfiguration is obtained using the virtual actuator approach, Steen (2005). The paper investigates properties of a centralised versus a decentralised implementation an...... an underwater drill needs to be transported and positioned by three collaborating robots as part of an underwater autonomous operation....

Sensing and control for autonomous vehicles applications to land, water and air vehicles

CERN Document Server

Pettersen, Kristin; Nijmeijer, Henk

2017-01-01

This edited volume includes thoroughly collected on sensing and control for autonomous vehicles. Guidance, navigation and motion control systems for autonomous vehicles are increasingly important in land-based, marine and aerial operations. Autonomous underwater vehicles may be used for pipeline inspection, light intervention work, underwater survey and collection of oceanographic/biological data. Autonomous unmanned aerial systems can be used in a large number of applications such as inspection, monitoring, data collection, surveillance, etc. At present, vehicles operate with limited autonomy and a minimum of intelligence. There is a growing interest for cooperative and coordinated multi-vehicle systems, real-time re-planning, robust autonomous navigation systems and robust autonomous control of vehicles. Unmanned vehicles with high levels of autonomy may be used for safe and efficient collection of environmental data, for assimilation of climate and environmental models and to complement global satellite sy...

Integrating Multiple Autonomous Underwater Vessels, Surface Vessels and Aircraft into Oceanographic Research Vessel Operations

Science.gov (United States)

McGillivary, P. A.; Borges de Sousa, J.; Martins, R.; Rajan, K.

2012-12-01

Autonomous platforms are increasingly used as components of Integrated Ocean Observing Systems and oceanographic research cruises. Systems deployed can include gliders or propeller-driven autonomous underwater vessels (AUVs), autonomous surface vessels (ASVs), and unmanned aircraft systems (UAS). Prior field campaigns have demonstrated successful communication, sensor data fusion and visualization for studies using gliders and AUVs. However, additional requirements exist for incorporating ASVs and UASs into ship operations. For these systems to be optimally integrated into research vessel data management and operational planning systems involves addressing three key issues: real-time field data availability, platform coordination, and data archiving for later analysis. A fleet of AUVs, ASVs and UAS deployed from a research vessel is best operated as a system integrated with the ship, provided communications among them can be sustained. For this purpose, Disruptive Tolerant Networking (DTN) software protocols for operation in communication-challenged environments help ensure reliable high-bandwidth communications. Additionally, system components need to have considerable onboard autonomy, namely adaptive sampling capabilities using their own onboard sensor data stream analysis. We discuss Oceanographic Decision Support System (ODSS) software currently used for situational awareness and planning onshore, and in the near future event detection and response will be coordinated among multiple vehicles. Results from recent field studies from oceanographic research vessels using AUVs, ASVs and UAS, including the Rapid Environmental Picture (REP-12) cruise, are presented describing methods and results for use of multi-vehicle communication and deliberative control networks, adaptive sampling with single and multiple platforms, issues relating to data management and archiving, and finally challenges that remain in addressing these technological issues. Significantly, the

H2-O2 fuel cell and advanced battery power systems for autonomous underwater vehicles: performance envelope comparisons

International Nuclear Information System (INIS)

Schubak, G.E.; Scott, D.S.

1993-01-01

Autonomous underwater vehicles have traditionally been powered by low energy density lead-acid batteries. Recently, advanced battery technologies and H 2 -O 2 fuel cells have become available, offering significant improvements in performance. This paper compares the solid polymer fuel cell to the lithium-thionyl chloride primary battery, sodium-sulfur battery, and lead acid battery for a variety of missions. The power system performance is simulated using computer modelling techniques. Performance envelopes are constructed, indicating domains of preference for competing power system technologies. For most mission scenarios, the solid polymer fuel cell using liquid reactant storage is the preferred system. Nevertheless, the advanced battery systems are competitive with the fuel cell systems using gaseous hydrogen storage, and they illustrate preferred performance for missions requiring high power density. 11 figs., 4 tabs., 15 refs

Current State of Technology of Fuel Cell Power Systems for Autonomous Underwater Vehicles

Directory of Open Access Journals (Sweden)

Alejandro Mendez

2014-07-01

Full Text Available Autonomous Underwater Vehicles (AUVs are vehicles that are primarily used to accomplish oceanographic research data collection and auxiliary offshore tasks. At the present time, they are usually powered by lithium-ion secondary batteries, which have insufficient specific energies. In order for this technology to achieve a mature state, increased endurance is required. Fuel cell power systems have been identified as an effective means to achieve this endurance but no implementation in a commercial device has yet been realized. This paper summarizes the current state of development of the technology in this field of research. First, the most adequate type of fuel cell for this application is discussed. The prototypes and design concepts of AUVs powered by fuel cells which have been developed in the last few years are described. Possible commercial and experimental fuel cell stack options are analyzed, examining solutions adopted in the analogous aerial vehicle applications, as well as the underwater ones, to see if integration in an AUV is feasible. Current solutions in oxygen and hydrogen storage systems are overviewed and energy density is objectively compared between battery power systems and fuel cell power systems for AUVs. A couple of system configuration solutions are described including the necessary lithium-ion battery hybrid system. Finally, some closing remarks on the future of this technology are given.

Experiences from using Autonomous Underwater Vehicles and Synthetic Aperture Sonar for Sediment and Habitat Mapping

Science.gov (United States)

Thorsnes, T.; Bjarnadóttir, L. R.

2017-12-01

Emerging platforms and tools like autonomous underwater vehicles and synthetic aperture sonars provide interesting opportunities for making seabed mapping more efficient and precise. Sediment grain-size maps are an important product in their own right and a key input for habitat and biotope maps. National and regional mapping programmes are tasked with mapping large areas, and survey efficiency, data quality, and resulting map confidence are important considerations when selecting the mapping strategy. Since 2005, c. 175,000 square kilometres of the Norwegian continental shelf and continental slope has been mapped with respect to sediments, habitats and biodiversity, and pollution under the MAREANO programme (www.mareano.no). At present the sediment mapping is based on a combination of ship-borne multibeam bathymetry and backscatter, visual documentation using a towed video platform, and grab sampling. We have now tested a new approach, using an Autonomous Underwater Vehicle (AUV) as the survey platform for the collection of acoustic data (Synthetic Aperture Sonar (SAS), EM2040 bathymetry and backscatter) and visual data (still images using a TFish colour photo system). This pilot project was conducted together the Norwegian Hydrographic Service, the Institute of Marine Research (biology observations) and the Norwegian Defence Research Establishment (operation of ship and AUV). The test site reported here is the Vesterdjupet area, offshore Lofoten, northern Norway. The water depth is between 170 and 300 metres, with sediments ranging from gravel, cobbles and boulders to sandy mud. A cold-water coral reef, associated with bioclastic sediments was also present in the study area. The presentation will give an overview of the main findings and experiences gained from this pilot project with a focus on geological mapping and will also discuss the relevance of AUV-based mapping to large-area mapping programmes like MAREANO.

New Methods for Estimating Water Current Velocity Fields from Autonomous Underwater Vehicles

Science.gov (United States)

Kinsey, J. C.; Medagoda, L.

2016-02-01

Water current velocities are a crucial component of understanding oceanographic processes and underwater robots, such as autonomous underwater vehicles (AUVs), provide a mobile platform for obtaining these observations. Estimating water current velocities requires both measurements of the water velocity, often obtained with an Acoustic Doppler Current Profiler (ADCP), as well as estimates of the vehicle velocity. Presently, vehicle velocities are supplied on the sea surface with velocity from GPS, or near the seafloor where Doppler Velocity Log (DVL) in bottom-lock is available; however, this capability is unavailable in the mid-water column where DVL bottom-lock and GPS are unavailable. Here we present a method which calculates vehicle velocities using consecutive ADCP measurements in the mid-water using an extended Kalman filter (EKF). The correlation of the spatially changing water current states, along with mass transport and shear constraints on the water current field, is formulated using least square constraints. Results from the Sentry AUV from a mid-water surveying mission at Deepwater Horizon and a small-scale hydrothermal vent flux estimation mission suggest the method is suitable for real-time use. DVL data is denied to simulate mid-water missions and the results compared to ground truth water velocity measurements estimated using DVL velocities. Results show quantifiable uncertainties in the water current velocities, along with similar performance, for the DVL and no-DVL case in the mid-water. This method has the potential to provide geo-referenced water velocity measurements from mobile ocean robots in the absence of GPS and DVL as well as estimate the uncertainty associated with the measurements.

An apparatus to estimate the hydrodynamic coefficients of autonomous underwater vehicles using water tunnel testing.

Science.gov (United States)

Nouri, N M; Mostafapour, K; Bahadori, R

2016-06-01

Hydrodynamic coefficients or hydrodynamic derivatives of autonomous underwater vehicles (AUVs) play an important role in their development and maneuverability. The most popular way of estimating their coefficients is to implement captive model tests such as straight line tests and planar motion mechanism (PMM) tests in the towing tanks. This paper aims to develop an apparatus based on planar experiments of water tunnel in order to estimate hydrodynamic derivatives due to AUVs' acceleration and velocity. The capability of implementing straight line tests and PMM ones using mechanical oscillators located in the downstream flow of the model is considered in the design procedure of the system. The hydrodynamic derivatives that resulted from the acceleration and velocity of the AUV model were estimated using the apparatus that we developed. Static and dynamics test results were compared for the similar derivatives. The findings showed that the system provided the basis for conducting static tests, i.e., straight-line and dynamic tests that included pure pitch and pure heave. By conducting such tests in a water tunnel, we were able to eliminate errors related to the time limitation of the tests and the effects of surface waves in the towing tank on AUVs with applications in the deep sea.

Automated gravity gradient tensor inversion for underwater object detection

International Nuclear Information System (INIS)

Wu, Lin; Tian, Jinwen

2010-01-01

Underwater abnormal object detection is a current need for the navigation security of autonomous underwater vehicles (AUVs). In this paper, an automated gravity gradient tensor inversion algorithm is proposed for the purpose of passive underwater object detection. Full-tensor gravity gradient anomalies induced by an object in the partial area can be measured with the technique of gravity gradiometry on an AUV. Then the automated algorithm utilizes the anomalies, using the inverse method to estimate the mass and barycentre location of the arbitrary-shaped object. A few tests on simple synthetic models will be illustrated, in order to evaluate the feasibility and accuracy of the new algorithm. Moreover, the method is applied to a complicated model of an abnormal object with gradiometer and AUV noise, and interference from a neighbouring illusive smaller object. In all cases tested, the estimated mass and barycentre location parameters are found to be in good agreement with the actual values

3D Photo Mosaicing of Tagiri Shallow Vent Field by an Autonomous Underwater Vehicle

Science.gov (United States)

Maki, Toshihiro; Kondo, Hayato; Ura, Tamaki; Sakamaki, Takashi; Mizushima, Hayato; Yanagisawa, Masao

Although underwater visual observation is an ideal method for detailed survey of seafloors, it is currently a costly process that requires the use of Remotely Operated Vehicles (ROVs) or Human Occupied Vehicles (HOVs), and can cover only a limited area. This paper proposes an innovative method to navigate an autonomous underwater vehicle (AUV) to create both 2D and 3D photo mosaics of seafloors with high positioning accuracy without using any vision-based matching. The vehicle finds vertical pole-like acoustic reflectors to use as positioning landmarks using a profiling sonar based on a SLAM (Simultaneous Localization And Mapping) technique. These reflectors can be either artificial or natural objects, and so the method can be applied to shallow vent fields where conventional acoustic positioning is difficult, since bubble plumes can also be used as landmarks as well as artificial reflectors. Path-planning is performed in real-time based on the positions and types of landmarks so as to navigate safely and stably using landmarks of different types (artificial reflector or bubble plume) found at arbitrary times and locations. Terrain tracker switches control reference between depth and altitude from the seafloor based on a local map of hazardous area created in real-time using onboard perceptual sensors, in order to follow rugged terrains at an altitude of 1 to 2 meters, as this range is ideal for visual observation. The method was implemented in the AUV Tri-Dog 1 and experiments were carried out at Tagiri vent field, Kagoshima Bay in Japan. The AUV succeeded in fully autonomous observation for more than 160 minutes to create a photo mosaic with an area larger than 600 square meters, which revealed the spatial distribution of detailed features such as tube-worm colonies, bubble plumes and bacteria mats. A fine bathymetry of the same area was also created using a light-section ranging system mounted on the vehicle. Finally a 3 D representation of the environment was

Subsea Cable Tracking by Autonomous Underwater Vehicle with Magnetic Sensing Guidance.

Science.gov (United States)

Xiang, Xianbo; Yu, Caoyang; Niu, Zemin; Zhang, Qin

2016-08-20

The changes of the seabed environment caused by a natural disaster or human activities dramatically affect the life span of the subsea buried cable. It is essential to track the cable route in order to inspect the condition of the buried cable and protect its surviving seabed environment. The magnetic sensor is instrumental in guiding the remotely-operated vehicle (ROV) to track and inspect the buried cable underseas. In this paper, a novel framework integrating the underwater cable localization method with the magnetic guidance and control algorithm is proposed, in order to enable the automatic cable tracking by a three-degrees-of-freedom (3-DOF) under-actuated autonomous underwater vehicle (AUV) without human beings in the loop. The work relies on the passive magnetic sensing method to localize the subsea cable by using two tri-axial magnetometers, and a new analytic formulation is presented to compute the heading deviation, horizontal offset and buried depth of the cable. With the magnetic localization, the cable tracking and inspection mission is elaborately constructed as a straight-line path following control problem in the horizontal plane. A dedicated magnetic line-of-sight (LOS) guidance is built based on the relative geometric relationship between the vehicle and the cable, and the feedback linearizing technique is adopted to design a simplified cable tracking controller considering the side-slip effects, such that the under-actuated vehicle is able to move towards the subsea cable and then inspect its buried environment, which further guides the environmental protection of the cable by setting prohibited fishing/anchoring zones and increasing the buried depth. Finally, numerical simulation results show the effectiveness of the proposed magnetic guidance and control algorithm on the envisioned subsea cable tracking and the potential protection of the seabed environment along the cable route.

A Real-Time Reaction Obstacle Avoidance Algorithm for Autonomous Underwater Vehicles in Unknown Environments.

Science.gov (United States)

Yan, Zheping; Li, Jiyun; Zhang, Gengshi; Wu, Yi

2018-02-02

A novel real-time reaction obstacle avoidance algorithm (RRA) is proposed for autonomous underwater vehicles (AUVs) that must adapt to unknown complex terrains, based on forward looking sonar (FLS). To accomplish this algorithm, obstacle avoidance rules are planned, and the RRA processes are split into five steps Introduction only lists 4 so AUVs can rapidly respond to various environment obstacles. The largest polar angle algorithm (LPAA) is designed to change detected obstacle's irregular outline into a convex polygon, which simplifies the obstacle avoidance process. A solution is designed to solve the trapping problem existing in U-shape obstacle avoidance by an outline memory algorithm. Finally, simulations in three unknown obstacle scenes are carried out to demonstrate the performance of this algorithm, where the obtained obstacle avoidance trajectories are safety, smooth and near-optimal.

Modifications of Control Loop to Improve the Depth Response of Autonomous Underwater Vehicles

Directory of Open Access Journals (Sweden)

Sheng-Ping Hsu

2014-01-01

Full Text Available During a constant depth maneuver of an autonomous underwater vehicle (AUV, its pitch attitude and stern plane deflections create forces and moments to achieve equilibrium in the vertical plane. If an AUV has a proportional controller only in its depth control loop, then different weights or centers of gravity will cause different steady-state depth errors at trimmed conditions. In general, a steady-state depth error can be eliminated by adding an integral controller in the depth control loop. However, an improper integrator may lead to a bad transient response, even though the steady-state depth error can finally be eliminated. To remove the steady-state depth error, this study proposes methods that adjust the depth command and add a switching integral controller in the depth control loop. Simulation results demonstrate that the steady-state depth error can be eliminated and the transient response can be improved.

An Optimized, Data Distribution Service-Based Solution for Reliable Data Exchange Among Autonomous Underwater Vehicles

Directory of Open Access Journals (Sweden)

Jesús Rodríguez-Molina

2017-08-01

Full Text Available Major challenges are presented when managing a large number of heterogeneous vehicles that have to communicate underwater in order to complete a global mission in a cooperative manner. In this kind of application domain, sending data through the environment presents issues that surpass the ones found in other overwater, distributed, cyber-physical systems (i.e., low bandwidth, unreliable transport medium, data representation and hardware high heterogeneity. This manuscript presents a Publish/Subscribe-based semantic middleware solution for unreliable scenarios and vehicle interoperability across cooperative and heterogeneous autonomous vehicles. The middleware relies on different iterations of the Data Distribution Service (DDS software standard and their combined work between autonomous maritime vehicles and a control entity. It also uses several components with different functionalities deemed as mandatory for a semantic middleware architecture oriented to maritime operations (device and service registration, context awareness, access to the application layer where other technologies are also interweaved with middleware (wireless communications, acoustic networks. Implementation details and test results, both in a laboratory and a deployment scenario, have been provided as a way to assess the quality of the system and its satisfactory performance.

An Optimized, Data Distribution Service-Based Solution for Reliable Data Exchange Among Autonomous Underwater Vehicles.

Science.gov (United States)

Rodríguez-Molina, Jesús; Bilbao, Sonia; Martínez, Belén; Frasheri, Mirgita; Cürüklü, Baran

2017-08-05

Major challenges are presented when managing a large number of heterogeneous vehicles that have to communicate underwater in order to complete a global mission in a cooperative manner. In this kind of application domain, sending data through the environment presents issues that surpass the ones found in other overwater, distributed, cyber-physical systems (i.e., low bandwidth, unreliable transport medium, data representation and hardware high heterogeneity). This manuscript presents a Publish/Subscribe-based semantic middleware solution for unreliable scenarios and vehicle interoperability across cooperative and heterogeneous autonomous vehicles. The middleware relies on different iterations of the Data Distribution Service (DDS) software standard and their combined work between autonomous maritime vehicles and a control entity. It also uses several components with different functionalities deemed as mandatory for a semantic middleware architecture oriented to maritime operations (device and service registration, context awareness, access to the application layer) where other technologies are also interweaved with middleware (wireless communications, acoustic networks). Implementation details and test results, both in a laboratory and a deployment scenario, have been provided as a way to assess the quality of the system and its satisfactory performance.

Short-Range Sensor for Underwater Robot Navigation using Line-lasers and Vision

DEFF Research Database (Denmark)

Hansen, Peter Nicholas; Nielsen, Mikkel Cornelius; Christensen, David Johan

2015-01-01

This paper investigates a minimalistic laser-based range sensor, used for underwater inspection by Autonomous Underwater Vehicles (AUV). This range detection system system comprise two lasers projecting vertical lines, parallel to a camera’s viewing axis, into the environment. Using both lasers...

An Effective Terrain Aided Navigation for Low-Cost Autonomous Underwater Vehicles.

Science.gov (United States)

Zhou, Ling; Cheng, Xianghong; Zhu, Yixian; Dai, Chenxi; Fu, Jinbo

2017-03-25

Terrain-aided navigation is a potentially powerful solution for obtaining submerged position fixes for autonomous underwater vehicles. The application of terrain-aided navigation with high-accuracy inertial navigation systems has demonstrated meter-level navigation accuracy in sea trials. However, available sensors may be limited depending on the type of the mission. Such limitations, especially for low-grade navigation sensors, not only degrade the accuracy of traditional navigation systems, but further impact the ability to successfully employ terrain-aided navigation. To address this problem, a tightly-coupled navigation is presented to successfully estimate the critical sensor errors by incorporating raw sensor data directly into an augmented navigation system. Furthermore, three-dimensional distance errors are calculated, providing measurement updates through the particle filter for absolute and bounded position error. The development of the terrain aided navigation system is elaborated for a vehicle equipped with a non-inertial-grade strapdown inertial navigation system, a 4-beam Doppler Velocity Log range sensor and a sonar altimeter. Using experimental data for navigation performance evaluation in areas with different terrain characteristics, the experiment results further show that the proposed method can be successfully applied to the low-cost AUVs and significantly improves navigation performance.

Formation Learning Control of Multiple Autonomous Underwater Vehicles With Heterogeneous Nonlinear Uncertain Dynamics.

Science.gov (United States)

Yuan, Chengzhi; Licht, Stephen; He, Haibo

2017-09-26

In this paper, a new concept of formation learning control is introduced to the field of formation control of multiple autonomous underwater vehicles (AUVs), which specifies a joint objective of distributed formation tracking control and learning/identification of nonlinear uncertain AUV dynamics. A novel two-layer distributed formation learning control scheme is proposed, which consists of an upper-layer distributed adaptive observer and a lower-layer decentralized deterministic learning controller. This new formation learning control scheme advances existing techniques in three important ways: 1) the multi-AUV system under consideration has heterogeneous nonlinear uncertain dynamics; 2) the formation learning control protocol can be designed and implemented by each local AUV agent in a fully distributed fashion without using any global information; and 3) in addition to the formation control performance, the distributed control protocol is also capable of accurately identifying the AUVs' heterogeneous nonlinear uncertain dynamics and utilizing experiences to improve formation control performance. Extensive simulations have been conducted to demonstrate the effectiveness of the proposed results.

Geomagnetic Navigation of Autonomous Underwater Vehicle Based on Multi-objective Evolutionary Algorithm.

Science.gov (United States)

Li, Hong; Liu, Mingyong; Zhang, Feihu

2017-01-01

This paper presents a multi-objective evolutionary algorithm of bio-inspired geomagnetic navigation for Autonomous Underwater Vehicle (AUV). Inspired by the biological navigation behavior, the solution was proposed without using a priori information, simply by magnetotaxis searching. However, the existence of the geomagnetic anomalies has significant influence on the geomagnetic navigation system, which often disrupts the distribution of the geomagnetic field. An extreme value region may easily appear in abnormal regions, which makes AUV lost in the navigation phase. This paper proposes an improved bio-inspired algorithm with behavior constraints, for sake of making AUV escape from the abnormal region. First, the navigation problem is considered as the optimization problem. Second, the environmental monitoring operator is introduced, to determine whether the algorithm falls into the geomagnetic anomaly region. Then, the behavior constraint operator is employed to get out of the abnormal region. Finally, the termination condition is triggered. Compared to the state-of- the-art, the proposed approach effectively overcomes the disturbance of the geomagnetic abnormal. The simulation result demonstrates the reliability and feasibility of the proposed approach in complex environments.

A Dynamic Bioinspired Neural Network Based Real-Time Path Planning Method for Autonomous Underwater Vehicles.

Science.gov (United States)

Ni, Jianjun; Wu, Liuying; Shi, Pengfei; Yang, Simon X

2017-01-01

Real-time path planning for autonomous underwater vehicle (AUV) is a very difficult and challenging task. Bioinspired neural network (BINN) has been used to deal with this problem for its many distinct advantages: that is, no learning process is needed and realization is also easy. However, there are some shortcomings when BINN is applied to AUV path planning in a three-dimensional (3D) unknown environment, including complex computing problem when the environment is very large and repeated path problem when the size of obstacles is bigger than the detection range of sensors. To deal with these problems, an improved dynamic BINN is proposed in this paper. In this proposed method, the AUV is regarded as the core of the BINN and the size of the BINN is based on the detection range of sensors. Then the BINN will move with the AUV and the computing could be reduced. A virtual target is proposed in the path planning method to ensure that the AUV can move to the real target effectively and avoid big-size obstacles automatically. Furthermore, a target attractor concept is introduced to improve the computing efficiency of neural activities. Finally, some experiments are conducted under various 3D underwater environments. The experimental results show that the proposed BINN based method can deal with the real-time path planning problem for AUV efficiently.

Machine Visual Guidance For An Autonomous Undersea Submersible

Science.gov (United States)

Nguyen, Hoa G.; Kaomea, Peter K.; Heckman, Paul J.

1988-12-01

Optical imaging is the preferred sensory modality for underwater robotic activities requiring high resolution at close range, such as station keeping, docking, control of manipulator, and object retrieval. Machine vision will play a vital part in the design of next generation autonomous underwater submersibles. This paper describes an effort to demonstrate that real-time vision-based guidance and control of autonomous underwater submersibles is possible with compact, low-power, and vehicle-imbeddable hardware. The Naval Ocean Systems Center's EAVE-WEST (Experimental Autonomous Vehicle-West) submersible is being used as the testbed. The vision hardware consists of a PC-bus video frame grabber and an IBM-PC/AT compatible single-board computer, both residing in the artificial intelligence/vision electronics bottle of the submersible. The specific application chosen involves the tracking of underwater buoy cables. Image recognition is performed in two steps. Feature points are identified in the underwater video images using a technique which detects one-dimensional local brightness minima and maxima. Hough transformation is then used to detect the straight line among these feature points. A hierarchical coarse-to-fine processing method is employed which terminates when enough feature points have been identified to allow a reliable fit. The location of the cable identified is then reported to the vehicle controller computer for automatic steering control. The process currently operates successfully with a throughput of approximately 2 frames per second.

Introduction to autonomous manipulation case study with an underwater robot, SAUVIM

CERN Document Server

Marani, Giacomo

2014-01-01

“Autonomous manipulation” is a challenge in robotic technologies. It refers to the capability of a mobile robot system with one or more manipulators that performs intervention tasks requiring physical contacts in unstructured environments and without continuous human supervision. Achieving autonomous manipulation capability is a quantum leap in robotic technologies as it is currently beyond the state of the art in robotics. This book addresses issues with the complexity of the problems encountered in autonomous manipulation including representation and modeling of robotic structures, kinematic and dynamic robotic control, kinematic and algorithmic singularity avoidance, dynamic task priority, workspace optimization and environment perception. Further development in autonomous manipulation should be able to provide robust improvements of the solutions for all of the above issues. The book provides an extensive tract on sensory-based autonomous manipulation for intervention tasks in unstructured environment...

Tactical Decision Aids High Bandwidth Links Using Autonomous Vehicles

Science.gov (United States)

2004-01-01

1 Tactical Decision Aids (High Bandwidth Links Using Autonomous Vehicles ) A. J. Healey, D. P. Horner, Center for Autonomous Underwater Vehicle...SUBTITLE Tactical Decision Aids (High Bandwidth Links Using Autonomous Vehicles ) 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6

Etat de l'art des véhicules sous-marins autonomes, verrous technologiques

OpenAIRE

Michel, J; Duranton, R

1990-01-01

Autonomous Underwater Vehicles, also called "free-swimming vehicles" are self propelled bodies, equipped with their own energy package and with no solid communication link with the surface. At the beginning of the 90s, a renewed interest from the Underwater Intervention Community for autonomous vehicles and quite a number of new projects were announced or started. The present paper aims at presenting an updated State of the Art on the development of autonomous vehicles. It addresses the follo...

12th International Conference on Intelligent Autonomous Systems

CERN Document Server

Cho, Hyungsuck; Yoon, Kwang-Joon; Lee, Jangmyung

2013-01-01

Intelligent autonomous systems are emerged as a key enabler for the creation of a new paradigm of services to humankind, as seen by the recent advancement of autonomous cars licensed for driving in our streets, of unmanned aerial and underwater vehicles carrying out hazardous tasks on-site, and of space robots engaged in scientific as well as operational missions, to list only a few. This book aims at serving the researchers and practitioners in related fields with a timely dissemination of the recent progress on intelligent autonomous systems, based on a collection of papers presented at the 12th International Conference on Intelligent Autonomous Systems, held in Jeju, Korea, June 26-29, 2012. With the theme of “Intelligence and Autonomy for the Service to Humankind, the conference has covered such diverse areas as autonomous ground, aerial, and underwater vehicles, intelligent transportation systems, personal/domestic service robots, professional service robots for surgery/rehabilitation, rescue/security ...

Efficient Weibull channel model for salinity induced turbulent underwater wireless optical communications

KAUST Repository

Oubei, Hassan M.

2017-12-13

Recent advances in underwater wireless optical communications necessitate a better understanding of the underwater channel. We propose the Weibull model to characterize the fading of salinity induced turbulent underwater wireless optical channels. The model shows an excellent agreement with the measured data under all channel conditions.

Large-scale assessment of benthic communities across multiple marine protected areas using an autonomous underwater vehicle.

Science.gov (United States)

Ferrari, Renata; Marzinelli, Ezequiel M; Ayroza, Camila Rezende; Jordan, Alan; Figueira, Will F; Byrne, Maria; Malcolm, Hamish A; Williams, Stefan B; Steinberg, Peter D

2018-01-01

Marine protected areas (MPAs) are designed to reduce threats to biodiversity and ecosystem functioning from anthropogenic activities. Assessment of MPAs effectiveness requires synchronous sampling of protected and non-protected areas at multiple spatial and temporal scales. We used an autonomous underwater vehicle to map benthic communities in replicate 'no-take' and 'general-use' (fishing allowed) zones within three MPAs along 7o of latitude. We recorded 92 taxa and 38 morpho-groups across three large MPAs. We found that important habitat-forming biota (e.g. massive sponges) were more prevalent and abundant in no-take zones, while short ephemeral algae were more abundant in general-use zones, suggesting potential short-term effects of zoning (5-10 years). Yet, short-term effects of zoning were not detected at the community level (community structure or composition), while community structure varied significantly among MPAs. We conclude that by allowing rapid, simultaneous assessments at multiple spatial scales, autonomous underwater vehicles are useful to document changes in marine communities and identify adequate scales to manage them. This study advanced knowledge of marine benthic communities and their conservation in three ways. First, we quantified benthic biodiversity and abundance, generating the first baseline of these benthic communities against which the effectiveness of three large MPAs can be assessed. Second, we identified the taxonomic resolution necessary to assess both short and long-term effects of MPAs, concluding that coarse taxonomic resolution is sufficient given that analyses of community structure at different taxonomic levels were generally consistent. Yet, observed differences were taxa-specific and may have not been evident using our broader taxonomic classifications, a classification of mid to high taxonomic resolution may be necessary to determine zoning effects on key taxa. Third, we provide an example of statistical analyses and

A Game-theoretical Approach for Distributed Cooperative Control of Autonomous Underwater Vehicles

KAUST Repository

Lu, Yimeng

2018-01-01

design and learning process of the algorithm are modified to fit specific constraints of underwater exploration/monitoring tasks. The revised approach can take the real scenario of underwater monitoring applications such as the effect of sea current

An Integrated Model of Motion, Steering, Positioning and Stabilization of an Unmanned Autonomous Maritime Vehicle

Directory of Open Access Journals (Sweden)

Miroslaw Gerigk

2015-12-01

Full Text Available In the paper the aim of an interdisciplinary research is presented. The research method is introduced. An object the unmanned autonomous maritime vehicle is briefly described. The key research problem concerns a combined model of the vehicle motion including the loads of lift and hydrodynamic nature. The model takes into account the gravity and displacement forces, resistance and thrust forces, lift and other hydrodynamic forces. One of the major research tasks is to precisely predict the position of the vehicle. To do that an integrated model of acquiring, analyzing and processing the signals is necessary. The processed signals may then be used for the precise steering of the vehicle. The vehicle should be equipped with a stabilization system. Some information on an integrated steering, positioning and stabilization system of the vehicle is briefly presented in the paper. Such the system enables to obtain a fully autonomous vehicle. Some information on the propulsion and underwater energy supply systems are presented in the paper, too.

Autopilot Using Differential Thrust for ARIES Autonomous Underwater Vehicle

National Research Council Canada - National Science Library

Sarton, Christopher

2003-01-01

.... Unfortunately, communication antennas must point to specific satellites in this system and thus underwater vehicles must steer a specific course on the surface during the communication process...

Study the content relationship between science and technology documents: A compression of papers and patent in Autonomous Underwater Vehicle Dominos

Directory of Open Access Journals (Sweden)

Soraia Zolfaghari

2016-08-01

Full Text Available The current research aims at studying the conceptual relationship between the science and technology documents through the comparison of vocabularies that are used within the patents and the papers in the field of Autonomous Underwater Vehicles (AUV.  The research method is descriptive. To perform the research, the patents were retrieved from Google Patents and Lens websites, and the papers from IEEE Explore database. A hybrid keyword-class method was used to conduct the search. It means that the search query was consisted of "Autonomous Underwater Vehicle" keyword and “H” class. The titles and the abstracts of the patents and the papers were automatically indexed through a semi-automatic method. This resulted in 195 keywords for patents and 114 ones for papers. Co-occurrence matrices of these two sets of keywords were created through RavarMatrix software. The hierarchical maps of keywords were drawn by SPSS. Findings show that 65 percent of papers’ keywords are those that occurred within the patents but 23 percent of patents’ keywords are similar to the papers’.  The structural comparison of patents and papers clustering’s also revealed that the structural proximity between patents and papers vocabularies is equal to zero. The other finding showed that the similarity between the members of ego networks of prominent keywords is for two cases zero and for others fewer than 15 percent except for the keyword “data”. It may be concluded that the science is affected by technology in the field of AUV.

Design and implementation of a biomimetic turtle hydrofoil for an autonomous underwater vehicle.

Science.gov (United States)

Font, Davinia; Tresanchez, Marcel; Siegentahler, Cedric; Pallejà, Tomàs; Teixidó, Mercè; Pradalier, Cedric; Palacin, Jordi

2011-01-01

This paper presents the design and implementation of a turtle hydrofoil for an Autonomous Underwater Vehicle (AUV). The final design of the AUV must have navigation performance like a turtle, which has also been the biomimetic inspiration for the design of the hydrofoil and propulsion system. The hydrofoil design is based on a National Advisory Committee for Aeronautics (NACA) 0014 hydrodynamic profile. During the design stage, four different propulsion systems were compared in terms of propulsion path, compactness, sealing and required power. The final implementation is based on a ball-and-socket mechanism because it is very compact and provides three degrees of freedom (DoF) to the hydrofoil with very few restrictions on the propulsion path. The propulsion obtained with the final implementation of the hydrofoil has been empirically evaluated in a water channel comparing different motion strategies. The results obtained have confirmed that the proposed turtle hydrofoil controlled with a mechanism with three DoF generates can be used in the future implementation of the planned AUV.

Design and Implementation of a Biomimetic Turtle Hydrofoil for an Autonomous Underwater Vehicle

Science.gov (United States)

Font, Davinia; Tresanchez, Marcel; Siegentahler, Cedric; Pallejà, Tomàs; Teixidó, Mercè; Pradalier, Cedric; Palacin, Jordi

2011-01-01

This paper presents the design and implementation of a turtle hydrofoil for an Autonomous Underwater Vehicle (AUV). The final design of the AUV must have navigation performance like a turtle, which has also been the biomimetic inspiration for the design of the hydrofoil and propulsion system. The hydrofoil design is based on a National Advisory Committee for Aeronautics (NACA) 0014 hydrodynamic profile. During the design stage, four different propulsion systems were compared in terms of propulsion path, compactness, sealing and required power. The final implementation is based on a ball-and-socket mechanism because it is very compact and provides three degrees of freedom (DoF) to the hydrofoil with very few restrictions on the propulsion path. The propulsion obtained with the final implementation of the hydrofoil has been empirically evaluated in a water channel comparing different motion strategies. The results obtained have confirmed that the proposed turtle hydrofoil controlled with a mechanism with three DoF generates can be used in the future implementation of the planned AUV. PMID:22247660

Design and Implementation of a Biomimetic Turtle Hydrofoil for an Autonomous Underwater Vehicle

Directory of Open Access Journals (Sweden)

Jordi Palacin

2011-11-01

Full Text Available This paper presents the design and implementation of a turtle hydrofoil for an Autonomous Underwater Vehicle (AUV. The final design of the AUV must have navigation performance like a turtle, which has also been the biomimetic inspiration for the design of the hydrofoil and propulsion system. The hydrofoil design is based on a National Advisory Committee for Aeronautics (NACA 0014 hydrodynamic profile. During the design stage, four different propulsion systems were compared in terms of propulsion path, compactness, sealing and required power. The final implementation is based on a ball-and-socket mechanism because it is very compact and provides three degrees of freedom (DoF to the hydrofoil with very few restrictions on the propulsion path. The propulsion obtained with the final implementation of the hydrofoil has been empirically evaluated in a water channel comparing different motion strategies. The results obtained have confirmed that the proposed turtle hydrofoil controlled with a mechanism with three DoF generates can be used in the future implementation of the planned AUV.

Efficient Weibull channel model for salinity induced turbulent underwater wireless optical communications

KAUST Repository

Oubei, Hassan M.; Zedini, Emna; Elafandy, Rami T.; Kammoun, Abla; Ng, Tien Khee; Alouini, Mohamed-Slim; Ooi, Boon S.

2017-01-01

Recent advances in underwater wireless optical communications necessitate a better understanding of the underwater channel. We propose the Weibull model to characterize the fading of salinity induced turbulent underwater wireless optical channels

Underwater target positioning with a single acoustic sensor

Digital Repository Service at National Institute of Oceanography (India)

David, M-S; Pascoal, A.M.; Joaquin, A.

The availability of reliable underwater positioning systems to localize one or more vehicles simultaneously based on information received on-board a support ship or an autonomous surface vessel is key to the operation of some classes of AUVs...

Underwater wireless optical communications: From system-level demonstrations to channel modelling

KAUST Repository

Oubei, Hassan M.

2018-01-09

In this paper, we discuss about recent experimental advances in underwater wireless optical communications (UWOC) over various underwater channel water types using different modulation schemes as well as modelling and describing the statistical properties of turbulence-induced fading in underwater wireless optical channels using laser beam intensity fluctuations measurements.

Intelligent autonomous systems 12. Vol. 2. Proceedings

Energy Technology Data Exchange (ETDEWEB)

Lee, Sukhan [Sungkyunkwan Univ., Gyeonggi-Do (Korea, Republic of). College of Information and Communication Engineering; Yoon, Kwang-Joon [Konkuk Univ., Seoul (Korea, Republic of); Cho, Hyungsuck [Daegu Gyeongbuk Institute of Science and Technology, Daegu (Korea, Republic of); Lee, Jangmyung (eds.) [Pusan National Univ. (Korea, Republic of). Dept. of Electronics Engineering

2013-02-01

Recent research in Intelligent and Autonomous Systems. Volume 2 of the proceedings of the 12th International Conference IAS-12, held June 26-29, 2012, jeju Island, Korea. Written by leading experts in the field. Intelligent autonomous systems are emerged as a key enabler for the creation of a new paradigm of services to humankind, as seen by the recent advancement of autonomous cars licensed for driving in our streets, of unmanned aerial and underwater vehicles carrying out hazardous tasks on-site, and of space robots engaged in scientific as well as operational missions, to list only a few. This book aims at serving the researchers and practitioners in related fields with a timely dissemination of the recent progress on intelligent autonomous systems, based on a collection of papers presented at the 12th International Conference on Intelligent Autonomous Systems, held in Jeju, Korea, June 26-29, 2012. With the theme of ''Intelligence and Autonomy for the Service to Humankind, the conference has covered such diverse areas as autonomous ground, aerial, and underwater vehicles, intelligent transportation systems, personal/domestic service robots, professional service robots for surgery/rehabilitation, rescue/security and space applications, and intelligent autonomous systems for manufacturing and healthcare. This volume 2 includes contributions devoted to Service Robotics and Human-Robot Interaction and Autonomous Multi-Agent Systems and Life Engineering.

Marine self potential and CSEM measurements using an autonomous underwater vehicle

Science.gov (United States)

Constable, S.; Kowalczyk, P.; Bloomer, S.

2017-12-01

Marine self potential (SP) and controlled source EM (CSEM) measurements are commonly made using instruments towed close to the seafloor, which requires dedicated ship time, is limited to slow speeds, and is subject to navigation errors of 5 to 10 m. An alternative is to mount SP and CSEM sensors on an autonomous underwater vehicle (AUV). We tested this with a pilot study in the Iheya area of the Okinawa Trough, off Japan, using an ISE Explorer-class AUV operated by Fukada Salvage and Marine Works and equipped with a Scripps CSEM receiver system. Parts of this prospect have documented hydrothermal venting and seafloor massive sulfide (SMS) deposits. CSEM signals were generated by deploying battery-powered seafloor transmitters, which emitted 20 amps, alternately every 30 seconds on orthogonal, 10 m antennas. CSEM signals were recorded by 3-axis AC-coupled sensors on the AUV as it flew a pattern 70 m above the seafloor around the transmitters. By transmitting two slightly different frequencies, two or more transmitters can broadcast simultaneously. Measurements were made at the same time using DC-coupled electric field amplifiers, from which self potentials were estimated using regularized inversion, yielding negative anomalies of 10 to 25 mV. Modeling suggests that the anomalies are localized and close to the seafloor. Apparent conductivities as high as 30 S/m were fit to the CSEM data, which strongly suggests that SMS mineralization is associated with the SP anomalies, although it is possible the causative mechanism is at least partly due to hydrothermal venting. In either case, we have demonstrated that AUV-mounted instrument systems are an efficient, effective, and low noise means of collecting marine CSEM and SP data. The entire data set was collected in a single day on station with a 10-hour AUV deployment.

Robust Huber-based iterated divided difference filtering with application to cooperative localization of autonomous underwater vehicles.

Science.gov (United States)

Gao, Wei; Liu, Yalong; Xu, Bo

2014-12-19

A new algorithm called Huber-based iterated divided difference filtering (HIDDF) is derived and applied to cooperative localization of autonomous underwater vehicles (AUVs) supported by a single surface leader. The position states are estimated using acoustic range measurements relative to the leader, in which some disadvantages such as weak observability, large initial error and contaminated measurements with outliers are inherent. By integrating both merits of iterated divided difference filtering (IDDF) and Huber's M-estimation methodology, the new filtering method could not only achieve more accurate estimation and faster convergence contrast to standard divided difference filtering (DDF) in conditions of weak observability and large initial error, but also exhibit robustness with respect to outlier measurements, for which the standard IDDF would exhibit severe degradation in estimation accuracy. The correctness as well as validity of the algorithm is demonstrated through experiment results.

A Data Link Layer in Support of Swarming of Autonomous Underwater Vehicles

Science.gov (United States)

Jabba Molinares, Daladier

2009-01-01

Communication underwater is challenging because of the inherent characteristics of the media. First, common radio frequency (RF) signals utilized in wireless communications cannot be used under water. RF signals are attenuated in such as way that RF communication underwater is restricted to very few meters. As a result, acoustic-based…

Heterogeneous Teams of Autonomous Vehicles: Advanced Sensing & Control

Science.gov (United States)

2009-03-01

Final Technical 3. DATES COVERED (From To) 7/1/05-12/31708 4. TITLE AND SUBTITLE Heterogeneous Teams of Autonomous Vehicles Advanced Sensing...assimilating data from underwater and surface autonomous vehicles in addition to the usual sources of Eulerian and Lagrangian systems into a small scale

Modeling and Control of Underwater Robotic Systems

Energy Technology Data Exchange (ETDEWEB)

Schjoelberg, I:

1996-12-31

This doctoral thesis describes modeling and control of underwater vehicle-manipulator systems. The thesis also presents a model and a control scheme for a system consisting of a surface vessel connected to an underwater robotic system by means of a slender marine structure. The equations of motion of the underwater vehicle and manipulator are described and the system kinematics and properties presented. Feedback linearization technique is applied to the system and evaluated through a simulation study. Passivity-based controllers for vehicle and manipulator control are presented. Stability of the closed loop system is proved and simulation results are given. The equation of motion for lateral motion of a cable/riser system connected to a surface vessel at the top end and to a thruster at the bottom end is described and stability analysis and simulations are presented. The equations of motion in 3 degrees of freedom of the cable/riser, surface vessel and robotic system are given. Stability analysis of the total system with PD-controllers is presented. 47 refs., 32 figs., 7 tabs.

Synthesis of a Controller for Swarming Robots Performing Underwater Mine Countermeasures

National Research Council Canada - National Science Library

Tan, Yong

2004-01-01

This Trident Scholar project involved the synthesis of a swarm controller that is suitable for controlling movements of a group of autonomous robots performing underwater mine countermeasures (UMCM...

12th International Conference on Intelligent Autonomous Systems (IAS-12)

CERN Document Server

Yoon, Kwang-Joon; Lee, Jangmyung; Frontiers of Intelligent Autonomous Systems

2013-01-01

This carefully edited volume aims at providing readers with the most recent progress on intelligent autonomous systems, with its particular emphasis on intelligent autonomous ground, aerial and underwater vehicles as well as service robots for home and healthcare under the context of the aforementioned convergence. “Frontiers of Intelligent Autonomous Systems” includes thoroughly revised and extended papers selected from the 12th International Conference on Intelligent Autonomous Systems (IAS-12), held in Jeju, Korea, June 26-29, 2012. The editors chose 35 papers out of the 202 papers presented at IAS-12 which are organized into three chapters: Chapter 1 is dedicated to autonomous navigation and mobile manipulation, Chapter 2 to unmanned aerial and underwater vehicles and Chapter 3 to service robots for home and healthcare. To help the readers to easily access this volume, each chapter starts with a chapter summary introduced by one of the editors: Chapter 1 by Sukhan Lee, Chapter 2 by Kwang Joon Yoon and...

Oscillatory Adaptive Yaw-Plane Control of Biorobotic Autonomous Underwater Vehicles Using Pectoral-Like Fins

Directory of Open Access Journals (Sweden)

Mugdha S. Naik

2007-01-01

Full Text Available This article considers the control of a biorobotic autonomous underwater vehicle (BAUV in the yaw plane using biologically inspired oscillatory pectoral-like fins of marine animals. The fins are assumed to be oscillating harmonically with a combined linear (sway and angular (yaw motion producing unsteady forces, which are used for fish-like control of BAUVs. Manoeuvring of the BAUV in the yaw plane is accomplished by altering the bias (mean angle of the angular motion of the fin. For the derivation of the adaptive control system, it is assumed that the physical parameters, the hydrodynamic coefficients, and the fin force and moment are not known. A direct adaptive sampled-data control system for the trajectory control of the yaw-angle using only yaw-angle measurement is derived. The parameter adaptation law is based on the normalised gradient scheme. Simulation results for the set point control, sinusoidal trajectory tracking and turning manoeuvres are presented, which show that the control system accomplishes precise trajectory control in spite of the parameter uncertainties.

MECHANICAL DESIGN OF AN AUTONOMOUS MARINE ROBOTIC SYSTEM FOR INTERACTION WITH DIVERS

Directory of Open Access Journals (Sweden)

Nikola Stilinović

2016-09-01

Full Text Available SCUBA diving, professional or recreational, remains one of the most hazardous activities known by man, mostly due to the fact that the human survival in the underwater environment requires use of technical equipment such as breathing regulators. Loss of breathing gas supply, burst eardrum, decompression sickness and nitrogen narcosis are just a few problems which can occur during an ordinary dive and result in injuries, long-term illnesses or even death. Most common way to reduce the risk of diving is to dive in pairs, thus allowing divers to cooperate with each other and react when uncommon situation occurs. Having the ability to react before an unwanted situation happens would improve diver safety. This paper describes an autonomous marine robotic system that replaces a human dive buddy. Such a robotic system, developed within an FP7 project “CADDY – Cognitive Autonomous Diving Buddy” provides a symbiotic link between robots and human divers in the underwater. The proposed concept consists of a diver, an autonomous underwater vehicle (AUV Buddy and an autonomous surface vehicle (ASV PlaDyPos, acting within a cooperative network linked via an acoustic communication channel. This is a first time that an underwater human-robot system of such a scale has ever been developed. In this paper, focus is put on mechanical characteristics of the robotic vehicles.

Localization and Tracking of Submerged Phytoplankton Bloom Patches by an Autonomous Underwater Vehicle

Science.gov (United States)

Godin, M. A.; Ryan, J. P.; Zhang, Y.; Bellingham, J. G.

2012-12-01

Observing plankton in their drifting frame of reference permits effective studies of marine ecology from the perspective of microscopic life itself. By minimizing variation caused simply by advection, observations in a plankton-tracking frame of reference focus measurement capabilities on the processes that influence the life history of populations. Further, the patchy nature of plankton populations motivates use of sensor data in real-time to resolve patch boundaries and adapt observing resources accordingly. We have developed capabilities for population-centric plankton observation and sampling by autonomous underwater vehicles (AUVs). Our focus has been on phytoplankton populations, both because of their ecological significance - as the core of the oceanic food web and yet potentially harmful under certain bloom conditions, as well as the accessibility of their signal to simple optical sensing. During the first field deployment of these capabilities in 2010, we tracked a phytoplankton patch containing toxigenic diatoms and found that their toxicity correlated with exposure to resuspended sediments. However, this first deployment was labor intensive as the AUV drove in a pre-programmed pattern centered around a patch-marking drifter; it required a boat deployment of the patch-marking drifter and required full-time operators to periodically estimate of the position of the patch with respect to the drifter and adjust the AUV path accordingly. In subsequent field experiments during 2011 and 2012, the Tethys-class long-range AUVs ran fully autonomous patch tracking algorithms which detected phytoplankton patches and continually updated estimates of each patch center by driving adaptive patterns through the patch. Iterations of the algorithm were generated to overcome the challenges of tracking advecting and evolving patches while minimizing human involvement in vehicle control. Such fully autonomous monitoring will be necessary to perform long-term in

Autonomous docking control of visual-servo type underwater vehicle system aiming at underwater automatic charging

International Nuclear Information System (INIS)

Yanou, Akira; Ohnishi, Shota; Ishiyama, Shintaro; Minami, Mamoru

2015-01-01

A visual-servo type remotely operated vehicle (ROV) system with binocular wide-angle lens was developed to survey submarine resources, decontaminate radiation from mud in dam lake and so on. This paper explores the experiments on regulator performance and underwater docking of the robot system utilizing Genetic Algorithm (GA) for real-time recognition of the robot's relative position and posture through 3D marker. The visual servoing performances have been verified as follows; (1) The stability performances of the proposed regulator system have been evaluated by exerting abrupt distrubane force while the ROV is controlled by visual servoing. (2) The proposed system can track time-variant desired target position in x-axis (front-back direction of the robot). (3) The underwater docking can be completed by switching visual servoing and docking modes based on the error threshold, and by giving time-varying desired target position and orientation to the controller as a desired pose. (author)

Optimization of an Intelligent Controller for an Unmanned Underwater Vehicle

Directory of Open Access Journals (Sweden)

M. Fauzi Nor Shah

2011-08-01

Full Text Available Underwater environment poses a difficult challenge for autonomous underwater navigation. A standard problem of underwater vehicles is to maintain it position at a certain depth in order to perform desired operations. An effective controller is required for this purpose and hence the design of a depth controller for an unmanned underwater vehicle is described in this paper. The control algorithm is simulated by using the marine guidance navigation and control simulator. The project shows a radial basis function metamodel can be used to tune the scaling factors of a fuzzy logic controller. By using offline optimization approach, a comparison between genetic algorithm and metamodeling has been done to minimize the integral square error between the set point and the measured depth of the underwater vehicle. The results showed that it is possible to obtain a reasonably good error using metamodeling approach in much a shorter time compared to the genetic algorithm approach.

Remote sensing of deep hermatypic coral reefs in Puerto Rico and the U.S. Virgin Islands using the Seabed autonomous underwater vehicle

Science.gov (United States)

Armstrong, Roy A.; Singh, Hanumant

2006-09-01

Optical imaging of coral reefs and other benthic communities present below one attenuation depth, the limit of effective airborne and satellite remote sensing, requires the use of in situ platforms such as autonomous underwater vehicles (AUVs). The Seabed AUV, which was designed for high-resolution underwater optical and acoustic imaging, was used to characterize several deep insular shelf reefs of Puerto Rico and the US Virgin Islands using digital imagery. The digital photo transects obtained by the Seabed AUV provided quantitative data on living coral, sponge, gorgonian, and macroalgal cover as well as coral species richness and diversity. Rugosity, an index of structural complexity, was derived from the pencil-beam acoustic data. The AUV benthic assessments could provide the required information for selecting unique areas of high coral cover, biodiversity and structural complexity for habitat protection and ecosystem-based management. Data from Seabed sensors and related imaging technologies are being used to conduct multi-beam sonar surveys, 3-D image reconstruction from a single camera, photo mosaicking, image based navigation, and multi-sensor fusion of acoustic and optical data.

Underwater lidar system: design challenges and application in pollution detection

Science.gov (United States)

Gupta, Pradip; Sankolli, Swati; Chakraborty, A.

2016-05-01

The present remote sensing techniques have imposed limitations in the applications of LIDAR Technology. The fundamental sampling inadequacy of the remote sensing data obtained from satellites is that they cannot resolve in the third spatial dimension, the vertical. This limits our possibilities of measuring any vertical variability in the water column. Also the interaction between the physical and biological process in the oceans and their effects at subsequent depths cannot be modeled with present techniques. The idea behind this paper is to introduce underwater LIDAR measurement system by using a LIDAR mounted on an Autonomous Underwater Vehicle (AUV). The paper introduces working principles and design parameters for the LIDAR mounted AUV (AUV-LIDAR). Among several applications the papers discusses the possible use and advantages of AUV-LIDAR in water pollution detection through profiling of Dissolved Organic Matter (DOM) in water bodies.

Optimal Estimation of Glider’s Underwater Trajectory with Depth-Dependent Correction Using the Navy Coastal Ocean Model with Application to Antisubmarine Warfare

Science.gov (United States)

2014-09-01

step study. 2010 IEEE International Conf. on Robotics and Autonomation, Anchorage, Alaska, IEEE Xplore , 4770‒4777, doi:10.1109/ ROBOT.2010.5509240...Autonomation, Karlsruhe, Germany, IEEE Xplore , 5565‒5570, doi:10.1109/ ICRA.2013.6631376. Webb, D. C., P. J. Simonetti, C. P. Jones, 2001: SLOCUM: An...unmanned underwater vehicles for very shallow water mine countermeasures. Proc. OCEANS 2003, San Diego, California, IEEE , 1417‒1423. doi:10.1109

Underwater noise modelling for environmental impact assessment

Energy Technology Data Exchange (ETDEWEB)

Farcas, Adrian [Centre for Environment, Fisheries and Aquaculture Science (Cefas), Pakefield Road, Lowestoft, NR33 0HT (United Kingdom); Thompson, Paul M. [Lighthouse Field Station, Institute of Biological and Environmental Sciences, University of Aberdeen, Cromarty IV11 8YL (United Kingdom); Merchant, Nathan D., E-mail: nathan.merchant@cefas.co.uk [Centre for Environment, Fisheries and Aquaculture Science (Cefas), Pakefield Road, Lowestoft, NR33 0HT (United Kingdom)

2016-02-15

Assessment of underwater noise is increasingly required by regulators of development projects in marine and freshwater habitats, and noise pollution can be a constraining factor in the consenting process. Noise levels arising from the proposed activity are modelled and the potential impact on species of interest within the affected area is then evaluated. Although there is considerable uncertainty in the relationship between noise levels and impacts on aquatic species, the science underlying noise modelling is well understood. Nevertheless, many environmental impact assessments (EIAs) do not reflect best practice, and stakeholders and decision makers in the EIA process are often unfamiliar with the concepts and terminology that are integral to interpreting noise exposure predictions. In this paper, we review the process of underwater noise modelling and explore the factors affecting predictions of noise exposure. Finally, we illustrate the consequences of errors and uncertainties in noise modelling, and discuss future research needs to reduce uncertainty in noise assessments.

Underwater noise modelling for environmental impact assessment

International Nuclear Information System (INIS)

Farcas, Adrian; Thompson, Paul M.; Merchant, Nathan D.

2016-01-01

Assessment of underwater noise is increasingly required by regulators of development projects in marine and freshwater habitats, and noise pollution can be a constraining factor in the consenting process. Noise levels arising from the proposed activity are modelled and the potential impact on species of interest within the affected area is then evaluated. Although there is considerable uncertainty in the relationship between noise levels and impacts on aquatic species, the science underlying noise modelling is well understood. Nevertheless, many environmental impact assessments (EIAs) do not reflect best practice, and stakeholders and decision makers in the EIA process are often unfamiliar with the concepts and terminology that are integral to interpreting noise exposure predictions. In this paper, we review the process of underwater noise modelling and explore the factors affecting predictions of noise exposure. Finally, we illustrate the consequences of errors and uncertainties in noise modelling, and discuss future research needs to reduce uncertainty in noise assessments.

Validation of multi-body modelling methodology for reconfigurable underwater robots

DEFF Research Database (Denmark)

Nielsen, M.C.; Eidsvik, O. A.; Blanke, Mogens

2016-01-01

This paper investigates the problem of employing reconfigurable robots in an underwater setting. The main results presented is the experimental validation of a modelling methodology for a system consisting of N dynamically connected robots with heterogeneous dynamics. Two distinct types...... of experiments are performed, a series of hydrostatic free-decay tests and a series of open-loop trajectory tests. The results are compared to a simulation based on the modelling methodology. The modelling methodology shows promising results for usage with systems composed of reconfigurable underwater modules...

Infrastructure for thulium-170 isotope power systems for autonomous underwater vehicle fleets

International Nuclear Information System (INIS)

Walter, C.E.

1991-07-01

The radioisotope thulium-170 is a safe and environmentally benign heat source for providing the high endurance and energy densities needed by advanced power systems for autonomous underwater vehicles (AUV). Thulium Isotope Power (TIP) systems have an endurance of ∼3000 h, and gravimetric and volumetric energy densities of 3 x 10 4 Wh/kg and 3 x 10 8 Wh/m 3 , respectively. These energy densities are more than 200 times higher than those currently provided by Ag-Zn battery technology. In order to capitalize on these performance levels with about one hundred AUVs in continuous use, it will be necessary to establish an infrastructure for isotope production and heat-source refurbishment. The infrastructure cost is not trivial, and studies are needed to determine its optimum configuration. The major component of the projected infrastructure is the nuclear reactor used to produce Tm- 170 by neutron absorption in Tm-169. The reactor design should ideally be optimized for TM-170 production. Using the byproduct ''waste'' heat beneficially would help defray the cost of isotope production. However, generating electric power with the reactor would compromise both the cost of electricity and the isotope production capacity. A coastal location for the reactor would be most convenient from end-use considerations, and the ''waste'' heat could be used to desalinate seawater in water-thirsty states. 13 refs., 6 figs., 2 tabs

Investigation of the Propagation Characteristics of Underwater Shock Waves in Underwater Drilling Blasting

Directory of Open Access Journals (Sweden)

Xin Liu

2018-01-01

Full Text Available During the first-stage project of the main channel of Ningbo-Zhoushan Port’s Shipu Harbor, underwater shock waves were monitored. By analyzing a typical measured pressure time history curve, the characteristics of underwater shock waves in an engineering context were obtained. We obtained a traditional exponential attenuation formula for underwater shock waves based on the measured data, simplified the model of underwater drilling blasting based on engineering practice, deduced a revised formula for underwater shock wave peak overpressure on the basis of dimensional analysis, established a linear fitting model, and obtained the undetermined coefficients of the revised formula using a linear regression analysis. In addition, the accuracies of the two formulas used to predict underwater shock wave peak overpressure and the significance order of influence and influence mechanism of factors included in the revised formula on the underwater shock wave peak overpressure were discussed.

3D MODELING FOR UNDERWATER ARCHAEOLOGICAL DOCUMENTATION: METRIC VERIFICATIONS

Directory of Open Access Journals (Sweden)

S. D’Amelio

2015-04-01

Full Text Available The survey in underwater environment has always presented considerable difficulties both operative and technical and this has sometimes made it difficult to use the techniques of survey commonly used for the documentation of Cultural Heritage in dry environment. The work of study concerns the evaluation in terms of capability and accuracy of the Autodesk123DCatch software for the reconstruction of a three-dimensional model of an object in underwater context. The subjects of the study are models generated from sets of photographs and sets of frames extracted from video sequence. The study is based on comparative method, using a reference model, obtained with laser scanner technique.

The Research of Optical Turbulence Model in Underwater Imaging System

Directory of Open Access Journals (Sweden)

Liying Sun

2014-01-01

Full Text Available In order to research the effect of turbulence on underwater imaging system and image restoration, the underwater turbulence model is simulated by computer fluid dynamics. This model is obtained in different underwater turbulence intensity, which contains the pressure data that influences refractive index distribution. When the pressure value is conversed to refractive index, the refractive index distribution can be received with the refraction formula. In the condition of same turbulent intensity, the distribution of refractive index presents gradient in the whole region, with disorder and mutations in the local region. With the turbulence intensity increase, the holistic variation of the refractive index in the image is larger, and the refractive index change more tempestuously in the local region. All the above are illustrated by the simulation results with he ray tracing method and turbulent refractive index model. According to different turbulence intensity analysis, it is proved that turbulence causes image distortion and increases noise.

Towards an Autonomous Space In-Situ Marine Sensorweb

Science.gov (United States)

Chien, S.; Doubleday, J.; Tran, D.; Thompson, D.; Mahoney, G.; Chao, Y.; Castano, R.; Ryan, J.; Kudela, R.; Palacios, S.;

Modelling of the underwater disposal of uranium mine tailings in Elliot Lake

International Nuclear Information System (INIS)

Halbert, B.E.; Scharer, J.M.; Chakravatti, J.L.; Barnes, E.

1982-01-01

Underwater disposal of uranium mine tailings from the Elliot Lake area operations offers potential advantages in controlling radon gas release, emission of airborne particulate matter, and acid production from pyrites in the tailings. In addition, the proximity of the three active properties, one owned by Denison Mines Limited and two by Rio Algom Limited, to a large deep lake has spurred interest in the concept. It has been estimated that the placement of approximately 150 million tonnes of tailings from future planned production would occupy less than 20% of the lake volume. To assess the applicability of the underwater tailings disposal concept, a multi-stage study was developed in conjunction with the regulatory agencies. The most important facet identified for investigation during the first-stage investigations was an assessment of the effects of underwater disposal on water quality in the Serpent River Basin watershed. To simulate the effects of underwater disposal, a computer simulation routine was developed and integrated with a water quality model previously developed for the Basin which predicts levels of total dissolved solids, ammonia, dissolved radium-226 and pH. The underwater disposal model component reflects the effects of direct input of tailings into the hypolimnion, the chemical/biological transformation of dissolved constituents in the water column, the reactions of pyritic tailings deposited on the bottom, and the flux of dissolved constituents from the tailings into the water column. To establish site-specific values for the underwater disposal model, field and laboratory experiments were utilized to evaluate rates of pyrite and ammonia oxidation, and pH-alkalinity relationships. The results of these studies and their use in the water quality model are discussed. In addition, the results of two model run simulations are presented. (author)

Efficient Modelling Methodology for Reconfigurable Underwater Robots

DEFF Research Database (Denmark)

Nielsen, Mikkel Cornelius; Blanke, Mogens; Schjølberg, Ingrid

2016-01-01

This paper considers the challenge of applying reconfigurable robots in an underwater environment. The main result presented is the development of a model for a system comprised of N, possibly heterogeneous, robots dynamically connected to each other and moving with 6 Degrees of Freedom (DOF). Th...

Measurement and Modeling of Narrowband Channels for Ultrasonic Underwater Communications

Directory of Open Access Journals (Sweden)

Francisco J. Cañete

2016-02-01

Full Text Available Underwater acoustic sensor networks are a promising technology that allow real-time data collection in seas and oceans for a wide variety of applications. Smaller size and weight sensors can be achieved with working frequencies shifted from audio to the ultrasonic band. At these frequencies, the fading phenomena has a significant presence in the channel behavior, and the design of a reliable communication link between the network sensors will require a precise characterization of it. Fading in underwater channels has been previously measured and modeled in the audio band. However, there have been few attempts to study it at ultrasonic frequencies. In this paper, a campaign of measurements of ultrasonic underwater acoustic channels in Mediterranean shallow waters conducted by the authors is presented. These measurements are used to determine the parameters of the so-called κ-μ shadowed distribution, a fading model with a direct connection to the underlying physical mechanisms. The model is then used to evaluate the capacity of the measured channels with a closed-form expression.

A PROPOSAL FOR A SUSTAINABLE MODEL BASED UPON UNDERWATER TOURISM RESEARCH IN AYVALIK

Directory of Open Access Journals (Sweden)

A. GÖKDENİZ

2013-03-01

Full Text Available Underwater sports are the activities being done with the aims of witnessing the beauties, hunting, taking photos, the ecology and the archaeology of underwater analysing or finding out the human being’s boundaries by improving the physical and psychological skills of men. The initial aim of this project is to increase the underwater flora and the fauna heritage of Ayvalık and to bring them in tourism. Ayvalık is on the west coast of Turkey. It is getting more and more famous with its underwater richness. Also, to form a new underwater sports centre in order to contribute to the improvement of the region. By providing visual attractiveness, the tourists related to underwater sports will pay attention to Ayvalık and underwater tourism will contribute much to the economy of the region. The aim of this project is to improve the underwater sports which is now a hobby than a sport. In Ayvalık Underwater World study, we dealt with 247 divers and 4 underwater sports club. In this study, we analysed the expectation, satisfaction, demographic and economic level of 247 divers about the services in the region. Interview technique has been used in the study on the 4 underwater sports clubs which are hosting divers. As a conclusion, a report has been prepared in which detailed information and proposals are presented by developing a sustainable marketing model concerned with the underwater sports for those who want to possess information, shareholders of the sector and make analyse about tourism.

Second Order Sliding Mode Control Scheme for an Autonomous Underwater Vehicle with Dynamic Region Concept

Directory of Open Access Journals (Sweden)

Zool H. Ismail

2015-01-01

Full Text Available The main goal in developing closed loop control system for an Autonomous Underwater Vehicle (AUV is to make a robust vehicle from natural and exogenous perturbations such as wind, wave, and ocean currents. However a well-known robust control, for instance, Sliding Mode Controller (SMC, gives a chattering effect and it influences the stability of an AUV. Furthermore, some researchers combined other controls to get better result but it tends to present long computational time and causes large energy consumption. Thus, this paper proposed a Super Twisting Sliding Mode Controller (STSMC with dynamic region concept for an AUV. STSMC or a second order SMC is adopted as a robust controller which is free from chattering effect. Meanwhile, the implementation of dynamic region is useful to reduce the energy usage. As a result, the proposed controller obtains global asymptotic stability which is validated by using Lyapunov-like function. Moreover, some simulations present the efficiency of proposed controller. In conclusion, STSMC with region based control is effective to be applied for the robust tracking of an AUV. It contributes to give a fast response when handling the perturbations, short computational time, and low energy demand.

High resolution study of the spatial distributions of abyssal fishes by autonomous underwater vehicle.

Science.gov (United States)

Milligan, R J; Morris, K J; Bett, B J; Durden, J M; Jones, D O B; Robert, K; Ruhl, H A; Bailey, D M

2016-05-16

On abyssal plains, demersal fish are believed to play an important role in transferring energy across the seafloor and between the pelagic and benthic realms. However, little is known about their spatial distributions, making it difficult to quantify their ecological significance. To address this, we employed an autonomous underwater vehicle to conduct an exceptionally large photographic survey of fish distributions on the Porcupine Abyssal Plain (NE Atlantic, 4850 m water depth) encompassing two spatial scales (1-10 km(2)) on and adjacent to a small abyssal hill (240 m elevation). The spatial distributions of the total fish fauna and that of the two dominant morphotypes (Coryphaenoides sp. 1 and C. profundicolus) appeared to be random, a result contrary to common expectation but consistent with previous predictions for these fishes. We estimated total fish density on the abyssal plain to be 723 individuals km(-2) (95% CI: 601-844). This estimate is higher, and likely more precise, than prior estimates from trawl catch and baited camera techniques (152 and 188 individuals km(-2) respectively). We detected no significant difference in fish density between abyssal hill and plain, nor did we detect any evidence for the existence of fish aggregations at any spatial scale assessed.

Ocean Research Enabled by Underwater Gliders.

Science.gov (United States)

Rudnick, Daniel L

2016-01-01

Underwater gliders are autonomous underwater vehicles that profile vertically by changing their buoyancy and use wings to move horizontally. Gliders are useful for sustained observation at relatively fine horizontal scales, especially to connect the coastal and open ocean. In this review, research topics are grouped by time and length scales. Large-scale topics addressed include the eastern and western boundary currents and the regional effects of climate variability. The accessibility of horizontal length scales of order 1 km allows investigation of mesoscale and submesoscale features such as fronts and eddies. Because the submesoscales dominate vertical fluxes in the ocean, gliders have found application in studies of biogeochemical processes. At the finest scales, gliders have been used to measure internal waves and turbulent dissipation. The review summarizes gliders' achievements to date and assesses their future in ocean observation.

An explanatory model of underwater adaptation

Directory of Open Access Journals (Sweden)

Joaquín Colodro

Full Text Available The underwater environment is an extreme environment that requires a process of human adaptation with specific psychophysiological demands to ensure survival and productive activity. From the standpoint of existing models of intelligence, personality and performance, in this explanatory study we have analyzed the contribution of individual differences in explaining the adaptation of military personnel in a stressful environment. Structural equation analysis was employed to verify a model representing the direct effects of psychological variables on individual adaptation to an adverse environment, and we have been able to confirm, during basic military diving courses, the structural relationships among these variables and their ability to predict a third of the variance of a criterion that has been studied very little to date. In this way, we have confirmed in a sample of professionals (N = 575 the direct relationship of emotional adjustment, conscientiousness and general mental ability with underwater adaptation, as well as the inverse relationship of emotional reactivity. These constructs are the psychological basis for working under water, contributing to an improved adaptation to this environment and promoting risk prevention and safety in diving activities.

Measurement and analysis of self-noise in hybrid-driven underwater gliders

Directory of Open Access Journals (Sweden)

LIU Lu

2017-08-01

Full Text Available The Hybrid-driven Underwater Glider (HUG is a new type of submersible vehicle which combines the functions of traditional Autonomous Underwater Vehicles(AUVand Autonomous Underwater Gliders(AUG. In order to study its noise source distribution and basic self-noise characteristics, a self-noise acquisition system based on the HUG was designed and developed, and a noise analysis test carried out in a free-field pool. In August 2016, the sea trial of the Petrel II glider was conducted in the South China Sea, with observation data at a depth range of 1 000 m as the research object. The self-noise data of the glider platform under different working conditions was obtained through the step-by-step operation method. The experimental analysis and results show that the self-noise acquisition system is stable. The contribution of mechanical noise to self-noise is greatest when the glider works in the gliding mode, while the self-noise band above 500 Hz is closely related to the work of the buoyancy adjustment unit, and peaks at 1 kHz. According to the analysis of the basic characteristics of self-noise, this provides some guidance for the implementation of vibration and noise reduction.

DE-Sync: A Doppler-Enhanced Time Synchronization for Mobile Underwater Sensor Networks.

Science.gov (United States)

Zhou, Feng; Wang, Qi; Nie, DongHu; Qiao, Gang

2018-05-25

Time synchronization is the foundation of cooperative work among nodes of underwater sensor networks; it takes a critical role in the research and application of underwater sensor networks. Although numerous time synchronization protocols have been proposed for terrestrial wireless sensor networks, they cannot be directly applied to underwater sensor networks. This is because most of them typically assume that the propagation delay among sensor nodes is negligible, which is not the case in underwater sensor networks. Time synchronization is mainly affected by a long propagation delay among sensor nodes due to the low propagation speed of acoustic signals. Furthermore, sensor nodes in underwater tend to experience some degree of mobility due to wind or ocean current, or some other nodes are on self-propelled vehicles, such as autonomous underwater vehicles (AUVs). In this paper, we propose a Doppler-enhanced time synchronization scheme for mobile underwater sensor networks, called DE-Sync. Our new scheme considers the effect of the clock skew during the process of estimating the Doppler scale factor and directly substitutes the Doppler scale factor into linear regression to achieve the estimation of the clock skew and offset. Simulation results show that DE-Sync outperforms existing time synchronization protocols in both accuracy and energy efficiency.

On the Impacts and Benefits of Implementing Full-Duplex Communications Links in an Underwater Acoustic Network

National Research Council Canada - National Science Library

Gibson, J; Larraza, A; Rice, J; Smith, K; Xie, G

2002-01-01

.... These networks may provide command and control for autonomous underwater vehicles, forward reporting by arrays of sensor grids, ad hoc communications links to covert forces, or positive control...

CFD approach to modelling, hydrodynamic analysis and motion characteristics of a laboratory underwater glider with experimental results

Directory of Open Access Journals (Sweden)

Yogang Singh

2017-06-01

Full Text Available Underwater gliders are buoyancy propelled vehicle which make use of buoyancy for vertical movement and wings to propel the glider in forward direction. Autonomous underwater gliders are a patented technology and are manufactured and marketed by corporations. In this study, we validate the experimental lift and drag characteristics of a glider from the literature using Computational fluid dynamics (CFD approach. This approach is then used for the assessment of the steady state characteristics of a laboratory glider designed at Indian Institute of Technology (IIT Madras. Flow behaviour and lift and drag force distribution at different angles of attack are studied for Reynolds numbers varying from 105 to 106 for NACA0012 wing configurations. The state variables of the glider are the velocity, gliding angle and angle of attack which are simulated by making use of the hydrodynamic drag and lift coefficients obtained from CFD. The effect of the variable buoyancy is examined in terms of the gliding angle, velocity and angle of attack. Laboratory model of glider is developed from the final design asserted by CFD. This model is used for determination of static and dynamic properties of an underwater glider which were validated against an equivalent CAD model and simulation results obtained from equations of motion of glider in vertical plane respectively. In the literature, only empirical approach has been adopted to estimate the hydrodynamic coefficients of the AUG that are required for its trajectory simulation. In this work, a CFD approach has been proposed to estimate the hydrodynamic coefficients and validated with experimental data. A two-mass variable buoyancy engine has been designed and implemented. The equations of motion for this two-mass engine have been obtained by modifying the single mass version of the equations described in the literature. The objectives of the present study are to understand the glider dynamics adopting a CFD approach

Implementation of Autonomous Mission Control for Mine Reconnaissance AUVs

National Research Council Canada - National Science Library

Evans, B; Davies, G; Myers, V; Bellettini, A; Pinto, Manuel; Munk, P

2007-01-01

Whilst autonomous underwater vehicles (AUVs) are increasingly being used to perform MCM tasks, the capability of these systems is limited in terms of their ability to network and co-operate effectively with other manned or unmanned assets...

ULTRA: Underwater Localization for Transit and Reconnaissance Autonomy

Science.gov (United States)

Huntsberger, Terrance L.

2013-01-01

This software addresses the issue of underwater localization of unmanned vehicles and the inherent drift in their onboard sensors. The software gives a 2 to 3 factor of improvement over the state-of-the-art underwater localization algorithms. The software determines the localization (position, heading) of an AUV (autonomous underwater vehicle) in environments where there is no GPS signal. It accomplishes this using only the commanded position, onboard gyros/accelerometers, and the bathymetry of the bottom provided by an onboard sonar system. The software does not rely on an onboard bathymetry dataset, but instead incrementally determines the position of the AUV while mapping the bottom. In order to enable long-distance underwater navigation by AUVs, a localization method called ULTRA uses registration of the bathymetry data products produced by the onboard forward-looking sonar system for hazard avoidance during a transit to derive the motion and pose of the AUV in order to correct the DR (dead reckoning) estimates. The registration algorithm uses iterative point matching (IPM) combined with surface interpolation of the Iterative Closest Point (ICP) algorithm. This method was used previously at JPL for onboard unmanned ground vehicle localization, and has been optimized for efficient computational and memory use.

Accuracy Assessment of Underwater Photogrammetric Three Dimensional Modelling for Coral Reefs

Science.gov (United States)

Guo, T.; Capra, A.; Troyer, M.; Gruen, A.; Brooks, A. J.; Hench, J. L.; Schmitt, R. J.; Holbrook, S. J.; Dubbini, M.

2016-06-01

Recent advances in automation of photogrammetric 3D modelling software packages have stimulated interest in reconstructing highly accurate 3D object geometry in unconventional environments such as underwater utilizing simple and low-cost camera systems. The accuracy of underwater 3D modelling is affected by more parameters than in single media cases. This study is part of a larger project on 3D measurements of temporal change of coral cover in tropical waters. It compares the accuracies of 3D point clouds generated by using images acquired from a system camera mounted in an underwater housing and the popular GoPro cameras respectively. A precisely measured calibration frame was placed in the target scene in order to provide accurate control information and also quantify the errors of the modelling procedure. In addition, several objects (cinder blocks) with various shapes were arranged in the air and underwater and 3D point clouds were generated by automated image matching. These were further used to examine the relative accuracy of the point cloud generation by comparing the point clouds of the individual objects with the objects measured by the system camera in air (the best possible values). Given a working distance of about 1.5 m, the GoPro camera can achieve a relative accuracy of 1.3 mm in air and 2.0 mm in water. The system camera achieved an accuracy of 1.8 mm in water, which meets our requirements for coral measurement in this system.

Hybrid Underwater Vehicle: ARV Design and Development

Directory of Open Access Journals (Sweden)

Zhigang DENG

2014-02-01

Full Text Available The development of SMU-I, a new autonomous & remotely-operated vehicle (ARV is described. Since it has both the characteristics of autonomous underwater vehicle (AUV and remote operated underwater vehicle (ROV, it is able to achieve precision fix station operation and manual timely intervention. In the paper the initial design of basic components, such as vehicle, propulsion, batteries etc. and the control design of motion are introduced and analyzed. ROV’s conventional cable is replaced by a fiber optic cable, which makes it available for high-bandwidth real-time video, data telemetry and high-quality teleoperation. Furthermore, with the aid of the manual real-time remote operation and ranging sonar, it also resolves the AUV’s conflicting issue, which can absolutely adapt the actual complex sea environment and satisfy the unknown mission need. The whole battery system is designed as two-battery banks, whose voltages and temperatures are monitored through CAN (controller area network bus to avoid battery fire and explosion. A fuzzy-PID controller is designed for its motion control, including depth control and direction control. The controller synthesizes the advantage of fuzzy control and PID control, utilizes the fuzzy rules to on-line tune the parameters of PID controller, and achieves a better control effect. Experiment results demonstrate to show the effectiveness of the test-bed.

Underwater striling engine design with modified one-dimensional model

Directory of Open Access Journals (Sweden)

Daijin Li

2015-05-01

Full Text Available Stirling engines are regarded as an efficient and promising power system for underwater devices. Currently, many researches on one-dimensional model is used to evaluate thermodynamic performance of Stirling engine, but in which there are still some aspects which cannot be modeled with proper mathematical models such as mechanical loss or auxiliary power. In this paper, a four-cylinder double-acting Stirling engine for Unmanned Underwater Vehicles (UUVs is discussed. And a one-dimensional model incorporated with empirical equations of mechanical loss and auxiliary power obtained from experiments is derived while referring to the Stirling engine computer model of National Aeronautics and Space Administration (NASA. The P-40 Stirling engine with sufficient testing results from NASA is utilized to validate the accuracy of this one-dimensional model. It shows that the maximum error of output power of theoretical analysis results is less than 18% over testing results, and the maximum error of input power is no more than 9%. Finally, a Stirling engine for UUVs is designed with Schmidt analysis method and the modified one-dimensional model, and the results indicate this designed engine is capable of showing desired output power.

Task Assignment and Path Planning for Multiple Autonomous Underwater Vehicles Using 3D Dubins Curves †.

Science.gov (United States)

Cai, Wenyu; Zhang, Meiyan; Zheng, Yahong Rosa

2017-07-11

This paper investigates the task assignment and path planning problem for multiple AUVs in three dimensional (3D) underwater wireless sensor networks where nonholonomic motion constraints of underwater AUVs in 3D space are considered. The multi-target task assignment and path planning problem is modeled by the Multiple Traveling Sales Person (MTSP) problem and the Genetic Algorithm (GA) is used to solve the MTSP problem with Euclidean distance as the cost function and the Tour Hop Balance (THB) or Tour Length Balance (TLB) constraints as the stop criterion. The resulting tour sequences are mapped to 2D Dubins curves in the X - Y plane, and then interpolated linearly to obtain the Z coordinates. We demonstrate that the linear interpolation fails to achieve G 1 continuity in the 3D Dubins path for multiple targets. Therefore, the interpolated 3D Dubins curves are checked against the AUV dynamics constraint and the ones satisfying the constraint are accepted to finalize the 3D Dubins curve selection. Simulation results demonstrate that the integration of the 3D Dubins curve with the MTSP model is successful and effective for solving the 3D target assignment and path planning problem.

ACCURACY ASSESSMENT OF UNDERWATER PHOTOGRAMMETRIC THREE DIMENSIONAL MODELLING FOR CORAL REEFS

Directory of Open Access Journals (Sweden)

T. Guo

2016-06-01

Full Text Available Recent advances in automation of photogrammetric 3D modelling software packages have stimulated interest in reconstructing highly accurate 3D object geometry in unconventional environments such as underwater utilizing simple and low-cost camera systems. The accuracy of underwater 3D modelling is affected by more parameters than in single media cases. This study is part of a larger project on 3D measurements of temporal change of coral cover in tropical waters. It compares the accuracies of 3D point clouds generated by using images acquired from a system camera mounted in an underwater housing and the popular GoPro cameras respectively. A precisely measured calibration frame was placed in the target scene in order to provide accurate control information and also quantify the errors of the modelling procedure. In addition, several objects (cinder blocks with various shapes were arranged in the air and underwater and 3D point clouds were generated by automated image matching. These were further used to examine the relative accuracy of the point cloud generation by comparing the point clouds of the individual objects with the objects measured by the system camera in air (the best possible values. Given a working distance of about 1.5 m, the GoPro camera can achieve a relative accuracy of 1.3 mm in air and 2.0 mm in water. The system camera achieved an accuracy of 1.8 mm in water, which meets our requirements for coral measurement in this system.

Modelling cavitating flow around underwater missiles

Directory of Open Access Journals (Sweden)

Fabien Petitpas

2011-12-01

Full Text Available The diffuse interface model of Saurel et al. (2008 is used for the computation of compressible cavitating flows around underwater missiles. Such systems use gas injection and natural cavitation to reduce drag effects. Consequently material interfaces appear separating liquid and gas. These interfaces may have a really complex dynamics such that only a few formulations are able to predict their evolution. Contrarily to front tracking or interface reconstruction method the interfaces are computed as diffused numerical zones, that are captured in a routinely manner, as is done usually with gas dynamics solvers for shocks and contact discontinuity. With the present approach, a single set of partial differential equations is solved everywhere, with a single numerical scheme. This leads to very efficient solvers. The algorithm derived in Saurel et al. (2009 is used to compute cavitation pockets around solid bodies. It is first validated against experiments done in cavitation tunnel at CNU. Then it is used to compute flows around high speed underwater systems (Shkval-like missile. Performance data are then computed showing method ability to predict forces acting on the system.

Apparatus for Changing the Attack Angle of a Cavitator on a Supercavatating Underwater Research Model

Science.gov (United States)

2005-07-18

the Invention 14 The present invention generally relates to an apparatus 15 for changing the attack of a cavitator on a supercavitating 16 underwater...research model. 17 2. Description of the Prior Art 18 Supercavitating underwater vehicles and projectiles are 19 known in the art. One such... supercavitating underwater 20 projectile is described in Harkins et al., U.S. Patent No. 21 5,955,698. This projectile uses a supercavitating nose 22 section that

Parametric geometric model and hydrodynamic shape optimization of a flying-wing structure underwater glider

Science.gov (United States)

Wang, Zhen-yu; Yu, Jian-cheng; Zhang, Ai-qun; Wang, Ya-xing; Zhao, Wen-tao

2017-12-01

Combining high precision numerical analysis methods with optimization algorithms to make a systematic exploration of a design space has become an important topic in the modern design methods. During the design process of an underwater glider's flying-wing structure, a surrogate model is introduced to decrease the computation time for a high precision analysis. By these means, the contradiction between precision and efficiency is solved effectively. Based on the parametric geometry modeling, mesh generation and computational fluid dynamics analysis, a surrogate model is constructed by adopting the design of experiment (DOE) theory to solve the multi-objects design optimization problem of the underwater glider. The procedure of a surrogate model construction is presented, and the Gaussian kernel function is specifically discussed. The Particle Swarm Optimization (PSO) algorithm is applied to hydrodynamic design optimization. The hydrodynamic performance of the optimized flying-wing structure underwater glider increases by 9.1%.

Autonomous Learner Model Resource Book

Science.gov (United States)

Betts, George T.; Carey, Robin J.; Kapushion, Blanche M.

2016-01-01

"Autonomous Learner Model Resource Book" includes activities and strategies to support the development of autonomous learners. More than 40 activities are included, all geared to the emotional, social, cognitive, and physical development of students. Teachers may use these activities and strategies with the entire class, small groups, or…

Self-generation of controller of an underwater robot with neural network

International Nuclear Information System (INIS)

Suto, T.; Ura, T.

1994-01-01

A self-organizing controller system is constructed based on artificial neural networks and applied to constant altitude swimming of the autonomous underwater robot PTEROA 150. The system consists of a controller and a forward model which calculates the values for evaluation as a result of control. Some methods are introduced for quick and appropriate adjustment of the controller network. Modification of the controller network is executed based on error-back-propagation method utilizing the forward model network. The forward model is divided into three sub-networks which represent dynamics of the vehicle, estimation of relative position to the seabed and calculation of the altitude. The proposed adaptive system is demonstrated in computer simulations where objective of a vehicle is keeping a constant altitude from seabed which is constituted of triangular ridges

Determining spherical lens correction for astronaut training underwater.

Science.gov (United States)

Porter, Jason; Gibson, C Robert; Strauss, Samuel

2011-09-01

To develop a model that will accurately predict the distance spherical lens correction needed to be worn by National Aeronautics and Space Administration astronauts while training underwater. The replica space suit's helmet contains curved visors that induce refractive power when submersed in water. Anterior surface powers and thicknesses were measured for the helmet's protective and inside visors. The impact of each visor on the helmet's refractive power in water was analyzed using thick lens calculations and Zemax optical design software. Using geometrical optics approximations, a model was developed to determine the optimal distance spherical power needed to be worn underwater based on the helmet's total induced spherical power underwater and the astronaut's manifest spectacle plane correction in air. The validity of the model was tested using data from both eyes of 10 astronauts who trained underwater. The helmet's visors induced a total power of -2.737 D when placed underwater. The required underwater spherical correction (FW) was linearly related to the spectacle plane spherical correction in air (FAir): FW = FAir + 2.356 D. The mean magnitude of the difference between the actual correction worn underwater and the calculated underwater correction was 0.20 ± 0.11 D. The actual and calculated values were highly correlated (r = 0.971) with 70% of eyes having a difference in magnitude of astronauts. The model accurately predicts the actual values worn underwater and can be applied (more generally) to determine a suitable spectacle lens correction to be worn behind other types of masks when submerged underwater.

An Underwater Image Enhancement Algorithm for Environment Recognition and Robot Navigation

Directory of Open Access Journals (Sweden)

Kun Xie

2018-03-01

Full Text Available There are many tasks that require clear and easily recognizable images in the field of underwater robotics and marine science, such as underwater target detection and identification of robot navigation and obstacle avoidance. However, water turbidity makes the underwater image quality too low to recognize. This paper proposes the use of the dark channel prior model for underwater environment recognition, in which underwater reflection models are used to obtain enhanced images. The proposed approach achieves very good performance and multi-scene robustness by combining the dark channel prior model with the underwater diffuse model. The experimental results are given to show the effectiveness of the dark channel prior model in underwater scenarios.

Intelligent Autonomy for Unmanned Surface and Underwater Vehicles

Science.gov (United States)

Huntsberger, Terry; Woodward, Gail

2011-01-01

As the Autonomous Underwater Vehicle (AUV) and Autonomous Surface Vehicle (ASV) platforms mature in endurance and reliability, a natural evolution will occur towards longer, more remote autonomous missions. This evolution will require the development of key capabilities that allow these robotic systems to perform a high level of on-board decisionmaking, which would otherwise be performed by humanoperators. With more decision making capabilities, less a priori knowledge of the area of operations would be required, as these systems would be able to sense and adapt to changing environmental conditions, such as unknown topography, currents, obstructions, bays, harbors, islands, and river channels. Existing vehicle sensors would be dual-use; that is they would be utilized for the primary mission, which may be mapping or hydrographic reconnaissance; as well as for autonomous hazard avoidance, route planning, and bathymetric-based navigation. This paper describes a tightly integrated instantiation of an autonomous agent called CARACaS (Control Architecture for Robotic Agent Command and Sensing) developed at JPL (Jet Propulsion Laboratory) that was designed to address many of the issues for survivable ASV/AUV control and to provide adaptive mission capabilities. The results of some on-water tests with US Navy technology test platforms are also presented.

Task Assignment and Path Planning for Multiple Autonomous Underwater Vehicles Using 3D Dubins Curves †

Directory of Open Access Journals (Sweden)

Wenyu Cai

2017-07-01

Full Text Available This paper investigates the task assignment and path planning problem for multiple AUVs in three dimensional (3D underwater wireless sensor networks where nonholonomic motion constraints of underwater AUVs in 3D space are considered. The multi-target task assignment and path planning problem is modeled by the Multiple Traveling Sales Person (MTSP problem and the Genetic Algorithm (GA is used to solve the MTSP problem with Euclidean distance as the cost function and the Tour Hop Balance (THB or Tour Length Balance (TLB constraints as the stop criterion. The resulting tour sequences are mapped to 2D Dubins curves in the X − Y plane, and then interpolated linearly to obtain the Z coordinates. We demonstrate that the linear interpolation fails to achieve G 1 continuity in the 3D Dubins path for multiple targets. Therefore, the interpolated 3D Dubins curves are checked against the AUV dynamics constraint and the ones satisfying the constraint are accepted to finalize the 3D Dubins curve selection. Simulation results demonstrate that the integration of the 3D Dubins curve with the MTSP model is successful and effective for solving the 3D target assignment and path planning problem.

A flexible liquid crystal polymer MEMS pressure sensor array for fish-like underwater sensing

International Nuclear Information System (INIS)

Kottapalli, A G P; Asadnia, M; Miao, J M; Barbastathis, G; Triantafyllou, M S

2012-01-01

In order to perform underwater surveillance, autonomous underwater vehicles (AUVs) require flexible, light-weight, reliable and robust sensing systems that are capable of flow sensing and detecting underwater objects. Underwater animals like fish perform a similar task using an efficient and ubiquitous sensory system called a lateral-line constituting of an array of pressure-gradient sensors. We demonstrate here the development of arrays of polymer microelectromechanical systems (MEMS) pressure sensors which are flexible and can be readily mounted on curved surfaces of AUV bodies. An array of ten sensors with a footprint of 60 (L) mm × 25 (W) mm × 0.4 (H) mm is fabricated using liquid crystal polymer (LCP) as the sensing membrane material. The flow sensing and object detection capabilities of the array are illustrated with proof-of-concept experiments conducted in a water tunnel. The sensors demonstrate a pressure sensitivity of 14.3 μV Pa −1 . A high resolution of 25 mm s −1 is achieved in water flow sensing. The sensors can passively sense underwater objects by transducing the pressure variations generated underwater by the movement of objects. The experimental results demonstrate the array’s ability to detect the velocity of underwater objects towed past by with high accuracy, and an average error of only 2.5%. (paper)

A swarm of autonomous miniature underwater robot drifters for exploring submesoscale ocean dynamics.

Science.gov (United States)

Jaffe, Jules S; Franks, Peter J S; Roberts, Paul L D; Mirza, Diba; Schurgers, Curt; Kastner, Ryan; Boch, Adrien

2017-01-24

Measuring the ever-changing 3-dimensional (3D) motions of the ocean requires simultaneous sampling at multiple locations. In particular, sampling the complex, nonlinear dynamics associated with submesoscales (swarm of 16 independent vehicles whose 3D trajectories are measured near-continuously, underwater. As the vehicles drift with the ambient flow or execute preprogrammed vertical behaviours, the simultaneous measurements at multiple, known locations resolve the details of the flow within the swarm. We describe the design, construction, control and underwater navigation of the M-AUE. A field programme in the coastal ocean using a swarm of these robots programmed with a depth-holding behaviour provides a unique test of a physical-biological interaction leading to plankton patch formation in internal waves. The performance of the M-AUE vehicles illustrates their novel capability for measuring submesoscale dynamics.

The Sentry Autonomous Underwater Vehicle: Field Trial Results and Future Capabilities

Science.gov (United States)

Yoerger, D. R.; Bradley, A. M.; Martin, S. C.; Whitcomb, L. L.

2006-12-01

The Sentry autonomous underwater vehicle combines an efficient long range survey capability with the ability to maneuver at low speeds. These attributes will permit Sentry to perform a variety of conventional and unconventional surveys including long range sonar surveys, hydrothermal plume surveys and near-bottom photo surveys. Sentry's streamlined body and fore and aft tilting planes, each possessing an independently controlled thruster, enable efficient operation in both near-bottom and cruising operations. Sentry is capable of being configured in two modes: hover mode, which commands Sentry's control surfaces to be aligned vertically, and forward flight mode, which allows Sentry's control surfaces to actuate between plus or minus 45 degrees. Sentry is equipped for full 6-Degrees of freedom position measurement. Vehicle heading, roll, and pitch are instrumented with a TCM2 PNI heading and attitude sensor. A Systron Donner yaw rate sensor instrumented heading rate. Depth is instrumented by a Paroscientific depth sensor. A 300kHz RD Instruments Doppler Sonar provides altitude and XYZ velocity measurements. In April 2006, we conducted our first deep water field trials of Sentry in Bermuda. These trials enabled us to examine a variety of issues, including the control software, vehicle safety systems, launch and recovery procedures, operation at depth, heading and depth controllers over a range of speeds, and power consumption. Sentry employ's a control system based upon the Jason 2 control system for low-level control, which has proven effective and reliable over several hundred deep-water dives. The Jason 2 control system, developed jointly at Johns Hopkins University and Woods Hole Oceanographic Institution, was augmented to manage Sentry-specific devices (sensors, actuators, and power storage) and to employ a high-level mission controller that supported autonomous mission scripting and error detection and response. This control suite will also support the Nereus

Cognitive Routing in Software-Defined Underwater Acoustic Networks

Directory of Open Access Journals (Sweden)

Huma Ghafoor

2017-12-01

Full Text Available There are two different types of primary users (natural acoustic and artificial acoustic, and there is a long propagation delay for acoustic links in underwater cognitive acoustic networks (UCANs. Thus, the selection of a stable route is one of the key design factors for improving overall network stability, thereby reducing end-to-end delay. Software-defined networking (SDN is a novel approach that improves network intelligence. To this end, we propose a novel SDN-based routing protocol for UCANs in order to find a stable route between source and destination. A main controller is placed in a surface buoy that is responsible for the global view of the network, whereas local controllers are placed in different autonomous underwater vehicles (AUVs that are responsible for a localized view of the network. The AUVs have fixed trajectories, and sensor nodes within transmission range of the AUVs serve as gateways to relay the gathered information to the controllers. This is an SDN-based underwater communications scheme whereby two nodes can only communicate when they have a consensus about a common idle channel. To evaluate our proposed scheme, we perform extensive simulations and improve network performance in terms of end-to-end delay, delivery ratio, and overhead.

Autonomous Vehicles Navigation with Visual Target Tracking: Technical Approaches

Directory of Open Access Journals (Sweden)

Zhen Jia

2008-12-01

Full Text Available This paper surveys the developments of last 10 years in the area of vision based target tracking for autonomous vehicles navigation. First, the motivations and applications of using vision based target tracking for autonomous vehicles navigation are presented in the introduction section. It can be concluded that it is very necessary to develop robust visual target tracking based navigation algorithms for the broad applications of autonomous vehicles. Then this paper reviews the recent techniques in three different categories: vision based target tracking for the applications of land, underwater and aerial vehicles navigation. Next, the increasing trends of using data fusion for visual target tracking based autonomous vehicles navigation are discussed. Through data fusion the tracking performance is improved and becomes more robust. Based on the review, the remaining research challenges are summarized and future research directions are investigated.

A Comprehensive Study on the Internet of Underwater Things: Applications, Challenges, and Channel Models.

Science.gov (United States)

Kao, Chien-Chi; Lin, Yi-Shan; Wu, Geng-De; Huang, Chun-Ju

2017-06-22

The Internet of Underwater Things (IoUT) is a novel class of Internet of Things (IoT), and is defined as the network of smart interconnected underwater objects. IoUT is expected to enable various practical applications, such as environmental monitoring, underwater exploration, and disaster prevention. With these applications, IoUT is regarded as one of the potential technologies toward developing smart cities. To support the concept of IoUT, Underwater Wireless Sensor Networks (UWSNs) have emerged as a promising network system. UWSNs are different from the traditional Territorial Wireless Sensor Networks (TWSNs), and have several unique properties, such as long propagation delay, narrow bandwidth, and low reliability. These unique properties would be great challenges for IoUT. In this paper, we provide a comprehensive study of IoUT, and the main contributions of this paper are threefold: (1) we introduce and classify the practical underwater applications that can highlight the importance of IoUT; (2) we point out the differences between UWSNs and traditional TWSNs, and these differences are the main challenges for IoUT; and (3) we investigate and evaluate the channel models, which are the technical core for designing reliable communication protocols on IoUT.

Evaluation of an Efficient Approach for Target Tracking from Acoustic Imagery for the Perception System of an Autonomous Underwater Vehicle

Directory of Open Access Journals (Sweden)

Sebastián A. Villar

2014-02-01

Full Text Available This article describes the core algorithms of the perception system to be included within an autonomous underwater vehicle (AUV. This perception system is based on the acoustic data acquired from side scan sonar (SSS. These data should be processed in an efficient time, so that the perception system is able to detect and recognize a predefined target. This detection and recognition outcome is therefore an important piece of knowledge for the AUVs dynamic mission planner (DMP. Effectively, the DMP should propose different trajectories, navigation depths and other parameters that will change the robot's behaviour according to the perception system output. Hence, the time in which to make a decision is critical in order to assure safe robot operation and to acquire good quality data; consequently, the efficiency of the on-line image processing from acoustic data is a key issue. Current techniques for acoustic data processing are time and computationally intensive. Hence, it was decided to process data coming from a SSS using a technique that is used for radars, due to its efficiency and its amenability to on-line processing. The engineering problem to solve in this case was underwater pipeline tracking for routine inspections in the off-shore industry. Then, an automatic oil pipeline detection system was developed borrowing techniques from the processing of radar measurements. The radar technique is known as Cell Average – Constant False Alarm Rate (CA – CFAR. With a slight variation of the algorithms underlying this radar technique, which consisted of the previous accumulation of partial sums, a great improvement in computing time and effort was achieved. Finally, a comparison with previous approaches over images acquired with a SSS from a vessel in the Salvador de Bahia bay in Brazil showed the feasibility of using this on-board technique for AUV perception.

Efficient Data Gathering in 3D Linear Underwater Wireless Sensor Networks Using Sink Mobility.

Science.gov (United States)

Akbar, Mariam; Javaid, Nadeem; Khan, Ayesha Hussain; Imran, Muhammad; Shoaib, Muhammad; Vasilakos, Athanasios

2016-03-19

Due to the unpleasant and unpredictable underwater environment, designing an energy-efficient routing protocol for underwater wireless sensor networks (UWSNs) demands more accuracy and extra computations. In the proposed scheme, we introduce a mobile sink (MS), i.e., an autonomous underwater vehicle (AUV), and also courier nodes (CNs), to minimize the energy consumption of nodes. MS and CNs stop at specific stops for data gathering; later on, CNs forward the received data to the MS for further transmission. By the mobility of CNs and MS, the overall energy consumption of nodes is minimized. We perform simulations to investigate the performance of the proposed scheme and compare it to preexisting techniques. Simulation results are compared in terms of network lifetime, throughput, path loss, transmission loss and packet drop ratio. The results show that the proposed technique performs better in terms of network lifetime, throughput, path loss and scalability.

Efficient Data Gathering in 3D Linear Underwater Wireless Sensor Networks Using Sink Mobility

Directory of Open Access Journals (Sweden)

Mariam Akbar

2016-03-01

Full Text Available Due to the unpleasant and unpredictable underwater environment, designing an energy-efficient routing protocol for underwater wireless sensor networks (UWSNs demands more accuracy and extra computations. In the proposed scheme, we introduce a mobile sink (MS, i.e., an autonomous underwater vehicle (AUV, and also courier nodes (CNs, to minimize the energy consumption of nodes. MS and CNs stop at specific stops for data gathering; later on, CNs forward the received data to the MS for further transmission. By the mobility of CNs and MS, the overall energy consumption of nodes is minimized. We perform simulations to investigate the performance of the proposed scheme and compare it to preexisting techniques. Simulation results are compared in terms of network lifetime, throughput, path loss, transmission loss and packet drop ratio. The results show that the proposed technique performs better in terms of network lifetime, throughput, path loss and scalability.

Explicit Modeling of Solid Ocean Floor in Shallow Underwater Explosions

Directory of Open Access Journals (Sweden)

A.P. Walters

2013-01-01

Full Text Available Current practices for modeling the ocean floor in underwater explosion simulations call for application of an inviscid fluid with soil properties. A method for modeling the ocean floor as a Lagrangian solid, vice an Eulerian fluid, was developed in order to determine its effects on underwater explosions in shallow water using the DYSMAS solver. The Lagrangian solid bottom model utilized transmitting boundary segments, exterior nodal forces acting as constraints, and the application of prestress to minimize any distortions into the fluid domain. For simplicity, elastic materials were used in this current effort, though multiple constitutive soil models can be applied to improve the overall accuracy of the model. Even though this method is unable to account for soil cratering effects, it does however provide the distinct advantage of modeling contoured ocean floors such as dredged channels and sloped bottoms absent in Eulerian formulations. The study conducted here showed significant differences among the initial bottom reflections for the different solid bottom contours that were modeled. The most important bottom contour effect was the distortion to the gas bubble and its associated first pulse timing. In addition to its utility in bottom modeling, implementation of the non-reflecting boundary along with realistic material models can be used to drastically reduce the size of current fluid domains.

Model of a thermal driven volumetric pump for energy harvesting in an underwater glider

International Nuclear Information System (INIS)

Falcão Carneiro, J.; Gomes de Almeida, F.

2016-01-01

Underwater gliders are one of the most promising approaches to achieve an increase of human presence in the oceans. Among existing solutions, thermal driven gliders present long range and endurance capabilities, offering the possibility of remaining years beneath water collecting and transmitting data to shore. A key component in thermal gliders lies in the process used to collect ocean's thermal energy. In this paper a new quasi-static model of a thermal driven volumetric pump, for use in underwater gliders, is presented. The study also encompasses an analysis of the influence different hydraulic system parameters have on the thermodynamic cycle efficiency. Finally, the paper proposes a simple dynamic model of a heat exchanger that uses commercially available materials for the Phase Change Material (PCM) container. Simulation results validate the models developed. - Highlights: • A new model of a thermal driven volumetric pump for underwater gliders is proposed. • The effect hydraulic system parameters have on the cycle efficiency is analyzed. • The energy efficiency may be increased tenfold using adequate hydraulic parameters. • It's shown that the PCM PVT transition surface may not alter the cycle efficiency.

Identification of a putative man-made object from an underwater crash site using CAD model superimposition.

Science.gov (United States)

Vincelli, Jay; Calakli, Fatih; Stone, Michael; Forrester, Graham; Mellon, Timothy; Jarrell, John

2018-04-01

In order to identify an object in video, a comparison with an exemplar object is typically needed. In this paper, we discuss the methodology used to identify an object detected in underwater video that was recorded during an investigation into Amelia Earhart's purported crash site. A computer aided design (CAD) model of the suspected aircraft component was created based on measurements made from orthogonally rectified images of a reference aircraft, and validated against historical photographs of the subject aircraft prior to the crash. The CAD model was then superimposed on the underwater video, and specific features on the object were geometrically compared between the CAD model and the video. This geometrical comparison was used to assess the goodness of fit between the purported object and the object identified in the underwater video. Copyright © 2018 Elsevier B.V. All rights reserved.

Hidrodinamički model podvodnog projektila / Hidrodinamical model of an underwater projectile

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Miroslav Radosavljević

2008-07-01

Full Text Available Radi dobijanja kvalitetnog matematičkog modela podvodnog projektila u radu su definisane ulazne i izlazne veličine, brzine i ubrzanje projektila. Uz zadate uslove mogućeg kretanja projektila definisan je model podvodnog projektila sa šest jednačina. / The paper analyzes an underwater projectile. The input and output values, the projectile speed and acceleration are defined for a quality definition of the projectile mathematical model. With the conditions of the projectile potential movement previously set out, the torpedo model is defined by six equations.

Development of a highly maneuverable unmanned underwater vehicle on the basis of quad-copter dynamics

Science.gov (United States)

Amin, Osman Md; Karim, Md. Arshadul; Saad, Abdullah His

2017-12-01

At present, research on unmanned underwater vehicle (UUV) has become a significant & familiar topic for researchers from various engineering fields. UUV is of mainly two types - AUV (Autonomous Underwater vehicle) & ROV (Remotely Operated Vehicle). There exist a significant number of published research papers on UUV, where very few researchers emphasize on the ease of maneuvering and control of UUV. Maneuvering is important for underwater vehicle in avoiding obstacles, installing underwater piping system, searching undersea resources, underwater mine disposal operations, oceanographic surveys etc. A team from Dept. of Naval Architecture & Marine Engineering of MIST has taken a project to design a highly maneuverable unmanned underwater vehicle on the basis of quad-copter dynamics. The main objective of the research is to develop a control system for UUV which would be able to maneuver the vehicle in six DOF (Degrees of Freedom) with great ease. For this purpose we are not only focusing on controllability but also designing an efficient hull with minimal drag force & optimized propeller using CFD technique. Motors were selected on the basis of the simulated thrust generated by propellers in ANSYS Fluent software module. Settings for control parameters to carry out different types of maneuvering such as hovering, spiral, one point rotation about its centroid, gliding, rolling, drifting and zigzag motions were explained in short at the end.

Recent Advances in Bathymetric Surveying of Continental Shelf Regions Using Autonomous Vehicles

Science.gov (United States)

Holland, K. T.; Calantoni, J.; Slocum, D.

2016-02-01

Obtaining bathymetric observations within the continental shelf in areas closer to the shore is often time consuming and dangerous, especially when uncharted shoals and rocks present safety concerns to survey ships and launches. However, surveys in these regions are critically important to numerical simulation of oceanographic processes, as bathymetry serves as the bottom boundary condition in operational forecasting models. We will present recent progress in bathymetric surveying using both traditional vessels retrofitted for autonomous operations and relatively inexpensive, small team deployable, Autonomous Underwater Vehicles (AUV). Both systems include either high-resolution multibeam echo sounders or interferometric sidescan sonar sensors with integrated inertial navigation system capabilities consistent with present commercial-grade survey operations. The advantages and limitations of these two configurations employing both unmanned and autonomous strategies are compared using results from several recent survey operations. We will demonstrate how sensor data collected from unmanned platforms can augment or even replace traditional data collection technologies. Oceanographic observations (e.g., sound speed, temperature and currents) collected simultaneously with bathymetry using autonomous technologies provide additional opportunities for advanced data assimilation in numerical forecasts. Discussion focuses on our vision for unmanned and autonomous systems working in conjunction with manned or in-situ systems to optimally and simultaneously collect data in environmentally hostile or difficult to reach areas.

A Comprehensive Study on the Internet of Underwater Things: Applications, Challenges, and Channel Models

Directory of Open Access Journals (Sweden)

Chien-Chi Kao

2017-06-01

Full Text Available The Internet of Underwater Things (IoUT is a novel class of Internet of Things (IoT, and is defined as the network of smart interconnected underwater objects. IoUT is expected to enable various practical applications, such as environmental monitoring, underwater exploration, and disaster prevention. With these applications, IoUT is regarded as one of the potential technologies toward developing smart cities. To support the concept of IoUT, Underwater Wireless Sensor Networks (UWSNs have emerged as a promising network system. UWSNs are different from the traditional Territorial Wireless Sensor Networks (TWSNs, and have several unique properties, such as long propagation delay, narrow bandwidth, and low reliability. These unique properties would be great challenges for IoUT. In this paper, we provide a comprehensive study of IoUT, and the main contributions of this paper are threefold: (1 we introduce and classify the practical underwater applications that can highlight the importance of IoUT; (2 we point out the differences between UWSNs and traditional TWSNs, and these differences are the main challenges for IoUT; and (3 we investigate and evaluate the channel models, which are the technical core for designing reliable communication protocols on IoUT.

Underwater Noise from a Wave Energy Converter is unlikely to Affect Marine Mammals

DEFF Research Database (Denmark)

Tougaard, Jakob

2015-01-01

Underwater noise was recorded from the Wavestar wave energy converter; a full-scale hydraulic point absorber, placed on a jack-up rig on the Danish North Sea coast. Noise was recorded 25 m from the converter with an autonomous recording unit (10 Hz to 20 kHz bandwidth). Median sound pressure leve...... on a jack-up rig. The results may thus not be directly transferable to other wave converter designs but do demonstrate that it is possible to harness wave energy without noise pollution to the marine environment.......Underwater noise was recorded from the Wavestar wave energy converter; a full-scale hydraulic point absorber, placed on a jack-up rig on the Danish North Sea coast. Noise was recorded 25 m from the converter with an autonomous recording unit (10 Hz to 20 kHz bandwidth). Median sound pressure levels...... were so low that they would barely be audible to marine mammals and the likelihood of negative impact from the noise appears minimal. A likely explanation for the low noise emissions is the construction of the converter where all moving parts, except for the absorbers themselves, are placed above water...

PASSIVE ACOUSTIC MONITORING OF ODONTOCETES IN THE VICINITY OF PUULOA UNDERWATER DETONATION TRAINING RANGE, HAWAII RANGE COMPLEX, OAHU

Science.gov (United States)

2016-09-25

Printed on recycled paper Approved for public release; distribution is unlimited. SITE SPECIFIC REPORT SSR-NAVFAC-EXWC-EV-1702 SEPTEMBER 2016...NOAA’s Coral Reef Ecosystem Division. The EAR is an autonomous underwater recorder controlled by a Persistor CF2 microcontroller that may be

Visual feedback navigation for cable tracking by autonomous underwater vehicles; Jiritsugata kaichu robot no gazo shori ni motozuku cable jido tsuiju

Energy Technology Data Exchange (ETDEWEB)

Takai, M.; Ura, T. [The University of Tokyo, Tokyo (Japan). Institute of Industrial Science; Balasuriya, B.; Lam, W. [The University of Tokyo, Tokyo (Japan); Kuroda, Y. [Meiji Univ., Tokyo (Japan)

1997-08-01

A vision processing unit was introduced into autonomous underwater vehicles (AUV) to judge the visual situation and to construct an environmental observation platform that can collect wide-range and high-precision measurement data. The cable optionally installed at the bottom of the sea was recognized by vision processing to propose automatic tracking technique. An estimator that compensates for the hough conversion or time delay and a PSA controller that is used as a target value set mechanism or lower-level controller were introduced as the factor technology required for automatic tracking. The feature of the automatic tracking is that a general-purpose platform which can observe the prescribed range environmentally in high precision and density can be constructed because the observation range required by the observer can be prescribed near the sea-bottom surface using a cable. The verification result off Omi Hachiman at Lake Biwa showed that AUV can be used for the high-precision environmental survey in the range prescribed near the sea-bottom surface using a cable. 8 refs., 8 figs., 1 tab.

Human Injury Criteria for Underwater Blasts.

Directory of Open Access Journals (Sweden)

Rachel M Lance

Full Text Available Underwater blasts propagate further and injure more readily than equivalent air blasts. Development of effective personal protection and countermeasures, however, requires knowledge of the currently unknown human tolerance to underwater blast. Current guidelines for prevention of underwater blast injury are not based on any organized injury risk assessment, human data or experimental data. The goal of this study was to derive injury risk assessments for underwater blast using well-characterized human underwater blast exposures in the open literature. The human injury dataset was compiled using 34 case reports on underwater blast exposure to 475 personnel, dating as early as 1916. Using severity ratings, computational reconstructions of the blasts, and survival information from a final set of 262 human exposures, injury risk models were developed for both injury severity and risk of fatality as functions of blast impulse and blast peak overpressure. Based on these human data, we found that the 50% risk of fatality from underwater blast occurred at 302±16 kPa-ms impulse. Conservatively, there is a 20% risk of pulmonary injury at a kilometer from a 20 kg charge. From a clinical point of view, this new injury risk model emphasizes the large distances possible for potential pulmonary and gut injuries in water compared with air. This risk value is the first impulse-based fatality risk calculated from human data. The large-scale inconsistency between the blast exposures in the case reports and the guidelines available in the literature prior to this study further underscored the need for this new guideline derived from the unique dataset of actual injuries in this study.

Longitudinal Control for Mengshi Autonomous Vehicle via Gauss Cloud Model

Directory of Open Access Journals (Sweden)

Hongbo Gao

2017-12-01

Full Text Available Dynamic robustness and stability control is a requirement for self-driving of autonomous vehicle. Longitudinal control technique of autonomous vehicle is basic theory and one key complex technique which must have the reliability and precision of vehicle controller. The longitudinal control technique is one of the foundations of the safety and stability of autonomous vehicle control. In our paper, we present a longitudinal control algorithm based on cloud model for Mengshi autonomous vehicle to ensure the dynamic stability and tracking performance of Mengshi autonomous vehicle. The longitudinal control algorithm mainly uses cloud model generator to control the acceleration of the autonomous vehicle to achieve the goal that controls the speed of Mengshi autonomous vehicle. The proposed longitudinal control algorithm based on cloud model is verified by real experiments on Highway driving scene. The experiments results of the acceleration and speed show that the algorithm is validity and stability.

Hydrodynamic Coefficients Identification and Experimental Investigation for an Underwater Vehicle

Directory of Open Access Journals (Sweden)

Shaorong XIE

2014-02-01

Full Text Available Hydrodynamic coefficients are the foundation of unmanned underwater vehicles modeling and controller design. In order to reduce identification complexity and acquire necessary hydrodynamic coefficients for controllers design, the motion of the unmanned underwater vehicle was separated into vertical motion and horizontal motion models. Hydrodynamic coefficients were regarded as mapping parameters from input forces and moments to output velocities and acceleration of the unmanned underwater vehicle. The motion models of the unmanned underwater vehicle were nonlinear and Genetic Algorithm was adopted to identify those hydrodynamic coefficients. To verify the identification quality, velocities and acceleration of the unmanned underwater vehicle was measured using inertial sensor under the same conditions as Genetic Algorithm identification. Curves similarity between measured velocities and acceleration and those identified by Genetic Algorithm were used as optimizing standard. It is found that the curves similarity were high and identified hydrodynamic coefficients of the unmanned underwater vehicle satisfied the measured motion states well.

Passive aquatic listener (PAL): An adoptive underwater acoustic recording system for the marine environment

International Nuclear Information System (INIS)

Anagnostou, Marios N.; Nystuen, Jeffrey A.; Anagnostou, Emmanouil N.; Papadopoulos, Anastasios; Lykousis, Vassilios

2011-01-01

The ambient sound field in the ocean is a combination of natural and manmade sounds. Consequently, the interpretation of the ambient sound field can be used to quantify these processes. In the frequency range from 1 to 50 kHz, the general character of ocean ambient sound is a slowly changing background that is closely associated with local wind speed, interspersed with shorter time scale events such as rain storms, ships and animal calls. At lower frequencies the underwater ambient sound budget includes geologically generated sound activities including underwater volcanic eruptions, seismic and seepage faults that generate bubbles, etc. that can also potentially be classified and quantified. Acoustic data are collected on hydrophones. Hydrophones are simple, robust sensors that can be deployed on most ocean instrumentation systems including surface or sub-surface moorings, bottom mounted systems, drifters, ARGO floats or autonomous underwater platforms. A dedicated oceanic underwater recorder called a passive acoustic listener (PAL) has been developed. A principal issue is to accurately distinguish different sound sources so that they can be quantified as part of a sound budget, and then quantified if appropriate. Based on ongoing data collected from the Poseidon II network the retrieval potential of multi-parameters from underwater sound, including meteorological (i.e., precipitation and winds) and in general geophysical, anthropogenetic (i.e., ships, submarines, etc.) and biological (whales, etc.) sources is presented.

Passive aquatic listener (PAL): An adoptive underwater acoustic recording system for the marine environment

Energy Technology Data Exchange (ETDEWEB)

Anagnostou, Marios N., E-mail: managnostou@ath.hcmr.g [Hellenic Center for Marine Research, Department of Inland Waters, Anavissos (Greece); Nystuen, Jeffrey A. [Hellenic Center for Marine Research, Department of Inland Waters, Anavissos (Greece); Applied Physics Laboratory, University of Washington, Seattle, WA (United States); Anagnostou, Emmanouil N. [Hellenic Center for Marine Research, Department of Inland Waters, Anavissos (Greece); Department of Civil and Environmental Engineering, University of Connecticut, CT (United States); Papadopoulos, Anastasios [Hellenic Center for Marine Research, Department of Inland Waters, Anavissos (Greece); Lykousis, Vassilios [Hellenic Center for Marine Research, Department of Oceanography, Anavissos (Greece)

2011-01-21

The ambient sound field in the ocean is a combination of natural and manmade sounds. Consequently, the interpretation of the ambient sound field can be used to quantify these processes. In the frequency range from 1 to 50 kHz, the general character of ocean ambient sound is a slowly changing background that is closely associated with local wind speed, interspersed with shorter time scale events such as rain storms, ships and animal calls. At lower frequencies the underwater ambient sound budget includes geologically generated sound activities including underwater volcanic eruptions, seismic and seepage faults that generate bubbles, etc. that can also potentially be classified and quantified. Acoustic data are collected on hydrophones. Hydrophones are simple, robust sensors that can be deployed on most ocean instrumentation systems including surface or sub-surface moorings, bottom mounted systems, drifters, ARGO floats or autonomous underwater platforms. A dedicated oceanic underwater recorder called a passive acoustic listener (PAL) has been developed. A principal issue is to accurately distinguish different sound sources so that they can be quantified as part of a sound budget, and then quantified if appropriate. Based on ongoing data collected from the Poseidon II network the retrieval potential of multi-parameters from underwater sound, including meteorological (i.e., precipitation and winds) and in general geophysical, anthropogenetic (i.e., ships, submarines, etc.) and biological (whales, etc.) sources is presented.

Subsurface observations of white shark Carcharodon carcharias predatory behaviour using an autonomous underwater vehicle.

Science.gov (United States)

Skomal, G B; Hoyos-Padilla, E M; Kukulya, A; Stokey, R

2015-12-01

In this study, an autonomous underwater vehicle (AUV) was used to test this technology as a viable tool for directly observing the behaviour of marine animals and to investigate the behaviour, habitat use and feeding ecology of white sharks Carcharodon carcharias near Guadalupe Island off the coast of Mexico. During the period 31 October to 7 November 2013, six AUV missions were conducted to track one male and three female C. carcharias, ranging in estimated total length (LT ) from 3·9 to 5·7 m, off the north-east coast of Guadalupe Island. In doing so, the AUV generated over 13 h of behavioural data for C. carcharias at depths down to 90 m. The sharks remained in the area for the duration of each mission and moved through broad depth and temperature ranges from the surface to 163·8 m depth (mean ± S.D. = 112·5 ± 40·3 m) and 7·9-27·1° C (mean ± S.D. = 12·7 ± 2·9° C), respectively. Video footage and AUV sensor data revealed that two of the C. carcharias being tracked and eight other C. carcharias in the area approached (n = 17), bumped (n = 4) and bit (n = 9) the AUV during these tracks. This study demonstrated that an AUV can be used to effectively track and observe the behaviour of a large pelagic animal, C. carcharias. In doing so, the first observations of subsurface predatory behaviour were generated for this species. At its current state of development, this technology clearly offers a new and innovative tool for tracking the fine-scale behaviour of marine animals. © 2015 The Fisheries Society of the British Isles.

A Probabilistic and Highly Efficient Topology Control Algorithm for Underwater Cooperating AUV Networks.

Science.gov (United States)

Li, Ning; Cürüklü, Baran; Bastos, Joaquim; Sucasas, Victor; Fernandez, Jose Antonio Sanchez; Rodriguez, Jonathan

2017-05-04

The aim of the Smart and Networking Underwater Robots in Cooperation Meshes (SWARMs) project is to make autonomous underwater vehicles (AUVs), remote operated vehicles (ROVs) and unmanned surface vehicles (USVs) more accessible and useful. To achieve cooperation and communication between different AUVs, these must be able to exchange messages, so an efficient and reliable communication network is necessary for SWARMs. In order to provide an efficient and reliable communication network for mission execution, one of the important and necessary issues is the topology control of the network of AUVs that are cooperating underwater. However, due to the specific properties of an underwater AUV cooperation network, such as the high mobility of AUVs, large transmission delays, low bandwidth, etc., the traditional topology control algorithms primarily designed for terrestrial wireless sensor networks cannot be used directly in the underwater environment. Moreover, these algorithms, in which the nodes adjust their transmission power once the current transmission power does not equal an optimal one, are costly in an underwater cooperating AUV network. Considering these facts, in this paper, we propose a Probabilistic Topology Control (PTC) algorithm for an underwater cooperating AUV network. In PTC, when the transmission power of an AUV is not equal to the optimal transmission power, then whether the transmission power needs to be adjusted or not will be determined based on the AUV's parameters. Each AUV determines their own transmission power adjustment probability based on the parameter deviations. The larger the deviation, the higher the transmission power adjustment probability is, and vice versa. For evaluating the performance of PTC, we combine the PTC algorithm with the Fuzzy logic Topology Control (FTC) algorithm and compare the performance of these two algorithms. The simulation results have demonstrated that the PTC is efficient at reducing the transmission power

A Probabilistic and Highly Efficient Topology Control Algorithm for Underwater Cooperating AUV Networks

Directory of Open Access Journals (Sweden)

Ning Li

2017-05-01

Full Text Available The aim of the Smart and Networking Underwater Robots in Cooperation Meshes (SWARMs project is to make autonomous underwater vehicles (AUVs, remote operated vehicles (ROVs and unmanned surface vehicles (USVs more accessible and useful. To achieve cooperation and communication between different AUVs, these must be able to exchange messages, so an efficient and reliable communication network is necessary for SWARMs. In order to provide an efficient and reliable communication network for mission execution, one of the important and necessary issues is the topology control of the network of AUVs that are cooperating underwater. However, due to the specific properties of an underwater AUV cooperation network, such as the high mobility of AUVs, large transmission delays, low bandwidth, etc., the traditional topology control algorithms primarily designed for terrestrial wireless sensor networks cannot be used directly in the underwater environment. Moreover, these algorithms, in which the nodes adjust their transmission power once the current transmission power does not equal an optimal one, are costly in an underwater cooperating AUV network. Considering these facts, in this paper, we propose a Probabilistic Topology Control (PTC algorithm for an underwater cooperating AUV network. In PTC, when the transmission power of an AUV is not equal to the optimal transmission power, then whether the transmission power needs to be adjusted or not will be determined based on the AUV’s parameters. Each AUV determines their own transmission power adjustment probability based on the parameter deviations. The larger the deviation, the higher the transmission power adjustment probability is, and vice versa. For evaluating the performance of PTC, we combine the PTC algorithm with the Fuzzy logic Topology Control (FTC algorithm and compare the performance of these two algorithms. The simulation results have demonstrated that the PTC is efficient at reducing the

Polarization Calculation and Underwater Target Detection Inspired by Biological Visual Imaging

Directory of Open Access Journals (Sweden)

Jie Shen

2014-04-01

Full Text Available In challenging underwater environments, the polarization parameter maps calculated by the Stokes model are characterized by the high noise and error, harassing the underwater target detection tasks. In order to solve this problem, this paper proposes a novel bionic polarization calculation and underwater target detection method by modeling the visual system of mantis shrimps. This system includes many operators including a polarization-opposition calculation, a factor optimization and a visual neural network model. A calibration learning method is proposed to search the optimal value of the factors in the linear subtraction model. Finally, a six-channel visual neural network model is proposed to detect the underwater targets. Experimental results proved that the maps produced by the polarization-opposition parameter is more accurate and have lower noise than that produced by the Stokes parameter, achieving better performance in underwater target detection tasks.

Longitudinal Control for Mengshi Autonomous Vehicle via Cloud Model

Science.gov (United States)

Gao, H. B.; Zhang, X. Y.; Li, D. Y.; Liu, Y. C.

2018-03-01

Dynamic robustness and stability control is a requirement for self-driving of autonomous vehicle. Longitudinal control method of autonomous is a key technique which has drawn the attention of industry and academe. In this paper, we present a longitudinal control algorithm based on cloud model for Mengshi autonomous vehicle to ensure the dynamic stability and tracking performance of Mengshi autonomous vehicle. An experiments is applied to test the implementation of the longitudinal control algorithm. Empirical results show that if the longitudinal control algorithm based Gauss cloud model are applied to calculate the acceleration, and the vehicles drive at different speeds, a stable longitudinal control effect is achieved.

The NESTOR underwater neutrino telescope project

Energy Technology Data Exchange (ETDEWEB)

Rapidis, Petros A. [Institute of Nuclear Physics, National Center for Scientific Research ' Demokritos' , Athens 15310 (Greece)], E-mail: rapidis@inp.demokritos.gr

2009-04-11

The NESTOR collaboration is continuing its efforts towards deploying an underwater neutrino telescope. Further site studies (e.g. water light transmission measurements, sedimentation rates, etc.) are being carried out within the context of characterizing a site that may host the proposed KM3NeT infrastructure. In addition, following the successful deployment of a single floor of a NESTOR tower in 2003, five floors are now in the final stages of preparation. The use of these five floors in a form of a truncated tower together with four autonomous strings to be located some 300 m away from the tower is being contemplated. This arrangement, named NuBE (for Neutrino Burst Experiment), that may allow the detection neutrinos in coincidence with Gamma Ray Bursts, will be described.

The NESTOR underwater neutrino telescope project

International Nuclear Information System (INIS)

Rapidis, Petros A.

2009-01-01

The NESTOR collaboration is continuing its efforts towards deploying an underwater neutrino telescope. Further site studies (e.g. water light transmission measurements, sedimentation rates, etc.) are being carried out within the context of characterizing a site that may host the proposed KM3NeT infrastructure. In addition, following the successful deployment of a single floor of a NESTOR tower in 2003, five floors are now in the final stages of preparation. The use of these five floors in a form of a truncated tower together with four autonomous strings to be located some 300 m away from the tower is being contemplated. This arrangement, named NuBE (for Neutrino Burst Experiment), that may allow the detection neutrinos in coincidence with Gamma Ray Bursts, will be described.

3D photo mosaicing of Tagiri shallow vent field by an autonomous underwater vehicle (3rd report) - Mosaicing method based on navigation data and visual features -

Science.gov (United States)

Maki, Toshihiro; Ura, Tamaki; Singh, Hanumant; Sakamaki, Takashi

Large-area seafloor imaging will bring significant benefits to various fields such as academics, resource survey, marine development, security, and search-and-rescue. The authors have proposed a navigation method of an autonomous underwater vehicle for seafloor imaging, and verified its performance through mapping tubeworm colonies with the area of 3,000 square meters using the AUV Tri-Dog 1 at Tagiri vent field, Kagoshima bay in Japan (Maki et al., 2008, 2009). This paper proposes a post-processing method to build a natural photo mosaic from a number of pictures taken by an underwater platform. The method firstly removes lens distortion, invariances of color and lighting from each image, and then ortho-rectification is performed based on camera pose and seafloor estimated by navigation data. The image alignment is based on both navigation data and visual characteristics, implemented as an expansion of the image based method (Pizarro et al., 2003). Using the two types of information realizes an image alignment that is consistent both globally and locally, as well as making the method applicable to data sets with little visual keys. The method was evaluated using a data set obtained by the AUV Tri-Dog 1 at the vent field in Sep. 2009. A seamless, uniformly illuminated photo mosaic covering the area of around 500 square meters was created from 391 pictures, which covers unique features of the field such as bacteria mats and tubeworm colonies.

Modelling, Design and Robust Control of a Remotely Operated Underwater Vehicle

Directory of Open Access Journals (Sweden)

Luis Govinda García-Valdovinos

2014-01-01

Full Text Available Underwater remotely operated vehicles (ROVs play an important role in a number of shallow and deep-water missions for marine science, oil and gas extraction, exploration and salvage. In these applications, the motions of the ROV are guided either by a human pilot on a surface support vessel through an umbilical cord providing power and telemetry, or by an automatic pilot. In the case of automatic control, ROV state feedback is provided by acoustic and inertial sensors and this state information, along with a controller strategy, is used to perform several tasks such as station-keeping and auto-immersion/heading, among others. In this paper, the modelling, design and control of the Kaxan ROV is presented: i The complete six degrees of freedom, non linear hydrodynamic model with its parameters, ii the Kaxan hardware/software architecture, iii numerical simulations in Matlab/Simulink platform of a model-free second order sliding mode control along with ocean currents as disturbances and thruster dynamics, iv a virtual environment to visualize the motion of the Kaxan ROV and v experimental results of a one degree of freedom underwater system.

An OFDM Receiver with Frequency Domain Diversity Combined Impulsive Noise Canceller for Underwater Network

Science.gov (United States)

Saotome, Rie; Hai, Tran Minh; Matsuda, Yasuto; Suzuki, Taisaku; Wada, Tomohisa

2015-01-01

In order to explore marine natural resources using remote robotic sensor or to enable rapid information exchange between ROV (remotely operated vehicles), AUV (autonomous underwater vehicle), divers, and ships, ultrasonic underwater communication systems are used. However, if the communication system is applied to rich living creature marine environment such as shallow sea, it suffers from generated Impulsive Noise so-called Shrimp Noise, which is randomly generated in time domain and seriously degrades communication performance in underwater acoustic network. With the purpose of supporting high performance underwater communication, a robust digital communication method for Impulsive Noise environments is necessary. In this paper, we propose OFDM ultrasonic communication system with diversity receiver. The main feature of the receiver is a newly proposed Frequency Domain Diversity Combined Impulsive Noise Canceller. The OFDM receiver utilizes 20–28 KHz ultrasonic channel and subcarrier spacing of 46.875 Hz (MODE3) and 93.750 Hz (MODE2) OFDM modulations. In addition, the paper shows Impulsive Noise distribution data measured at a fishing port in Okinawa and at a barge in Shizuoka prefectures and then proposed diversity OFDM transceivers architecture and experimental results are described. By the proposed Impulsive Noise Canceller, frame bit error rate has been decreased by 20–30%. PMID:26351656

An OFDM Receiver with Frequency Domain Diversity Combined Impulsive Noise Canceller for Underwater Network.

Science.gov (United States)

Saotome, Rie; Hai, Tran Minh; Matsuda, Yasuto; Suzuki, Taisaku; Wada, Tomohisa

2015-01-01

In order to explore marine natural resources using remote robotic sensor or to enable rapid information exchange between ROV (remotely operated vehicles), AUV (autonomous underwater vehicle), divers, and ships, ultrasonic underwater communication systems are used. However, if the communication system is applied to rich living creature marine environment such as shallow sea, it suffers from generated Impulsive Noise so-called Shrimp Noise, which is randomly generated in time domain and seriously degrades communication performance in underwater acoustic network. With the purpose of supporting high performance underwater communication, a robust digital communication method for Impulsive Noise environments is necessary. In this paper, we propose OFDM ultrasonic communication system with diversity receiver. The main feature of the receiver is a newly proposed Frequency Domain Diversity Combined Impulsive Noise Canceller. The OFDM receiver utilizes 20-28 KHz ultrasonic channel and subcarrier spacing of 46.875 Hz (MODE3) and 93.750 Hz (MODE2) OFDM modulations. In addition, the paper shows Impulsive Noise distribution data measured at a fishing port in Okinawa and at a barge in Shizuoka prefectures and then proposed diversity OFDM transceivers architecture and experimental results are described. By the proposed Impulsive Noise Canceller, frame bit error rate has been decreased by 20-30%.

An OFDM Receiver with Frequency Domain Diversity Combined Impulsive Noise Canceller for Underwater Network

Directory of Open Access Journals (Sweden)

Rie Saotome

2015-01-01

Full Text Available In order to explore marine natural resources using remote robotic sensor or to enable rapid information exchange between ROV (remotely operated vehicles, AUV (autonomous underwater vehicle, divers, and ships, ultrasonic underwater communication systems are used. However, if the communication system is applied to rich living creature marine environment such as shallow sea, it suffers from generated Impulsive Noise so-called Shrimp Noise, which is randomly generated in time domain and seriously degrades communication performance in underwater acoustic network. With the purpose of supporting high performance underwater communication, a robust digital communication method for Impulsive Noise environments is necessary. In this paper, we propose OFDM ultrasonic communication system with diversity receiver. The main feature of the receiver is a newly proposed Frequency Domain Diversity Combined Impulsive Noise Canceller. The OFDM receiver utilizes 20–28 KHz ultrasonic channel and subcarrier spacing of 46.875 Hz (MODE3 and 93.750 Hz (MODE2 OFDM modulations. In addition, the paper shows Impulsive Noise distribution data measured at a fishing port in Okinawa and at a barge in Shizuoka prefectures and then proposed diversity OFDM transceivers architecture and experimental results are described. By the proposed Impulsive Noise Canceller, frame bit error rate has been decreased by 20–30%.

A Queueing Model for Supervisory Control of Unmanned Autonomous Vehicles

Science.gov (United States)

2013-09-01

Autonomous Vehicles Joseph DiVita, PhD Robert L. Morris Maria Olinda Rodas SSC Pacific Approved...298 (Rev. 8/98) Prescribed by ANSI Std. Z39.18 09–2013 Final A Queueing Model for Supervisory Control of Unmanned Autonomous Vehicles Joseph...Mission Area: Command and Control, Queueing Model; Supervisory Control; Unmanned Autonomous Vehicles M. O. Rodas U U U U 38 (619)

Underwater 3D Surface Measurement Using Fringe Projection Based Scanning Devices.

Science.gov (United States)

Bräuer-Burchardt, Christian; Heinze, Matthias; Schmidt, Ingo; Kühmstedt, Peter; Notni, Gunther

2015-12-23

In this work we show the principle of optical 3D surface measurements based on the fringe projection technique for underwater applications. The challenges of underwater use of this technique are shown and discussed in comparison with the classical application. We describe an extended camera model which takes refraction effects into account as well as a proposal of an effective, low-effort calibration procedure for underwater optical stereo scanners. This calibration technique combines a classical air calibration based on the pinhole model with ray-based modeling and requires only a few underwater recordings of an object of known length and a planar surface. We demonstrate a new underwater 3D scanning device based on the fringe projection technique. It has a weight of about 10 kg and the maximal water depth for application of the scanner is 40 m. It covers an underwater measurement volume of 250 mm × 200 mm × 120 mm. The surface of the measurement objects is captured with a lateral resolution of 150 μm in a third of a second. Calibration evaluation results are presented and examples of first underwater measurements are given.

Latency-Optimized and Energy-Efficient MAC Protocol for Underwater Acoustic Sensor Networks: A Cross-Layer Approach

Directory of Open Access Journals (Sweden)

Cheng Xiuzhen

2010-01-01

Full Text Available Considering the energy constraint for fixed sensor nodes and the unacceptable long propagation delay, especially for latency sensitive applications of underwater acoustic sensor networks, we propose a MAC protocol that is latency-optimized and energy-efficient scheme and combines the physical layer and the MAC layer to shorten transmission delay. On physical layer, we apply convolution coding and interleaver for transmitted information. Moreover, dynamic code rate is exploited at the receiver side to accelerate data reception rate. On MAC layer, unfixed frame length scheme is applied to reduce transmission delay, and to ensure the data successful transmission rate at the same time. Furthermore, we propose a network topology: an underwater acoustic sensor network with mobile agent. Through fully utilizing the supper capabilities on computation and mobility of autonomous underwater vehicles, the energy consumption for fixed sensor nodes can be extremely reduced, so that the lifetime of networks is extended.

Communication and cooperation in underwater acoustic networks

Science.gov (United States)

Yerramalli, Srinivas

In this thesis, we present a study of several problems related to underwater point to point communications and network formation. We explore techniques to improve the achievable data rate on a point to point link using better physical layer techniques and then study sensor cooperation which improves the throughput and reliability in an underwater network. Robust point-to-point communications in underwater networks has become increasingly critical in several military and civilian applications related to underwater communications. We present several physical layer signaling and detection techniques tailored to the underwater channel model to improve the reliability of data detection. First, a simplified underwater channel model in which the time scale distortion on each path is assumed to be the same (single scale channel model in contrast to a more general multi scale model). A novel technique, which exploits the nature of OFDM signaling and the time scale distortion, called Partial FFT Demodulation is derived. It is observed that this new technique has some unique interference suppression properties and performs better than traditional equalizers in several scenarios of interest. Next, we consider the multi scale model for the underwater channel and assume that single scale processing is performed at the receiver. We then derive optimized front end pre-processing techniques to reduce the interference caused during single scale processing of signals transmitted on a multi-scale channel. We then propose an improvised channel estimation technique using dictionary optimization methods for compressive sensing and show that significant performance gains can be obtained using this technique. In the next part of this thesis, we consider the problem of sensor node cooperation among rational nodes whose objective is to improve their individual data rates. We first consider the problem of transmitter cooperation in a multiple access channel and investigate the stability of

A Localization Based Cooperative Routing Protocol for Underwater Wireless Sensor Networks

Directory of Open Access Journals (Sweden)

Nadeem Javaid

2017-01-01

Full Text Available Localization is one of the major aspects in underwater wireless sensor networks (UWSNs. Therefore, it is important to know the accurate position of the sensor node in large scale applications like disaster prevention, tactical surveillance, and monitoring. Due to the inefficiency of the global positioning system (GPS in UWSN, it is very difficult to localize a node in underwater environment compared to terrestrial networks. To minimize the localization error and enhance the localization coverage of the network, two routing protocols are proposed; the first one is mobile autonomous underwater vehicle (MobiL-AUV and the second one is cooperative MobiL (CO-MobiL. In MobiL-AUV, AUVs are deployed and equipped with GPS and act as reference nodes. These reference nodes are used to localize all the nonlocalized ordinary sensor nodes in order to reduce the localization error and maximize the network coverage. CO-MobiL is presented in order to improve the network throughput by using the maximal ratio combining (MRC as diversity technique which combines both signals, received from the source and received from the relay at the destination. It uses amplify-and-forward (AF mechanism to improve the signal between the source and the destination. To support our claims, extensive simulations are performed.

Design of an Autonomous Underwater Vehicle to Calibrate the Europa Clipper Ice-Penetrating Radar

Science.gov (United States)

Stone, W.; Siegel, V.; Kimball, P.; Richmond, K.; Flesher, C.; Hogan, B.; Lelievre, S.

2013-12-01

Jupiter's moon Europa has been prioritized as the target for the Europa Clipper flyby mission. A key science objective for the mission is to remotely characterize the ice shell and any subsurface water, including their heterogeneity, and the nature of surface-ice-ocean exchange. This objective is a critical component of the mission's overarching goal of assessing the habitability of Europa. The instrument targeted for addressing key aspects of this goal is an ice-penetrating radar (IPR). As a primary goal of our work, we will tightly couple airborne IPR studies of the Ross Ice Shelf by the Europa Clipper radar team with ground-truth data to be obtained from sub-glacial sonar and bio-geochemical mapping of the corresponding ice-water and water-rock interfaces using an advanced autonomous underwater vehicle (AUV). The ARTEMIS vehicle - a heavily morphed long-range, low drag variant of the highly successful 4-degree-of-freedom hovering sub-ice ENDURANCE bot -- will be deployed from a sea-ice drill hole adjacent the McMurdo Ice Shelf (MIS) and will perform three classes of missions. The first includes original exploration and high definition mapping of both the ice-water interface and the benthic interface on a length scale (approximately 10 kilometers under-ice penetration radius) that will definitively tie it to the synchronous airborne IPR over-flights. These exploration and mapping missions will be conducted at up to 10 different locations along the MIS in order to capture varying ice thickness and seawater intrusion into the ice shelf. Following initial mapping characterization, the vehicle will conduct astrobiology-relevant proximity operations using bio-assay sensors (custom-designed UV fluorescence and machine-vision-processed optical imagery) followed by point-targeted studies at regions of interest. Sample returns from the ice-water interface will be triggered autonomously using real-time-processed instrument data and onboard decision-to-collect algorithms

Trajectory-Based Visual Localization in Underwater Surveying Missions

Directory of Open Access Journals (Sweden)

Antoni Burguera

2015-01-01

Full Text Available We present a new vision-based localization system applied to an autonomous underwater vehicle (AUV with limited sensing and computation capabilities. The traditional EKF-SLAM approaches are usually expensive in terms of execution time; the approach presented in this paper strengthens this method by adopting a trajectory-based schema that reduces the computational requirements. The pose of the vehicle is estimated using an extended Kalman filter (EKF, which predicts the vehicle motion by means of a visual odometer and corrects these predictions using the data associations (loop closures between the current frame and the previous ones. One of the most important steps in this procedure is the image registration method, as it reinforces the data association and, thus, makes it possible to close loops reliably. Since the use of standard EKFs entail linearization errors that can distort the vehicle pose estimations, the approach has also been tested using an iterated Kalman filter (IEKF. Experiments have been conducted using a real underwater vehicle in controlled scenarios and in shallow sea waters, showing an excellent performance with very small errors, both in the vehicle pose and in the overall trajectory estimates.

Trajectory-Based Visual Localization in Underwater Surveying Missions

Science.gov (United States)

Burguera, Antoni; Bonin-Font, Francisco; Oliver, Gabriel

2015-01-01

We present a new vision-based localization system applied to an autonomous underwater vehicle (AUV) with limited sensing and computation capabilities. The traditional EKF-SLAM approaches are usually expensive in terms of execution time; the approach presented in this paper strengthens this method by adopting a trajectory-based schema that reduces the computational requirements. The pose of the vehicle is estimated using an extended Kalman filter (EKF), which predicts the vehicle motion by means of a visual odometer and corrects these predictions using the data associations (loop closures) between the current frame and the previous ones. One of the most important steps in this procedure is the image registration method, as it reinforces the data association and, thus, makes it possible to close loops reliably. Since the use of standard EKFs entail linearization errors that can distort the vehicle pose estimations, the approach has also been tested using an iterated Kalman filter (IEKF). Experiments have been conducted using a real underwater vehicle in controlled scenarios and in shallow sea waters, showing an excellent performance with very small errors, both in the vehicle pose and in the overall trajectory estimates. PMID:25594602

Application of underwater radon measurements in geology

Energy Technology Data Exchange (ETDEWEB)

Varhegyi, A.; Baranyi, I.; Gerzson, I. (Mecsek Ore Mining Enterprise, Pecs (Hungary)); Somogyi, G.; Hakl, J.; Hunyadi, I. (Magyar Tudomanyos Akademia, Debrecen (Hungary). Atommag Kutato Intezete)

1988-01-01

Based on the observed phenomenon of geogas migration in microbubble form from deeper regions, the authors have developed a new model for the vertical transport of radon released from deeper sources. The physical properties of the rock relating to the upflow of microbubbles below the groundwater level are considered and the radon transport parameter of rocks is introduced. The vertical distribution of radon concentration in the case of a multi-layered geological model is given and the penetration depth of underwater radon measurements is examined. Aspects of underwater radon detection by the nuclear track detector technique are analyzed. The radon transport model gives a new theoretical basis for several applications of radon measurements in geology. The advantages of underwater radon detection have already been proved in uranium exploration. Further geological applications are proposed in earthquake prediction, in volcanology, in the survey of active faults and thermal waters. (author).

Model-based processing for underwater acoustic arrays

CERN Document Server

Sullivan, Edmund J

2015-01-01

This monograph presents a unified approach to model-based processing for underwater acoustic arrays. The use of physical models in passive array processing is not a new idea, but it has been used on a case-by-case basis, and as such, lacks any unifying structure. This work views all such processing methods as estimation procedures, which then can be unified by treating them all as a form of joint estimation based on a Kalman-type recursive processor, which can be recursive either in space or time, depending on the application. This is done for three reasons. First, the Kalman filter provides a natural framework for the inclusion of physical models in a processing scheme. Second, it allows poorly known model parameters to be jointly estimated along with the quantities of interest. This is important, since in certain areas of array processing already in use, such as those based on matched-field processing, the so-called mismatch problem either degrades performance or, indeed, prevents any solution at all. Third...

College English Students’ Autonomous Learning Motivation and Cultivation Model Research

Institute of Scientific and Technical Information of China (English)

王艳荣; 李娥

2015-01-01

Studying the autonomous learning motivation and excitation model can stimulate intrinsic motivation of foreign language learners,develop students self-management strategy evaluation are very necessary.The purpose of this paper is to give students the skills of listening and speaking for their autonomous learning.Then study the cultivation and motivation of college English students autonomous learning,hoping to make students to learn autonomous learning and stimulate their motivation fully.

4th Pacific Rim Underwater Acoustics Conference

CERN Document Server

Xu, Wen; Cheng, Qianliu; Zhao, Hangfang

2016-01-01

These proceedings are a collection of 16 selected scientific papers and reviews by distinguished international experts that were presented at the 4th Pacific Rim Underwater Acoustics Conference (PRUAC), held in Hangzhou, China in October 2013. The topics discussed at the conference include internal wave observation and prediction; environmental uncertainty and coupling to sound propagation; environmental noise and ocean dynamics; dynamic modeling in acoustic fields; acoustic tomography and ocean parameter estimation; time reversal and matched field processing; underwater acoustic localization and communication as well as measurement instrumentations and platforms. These proceedings provide insights into the latest developments in underwater acoustics, promoting the exchange of ideas for the benefit of future research.

Research on support effectiveness modeling and simulating of aviation materiel autonomic logistics system

Science.gov (United States)

Zhou, Yan; Zhou, Yang; Yuan, Kai; Jia, Zhiyu; Li, Shuo

2018-05-01

Aiming at the demonstration of autonomic logistics system to be used at the new generation of aviation materiel in our country, the modeling and simulating method of aviation materiel support effectiveness considering autonomic logistics are studied. Firstly, this paper introduced the idea of JSF autonomic logistics and analyzed the influence of autonomic logistics on support effectiveness from aspects of reliability, false alarm rate, troubleshooting time, and support delay time and maintenance level. On this basis, the paper studies the modeling and simulating methods of support effectiveness considering autonomic logistics, and puts forward the maintenance support simulation process considering autonomic logistics. Finally, taking the typical aviation materiel as an example, this paper analyzes and verifies the above-mentioned support effectiveness modeling and simulating method of aviation materiel considering autonomic logistics.

Models Supporting Trajectory Planning in Autonomous Vehicles

OpenAIRE

Ward, Erik

2018-01-01

Autonomous vehicles have the potential to drastically improve the safety, efficiency and cost of transportation. Instead of a driver, an autonomous vehicle is controlled by an algorithm, offering improved consistency and the potential to eliminate human error from driving: by far the most common cause of accidents. Data collected from different types of sensors, along with prior information such as maps, are used to build models of the surrounding traffic scene, encoding relevant aspects of t...

A bio-inspired electrocommunication system for small underwater robots.

Science.gov (United States)

Wang, Wei; Liu, Jindong; Xie, Guangming; Wen, Li; Zhang, Jianwei

2017-03-29

Weakly electric fishes (Gymnotid and Mormyrid) use an electric field to communicate efficiently (termed electrocommunication) in the turbid waters of confined spaces where other communication modalities fail. Inspired by this biological phenomenon, we design an artificial electrocommunication system for small underwater robots and explore the capabilities of such an underwater robotic communication system. An analytical model for electrocommunication is derived to predict the effect of the key parameters such as electrode distance and emitter current of the system on the communication performance. According to this model, a low-dissipation, and small-sized electrocommunication system is proposed and integrated into a small robotic fish. We characterize the communication performance of the robot in still water, flowing water, water with obstacles and natural water conditions. The results show that underwater robots are able to communicate electrically at a speed of around 1 k baud within about 3 m with a low power consumption (less than 1 W). In addition, we demonstrate that two leader-follower robots successfully achieve motion synchronization through electrocommunication in the three-dimensional underwater space, indicating that this bio-inspired electrocommunication system is a promising setup for the interaction of small underwater robots.

Design of underwater work systems

International Nuclear Information System (INIS)

Lovelace, R.B.

1980-01-01

In the near future, underwater vehicles will replace divers as the principal means for inspection and maintenance work. These vehicles will provide a maneuverable work platform for an underwater viewing system and manipulator/tool package. Some of the problems faced by the underwater designer, and some areas to consider in the design of an integrated underwater work system, are considered

Euclidean reconstruction of natural underwater scenes using optic imagery sequence

Science.gov (United States)

Hu, Han

The development of maritime applications require monitoring, studying and preserving of detailed and close observation on the underwater seafloor and objects. Stereo vision offers advanced technologies to build 3D models from 2D still overlapping optic images in a relatively inexpensive way. However, while image stereo matching is a necessary step in 3D reconstruction procedure, even the most robust dense matching techniques are not guaranteed to work for underwater images due to the challenging aquatic environment. In this thesis, in addition to a detailed introduction and research on the key components of building 3D models from optic images, a robust modified quasi-dense matching algorithm based on correspondence propagation and adaptive least square matching for underwater images is proposed and applied to some typical underwater image datasets. The experiments demonstrate the robustness and good performance of the proposed matching approach.

Development and application of underwater robot vehicle for close inspection of spent fuels

Energy Technology Data Exchange (ETDEWEB)

Yun, J. S.; Park, B. S.; Song, T. G.; Kim, S. H.; Cho, M. W.; Ahn, S. H.; Lee, J. Y.; Oh, S. C.; Oh, W. J.; Shin, K. W.; Woo, D. H.; Kim, H. G.; Park, J. S

1999-12-01

The research and development efforts of the underwater robotic vehicle for inspection of spent fuels are focused on the development of an robotic vehicle which inspects spent fuels in the storage pool through remotely controlled actuation. For this purpose, a self balanced vehicle actuated by propellers is designed and fabricated, which consists of a radiation resistance camera, two illuminators, a pressure transducer and a manipulator. the algorithm for autonomous navigation is developed and its performance is tested at the swimming pool. The results of the underwater vehicle shows that the vehicle can easily navigate into the arbitrary directions while maintaining its balanced position. The camera provides a clear view of working environment by using the macro and zoom functions. The camera tilt device provides a wide field of view which is enough for monitoring the operation of manipulator. Also, the manipulator can pick up the dropped objects up to 4 kgf of weight. (author)

Autonomous Navigation with Constrained Consistency for C-Ranger

Directory of Open Access Journals (Sweden)

Shujing Zhang

2014-06-01

Full Text Available Autonomous underwater vehicles (AUVs have become the most widely used tools for undertaking complex exploration tasks in marine environments. Their synthetic ability to carry out localization autonomously and build an environmental map concurrently, in other words, simultaneous localization and mapping (SLAM, are considered to be pivotal requirements for AUVs to have truly autonomous navigation. However, the consistency problem of the SLAM system has been greatly ignored during the past decades. In this paper, a consistency constrained extended Kalman filter (EKF SLAM algorithm, applying the idea of local consistency, is proposed and applied to the autonomous navigation of the C-Ranger AUV, which is developed as our experimental platform. The concept of local consistency (LC is introduced after an explicit theoretical derivation of the EKF-SLAM system. Then, we present a locally consistency-constrained EKF-SLAM design, LC-EKF, in which the landmark estimates used for linearization are fixed at the beginning of each local time period, rather than evaluated at the latest landmark estimates. Finally, our proposed LC-EKF algorithm is experimentally verified, both in simulations and sea trials. The experimental results show that the LC-EKF performs well with regard to consistency, accuracy and computational efficiency.

Optimal Node Placement in Underwater Acoustic Sensor Network

KAUST Repository

Felemban, Muhamad

2011-10-01

Almost 70% of planet Earth is covered by water. A large percentage of underwater environment is unexplored. In the past two decades, there has been an increase in the interest of exploring and monitoring underwater life among scientists and in industry. Underwater operations are extremely difficult due to the lack of cheap and efficient means. Recently, Wireless Sensor Networks have been introduced in underwater environment applications. However, underwater communication via acoustic waves is subject to several performance limitations, which makes the relevant research issues very different from those on land. In this thesis, we investigate node placement for building an initial Underwater Wireless Sensor Network infrastructure. Firstly, we formulated the problem into a nonlinear mathematic program with objectives of minimizing the total transmission loss under a given number of sensor nodes and targeted volume. We conducted experiments to verify the proposed formulation, which is solved using Matlab optimization tool. We represented each node with a truncated octahedron to fill out the 3D space. The truncated octahedrons are tiled in the 3D space with each node in the center where locations of the nodes are given using 3D coordinates. Results are supported using ns-3 simulator. Results from simulation are consistent with the obtained results from mathematical model with less than 10% error.

Taiwan's underwater cultural heritage documentation management

Science.gov (United States)

Tung, Y.-Y.

2015-09-01

Taiwan is an important trading and maritime channels for many countries since ancient time. Numerous relics lie underwater due to weather, wars, and other factors. In the year of 2006, Bureau of Cultural Heritage (BOCH) entrusted the Underwater Archaeological Team of Academia Sinica to execute the underwater archaeological investigation projects. Currently, we verified 78 underwater targets, with 78 site of those had been recognized as shipwrecks sites. Up to date, there is a collection of 638 underwater objects from different underwater archaeological sites. Those artefacts are distributed to different institutions and museums. As very diverse management methods/systems are applied for every individual institution, underwater cultural heritage data such as survey, excavation report, research, etc. are poorly organized and disseminated for use. For better communication regarding to Taiwan's underwater cultural heritage in every level, a universal format of documentation should be established. By comparing the existing checklist used in Taiwan with guidelines that are followed in other countries, a more intact and appropriate underwater cultural heritage condition documentation system can be established and adapted in Taiwan.

Autonomous long-term gamma-spectrometric monitoring of submarine groundwater discharge trends in Hawaii

International Nuclear Information System (INIS)

Dulai, Henrietta; Waters, Ch.A.; Kennedy, Joseph; Kamenik, Jan; Academy of Sciences of the Czech Republic, Rez; Babinec, James; Jolly, James; Williamson, Mario

2016-01-01

We developed a fully autonomous underwater gamma-spectrometer for long-term coastal submarine groundwater discharge (SGD) monitoring. The instrument represents a significant improvement over previous submarine gamma-spectrometers in that it is very robust, has high sensitivity allowing high temporal resolution, and is completely autonomous. Here we describe the technical parameters of the new instrument as well as data collected over its 9-month deployment in Kiholo Bay, HI, USA. We also present methods to convert the measured activities to SGD rates. In Kiholo Bay, the derived SGD matched previous estimates but in addition it revealed previously undocumented short- and long-term patterns in SGD. (author)

Development of underwater laser cutting technology

International Nuclear Information System (INIS)

Sato, Seiichi; Inaba, Takanori; Inose, Koutarou; Matsumoto, Naoyuki; Sakakibara, Yuji

2015-01-01

In is desirable to use remote underwater device for the decommissioning work of highly radioactive components such as the nuclear internals from a view point of reducing the ranitidine exposure to the worker. Underwater laser cutting technology has advantages. First advantage in underwater laser cutting technology is that low reaction force during cutting, namely, remote operability is superior. Second point is that underwater laser cutting generates a little amount of secondary waste, because cutting kerf size is very small. Third point is that underwater laser cutting has low risk of the process delay, because device trouble is hard to happen. While underwater laser cutting has many advantages, the careful consideration in the safe treatment of the offgas which underwater laser cutting generates is necessary. This paper describes outline of underwater laser cutting technology developed by IHI Corporation (IHI) and that this technology is effective in various dismantling works in water. (author)

Blind equalization for underwater communications

NARCIS (Netherlands)

Blom, K.C.H.

2014-01-01

Underwater wireless (sensor) networks would vastly improve man's ability to explore and exploit remote aquatic environments. Despite underwater sensor and vehicle technology being relatively mature, underwater communications is still a major challenge. The most challenging characteristics of the

An Efficient Data-Gathering Routing Protocol for Underwater Wireless Sensor Networks

Directory of Open Access Journals (Sweden)

Nadeem Javaid

2015-11-01

Full Text Available Most applications of underwater wireless sensor networks (UWSNs demand reliable data delivery over a longer period in an efficient and timely manner. However, the harsh and unpredictable underwater environment makes routing more challenging as compared to terrestrial WSNs. Most of the existing schemes deploy mobile sensors or a mobile sink (MS to maximize data gathering. However, the relatively high deployment cost prevents their usage in most applications. Thus, this paper presents an autonomous underwater vehicle (AUV-aided efficient data-gathering (AEDG routing protocol for reliable data delivery in UWSNs. To prolong the network lifetime, AEDG employs an AUV for data collection from gateways and uses a shortest path tree (SPT algorithm while associating sensor nodes with the gateways. The AEDG protocol also limits the number of associated nodes with the gateway nodes to minimize the network energy consumption and to prevent the gateways from overloading. Moreover, gateways are rotated with the passage of time to balance the energy consumption of the network. To prevent data loss, AEDG allows dynamic data collection at the AUV depending on the limited number of member nodes that are associated with each gateway. We also develop a sub-optimal elliptical trajectory of AUV by using a connected dominating set (CDS to further facilitate network throughput maximization. The performance of the AEDG is validated via simulations, which demonstrate the effectiveness of AEDG in comparison to two existing UWSN routing protocols in terms of the selected performance metrics.

An Efficient Data-Gathering Routing Protocol for Underwater Wireless Sensor Networks.

Science.gov (United States)

Javaid, Nadeem; Ilyas, Naveed; Ahmad, Ashfaq; Alrajeh, Nabil; Qasim, Umar; Khan, Zahoor Ali; Liaqat, Tayyaba; Khan, Majid Iqbal

2015-11-17

Most applications of underwater wireless sensor networks (UWSNs) demand reliable data delivery over a longer period in an efficient and timely manner. However, the harsh and unpredictable underwater environment makes routing more challenging as compared to terrestrial WSNs. Most of the existing schemes deploy mobile sensors or a mobile sink (MS) to maximize data gathering. However, the relatively high deployment cost prevents their usage in most applications. Thus, this paper presents an autonomous underwater vehicle (AUV)-aided efficient data-gathering (AEDG) routing protocol for reliable data delivery in UWSNs. To prolong the network lifetime, AEDG employs an AUV for data collection from gateways and uses a shortest path tree (SPT) algorithm while associating sensor nodes with the gateways. The AEDG protocol also limits the number of associated nodes with the gateway nodes to minimize the network energy consumption and to prevent the gateways from overloading. Moreover, gateways are rotated with the passage of time to balance the energy consumption of the network. To prevent data loss, AEDG allows dynamic data collection at the AUV depending on the limited number of member nodes that are associated with each gateway. We also develop a sub-optimal elliptical trajectory of AUV by using a connected dominating set (CDS) to further facilitate network throughput maximization. The performance of the AEDG is validated via simulations, which demonstrate the effectiveness of AEDG in comparison to two existing UWSN routing protocols in terms of the selected performance metrics.

A collision model for safety evaluation of autonomous intelligent cruise control.

Science.gov (United States)

Touran, A; Brackstone, M A; McDonald, M

1999-09-01

This paper describes a general framework for safety evaluation of autonomous intelligent cruise control in rear-end collisions. Using data and specifications from prototype devices, two collision models are developed. One model considers a train of four cars, one of which is equipped with autonomous intelligent cruise control. This model considers the car in front and two cars following the equipped car. In the second model, none of the cars is equipped with the device. Each model can predict the possibility of rear-end collision between cars under various conditions by calculating the remaining distance between cars after the front car brakes. Comparing the two collision models allows one to evaluate the effectiveness of autonomous intelligent cruise control in preventing collisions. The models are then subjected to Monte Carlo simulation to calculate the probability of collision. Based on crash probabilities, an expected value is calculated for the number of cars involved in any collision. It is found that given the model assumptions, while equipping a car with autonomous intelligent cruise control can significantly reduce the probability of the collision with the car ahead, it may adversely affect the situation for the following cars.

Energy Consumption Research of Mobile Data Collection Protocol for Underwater Nodes Using an USV

Directory of Open Access Journals (Sweden)

Zhichao Lv

2018-04-01

Full Text Available The Unmanned Surface Vehicle (USV integrated with an acoustic modem is a novel mobile vehicle for data collection, which has an advantage in terms of mobility, efficiency, and collection cost. In the scenario of data collection, the USV is controlled autonomously along the planning trajectory and the data of underwater nodes are dynamically collected. In order to improve the efficiency of data collection and extend the life of the underwater nodes, a mobile data collection protocol for underwater nodes using the USV was proposed. In the protocol, the stop-and-wait ARQ transmission mechanism is adopted, where the duty cycle is designed considering the ratio between the sleep mode and the detection mode, and the transmission ratio is defined by the duty cycle, wake-up signal cycles, and USV’s speed. According to protocol, the evaluation index for energy consumption is constructed based on the duty cycle and the transmission ratio. The energy consumption of the protocol is simulated and analyzed using the mobile communication experiment data of USV, taking into consideration USV’s speed, data sequence length, and duty cycle. Optimized protocol parameters are identified, which in turn denotes the proposed protocol’s feasibility and effectiveness.

Autonomous underwater vehicle motion tracking using a Kalman filter for sensor fusion

CSIR Research Space (South Africa)

Holtzhausen, S

2008-11-01

Full Text Available it will be shown how a Kalman Filter is used to estimate the position of an autonomous vehicle in a three dimensional space. The Kalman filter is used to estimate movement and position using measurements from multiple sensors...

Electrolocation-based underwater obstacle avoidance using wide-field integration methods

International Nuclear Information System (INIS)

Dimble, Kedar D; Faddy, James M; Humbert, J Sean

2014-01-01

Weakly electric fish are capable of efficiently performing obstacle avoidance in dark and navigationally challenging aquatic environments using electrosensory information. This sensory modality enables extraction of relevant proximity information about surrounding obstacles by interpretation of perturbations induced to the fish’s self-generated electric field. In this paper, reflexive obstacle avoidance is demonstrated by extracting relative proximity information using spatial decompositions of the perturbation signal, also called an electric image. Electrostatics equations were formulated for mathematically expressing electric images due to a straight tunnel to the electric field generated with a planar electro-sensor model. These equations were further used to design a wide-field integration based static output feedback controller. The controller was implemented in quasi-static simulations for environments with complicated geometries modelled using finite element methods to demonstrate sense and avoid behaviours. The simulation results were confirmed by performing experiments using a computer operated gantry system in environments lined with either conductive or non-conductive objects acting as global stimuli to the field of the electro-sensor. The proposed approach is computationally inexpensive and readily implementable, making underwater autonomous navigation in real-time feasible. (paper)

Integrated synoptic surveys using an autonomous underwater vehicle and manned boats

Science.gov (United States)

Jackson, P. Ryan

2013-01-01

Traditional surface-water surveys are being combined with autonomous technology to produce integrated surveys of bathymetry, water quality, and velocity in inland lakes and reservoirs. This new technology provides valuable, high-resolution, integrated data that allow a systems-based approach to understanding common environmental problems. This fact sheet presents several example applications of integrated surveys within inland lakes and coastal Lake Michigan and Lake Erie.

Underwater Scene Composition

Science.gov (United States)

Kim, Nanyoung

2009-01-01

In this article, the author describes an underwater scene composition for elementary-education majors. This project deals with watercolor with crayon or oil-pastel resist (medium); the beauty of nature represented by fish in the underwater scene (theme); texture and pattern (design elements); drawing simple forms (drawing skill); and composition…

Resources for Underwater Robotics Education

Science.gov (United States)

Wallace, Michael L.; Freitas, William M.

2016-01-01

4-H clubs can build and program underwater robots from raw materials. An annotated resource list for engaging youth in building underwater remotely operated vehicles (ROVs) is provided. This article is a companion piece to the Research in Brief article "Building Teen Futures with Underwater Robotics" in this issue of the "Journal of…

Simultaneous Localization and Mapping with Iterative Sparse Extended Information Filter for Autonomous Vehicles

Directory of Open Access Journals (Sweden)

Bo He

2015-08-01

Full Text Available In this paper, a novel iterative sparse extended information filter (ISEIF was proposed to solve the simultaneous localization and mapping problem (SLAM, which is very crucial for autonomous vehicles. The proposed algorithm solves the measurement update equations with iterative methods adaptively to reduce linearization errors. With the scalability advantage being kept, the consistency and accuracy of SEIF is improved. Simulations and practical experiments were carried out with both a land car benchmark and an autonomous underwater vehicle. Comparisons between iterative SEIF (ISEIF, standard EKF and SEIF are presented. All of the results convincingly show that ISEIF yields more consistent and accurate estimates compared to SEIF and preserves the scalability advantage over EKF, as well.

Simultaneous Localization and Mapping with Iterative Sparse Extended Information Filter for Autonomous Vehicles.

Science.gov (United States)

He, Bo; Liu, Yang; Dong, Diya; Shen, Yue; Yan, Tianhong; Nian, Rui

2015-08-13

In this paper, a novel iterative sparse extended information filter (ISEIF) was proposed to solve the simultaneous localization and mapping problem (SLAM), which is very crucial for autonomous vehicles. The proposed algorithm solves the measurement update equations with iterative methods adaptively to reduce linearization errors. With the scalability advantage being kept, the consistency and accuracy of SEIF is improved. Simulations and practical experiments were carried out with both a land car benchmark and an autonomous underwater vehicle. Comparisons between iterative SEIF (ISEIF), standard EKF and SEIF are presented. All of the results convincingly show that ISEIF yields more consistent and accurate estimates compared to SEIF and preserves the scalability advantage over EKF, as well.

Modeling of an autonomous microgrid for renewable energy sources integration

DEFF Research Database (Denmark)

Serban, I.; Teodorescu, Remus; Guerrero, Josep M.

2009-01-01

The frequency stability analysis in an autonomous microgrid (MG) with renewable energy sources (RES) is a continuously studied issue. This paper presents an original method for modeling an autonomous MG with a battery energy storage system (BESS) and a wind power plant (WPP), with the purpose...

The key kinematic determinants of undulatory underwater swimming at maximal velocity.

Science.gov (United States)

Connaboy, Chris; Naemi, Roozbeh; Brown, Susan; Psycharakis, Stelios; McCabe, Carla; Coleman, Simon; Sanders, Ross

2016-01-01

The optimisation of undulatory underwater swimming is highly important in competitive swimming performance. Nineteen kinematic variables were identified from previous research undertaken to assess undulatory underwater swimming performance. The purpose of the present study was to determine which kinematic variables were key to the production of maximal undulatory underwater swimming velocity. Kinematic data at maximal undulatory underwater swimming velocity were collected from 17 skilled swimmers. A series of separate backward-elimination analysis of covariance models was produced with cycle frequency and cycle length as dependent variables (DVs) and participant as a fixed factor, as including cycle frequency and cycle length would explain 100% of the maximal swimming velocity variance. The covariates identified in the cycle-frequency and cycle-length models were used to form the saturated model for maximal swimming velocity. The final parsimonious model identified three covariates (maximal knee joint angular velocity, maximal ankle angular velocity and knee range of movement) as determinants of the variance in maximal swimming velocity (adjusted-r2 = 0.929). However, when participant was removed as a fixed factor there was a large reduction in explained variance (adjusted r2 = 0.397) and only maximal knee joint angular velocity continued to contribute significantly, highlighting its importance to the production of maximal swimming velocity. The reduction in explained variance suggests an emphasis on inter-individual differences in undulatory underwater swimming technique and/or anthropometry. Future research should examine the efficacy of other anthropometric, kinematic and coordination variables to better understand the production of maximal swimming velocity and consider the importance of individual undulatory underwater swimming techniques when interpreting the data.

High-frequency autonomic modulation: a new model for analysis of autonomic cardiac control.

Science.gov (United States)

Champéroux, Pascal; Fesler, Pierre; Judé, Sebastien; Richard, Serge; Le Guennec, Jean-Yves; Thireau, Jérôme

2018-05-03

Increase in high-frequency beat-to-beat heart rate oscillations by torsadogenic hERG blockers appears to be associated with signs of parasympathetic and sympathetic co-activation which cannot be assessed directly using classic methods of heart rate variability analysis. The present work aimed to find a translational model that would allow this particular state of the autonomic control of heart rate to be assessed. High-frequency heart rate and heart period oscillations were analysed within discrete 10 s intervals in a cohort of 200 healthy human subjects. Results were compared to data collected in non-human primates and beagle dogs during pharmacological challenges and torsadogenic hERG blockers exposure, in 127 genotyped LQT1 patients on/off β-blocker treatment and in subgroups of smoking and non-smoking subjects. Three states of autonomic modulation, S1 (parasympathetic predominance) to S3 (reciprocal parasympathetic withdrawal/sympathetic activation), were differentiated to build a new model of heart rate variability referred to as high-frequency autonomic modulation. The S2 state corresponded to a specific state during which both parasympathetic and sympathetic systems were coexisting or co-activated. S2 oscillations were proportionally increased by torsadogenic hERG-blocking drugs, whereas smoking caused an increase in S3 oscillations. The combined analysis of the magnitude of high-frequency heart rate and high-frequency heart period oscillations allows a refined assessment of heart rate autonomic modulation applicable to long-term ECG recordings and offers new approaches to assessment of the risk of sudden death both in terms of underlying mechanisms and sensitivity. © 2018 The Authors. British Journal of Pharmacology published by John Wiley & Sons Ltd on behalf of British Pharmacological Society.

The influence of underwater turbulence on optical phase measurements

Science.gov (United States)

Redding, Brandon; Davis, Allen; Kirkendall, Clay; Dandridge, Anthony

2016-05-01

Emerging underwater optical imaging and sensing applications rely on phase-sensitive detection to provide added functionality and improved sensitivity. However, underwater turbulence introduces spatio-temporal variations in the refractive index of water which can degrade the performance of these systems. Although the influence of turbulence on traditional, non-interferometric imaging has been investigated, its influence on the optical phase remains poorly understood. Nonetheless, a thorough understanding of the spatio-temporal dynamics of the optical phase of light passing through underwater turbulence are crucial to the design of phase-sensitive imaging and sensing systems. To address this concern, we combined underwater imaging with high speed holography to provide a calibrated characterization of the effects of turbulence on the optical phase. By measuring the modulation transfer function of an underwater imaging system, we were able to calibrate varying levels of optical turbulence intensity using the Simple Underwater Imaging Model (SUIM). We then used high speed holography to measure the temporal dynamics of the optical phase of light passing through varying levels of turbulence. Using this method, we measured the variance in the amplitude and phase of the beam, the temporal correlation of the optical phase, and recorded the turbulence induced phase noise as a function of frequency. By bench marking the effects of varying levels of turbulence on the optical phase, this work provides a basis to evaluate the real-world potential of emerging underwater interferometric sensing modalities.

The Modular Optical Underwater Survey System

Directory of Open Access Journals (Sweden)

Ruhul Amin

2017-10-01

Full Text Available The Pacific Islands Fisheries Science Center deploys the Modular Optical Underwater Survey System (MOUSS to estimate the species-specific, size-structured abundance of commercially-important fish species in Hawaii and the Pacific Islands. The MOUSS is an autonomous stereo-video camera system designed for the in situ visual sampling of fish assemblages. This system is rated to 500 m and its low-light, stereo-video cameras enable identification, counting, and sizing of individuals at a range of 0.5–10 m. The modular nature of MOUSS allows for the efficient and cost-effective use of various imaging sensors, power systems, and deployment platforms. The MOUSS is in use for surveys in Hawaii, the Gulf of Mexico, and Southern California. In Hawaiian waters, the system can effectively identify individuals to a depth of 250 m using only ambient light. In this paper, we describe the MOUSS’s application in fisheries research, including the design, calibration, analysis techniques, and deployment mechanism.

High-Resolution Seafloor Mapping at A Deep-Sea Methane Seep Field with an Autonomous Underwater Vehicle

Science.gov (United States)

Skarke, A. D.

2017-12-01

A growing body of research indicates that points of seafloor gas emission, known as cold-seeps, are a common feature along many continental margins. Results from recent exploration efforts show that benthic environments at cold-seeps are characterized by extensive authigenic carbonate crusts and complex chemosynthetic communities. The seafloor morphology and geophysical properties of these locations are heterogeneous and relatively complex due to the three-dimensional structure created by carbonate buildups and dense bivalve beds. Seeps are often found clustered and the spatial extent of associated seafloor crusts and beds can reach multiple square kilometers. Here, the results of a 1.25 km2 autonomous underwater vehicle (AUV) survey of a deep-sea methane seep field with 13 vents, at a nominal depth of 1400 m, located near Veatch Canyon on the US Atlantic margin are presented. Multibeam sonar, sidescan sonar, and a sub bottom profiler on the AUV were used to make high-resolution observations of seafloor bathymetry (resolution 1m2) as well as water column, seafloor, and subsurface acoustic backscatter intensity. Additionally, a downward oriented camera was used to collect seafloor imagery coincident with acoustic observations at select locations. Acoustic results indicated the location of discrete gas plumes as well as a continuous area of elevated seafloor roughness and backscatter intensity consistent with the presence of large scale authigenic rock outcrops and extensive mussel beds, which were visually confirmed with camera imagery. Additionally, a linear area of particularly elevated seafloor roughness and acoustic backscatter intensity that lies sub-parallel to an adjacent ridge was interpreted to be controlled by underlying geologic processes such as soft sediment faulting. Automated analysis of camera imagery and coincident acoustic backscatter and bathymetry data as well as derivative metrics (e.g. slope and rugosity) was used to segment and classify bed

SOLON: An autonomous vehicle mission planner

Science.gov (United States)

Dudziak, M. J.

1987-01-01

The State-Operator Logic Machine (SOLON) Planner provides an architecture for effective real-time planning and replanning for an autonomous vehicle. The highlights of the system, which distinguish it from other AI-based planners that have been designed previously, are its hybrid application of state-driven control architecture and the use of both schematic representations and logic programming for the management of its knowledge base. SOLON is designed to provide multiple levels of planning for a single autonomous vehicle which is supplied with a skeletal, partially-specified mission plan at the outset of the vehicle's operations. This mission plan consists of a set of objectives, each of which will be decomposable by the planner into tasks. These tasks are themselves comparatively complex sets of actions which are executable by a conventional real-time control system which does not perform planning but which is capable of making adjustments or modifications to the provided tasks according to constraints and tolerances provided by the Planner. The current implementation of the SOLON is in the form of a real-time simulation of the Planner module of an Intelligent Vehicle Controller (IVC) on-board an autonomous underwater vehicle (AUV). The simulation is embedded within a larger simulator environment known as ICDS (Intelligent Controller Development System) operating on a Symbolics 3645/75 computer.

Design and Evaluation Methods for Underwater Control Systems

Energy Technology Data Exchange (ETDEWEB)

Chi, Lin

1996-12-31

This thesis on underwater control systems is written with the designer in mind, assuming that the reader has some knowledge of control theory. It can be used as a text for undergraduate students and engineers. To help readers better understand the system they will be working with, the thesis is organised in a stepwise way. The reader will gain basic knowledge about underwater operations, equipment and control systems. Then the reader will be able to follow the steps to develop a required control system for an underwater equipment by first understanding the characteristics of the design problem, customer requirement, functional requirement, and possible solution, and then to present a mathematical model of the control problem. Having developed the concept, the thesis guides the reader to develop evaluation criteria and different ways to make the decision. The thesis gives an overview of how to achieve a successful design rather than giving the techniques for detailed control system design. Chapter 1 describes underwater operations and systems. Chapter 2 discusses issues of underwater control systems and control methods. Chapter 3 deals with design method and control systems theory, focusing on human-centered control. Chapter 4 discusses methods used to evaluate and rank products, and chapter 5 applies the methods to an example. 113 refs., 115 figs., 80 tabs.

Design and Evaluation Methods for Underwater Control Systems

Energy Technology Data Exchange (ETDEWEB)

Chi, Lin

1997-12-31

This thesis on underwater control systems is written with the designer in mind, assuming that the reader has some knowledge of control theory. It can be used as a text for undergraduate students and engineers. To help readers better understand the system they will be working with, the thesis is organised in a stepwise way. The reader will gain basic knowledge about underwater operations, equipment and control systems. Then the reader will be able to follow the steps to develop a required control system for an underwater equipment by first understanding the characteristics of the design problem, customer requirement, functional requirement, and possible solution, and then to present a mathematical model of the control problem. Having developed the concept, the thesis guides the reader to develop evaluation criteria and different ways to make the decision. The thesis gives an overview of how to achieve a successful design rather than giving the techniques for detailed control system design. Chapter 1 describes underwater operations and systems. Chapter 2 discusses issues of underwater control systems and control methods. Chapter 3 deals with design method and control systems theory, focusing on human-centered control. Chapter 4 discusses methods used to evaluate and rank products, and chapter 5 applies the methods to an example. 113 refs., 115 figs., 80 tabs.

MOSES, development of an Underwater Warfare Testbed

NARCIS (Netherlands)

Lentze, S.G.

2001-01-01

The TNO underwater warfare (UWW) research programme results in a large number of models used in operational research projects. To enhance the accessibility and re-use of these models for new projects, TNO-FEL has developed the modelling environment ‘MOSES - Maritime Operations Simulation and

A review of underwater bio-mimetic propulsion: cruise and fast-start

Science.gov (United States)

Chao, Li-Ming; Cao, Yong-Hui; Pan, Guang

2017-08-01

This paper reviews recent developments in the understanding of underwater bio-mimetic propulsion. Two impressive models of underwater propulsion are considered: cruise and fast-start. First, we introduce the progression of bio-mimetic propulsion, especially underwater propulsion, where some primary conceptions are touched upon. Second, the understanding of flapping foils, considered as one of the most efficient cruise styles of aquatic animals, is introduced, where the effect of kinematics and the shape and flexibility of foils on generating thrust are elucidated respectively. Fast-start propulsion is always exhibited when predator behaviour occurs, and we provide an explicit introduction of corresponding zoological experiments and numerical simulations. We also provide some predictions about underwater bio-mimetic propulsion.

A review of underwater bio-mimetic propulsion: cruise and fast-start

Energy Technology Data Exchange (ETDEWEB)

Chao, Li-Ming; Cao, Yong-Hui; Pan, Guang, E-mail: PanGuang_010@163.com [School of Marine Science and Technology, Northwestern Polytechnical University, Xian 710072 (China)

2017-08-15

This paper reviews recent developments in the understanding of underwater bio-mimetic propulsion. Two impressive models of underwater propulsion are considered: cruise and fast-start. First, we introduce the progression of bio-mimetic propulsion, especially underwater propulsion, where some primary conceptions are touched upon. Second, the understanding of flapping foils, considered as one of the most efficient cruise styles of aquatic animals, is introduced, where the effect of kinematics and the shape and flexibility of foils on generating thrust are elucidated respectively. Fast-start propulsion is always exhibited when predator behaviour occurs, and we provide an explicit introduction of corresponding zoological experiments and numerical simulations. We also provide some predictions about underwater bio-mimetic propulsion. (review)

Predictive Model for the Analysis of the Effects of Underwater Impulsive Sources on Marine Life

National Research Council Canada - National Science Library

Lazauski, Colin J

2007-01-01

A method is provided to predict the biological consequences to marine animals from exposure to multiple underwater impulsive sources by simulating underwater explosions over a defined period of time...

Robotic Detection of Marine Litter Using Deep Visual Detection Models

OpenAIRE

Fulton, Michael; Hong, Jungseok; Islam, Md Jahidul; Sattar, Junaed

2018-01-01

Trash deposits in aquatic environments have a destructive effect on marine ecosystems and pose a long-term economic and environmental threat. Autonomous underwater vehicles (AUVs) could very well contribute to the solution of this problem by finding and eventually removing trash. A step towards this goal is the successful detection of trash in underwater environments. This paper evaluates a number of deep-learning algorithms to the task of visually detecting trash in realistic underwater envi...

GEMS: Underwater spectrometer for long-term radioactivity measurements

Energy Technology Data Exchange (ETDEWEB)

Sartini, Ludovica, E-mail: ludovica.sartini@ingv.i [Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sect.Roma 2, Roma (Italy); Genoa University, Genoa (Italy); Simeone, Francesco; Pani, Priscilla [' Sapienza' University and Istituto Nazionale di Fisica Nucleare (INFN), Sect.Roma, Roma (Italy); Lo Bue, Nadia; Marinaro, Giuditta [Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sect.Roma 2, Roma (Italy); Grubich, Andry; Lobko, Alexander [Institute for Nuclear Problems (INP), Belarus State University, Minsk (Belarus); Etiope, Giuseppe [Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sect.Roma 2, Roma (Italy); Capone, Antonio [' Sapienza' University and Istituto Nazionale di Fisica Nucleare (INFN), Sect.Roma, Roma (Italy); Favali, Paolo [Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sect.Roma 2, Roma (Italy); Gasparoni, Francesco; Bruni, Federico [Tecnomare S.p.A., Venice (Italy)

2011-01-21

GEMS (Gamma Energy Marine Spectrometer) is a prototype of an autonomous radioactivity sensor for underwater measurements, developed in the framework for a development of a submarine telescope for neutrino detection (KM3NeT Design Study Project). The spectrometer is highly sensitive to gamma rays produced by {sup 40}K decays but it can detect other natural (e.g., {sup 238}U,{sup 232}Th) and anthropogenic radio-nuclides (e.g., {sup 137}Cs). GEMS was firstly tested and calibrated in the laboratory using known sources and it was successfully deployed for a long-term (6 months) monitoring at a depth of 3200 m in the Ionian Sea (Capo Passero, offshore Eastern Sicily). The instrument recorded data for the whole deployment period within the expected specifications. This monitoring provided, for the first time, a continuous time-series of radioactivity in deep-sea.

Dynamics of the congestion control model in underwater wireless sensor networks with time delay

International Nuclear Information System (INIS)

Dong, Tao; Hu, Wenjie; Liao, Xiaofeng

2016-01-01

In this paper, a congestion control model in underwater wireless sensor network with time delay is considered. First, the boundedness of the positive equilibrium, where the samples density is positive for each node and the different event flows coexist, is investigated, which implies that the samples density of sensor node cannot exceed the Environmental carrying capacity. Then, by considering the time delay can be regarded as a bifurcating parameter, the dynamical behaviors, which include local stability and Hopf bifurcation, are investigated. It is found that when the communication time delay passes a critical value, the system loses its stability and a Hopf bifurcation occurs, which means the underwater wireless sensor network will be congested, even collapsed. Furthermore, the direction and stability of the bifurcating periodic solutions are derived by applying the normal form theory and the center manifold theorem. Finally, some numerical examples are finally performed to verify the theoretical results.

On the Performance of the Underwater Acoustic Sensor Networks

Science.gov (United States)

2015-05-01

performance of UWSN. 5.1 Hardware and Software Details 5.1.1 Equipment Our experimental model consisted of an indoor swimming pool , two pairs...UWSN has many constraints mainly due to limited capacity, propagation loss, as well as power limitation since in underwater environment solar energy ...since in underwater environment solar energy cannot be used to recharge batteries. In our approach, we estimate the number of operating receivers

Object detection from images obtained through underwater turbulence medium

Science.gov (United States)

Furhad, Md. Hasan; Tahtali, Murat; Lambert, Andrew

2017-09-01

Imaging through underwater experiences severe distortions due to random fluctuations of temperature and salinity in water, which produces underwater turbulence through diffraction limited blur. Lights reflecting from objects perturb and attenuate contrast, making the recognition of objects of interest difficult. Thus, the information available for detecting underwater objects of interest becomes a challenging task as they have inherent confusion among the background, foreground and other image properties. In this paper, a saliency-based approach is proposed to detect the objects acquired through an underwater turbulent medium. This approach has drawn attention among a wide range of computer vision applications, such as image retrieval, artificial intelligence, neuro-imaging and object detection. The image is first processed through a deblurring filter. Next, a saliency technique is used on the image for object detection. In this step, a saliency map that highlights the target regions is generated and then a graph-based model is proposed to extract these target regions for object detection.

Game Theory Models for the Verification of the Collective Behaviour of Autonomous Cars

OpenAIRE

Varga, László Z.

2017-01-01

The collective of autonomous cars is expected to generate almost optimal traffic. In this position paper we discuss the multi-agent models and the verification results of the collective behaviour of autonomous cars. We argue that non-cooperative autonomous adaptation cannot guarantee optimal behaviour. The conjecture is that intention aware adaptation with a constraint on simultaneous decision making has the potential to avoid unwanted behaviour. The online routing game model is expected to b...

ROV Based Underwater Blurred Image Restoration

Institute of Scientific and Technical Information of China (English)

LIU Zhishen; DING Tianfu; WANG Gang

2003-01-01

In this paper, we present a method of ROV based image processing to restore underwater blurry images from the theory of light and image transmission in the sea. Computer is used to simulate the maximum detection range of the ROV under different water body conditions. The receiving irradiance of the video camera at different detection ranges is also calculated. The ROV's detection performance under different water body conditions is given by simulation. We restore the underwater blurry images using the Wiener filter based on the simulation. The Wiener filter is shown to be a simple useful method for underwater image restoration in the ROV underwater experiments. We also present examples of restored images of an underwater standard target taken by the video camera in these experiments.

Natural hydrocarbon seeps observation with underwater gliders and UV fluorescence sensor

Science.gov (United States)

Rochet, V.

2016-02-01

Hydrocarbons may leak to the near-surface from subsurface accumulations, from mature source rock, or by buoyancy along major cross-strata routes. The presence of migrating near-surface hydrocarbons can provide strong evidence for the presence of a working petroleum system, as well as valuable information on source, maturity, and migration pathways. Detection and characterization of hydrocarbons in the water column may then help to de-risk hydrocarbon plays at a very preliminary stage of an exploration program. In order to detect hydrocarbons in the water column, an underwater glider survey was conducted in an offshore frontier area. Driven by buoyancy variation, underwater gliders enable collecting data autonomously along the water column for weeks to months. Underwater gliders are regularly piloted from shore by satellite telemetry and do not require a surface supervising vessel resulting in substantial operational costs savings. The data compiled, over 700m depth of the water column, included temperature, salinity, pressure, dissolved oxygen and hydrocarbon components (phenanthrene and naphthalene) measured by "MINIFLUO" sensors to particularly target representative crude oil compounds Two gliders were deployed at sea, one from coast in shallow water and the other one offshore on the survey area. Both accurately squared the survey area following pre-defined lines and cross lines. Data files were transmitted by satellite telemetry in near real time during the performance of the mission for real time observations and appropriate re-positioning of the gliders. Using rechargeable underwater gliders increased reliability reducing the risk of leakage and associated logistics during operation at sea. Despite strong evidences of seabed seepages such as pockmarks, faults, etc, over the area of interest, no hydrocarbon indices were detected in the water column, which was confirmed later by seabed sample analysis. The use of glider platforms for hydrocarbon detection has

Underwater 3D filming

Directory of Open Access Journals (Sweden)

Roberto Rinaldi

2014-12-01

Full Text Available After an experimental phase of many years, 3D filming is now effective and successful. Improvements are still possible, but the film industry achieved memorable success on 3D movie’s box offices due to the overall quality of its products. Special environments such as space (“Gravity” and the underwater realm look perfect to be reproduced in 3D. “Filming in space” was possible in “Gravity” using special effects and computer graphic. The underwater realm is still difficult to be handled. Underwater filming in 3D was not that easy and effective as filming in 2D, since not long ago. After almost 3 years of research, a French, Austrian and Italian team realized a perfect tool to film underwater, in 3D, without any constrains. This allows filmmakers to bring the audience deep inside an environment where they most probably will never have the chance to be.

Underwater welding of steel

International Nuclear Information System (INIS)

Ibarra, S.; Olson, D.L.

1992-01-01

A fundamental basis to understand the behavior of wet underwater welding of steel is introduced. Both the pyrometallurgical and physical metallurgy concepts are discussed. Modifications of welding consumables and practice are suggested. This chapter promotes further contributions of meatllurgical research to improve and promote wet underwater welding. (orig.)

Cooperative OFDM underwater acoustic communications

CERN Document Server

Cheng, Xilin; Cheng, Xiang

2016-01-01

Following underwater acoustic channel modeling, this book investigates the relationship between coherence time and transmission distances. It considers the power allocation issues of two typical transmission scenarios, namely short-range transmission and medium-long range transmission. For the former scenario, an adaptive system is developed based on instantaneous channel state information. The primary focus is on cooperative dual-hop orthogonal frequency division multiplexing (OFDM). This book includes the decomposed fountain codes designed to enable reliable communications with higher energy efficiency. It covers the Doppler Effect, which improves packet transmission reliability for effective low-complexity mirror-mapping-based intercarrier interference cancellation schemes capable of suppressing the intercarrier interference power level. Designed for professionals and researchers in the field of underwater acoustic communications, this book is also suitable for advanced-level students in electrical enginee...

Colour reconstruction of underwater images

OpenAIRE

Hoth, Julian; Kowalczyk, Wojciech

2017-01-01

Objects look very different in the underwater environment compared to their appearance in sunlight. Images with correct colouring simplify the detection of underwater objects and may allow the use of visual SLAM algorithms developed for land-based robots underwater. Hence, image processing is required. Current algorithms focus on the colour reconstruction of scenery at diving depth where different colours can still be distinguished. At greater depth this is not the case. In this study it is i...

Quantum imaging for underwater arctic navigation

Science.gov (United States)

Lanzagorta, Marco

2017-05-01

The precise navigation of underwater vehicles is a difficult task due to the challenges imposed by the variable oceanic environment. It is particularly difficult if the underwater vehicle is trying to navigate under the Arctic ice shelf. Indeed, in this scenario traditional navigation devices such as GPS, compasses and gyrocompasses are unavailable or unreliable. In addition, the shape and thickness of the ice shelf is variable throughout the year. Current Arctic underwater navigation systems include sonar arrays to detect the proximity to the ice. However, these systems are undesirable in a wartime environment, as the sound gives away the position of the underwater vehicle. In this paper we briefly describe the theoretical design of a quantum imaging system that could allow the safe and stealthy navigation of underwater Arctic vehicles.

The Trans-Contextual Model of Autonomous Motivation in Education

Science.gov (United States)

Hagger, Martin S.; Chatzisarantis, Nikos L. D.

2015-01-01

The trans-contextual model outlines the processes by which autonomous motivation toward activities in a physical education context predicts autonomous motivation toward physical activity outside of school, and beliefs about, intentions toward, and actual engagement in, out-of-school physical activity. In the present article, we clarify the fundamental propositions of the model and resolve some outstanding conceptual issues, including its generalizability across multiple educational domains, criteria for its rejection or failed replication, the role of belief-based antecedents of intentions, and the causal ordering of its constructs. We also evaluate the consistency of model relationships in previous tests of the model using path-analytic meta-analysis. The analysis supported model hypotheses but identified substantial heterogeneity in the hypothesized relationships across studies unattributed to sampling and measurement error. Based on our meta-analysis, future research needs to provide further replications of the model in diverse educational settings beyond physical education and test model hypotheses using experimental methods. PMID:27274585

3D MODELS COMPARISON OF COMPLEX SHELL IN UNDERWATER AND DRY ENVIRONMENTS

Directory of Open Access Journals (Sweden)

S. Troisi

2015-04-01

Full Text Available In marine biology the shape, morphology, texture and dimensions of the shells and organisms like sponges and gorgonians are very important parameters. For example, a particular type of gorgonian grows every year only few millimeters; this estimation was conducted without any measurement instrument but it has been provided after successive observational studies, because this organism is very fragile: the contact could compromise its structure and outliving. Non-contact measurement system has to be used to preserve such organisms: the photogrammetry is a method capable to assure high accuracy without contact. Nevertheless, the achievement of a 3D photogrammetric model of complex object (as gorgonians or particular shells is a challenge in normal environments, either with metric camera or with consumer camera. Indeed, the successful of automatic target-less image orientation and the image matching algorithms is strictly correlated to the object texture properties and of camera calibration quality as well. In the underwater scenario, the environment conditions strongly influence the results quality; in particular, water’s turbidity, the presence of suspension, flare and other optical aberrations decrease the image quality reducing the accuracy and increasing the noise on the 3D model. Furthermore, seawater density variability influences its refraction index and consequently the interior orientation camera parameters. For this reason, the camera calibration has to be performed in the same survey conditions. In this paper, a comparison between the 3D models of a Charonia Tritonis shell are carried out through surveys conducted both in dry and underwater environments.

ROV-based Underwater Vision System for Intelligent Fish Ethology Research

Directory of Open Access Journals (Sweden)

Rui Nian

2013-09-01

Full Text Available Fish ethology is a prospective discipline for ocean surveys. In this paper, one ROV-based system is established to perform underwater visual tasks with customized optical sensors installed. One image quality enhancement method is first presented in the context of creating underwater imaging models combined with homomorphic filtering and wavelet decomposition. The underwater vision system can further detect and track swimming fish from the resulting images with the strategies developed using curve evolution and particular filtering, in order to obtain a deeper understanding of fish behaviours. The simulation results have shown the excellent performance of the developed scheme, in regard to both robustness and effectiveness.

Underwater Shock Response Analysis of a Floating Vessel

Directory of Open Access Journals (Sweden)

J.E. van Aanhold

1998-01-01

Full Text Available The response of a surface vessel to underwater shock has been calculated using an explicit finite element analysis. The analysis model is two-dimensional and contains the floating steel structure, a large surrounding water volume and the free surface. The underwater shock is applied in the form of a plane shock wave and cavitation is considered in the analysis. Advanced computer graphics, in particular video animations, provide a powerful and indispensable means for the presentation and evaluation of the analysis results.

Computational Modeling of Hydrodynamics and Scour around Underwater Munitions

Science.gov (United States)

Liu, X.; Xu, Y.

2017-12-01

Munitions deposited in water bodies are a big threat to human health, safety, and environment. It is thus imperative to predict the motion and the resting status of the underwater munitions. A multitude of physical processes are involved, which include turbulent flows, sediment transport, granular material mechanics, 6 degree-of-freedom motion of the munition, and potential liquefaction. A clear understanding of this unique physical setting is currently lacking. Consequently, it is extremely hard to make reliable predictions. In this work, we present the computational modeling of two importance processes, i.e., hydrodynamics and scour, around munition objects. Other physical processes are also considered in our comprehensive model. However, they are not shown in this talk. To properly model the dynamics of the deforming bed and the motion of the object, an immersed boundary method is implemented in the open source CFD package OpenFOAM. Fixed bed and scour cases are simulated and compared with laboratory experiments. The future work of this project will implement the coupling between all the physical processes.

Estimating the Total Heat Flux from the ASHES Hydrothermal Vent Field Using the Sentry Autonomous Underwater Vehicle

Science.gov (United States)

Crone, T. J.; Kinsey, J. C.; Mittelstaedt, E. L.

2017-12-01

Hydrothermal venting at mid-ocean ridges influences ocean chemistry, the thermal and chemical structure of the oceanic crust, and the evolution of unique and diverse autolithotrophically-supported ecosystems. Axially-hosted hydrothermal systems are responsible for 20-25% of the total heat flux out of Earth's interior, and likely play a large role in local as well as global biogeochemical cycles. Despite the importance of these systems, only a few studies have attempted to constrain the volume and heat flux of an entire hydrothermal vent field. In July of 2014 we used the Sentry autonomous underwater vehicle (AUV) to survey the water column over the ASHES hydrothermal vent field which is located within the caldera of Axial Seamount, an active submarine volcano located on the Juan de Fuca Ridge. To estimate the total heat and mass flux from this vent field, we equipped Sentry with a Nortek acoustic Doppler velocimeter (ADV), an inertial measurement unit (IMU), two acoustic Doppler current profilers (ADCPs), and two SBE3 temperature probes, allowing us to obtain precise measurements of fluid temperature and water velocity. The survey was designed using a control volume approach in which Sentry was pre-programmed to survey a 150-m-square centered over the vent field flying a grid pattern with 5-m track line spacing followed by a survey of the perimeter. This pattern was repeated multiple times during several 10-h dives at different altitudes, including 10, 20, 40, and 60 m above the seafloor, and during one 40-h survey at an altitude of 10 m. During the 40-h survey, the pattern was repeated nine times allowing us to obtain observations over several tidal cycles. Water velocity data obtained with Sentry were corrected for platform motion and then combined with the temperature measurements to estimate heat flux. The analysis of these data will likely provide the most accurate and highest resolution heat and mass flux estimates at a seafloor hydrothermal field to date.

Underwater welding using remote controlled robots. Development of remote underwater welding technology with a high power YAG laser

International Nuclear Information System (INIS)

Miwa, Yasuhiro; Sato, Syuuichi; Kojima, Toshio; Owaki, Katsura; Hirose, Naoya

2002-01-01

As components in nuclear power plant have been periodically carried out their inspection and repair to keep their integrity, on radioactive liquid wastes storage facility, because of difficulty on their inspection by human beings, some are remained without inspection, and even when capable of inspection, conversion from human works to remote operations is desired from a viewpoint of their operation efficiency upgrading. For response to these needs, some developments on a technology capable of carrying out inspection of their inside at underwater environment and repairing welding with YAG laser by means of remote operation, have been performed. Remote underwater inspection and repair technology is a combination technology of already applied underwater mobile technique (underwater inspection robot) with underwater YAG laser welding technique which is recently at actual using level. Therefore, this technology is composed of an inspection robot and a repair welding robot. And, testing results using the underwater inspection robot and welding test results using the underwater repair welding robot, were enough preferable to obtain forecasting applicable to actual apparatuses. This technology is especially effective for inspection and repair of inside of nuclear fuel cycle apparatuses and relatively high dose apparatuses, and can be thought to be applicable also to large capacity tanks, tanks dealing with harmful matters, underwater structures, and so on, in general industries. (G.K.)

Design and Analysis of Underwater Acoustic Networks with Reflected Links

Science.gov (United States)

Emokpae, Lloyd

Underwater acoustic networks (UWANs) have applications in environmental state monitoring, oceanic profile measurements, leak detection in oil fields, distributed surveillance, and navigation. For these applications, sets of nodes are employed to collaboratively monitor an area of interest and track certain events or phenomena. In addition, it is common to find autonomous underwater vehicles (AUVs) acting as mobile sensor nodes that perform search-and-rescue missions, reconnaissance in combat zones, and coastal patrol. These AUVs are to work cooperatively to achieve a desired goal and thus need to be able to, in an ad-hoc manner, establish and sustain communication links in order to ensure some desired level of quality of service. Therefore, each node is required to adapt to environmental changes and be able to overcome broken communication links caused by external noise affecting the communication channel due to node mobility. In addition, since radio waves are quickly absorbed in the water medium, it is common for most underwater applications to rely on acoustic (or sound) rather than radio channels for mid-to-long range communications. However, acoustic channels pose multiple challenging issues, most notably the high transmission delay due to slow signal propagation and the limited channel bandwidth due to high frequency attenuation. Moreover, the inhomogeneous property of the water medium affects the sound speed profile while the signal surface and bottom reflections leads to multipath effects. In this dissertation, we address these networking challenges by developing protocols that take into consideration the underwater physical layer dynamics. We begin by introducing a novel surface-based reflection scheme (SBR), which takes advantage of the multipath effects of the acoustic channel. SBR works by using reflections from the water surface, and bottom, to establish non-line-of-sight (NLOS) communication links. SBR makes it possible to incorporate both line

High accuracy navigation information estimation for inertial system using the multi-model EKF fusing adams explicit formula applied to underwater gliders.

Science.gov (United States)

Huang, Haoqian; Chen, Xiyuan; Zhang, Bo; Wang, Jian

2017-01-01

The underwater navigation system, mainly consisting of MEMS inertial sensors, is a key technology for the wide application of underwater gliders and plays an important role in achieving high accuracy navigation and positioning for a long time of period. However, the navigation errors will accumulate over time because of the inherent errors of inertial sensors, especially for MEMS grade IMU (Inertial Measurement Unit) generally used in gliders. The dead reckoning module is added to compensate the errors. In the complicated underwater environment, the performance of MEMS sensors is degraded sharply and the errors will become much larger. It is difficult to establish the accurate and fixed error model for the inertial sensor. Therefore, it is very hard to improve the accuracy of navigation information calculated by sensors. In order to solve the problem mentioned, the more suitable filter which integrates the multi-model method with an EKF approach can be designed according to different error models to give the optimal estimation for the state. The key parameters of error models can be used to determine the corresponding filter. The Adams explicit formula which has an advantage of high precision prediction is simultaneously fused into the above filter to achieve the much more improvement in attitudes estimation accuracy. The proposed algorithm has been proved through theory analyses and has been tested by both vehicle experiments and lake trials. Results show that the proposed method has better accuracy and effectiveness in terms of attitudes estimation compared with other methods mentioned in the paper for inertial navigation applied to underwater gliders. Copyright © 2016 ISA. Published by Elsevier Ltd. All rights reserved.

Underwater Acoustic Networking Techniques

CERN Document Server

Otnes, Roald; Casari, Paolo; Goetz, Michael; Husøy, Thor; Nissen, Ivor; Rimstad, Knut; van Walree, Paul; Zorzi, Michele

2012-01-01

This literature study presents an overview of underwater acoustic networking. It provides a background and describes the state of the art of all networking facets that are relevant for underwater applications. This report serves both as an introduction to the subject and as a summary of existing protocols, providing support and inspiration for the development of network architectures.

Underwater electric field detection system based on weakly electric fish

Science.gov (United States)

Xue, Wei; Wang, Tianyu; Wang, Qi

2018-04-01

Weakly electric fish sense their surroundings in complete darkness by their active electric field detection system. However, due to the insufficient detection capacity of the electric field, the detection distance is not enough, and the detection accuracy is not high. In this paper, a method of underwater detection based on rotating current field theory is proposed to improve the performance of underwater electric field detection system. First of all, we built underwater detection system based on the theory of the spin current field mathematical model with the help of the results of previous researchers. Then we completed the principle prototype and finished the metal objects in the water environment detection experiments, laid the foundation for the further experiments.

Redundant manipulator techniques for partially decentralized path planning and control of a platoon of autonomous vehicles.

Science.gov (United States)

Stilwell, Daniel J; Bishop, Bradley E; Sylvester, Caleb A

2005-08-01

An approach to real-time trajectory generation for platoons of autonomous vehicles is developed from well-known control techniques for redundant robotic manipulators. The partially decentralized structure of this approach permits each vehicle to independently compute its trajectory in real-time using only locally generated information and low-bandwidth feedback generated by a system exogenous to the platoon. Our work is motivated by applications for which communications bandwidth is severely limited, such for platoons of autonomous underwater vehicles. The communication requirements for our trajectory generation approach are independent of the number of vehicles in the platoon, enabling platoons composed of a large number of vehicles to be coordinated despite limited communication bandwidth.

Distributed estimation of sensors position in underwater wireless sensor network

Science.gov (United States)

Zandi, Rahman; Kamarei, Mahmoud; Amiri, Hadi

2016-05-01

In this paper, a localisation method for determining the position of fixed sensor nodes in an underwater wireless sensor network (UWSN) is introduced. In this simple and range-free scheme, the node localisation is achieved by utilising an autonomous underwater vehicle (AUV) that transverses through the network deployment area, and that periodically emits a message block via four directional acoustic beams. A message block contains the actual known AUV position as well as a directional dependent marker that allows a node to identify the respective transmit beam. The beams form a fixed angle with the AUV body. If a node passively receives message blocks, it could calculate the arithmetic mean of the coordinates existing in each messages sequence, to find coordinates at two different time instants via two different successive beams. The node position can be derived from the two computed positions of the AUV. The major advantage of the proposed localisation algorithm is that it is silent, which leads to energy efficiency for sensor nodes. The proposed method does not require any synchronisation among the nodes owing to being silent. Simulation results, using MATLAB, demonstrated that the proposed method had better performance than other similar AUV-based localisation methods in terms of the rates of well-localised sensor nodes and positional root mean square error.

OFDM for underwater acoustic communications

CERN Document Server

Zhou, Shengli

2014-01-01

A blend of introductory material and advanced signal processing and communication techniques, of critical importance to underwater system and network development This book, which is the first to describe the processing techniques central to underwater OFDM, is arranged into four distinct sections: First, it describes the characteristics of underwater acoustic channels, and stresses the difference from wireless radio channels. Then it goes over the basics of OFDM and channel coding. The second part starts with an overview of the OFDM receiver, and develops various modules for the receiver des

TurtleCam: A “Smart” Autonomous Underwater Vehicle for Investigating Behaviors and Habitats of Sea Turtles

Directory of Open Access Journals (Sweden)

Kara L. Dodge

2018-03-01

Full Text Available Sea turtles inhabiting coastal environments routinely encounter anthropogenic hazards, including fisheries, vessel traffic, pollution, dredging, and drilling. To support mitigation of potential threats, it is important to understand fine-scale sea turtle behaviors in a variety of habitats. Recent advancements in autonomous underwater vehicles (AUVs now make it possible to directly observe and study the subsurface behaviors and habitats of marine megafauna, including sea turtles. Here, we describe a “smart” AUV capability developed to study free-swimming marine animals, and demonstrate the utility of this technology in a pilot study investigating the behaviors and habitat of leatherback turtles (Dermochelys coriacea. We used a Remote Environmental Monitoring UnitS (REMUS-100 AUV, designated “TurtleCam,” that was modified to locate, follow and film tagged turtles for up to 8 h while simultaneously collecting environmental data. The TurtleCam system consists of a 100-m depth rated vehicle outfitted with a circular Ultra-Short BaseLine receiver array for omni-directional tracking of a tagged animal via a custom transponder tag that we attached to the turtle with two suction cups. The AUV collects video with six high-definition cameras (five mounted in the vehicle nose and one mounted aft and we added a camera to the animal-borne transponder tag to record behavior from the turtle's perspective. Since behavior is likely a response to habitat factors, we collected concurrent in situ oceanographic data (bathymetry, temperature, salinity, chlorophyll-a, turbidity, currents along the turtle's track. We tested the TurtleCam system during 2016 and 2017 in a densely populated coastal region off Cape Cod, Massachusetts, USA, where foraging leatherbacks overlap with fixed fishing gear and concentrated commercial and recreational vessel traffic. Here we present example data from one leatherback turtle to demonstrate the utility of TurtleCam. The

Underwater Acoustic Tracer System

Science.gov (United States)

2009-03-13

for controlling and utilizing supercavitating projectile dynamics to produce a distinctive radiated noise signal. (2) Description of the Prior Art...metallic objects which travel relatively closely to a magnetic pickup. For larger, high speed, underwater projectiles, supercavitating underwater vehicles...have been proposed for use. The conditions for supercavitation are known in the art. Supercavitation allows for higher speeds to be sustainable

A 20 MW podded ship underwater electromagnetic signature - the alternative electric field; Signature electromagnetique sous-marine d'un paquebot de 20 MW a pods - le champ electrique alternatif

Energy Technology Data Exchange (ETDEWEB)

Lucas, B.; Henocq, H.; Rannou, C. [Delegation Generale pour l' Armement, DET/GESMA, 75 - Paris (France); Albert, Th.; Harpin, D. [ALSTOM Marine (France); Bourguet, S.; Guerin, P. [Institut de Recherche en Electrotechnique et Electronique de Nantes Atlantique, 44 (France)

2006-03-15

Today, electric podded propulsion is used for many ships, cruise liners and Navy vessels.This propulsion uses high currents in extremely low frequencies (ELFE); currents flow through electrical network, equipment and pods. These alternative currents could generate important underwater electromagnetic field. GESMA has to quantify the level of this field and its impact on the signature of this kind of ship. Then, GESMA carried out electromagnetic measurements using a multi-sensors underwater and autonomous facility named AMI. It was placed on the route of a 20 MW podded ship, at one hundred meters depth from the surface. Especially, AMI observed an alternative radiated electric field... (authors)

Integrated synoptic surveys of the hydrodynamics and water-quality distributions in two Lake Michigan rivermouth mixing zones using an autonomous underwater vehicle and a manned boat

Science.gov (United States)

Jackson, P. Ryan; Reneau, Paul C.

2014-01-01

The U.S. Geological Survey (USGS), in cooperation with the National Monitoring Network for U.S. Coastal Waters and Tributaries, launched a pilot project in 2010 to determine the value of integrated synoptic surveys of rivermouths using autonomous underwater vehicle technology in response to a call for rivermouth research, which includes study domains that envelop both the fluvial and lacustrine boundaries of the rivermouth mixing zone. The pilot project was implemented at two Lake Michigan rivermouths with largely different scales, hydrodynamics, and settings, but employing primarily the same survey techniques and methods. The Milwaukee River Estuary Area of Concern (AOC) survey included measurements in the lower 2 to 3 miles of the Milwaukee, Menomonee, and Kinnickinnic Rivers and inner and outer Milwaukee Harbor. This estuary is situated in downtown Milwaukee, Wisconsin, and is the most populated basin that flows directly into Lake Michigan. In contrast, the Manitowoc rivermouth has a relatively small harbor separating the rivermouth from Lake Michigan, and the Manitowoc River Watershed is primarily agricultural. Both the Milwaukee and Manitowoc rivermouths are unregulated and allow free exchange of water with Lake Michigan. This pilot study of the Milwaukee River Estuary and Manitowoc rivermouth using an autonomous underwater vehicle (AUV) paired with a manned survey boat resulted in high spatial and temporal resolution datasets of basic water-quality parameter distributions and hydrodynamics. The AUV performed well in these environments and was found primarily well-suited for harbor and nearshore surveys of three-dimensional water-quality distributions. Both case studies revealed that the use of a manned boat equipped with an acoustic Doppler current profiler (ADCP) and multiparameter sonde (and an optional flow-through water-quality sampling system) was the best option for riverine surveys. To ensure that the most accurate and highest resolution velocity data

Motion analysis and trials of the deep sea hybrid underwater glider Petrel-II

Science.gov (United States)

Liu, Fang; Wang, Yan-hui; Wu, Zhi-liang; Wang, Shu-xin

2017-03-01

A hybrid underwater glider Petrel-II has been developed and field tested. It is equipped with an active buoyancy unit and a compact propeller unit. Its working modes have been expanded to buoyancy driven gliding and propeller driven level-flight, which can make the glider work in strong currents, as well as many other complicated ocean environments. Its maximal gliding speed reaches 1 knot and the propelling speed is up to 3 knots. In this paper, a 3D dynamic model of Petrel-II is derived using linear momentum and angular momentum equations. According to the dynamic model, the spiral motion in the underwater space is simulated for the gliding mode. Similarly the cycle motion on water surface and the depth-keeping motion underwater are simulated for the level-flight mode. These simulations are important to the performance analysis and parameter optimization for the Petrel-II underwater glider. The simulation results show a good agreement with field trials.

Optimal Node Placement in Underwater Wireless Sensor Networks

KAUST Repository

Felamban, M.

2013-03-25

Wireless Sensor Networks (WSN) are expected to play a vital role in the exploration and monitoring of underwater areas which are not easily reachable by humans. However, underwater communication via acoustic waves is subject to several performance limitations that are very different from those used for terresstrial networks. In this paper, we investigate node placement for building an initial underwater WSN infrastructure. We formulate this problem as a nonlinear mathematical program with the objective of minimizing the total transmission loss under a given number of sensor nodes and targeted coverage volume. The obtained solution is the location of each node represented via a truncated octahedron to fill out the 3D space. Experiments are conducted to verify the proposed formulation, which is solved using Matlab optimization tool. Simulation is also conducted using an ns-3 simulator, and the simulation results are consistent with the obtained results from mathematical model with less than 10% error.

Toward efficient task assignment and motion planning for large-scale underwater missions

Directory of Open Access Journals (Sweden)

Somaiyeh MahmoudZadeh

2016-10-01

Full Text Available An autonomous underwater vehicle needs to possess a certain degree of autonomy for any particular underwater mission to fulfil the mission objectives successfully and ensure its safety in all stages of the mission in a large-scale operating field. In this article, a novel combinatorial conflict-free task assignment strategy, consisting of an interactive engagement of a local path planner and an adaptive global route planner, is introduced. The method takes advantage of the heuristic search potency of the particle swarm optimization algorithm to address the discrete nature of routing-task assignment approach and the complexity of nondeterministic polynomial-time-hard path planning problem. The proposed hybrid method is highly efficient as a consequence of its reactive guidance framework that guarantees successful completion of missions particularly in cluttered environments. To examine the performance of the method in a context of mission productivity, mission time management, and vehicle safety, a series of simulation studies are undertaken. The results of simulations declare that the proposed method is reliable and robust, particularly in dealing with uncertainties, and it can significantly enhance the level of a vehicle’s autonomy by relying on its reactive nature and capability of providing fast feasible solutions.

Design of Field Experiments for Adaptive Sampling of the Ocean with Autonomous Vehicles

Science.gov (United States)

Zheng, H.; Ooi, B. H.; Cho, W.; Dao, M. H.; Tkalich, P.; Patrikalakis, N. M.

2010-05-01

Due to the highly non-linear and dynamical nature of oceanic phenomena, the predictive capability of various ocean models depends on the availability of operational data. A practical method to improve the accuracy of the ocean forecast is to use a data assimilation methodology to combine in-situ measured and remotely acquired data with numerical forecast models of the physical environment. Autonomous surface and underwater vehicles with various sensors are economic and efficient tools for exploring and sampling the ocean for data assimilation; however there is an energy limitation to such vehicles, and thus effective resource allocation for adaptive sampling is required to optimize the efficiency of exploration. In this paper, we use physical oceanography forecasts of the coastal zone of Singapore for the design of a set of field experiments to acquire useful data for model calibration and data assimilation. The design process of our experiments relied on the oceanography forecast including the current speed, its gradient, and vorticity in a given region of interest for which permits for field experiments could be obtained and for time intervals that correspond to strong tidal currents. Based on these maps, resources available to our experimental team, including Autonomous Surface Craft (ASC) are allocated so as to capture the oceanic features that result from jets and vortices behind bluff bodies (e.g., islands) in the tidal current. Results are summarized from this resource allocation process and field experiments conducted in January 2009.

Dynamics and Control of Underwater Gliders I: Steady Motions

OpenAIRE

Mahmoudian, N.; Geisbert, J.; Woolsey, C.

2007-01-01

This paper describes analysis of steady motions for underwater gliders, a type of highly efficient underwater vehicle which uses gravity for propulsion. Underwater gliders are winged underwater vehicles which locomote by modulating their buoyancy and their attitude. Several such vehicles have been developed and have proven their worth as efficient long-distance, long-duration ocean sampling platforms. To date, the primary emphasis in underwater glider development has been on locomotive effici...

Monitoring Coral Growth - the Dichotomy Between Underwater Photogrammetry and Geodetic Control Network

Science.gov (United States)

Neyer, F.; Nocerino, E.; Gruen, A.

2018-05-01

Creating 3-dimensional (3D) models of underwater scenes has become a common approach for monitoring coral reef changes and its structural complexity. Also in underwater archeology, 3D models are often created using underwater optical imagery. In this paper, we focus on the aspect of detecting small changes in the coral reef using a multi-temporal photogrammetric modelling approach, which requires a high quality control network. We show that the quality of a good geodetic network limits the direct change detection, i.e., without any further registration process. As the photogrammetric accuracy is expected to exceed the geodetic network accuracy by at least one order of magnitude, we suggest to do a fine registration based on a number of signalized points. This work is part of the Moorea Island Digital Ecosystem Avatar (IDEA) project that has been initiated in 2013 by a group of international researchers (https://mooreaidea.ethz.ch/).

Safety performance monitoring of autonomous marine systems

International Nuclear Information System (INIS)

Thieme, Christoph A.; Utne, Ingrid B.

2017-01-01

The marine environment is vast, harsh, and challenging. Unanticipated faults and events might lead to loss of vessels, transported goods, collected scientific data, and business reputation. Hence, systems have to be in place that monitor the safety performance of operation and indicate if it drifts into an intolerable safety level. This article proposes a process for developing safety indicators for the operation of autonomous marine systems (AMS). The condition of safety barriers and resilience engineering form the basis for the development of safety indicators, synthesizing and further adjusting the dual assurance and the resilience based early warning indicator (REWI) approaches. The article locates the process for developing safety indicators in the system life cycle emphasizing a timely implementation of the safety indicators. The resulting safety indicators reflect safety in AMS operation and can assist in planning of operations, in daily operational decision-making, and identification of improvements. Operation of an autonomous underwater vehicle (AUV) exemplifies the process for developing safety indicators and their implementation. The case study shows that the proposed process leads to a comprehensive set of safety indicators. It is expected that application of the resulting safety indicators consequently will contribute to safer operation of current and future AMS. - Highlights: • Process for developing safety indicators for autonomous marine systems. • Safety indicators based on safety barriers and resilience thinking. • Location of the development process in the system lifecycle. • Case study on AUV demonstrating applicability of the process.

Underwater welding and repair technologies applied in PWR environment

International Nuclear Information System (INIS)

Scandella, Fabrice; Carpreau, Jean-Michel

2012-01-01

The authors describe several welding processes and technologies which have been used for underwater applications and which can be applied when repairing components of a PWR type reactor. They address, describe and discuss wet arc welding processes, the peculiarities of underwater welding, and the use of various processes such as 111, 114 and 135 processes, underwater welding with the hybrid plasma MIG-MAG process, underwater welding with the laser wire process, underwater welding with the FSW, FSP or UWFSW processes, underwater welding with variants of the friction welding process (friction surfacing, taper stitch welding, hydro-pillar processing

Network lifetime-aware data collection in Underwater Sensor ...

Indian Academy of Sciences (India)

Jalaja Janardanan Kartha

2017-09-07

Sep 7, 2017 ... existing models to assess their effectiveness and to investigate the trade-offs. Results show ... coverage drops below a predefined threshold and (vi) connectivity is .... Cost Clustering Protocol (MCCP), Distributed Underwater.

Underwater Optical Wireless Communications, Networking, and Localization: A Survey

KAUST Repository

Saeed, Nasir; Celik, Abdulkadir; Al-Naffouri, Tareq Y.; Alouini, Mohamed-Slim

2018-01-01

Underwater wireless communications can be carried out through acoustic, radio frequency (RF), and optical waves. Compared to its bandwidth limited acoustic and RF counterparts, underwater optical wireless communications (UOWCs) can support higher data rates at low latency levels. However, severe aquatic channel conditions (e.g., absorption, scattering, turbulence, etc.) pose great challenges for UOWCs and significantly reduce the attainable communication ranges, which necessitates efficient networking and localization solutions. Therefore, we provide a comprehensive survey on the challenges, advances, and prospects of underwater optical wireless networks (UOWNs) from a layer by layer perspective which includes: 1) Potential network architectures; 2) Physical layer issues including propagation characteristics, channel modeling, and modulation techniques 3) Data link layer problems covering link configurations, link budgets, performance metrics, and multiple access schemes; 4) Network layer topics containing relaying techniques and potential routing algorithms; 5) Transport layer subjects such as connectivity, reliability, flow and congestion control; 6) Application layer goals and state-of-the-art UOWN applications, and 7) Localization and its impacts on UOWN layers. Finally, we outline the open research challenges and point out the future directions for underwater optical wireless communications, networking, and localization research.

Underwater Optical Wireless Communications, Networking, and Localization: A Survey

KAUST Repository

Saeed, Nasir

2018-02-28

Underwater wireless communications can be carried out through acoustic, radio frequency (RF), and optical waves. Compared to its bandwidth limited acoustic and RF counterparts, underwater optical wireless communications (UOWCs) can support higher data rates at low latency levels. However, severe aquatic channel conditions (e.g., absorption, scattering, turbulence, etc.) pose great challenges for UOWCs and significantly reduce the attainable communication ranges, which necessitates efficient networking and localization solutions. Therefore, we provide a comprehensive survey on the challenges, advances, and prospects of underwater optical wireless networks (UOWNs) from a layer by layer perspective which includes: 1) Potential network architectures; 2) Physical layer issues including propagation characteristics, channel modeling, and modulation techniques 3) Data link layer problems covering link configurations, link budgets, performance metrics, and multiple access schemes; 4) Network layer topics containing relaying techniques and potential routing algorithms; 5) Transport layer subjects such as connectivity, reliability, flow and congestion control; 6) Application layer goals and state-of-the-art UOWN applications, and 7) Localization and its impacts on UOWN layers. Finally, we outline the open research challenges and point out the future directions for underwater optical wireless communications, networking, and localization research.

Particle Filter for Fault Diagnosis and Robust Navigation of Underwater Robot

DEFF Research Database (Denmark)

Zhao, Bo; Skjetne, Roger; Blanke, Mogens

2014-01-01

A particle filter based robust navigation with fault diagnosis is designed for an underwater robot, where 10 failure modes of sensors and thrusters are considered. The nominal underwater robot and its anomaly are described by a switchingmode hidden Markov model. By extensively running a particle...... filter on the model, the fault diagnosis and robust navigation are achieved. Closed-loop full-scale experimental results show that the proposed method is robust, can diagnose faults effectively, and can provide good state estimation even in cases where multiple faults occur. Comparing with other methods...

The vortex mechanism of suppression of tsunami waves by underwater obstacles

Science.gov (United States)

Boshenyatov, B. V.

2017-12-01

A theoretical model explaining the effect of anomalous suppression of the energy (up to 70%) of tsunami-type waves by thin (compared to the wavelength) underwater obstacles is developed based on the integral laws of conservation of mass and energy fluxes. It is shown that the analytical dependences for the coefficients of reflection and transmission of waves across an underwater obstacle that have been obtained using the theoretical model proposed by the author agree with the results of the experiments and numerical simulation based on the complete Navier-Stokes equations.

Autonomous underwater handling system for service, measurement and cutting tasks for the decommissioning of nuclear facilities

International Nuclear Information System (INIS)

Hahn, M.; Haferkamp, H.; Bach, W.; Rose, N.

1992-01-01

For about 10 years the Institute for Material Science at the Hanover University has worked on projects of underwater cutting and welding. Increasing tasks to be done in nuclear facilities led to the development of special handling systems to support and handle the cutting tools. Also sensors and computers for extensive and complex tasks were integrated. A small sized freediving handling system, equipped with 2 video cameras, ultrasonic and radiation sensors and a plasma cutting torch for inspection and decommissioning tasks in nuclear facilities is described in this paper. (Author)

Study of underwater laser propulsion using different target materials.

Science.gov (United States)

Qiang, Hao; Chen, Jun; Han, Bing; Shen, Zhong-Hua; Lu, Jian; Ni, Xiao-Wu

2014-07-14

In order to investigate the influence of target materials, including aluminum (Al), titanium (Ti) and copper (Cu), on underwater laser propulsion, the analytical formula of the target momentum IT is deduced from the enhanced coupling theory of laser propulsion in atmosphere with transparent overlay metal target. The high-speed photography method and numerical simulation are employed to verify the IT model. It is shown that the enhanced coupling theory, which was developed originally for laser propulsion in atmosphere, is also applicable to underwater laser propulsion with metal targets.

Cooperative Rendezvous and Docking for Underwater Robots Using Model Predictive Control and Dual Decomposition

DEFF Research Database (Denmark)

Nielsen, Mikkel Cornelius; Johansen, Tor Arne; Blanke, Mogens

2018-01-01

This paper considers the problem of rendezvous and docking with visual constraints in the context of underwater robots with camera-based navigation. The objective is the convergence of the vehicles to a common point while maintaining visual contact. The proposed solution includes the design of a ...... of a distributed model predictive controller based on dual decomposition, which allows for optimization in a decentralized fashion. The proposed distributed controller enables rendezvous and docking between vehicles while maintaining visual contact....

Underwater Electromagnetic Sensor Networks—Part I: Link Characterization

Directory of Open Access Journals (Sweden)

Gara Quintana-Díaz

2017-01-01

Full Text Available Underwater Wireless Sensor Networks (UWSNs using electromagnetic (EM technology in marine shallow waters are examined, not just for environmental monitoring but for further interesting applications. Particularly, the use of EM waves is reconsidered in shallow waters due to the benefits offered in this context, where acoustic and optical technologies have serious disadvantages. Sea water scenario is a harsh environment for radiocommunications, and there is no standard model for the underwater EM channel. The high conductivity of sea water, the effect of seabed and the surface make the behaviour of the channel hard to predict. This justifies the need of link characterization as the first step to approach the development of EM underwater sensor networks. To obtain a reliable link model, measurements and simulations are required. The measuring setup for this purpose is explained and described, as well as the procedures used. Several antennas have been designed and tested in low frequency bands. Agreement between attenuation measurements and simulations at different distances was analysed and made possible the validation of simulation setups and the design of different communications layers of the system. This leads to the second step of this work, where data and routing protocols for the sensor network are examined.

Physical and numerical modeling of hydrophysical proceses on the site of underwater pipelines

Science.gov (United States)

Garmakova, M. E.; Degtyarev, V. V.; Fedorova, N. N.; Shlychkov, V. A.

2018-03-01

The paper outlines issues related to ensuring the exploitation safety of underwater pipelines that are at risk of accidents. The performed research is based on physical and mathematical modeling of local bottom erosion in the area of pipeline location. The experimental studies were performed on the basis of the Hydraulics Laboratory of the Department of Hydraulic Engineering Construction, Safety and Ecology of NSUACE (Sibstrin). In the course of physical experiments it was revealed that the intensity of the bottom soil reforming depends on the deepening of the pipeline. The ANSYS software has been used for numerical modeling. The process of erosion of the sandy bottom was modeled under the pipeline. Comparison of computational results at various mass flow rates was made.

Simple statistical channel model for weak temperature-induced turbulence in underwater wireless optical communication systems

KAUST Repository

Oubei, Hassan M.

2017-06-16

In this Letter, we use laser beam intensity fluctuation measurements to model and describe the statistical properties of weak temperature-induced turbulence in underwater wireless optical communication (UWOC) channels. UWOC channels with temperature gradients are modeled by the generalized gamma distribution (GGD) with an excellent goodness of fit to the measured data under all channel conditions. Meanwhile, thermally uniform channels are perfectly described by the simple gamma distribution which is a special case of GGD. To the best of our knowledge, this is the first model that comprehensively describes both thermally uniform and gradient-based UWOC channels.

Underwater Ranging

OpenAIRE

S. P. Gaba

1984-01-01

The paper deals with underwater laser ranging system, its principle of operation and maximum depth capability. The sources of external noise and methods to improve signal-to-noise ratio are also discussed.

Modelling of a PMSG Wind Turbine with Autonomous Control

Directory of Open Access Journals (Sweden)

Chia-Nan Wang

2014-01-01

Full Text Available The aim of this research is to model an autonomous control wind turbine driven permanent magnetic synchronous generator (PMSG which feeds alternating current (AC power to the utility grid. Furthermore, this research also demonstrates the effects and the efficiency of PMSG wind turbine which is integrated by autonomous controllers. In order for well autonomous control, two voltage source inverters are used to control wind turbine connecting with the grid. The generator-side inverter is used to adjust the synchronous generator as well as separating the generator from the grid when necessary. The grid-side inverter controls the power flow between the direct current (DC bus and the AC side. Both of them are oriented control by space vector pulse width modulation (PWM with back-to-back frequency inverter. Moreover, the proportional-integral (PI controller is enhanced to control both of the inverters and the pitch angle of the wind turbine. Maximum power point tracking (MPPT is integrated in generator-side inverter to track the maximum power, when wind speed changes. The simulation results in Matlab Simulink 2012b showing the model have good dynamic and static performance. The maximum power can be tracked and the generator wind turbine can be operated with high efficiency.

UNDERWATER COATINGS FOR CONTAMINATION CONTROL

International Nuclear Information System (INIS)

Julia L. Tripp; Kip Archibald; Ann Marie Phillips; Joseph Campbell

2004-01-01

The Idaho National Laboratory (INL) deactivated several aging nuclear fuel storage basins. Planners for this effort were greatly concerned that radioactive contamination present on the basin walls could become airborne as the sides of the basins became exposed during deactivation and allowed to dry after water removal. One way to control this airborne contamination was to fix the contamination in place while the pool walls were still submerged. There are many underwater coatings available on the market for marine, naval and other applications. A series of tests were run to determine whether the candidate underwater fixatives were easily applied and adhered well to the substrates (pool wall materials) found in INL fuel pools. Lab-scale experiments were conducted by applying fourteen different commercial underwater coatings to four substrate materials representative of the storage basin construction materials, and evaluating their performance. The coupons included bare concrete, epoxy painted concrete, epoxy painted carbon steel, and stainless steel. The evaluation criteria included ease of application, adherence to the four surfaces of interest, no change on water clarity or chemistry, non-hazardous in final applied form and be proven in underwater applications. A proprietary two-part, underwater epoxy owned by S. G. Pinney and Associates was selected from the underwater coatings tested for application to all four pools. Divers scrubbed loose contamination off the basin walls and floors using a ship hull scrubber and vacuumed up the sludge. The divers then applied the coating using a special powered roller with two separate heated hoses that allowed the epoxy to mix at the roller surface was used to eliminate pot time concerns. The walls were successfully coated and water was removed from the pools with no detectable airborne contamination releases

Underwater Gliders: A Review

OpenAIRE

Javaid Muhammad Yasar; Ovinis Mark; Nagarajan T; Hashim Fakhruldin B M

2014-01-01

Underwater gliders are a type of underwater vehicle that transverse the oceans by shifting its buoyancy, during which its wings develop a component of the downward motion in the horizontal plane, thus producing a forward force. They are primarily used in oceanography sensing and data collection and play an important role in ocean research and development. Although there have been considerable developments in these gliders since the development of the first glider concept in 1989, to date, no ...

Underwater Calibration of Dome Port Pressure Housings

Science.gov (United States)

Nocerino, E.; Menna, F.; Fassi, F.; Remondino, F.

2016-03-01

Underwater photogrammetry using consumer grade photographic equipment can be feasible for different applications, e.g. archaeology, biology, industrial inspections, etc. The use of a camera underwater can be very different from its terrestrial use due to the optical phenomena involved. The presence of the water and camera pressure housing in front of the camera act as additional optical elements. Spherical dome ports are difficult to manufacture and consequently expensive but at the same time they are the most useful for underwater photogrammetry as they keep the main geometric characteristics of the lens unchanged. Nevertheless, the manufacturing and alignment of dome port pressure housing components can be the source of unexpected changes of radial and decentring distortion, source of systematic errors that can influence the final 3D measurements. The paper provides a brief introduction of underwater optical phenomena involved in underwater photography, then presents the main differences between flat and dome ports to finally discuss the effect of manufacturing on 3D measurements in two case studies.

Cluster protocols in Underwater Sensor Networks: a Research Review

Directory of Open Access Journals (Sweden)

K. Ovaliadis

2014-07-01

Full Text Available Underwater Wireless Sensor Networks (UWSN have different characteristics in relation to terrestrial wireless sensor networks; such as limited bandwidth capacity, high propagation delays and limited battery power. Although there has been much work completed in developing protocols and models for terrestrial networks, these are rarely applicable for underwater sensor networks. Up to today major efforts have been made for designing efficient protocols while considering the underwater communication characteristics. An important issue on this research area is the construction of an efficient clustering algorithm. Clustering in the context of UWSN is important as it contributes a great deal towards the efficient use of energy resources. This paper reviews the most significant cluster based protocols proposed for UWSN. Major performance issues of these protocols with respect to the network conditions such as packet delivery ratio, average packet delay, node mobility effect and energy consumption are examined. The advantages and disadvantages of each protocol are also pointed out.

Underwater floating robot-fish: a comparative analysis of the results of mathematical modelling and full-scale tests of the prototype

Directory of Open Access Journals (Sweden)

Jatsun Sergey

2017-01-01

Full Text Available The article presents a comparative analysis of the results of computer mathematical modelling of the motion of the underwater robot-fish implemented by using the MATLAB / Simulink package and fullscale tests of an experimental model developed in the laboratory of mechatronics and robotics of the SouthWest State University.

Nonlinear H∞ Optimal Control Scheme for an Underwater Vehicle with Regional Function Formulation

Directory of Open Access Journals (Sweden)

Zool H. Ismail

2013-01-01

Full Text Available A conventional region control technique cannot meet the demands for an accurate tracking performance in view of its inability to accommodate highly nonlinear system dynamics, imprecise hydrodynamic coefficients, and external disturbances. In this paper, a robust technique is presented for an Autonomous Underwater Vehicle (AUV with region tracking function. Within this control scheme, nonlinear H∞ and region based control schemes are used. A Lyapunov-like function is presented for stability analysis of the proposed control law. Numerical simulations are presented to demonstrate the performance of the proposed tracking control of the AUV. It is shown that the proposed control law is robust against parameter uncertainties, external disturbances, and nonlinearities and it leads to uniform ultimate boundedness of the region tracking error.

Study of Command and Control (C&C) Structures on Integrating Unmanned Autonomous Systems (UAS) into Manned Environments

Science.gov (United States)

2012-09-01

and traveled all the way around Lake Tahoe. The self - driving cars have logged over 140,000 miles since October 9, 2010 (Google 2010) pictured here...UNDERWATER VEHICLES (AUV) STARFISH is the name given to a small team of autonomous robotic fish - a project carried out by the Acoustic Research...www.scribd.com/doc/42245301/Manual-Mine- Clearance-Book1. Accessed July 23, 2012. Google. The Self - Driving Car Logs more Miles on New Wheels. August 7

A thermal engine for underwater glider driven by ocean thermal energy

International Nuclear Information System (INIS)

Yang, Yanan; Wang, Yanhui; Ma, Zhesong; Wang, Shuxin

2016-01-01

Highlights: • Thermal engine with a double-tube structure is developed for underwater glider. • Isostatic pressing technology is effective to increase volumetric change rate. • Actual volumetric change rate reaches 89.2% of the theoretical value. • Long term sailing of 677 km and 27 days is achieved by thermal underwater glider. - Graphical Abstract: - Abstract: Underwater glider is one of the most popular platforms for long term ocean observation. Underwater glider driven by ocean thermal energy extends the duration and range of underwater glider powered by battery. Thermal engine is the core device of underwater glider to harvest ocean thermal energy. In this paper, (1) model of thermal engine was raised by thermodynamics method and the performance of thermal engine was investigated, (2) thermal engine with a double-tube structure was developed and isostatic pressing technology was applied to improve the performance for buoyancy driven, referencing powder pressing theory, (3) wall thickness of thermal engine was optimized to reduce the overall weight of thermal engine, (4) material selection and dimension determination were discussed for a faster heat transfer design, by thermal resistance analysis, (5) laboratory test and long term sea trail were carried out to test the performance of thermal engine. The study shows that volumetric change rate is the most important indicator to evaluating buoyancy-driven performance of a thermal engine, isostatic pressing technology is effective to improve volumetric change rate, actual volumetric change rate can reach 89.2% of the theoretical value and the average power is about 124 W in a typical diving profile. Thermal engine developed by Tianjin University is a superior thermal energy conversion device for underwater glider. Additionally, application of thermal engine provides a new solution for miniaturization of ocean thermal energy conversion.

H∞ control of a remotely operated underwater vehicle

International Nuclear Information System (INIS)

Conte, G.; Serrani, A.

1994-01-01

The paper discusses the application of H∞ control techniques to the design of a control system for a remotely operated underwater vehicle. As the main problem in defining a control strategy for such vehicles is the nonlinear and uncertain nature of the modeled dynamics, the robustness properties of H∞ controllers can in principle be used to provide stability and nominal performances for the closed loop system. Therefore, a control strategy based on a scheduling of such controllers has been proposed, and the overall performance of the closed loop system have been evaluated by means of nonlinear simulation in a broad range of working conditions, with particular attention to the effects of the underwater current that acts on the vehicle

On the Accuracy Potential in Underwater/Multimedia Photogrammetry.

Science.gov (United States)

Maas, Hans-Gerd

2015-07-24

Underwater applications of photogrammetric measurement techniques usually need to deal with multimedia photogrammetry aspects, which are characterized by the necessity of handling optical rays that are refracted at interfaces between optical media with different refractive indices according to Snell's Law. This so-called multimedia geometry has to be incorporated into geometric models in order to achieve correct measurement results. The paper shows a flexible yet strict geometric model for the handling of refraction effects on the optical path, which can be implemented as a module into photogrammetric standard tools such as spatial resection, spatial intersection, bundle adjustment or epipolar line computation. The module is especially well suited for applications, where an object in water is observed by cameras in air through one or more planar glass interfaces, as it allows for some simplifications here. In the second part of the paper, several aspects, which are relevant for an assessment of the accuracy potential in underwater/multimedia photogrammetry, are discussed. These aspects include network geometry and interface planarity issues as well as effects caused by refractive index variations and dispersion and diffusion under water. All these factors contribute to a rather significant degradation of the geometric accuracy potential in underwater/multimedia photogrammetry. In practical experiments, a degradation of the quality of results by a factor two could be determined under relatively favorable conditions.

An adaptive grid to improve the efficiency and accuracy of modelling underwater noise from shipping

Science.gov (United States)

Trigg, Leah; Chen, Feng; Shapiro, Georgy; Ingram, Simon; Embling, Clare

2017-04-01

Underwater noise from shipping is becoming a significant concern and has been listed as a pollutant under Descriptor 11 of the Marine Strategy Framework Directive. Underwater noise models are an essential tool to assess and predict noise levels for regulatory procedures such as environmental impact assessments and ship noise monitoring. There are generally two approaches to noise modelling. The first is based on simplified energy flux models, assuming either spherical or cylindrical propagation of sound energy. These models are very quick but they ignore important water column and seabed properties, and produce significant errors in the areas subject to temperature stratification (Shapiro et al., 2014). The second type of model (e.g. ray-tracing and parabolic equation) is based on an advanced physical representation of sound propagation. However, these acoustic propagation models are computationally expensive to execute. Shipping noise modelling requires spatial discretization in order to group noise sources together using a grid. A uniform grid size is often selected to achieve either the greatest efficiency (i.e. speed of computations) or the greatest accuracy. In contrast, this work aims to produce efficient and accurate noise level predictions by presenting an adaptive grid where cell size varies with distance from the receiver. The spatial range over which a certain cell size is suitable was determined by calculating the distance from the receiver at which propagation loss becomes uniform across a grid cell. The computational efficiency and accuracy of the resulting adaptive grid was tested by comparing it to uniform 1 km and 5 km grids. These represent an accurate and computationally efficient grid respectively. For a case study of the Celtic Sea, an application of the adaptive grid over an area of 160×160 km reduced the number of model executions required from 25600 for a 1 km grid to 5356 in December and to between 5056 and 13132 in August, which

Novel microbial diversity retrieved by autonomous robotic exploration of the world's deepest vertical phreatic sinkhole.

Science.gov (United States)

Sahl, Jason W; Fairfield, Nathaniel; Harris, J Kirk; Wettergreen, David; Stone, William C; Spear, John R

2010-03-01

The deep phreatic thermal explorer (DEPTHX) is an autonomous underwater vehicle designed to navigate an unexplored environment, generate high-resolution three-dimensional (3-D) maps, collect biological samples based on an autonomous sampling decision, and return to its origin. In the spring of 2007, DEPTHX was deployed in Zacatón, a deep (approximately 318 m), limestone, phreatic sinkhole (cenote) in northeastern Mexico. As DEPTHX descended, it generated a 3-D map based on the processing of range data from 54 onboard sonars. The vehicle collected water column samples and wall biomat samples throughout the depth profile of the cenote. Post-expedition sample analysis via comparative analysis of 16S rRNA gene sequences revealed a wealth of microbial diversity. Traditional Sanger gene sequencing combined with a barcoded-amplicon pyrosequencing approach revealed novel, phylum-level lineages from the domains Bacteria and Archaea; in addition, several novel subphylum lineages were also identified. Overall, DEPTHX successfully navigated and mapped Zacatón, and collected biological samples based on an autonomous decision, which revealed novel microbial diversity in a previously unexplored environment.

Underwater 3D filming

OpenAIRE

Rinaldi, Roberto

2014-01-01

After an experimental phase of many years, 3D filming is now effective and successful. Improvements are still possible, but the film industry achieved memorable success on 3D movie’s box offices due to the overall quality of its products. Special environments such as space (“Gravity” ) and the underwater realm look perfect to be reproduced in 3D. “Filming in space” was possible in “Gravity” using special effects and computer graphic. The underwater realm is still difficult to be handled. Unde...

IVO develops a new repair technique for underwater sites. Viscous doughlike substance underwater cracks

Energy Technology Data Exchange (ETDEWEB)

Klingstedt, G.; Leisio, C. [ed.

1998-07-01

A viscous sealant is revolutionizing repair of the stone and concrete masonry of underwater dams, bridges and canals. There is now no need for expensive and time-consuming cofferdams, since a diver can extrude quick-setting mortar into underwater structures needing repair. This technique has worked well in recent years in various parts of Finland even in strongly flowing water. IVO experts are now starting to look more beyond the borders of Finland

A man-made object detection for underwater TV

Science.gov (United States)

Cheng, Binbin; Wang, Wenwu; Chen, Yao

2018-03-01

It is a great challenging task to complete an automatic search of objects underwater. Usually the forward looking sonar is used to find the target, and then the initial identification of the target is completed by the side-scan sonar, and finally the confirmation of the target is accomplished by underwater TV. This paper presents an efficient method for automatic extraction of man-made sensitive targets in underwater TV. Firstly, the image of underwater TV is simplified with taking full advantage of the prior knowledge of the target and the background; then template matching technology is used for target detection; finally the target is confirmed by extracting parallel lines on the target contour. The algorithm is formulated for real-time execution on limited-memory commercial-of-the-shelf platforms and is capable of detection objects in underwater TV.

Geographical positioning using laser optical instrument for near-shore underwater archaeological explorations

Digital Repository Service at National Institute of Oceanography (India)

Ganesan, P.

carefully identified comers of the underwater artifacts) is found to be more accurate, faster, and reliable. This method can be effectively used only for shallow water near shore underwater archaeo- GLIMPSES OF MARINE ARCHAEOLOGY IN INDIA logical... Trak (placed over selected ground controi station) and a multi-prism (placed over carefully identified comers of the artifact). The standard survey procedures prescribed in the Laser Trak operation manual (Make III model) were used to carry out...

A climatology of the California Current System from a network of underwater gliders

Science.gov (United States)

Rudnick, Daniel L.; Zaba, Katherine D.; Todd, Robert E.; Davis, Russ E.

2017-05-01

Autonomous underwater gliders offer the possibility of sustained observation of the coastal ocean. Since 2006 Spray underwater gliders in the California Underwater Glider Network (CUGN) have surveyed along California Cooperative Oceanic Fisheries Investigations (CalCOFI) lines 66.7, 80.0, and 90.0, constituting the world's longest sustained glider network, to our knowledge. In this network, gliders dive between the surface and 500 m, completing a cycle in 3 h and covering 3 km in that time. Sections extend 350-500 km offshore and take 2-3 weeks to occupy. Measured variables include pressure, temperature, salinity, and depth-average velocity. The CUGN has amassed over 10,000 glider-days, covering over 210,000 km with over 95,000 dives. These data are used to produce a climatology whose products are for each variable a mean field, an annual cycle, and the anomaly from the annual cycle. The analysis includes a weighted least-squares fit to derive the mean and annual cycle, and an objective map to produce the anomaly. The final results are variables on rectangular grids in depth, distance offshore, and time. The mean fields are finely resolved sections across the main flows in the California Current System, including the poleward California Undercurrent and the equatorward California Current. The annual cycle shows a phase change from the surface to the thermocline, reflecting the effects of air/sea fluxes at the surface and upwelling in the thermocline. The interannual anomalies are examined with an emphasis on climate events of the last ten years including the 2009-2010 El Niño, the 2010-2011 La Niña, the warm anomaly of 2014-2015, and the 2015-2016 El Niño.

Remote Underwater Characterization System - Innovative Technology Summary Report

International Nuclear Information System (INIS)

Willis, Walter David

1999-01-01

Characterization and inspection of water-cooled and moderated nuclear reactors and fuel storage pools requires equipment capable of operating underwater. Similarly, the deactivation and decommissioning of older nuclear facilities often requires the facility owner to accurately characterize underwater structures and equipment which may have been sitting idle for years. The underwater characterization equipment is often required to operate at depths exceeding 20 ft (6.1 m) and in relatively confined or congested spaces. The typical baseline approach has been the use of radiation detectors and underwater cameras mounted on long poles, or stationary cameras with pan and tilt features mounted on the sides of the underwater facility. There is a perceived need for an inexpensive, more mobile method of performing close-up inspection and radiation measurements in confined spaces underwater. The Remote Underwater Characterization System (RUCS) is a small, remotely operated submersible vehicle intended to serve multiple purposes in underwater nuclear operations. It is based on the commercially-available ''Scallop'' vehicle, but has been modified by Department of Energy's Robotics Technology Development Program to add auto-depth control, and vehicle orientation and depth monitoring at the operator control panel. The RUCS is designed to provide visual and gamma radiation characterization, even in confined or limited access areas. It was demonstrated in August 1998 at Idaho National Engineering and environmental Laboratory (INEEL) as part of the INEEL Large Scale Demonstration and Deployment Project. During the demonstration it was compared in a ''head-to-head'' fashion with the baseline characterization technology. This paper summarizes the results of the demonstration and lessons learned; comparing and contrasting both technologies in the areas of cost, visual characterization, radiological characterization, and overall operations

Limiting Performance Analysis of Underwater Shock Isolation of a System with Biodynamic Response Using Genetic Algorithm

Directory of Open Access Journals (Sweden)

Z. Zong

2000-01-01

Full Text Available Biodynamic response of shipboard crew to underwater shock is of a major concern to navies. An underwater shock can produce very high accelerations, resulting in severe human injuries aboard a battleship. Protection of human bodies from underwater shock is implemented by installing onboard isolators. In this paper, the optimal underwater shock isolation to protect human bodies is studied. A simple shock-structure-isolator-human interaction model is first constructed. The model incorporates the effect of fluid-structure interaction, biodynamic response of human body, isolator influence. Based on this model, the optimum shock isolation is then formulated. The performance index and restriction are defined. Thirdly, GA (genetic algorithm is employed to solve the formulated optimization problem. GA is a powerful evolutionary optimization scheme suitable for large-scale and multi-variable optimization problems that are otherwise hard to be solved by conventional methods. A brief introduction to GA is given in the paper. Finally, the method is applied to an example problem and the limiting performance characteristic is obtained.

Underwater fiber-wireless communication with a passive front end

Science.gov (United States)

Xu, Jing; Sun, Bin; Lyu, Weichao; Kong, Meiwei; Sarwar, Rohail; Han, Jun; Zhang, Wei; Deng, Ning

2017-11-01

We propose and experimentally demonstrate a novel concept on underwater fiber-wireless (Fi-Wi) communication system with a fully passive wireless front end. A low-cost step-index (SI) plastic optical fiber (POF) together with a passive collimating lens at the front end composes the underwater Fi-Wi architecture. We have achieved a 1.71-Gb/s transmission at a mean BER of 4.97 × 10-3 (1.30 × 10-3 when using power loading) over a 50-m SI-POF and 2-m underwater wireless channel using orthogonal frequency division multiplexing (OFDM). Although the wireless part is very short, it actually plays a crucial role in practical underwater implementation, especially in deep sea. Compared with the wired solution (e.g. using a 52-m POF cable without the UWOC part), the proposed underwater Fi-Wi scheme can save optical wet-mate connectors that are sophisticated, very expensive and difficult to install in deep ocean. By combining high-capacity robust POF with the mobility and ubiquity of underwater wireless optical communication (UWOC), the proposed underwater Fi-Wi technology will find wide application in ocean exploration.

Systems, methods and apparatus for modeling, specifying and deploying policies in autonomous and autonomic systems using agent-oriented software engineering

Science.gov (United States)

Hinchey, Michael G. (Inventor); Penn, Joaquin (Inventor); Sterritt, Roy (Inventor)

2011-01-01

Systems, methods and apparatus are provided through which in some embodiments, an agent-oriented specification modeled with MaCMAS, is analyzed, flaws in the agent-oriented specification modeled with MaCMAS are corrected, and an implementation is derived from the corrected agent-oriented specification. Described herein are systems, method and apparatus that produce fully (mathematically) tractable development of agent-oriented specification(s) modeled with methodology fragment for analyzing complex multiagent systems (MaCMAS) and policies for autonomic systems from requirements through to code generation. The systems, method and apparatus described herein are illustrated through an example showing how user formulated policies can be translated into a formal mode which can then be converted to code. The requirements-based programming systems, method and apparatus described herein may provide faster, higher quality development and maintenance of autonomic systems based on user formulation of policies.

Modeling of Combined Phenomena Affecting an AUV Stealth Vehicle

Directory of Open Access Journals (Sweden)

Miroslaw Gerigk

2016-12-01

Full Text Available In the paper some results of research connected with modeling the basic stealth characteristics of an AUV vehicle are presented. First of all a general approach to design of the stealth AUV autonomous underwater vehicles under consideration is introduced. Then the AUV stealth vehicle concept is briefly described. Next a method of modeling of the stealth characteristics is briefly described. As an example of the stealth characteristics investigations some results of modeling the boundary layer and wake are presented. Some remarks regarding the behavior of the AUV stealth vehicle in the submerged conditions are given. The final conclusions are presented.

Delay Tolerance in Underwater Wireless Communications: A Routing Perspective

Directory of Open Access Journals (Sweden)

Safdar Hussain Bouk

2016-01-01

Full Text Available Similar to terrestrial networks, underwater wireless networks (UWNs also aid several critical tasks including coastal surveillance, underwater pollution detection, and other maritime applications. Currently, once underwater sensor nodes are deployed at different levels of the sea, it is nearly impossible or very expensive to reconfigure the hardware, for example, battery. Taking this issue into account, considerable amount of research has been carried out to ensure minimum energy costs and reliable communication between underwater nodes and base stations. As a result, several different network protocols were proposed for UWN, including MAC, PHY, transport, and routing. Recently, a new paradigm was introduced claiming that the intermittent nature of acoustic channel and signal resulted in designing delay tolerant routing schemes for the UWN, known as an underwater delay tolerant network. In this paper, we provide a comprehensive survey of underwater routing protocols with emphasis on the limitations, challenges, and future open issues in the context of delay tolerant network routing.

Stress, autonomic imbalance, and the prediction of metabolic risk: A model and a proposal for research.

Science.gov (United States)

Wulsin, Lawson; Herman, James; Thayer, Julian F

2018-03-01

Devising novel prevention strategies for metabolic disorders will depend in part on the careful elucidation of the common pathways for developing metabolic risks. The neurovisceral integration model has proposed that autonomic imbalance plays an important role in the pathway from acute and chronic stress to cardiovascular disease. Though generally overlooked by clinicians, autonomic imbalance (sympathetic overactivity and/or parasympathetic underactivity) can be measured and modified by methods that are available in primary care. This review applies the neurovisceral integration concept to the clinical setting by proposing that autonomic imbalance plays a primary role in the development of metabolic risks. We present a testable model, a systematic review of the evidence in support of autonomic imbalance as a predictor for metabolic risks, and specific approaches to test this model as a guide to future research on the role of stress in metabolic disorders. We propose that autonomic imbalance deserves consideration by researchers, clinicians, and policymakers as a target for early interventions to prevent metabolic disorders. Published by Elsevier Ltd.

Autonomous learning derived from experimental modeling of physical laws.

Science.gov (United States)

Grabec, Igor

2013-05-01

This article deals with experimental description of physical laws by probability density function of measured data. The Gaussian mixture model specified by representative data and related probabilities is utilized for this purpose. The information cost function of the model is described in terms of information entropy by the sum of the estimation error and redundancy. A new method is proposed for searching the minimum of the cost function. The number of the resulting prototype data depends on the accuracy of measurement. Their adaptation resembles a self-organized, highly non-linear cooperation between neurons in an artificial NN. A prototype datum corresponds to the memorized content, while the related probability corresponds to the excitability of the neuron. The method does not include any free parameters except objectively determined accuracy of the measurement system and is therefore convenient for autonomous execution. Since representative data are generally less numerous than the measured ones, the method is applicable for a rather general and objective compression of overwhelming experimental data in automatic data-acquisition systems. Such compression is demonstrated on analytically determined random noise and measured traffic flow data. The flow over a day is described by a vector of 24 components. The set of 365 vectors measured over one year is compressed by autonomous learning to just 4 representative vectors and related probabilities. These vectors represent the flow in normal working days and weekends or holidays, while the related probabilities correspond to relative frequencies of these days. This example reveals that autonomous learning yields a new basis for interpretation of representative data and the optimal model structure. Copyright © 2012 Elsevier Ltd. All rights reserved.

Underwater Wireless Optical Communications Systems: from System-Level Demonstrations to Channel Modeling

KAUST Repository

Oubei, Hassan M.

2018-01-01

Approximately, two-thirds of earth's surface is covered by water. There is a growing interest from the military and commercial communities in having, an efficient, secure and high bandwidth underwater wireless communication (UWC) system for tactical

Tracking Controller Design for Diving Behavior of an Unmanned Underwater Vehicle

Directory of Open Access Journals (Sweden)

Yi-Hsiang Tseng

2013-01-01

Full Text Available The study has investigated the almost disturbance decoupling problem of nonlinear uncertain control systems via the fuzzy feedback linearization approach. The significant dedication of this paper is to organize a control algorithm such that the closed-loop system is active for given initial condition and bounded tracking trajectory with the input-to-state stability and almost disturbance decoupling performance. This study presents a feedback linearization controller for diving control of an unmanned underwater vehicle. Unmanned underwater vehicle proposes difficult control subject due to its nonlinear dynamics, uncertain models, and the existence of disturbances that are difficult to measure. In general, while investigating the diving dynamics of an unmanned underwater vehicle, the pitch angle is always assumed to be small. This assumption is a strong restricting constraint in many interesting practical applications and will be relaxed in this study.

An Environment-Friendly Multipath Routing Protocol for Underwater Acoustic Sensor Network

Directory of Open Access Journals (Sweden)

Yun Li

2017-01-01

Full Text Available Underwater Acoustic Sensor Network (UASN is a promising technique by facilitating a wide range of aquatic applications. However, routing scheme in UASN is a challenging task because of the characteristics of the nodes mobility, interruption of link, and interference caused by other underwater acoustic systems such as marine mammals. In order to achieve reliable data delivery in UASN, in this work, we present a disjoint multipath disruption-tolerant routing protocol for UASN (ENMR, which incorporates the Hue, Saturation, and Value color space (HSV model to establish routing paths to greedily forward data packets to sink nodes. ENMR applies the mechanism to maintain the network topology. Simulation results show that, compared with the classic underwater routing protocols named PVBF, ENMR can improve packet delivery ratio and reduce network latency while avoiding introducing additional energy consumption.

DualTrust: A Trust Management Model for Swarm-Based Autonomic Computing Systems

Energy Technology Data Exchange (ETDEWEB)

Maiden, Wendy M. [Washington State Univ., Pullman, WA (United States)

2010-05-01

Trust management techniques must be adapted to the unique needs of the application architectures and problem domains to which they are applied. For autonomic computing systems that utilize mobile agents and ant colony algorithms for their sensor layer, certain characteristics of the mobile agent ant swarm -- their lightweight, ephemeral nature and indirect communication -- make this adaptation especially challenging. This thesis looks at the trust issues and opportunities in swarm-based autonomic computing systems and finds that by monitoring the trustworthiness of the autonomic managers rather than the swarming sensors, the trust management problem becomes much more scalable and still serves to protect the swarm. After analyzing the applicability of trust management research as it has been applied to architectures with similar characteristics, this thesis specifies the required characteristics for trust management mechanisms used to monitor the trustworthiness of entities in a swarm-based autonomic computing system and describes a trust model that meets these requirements.

Underwater hearing in the great cormorant (Phalacrocorax carbo sinensis)

DEFF Research Database (Denmark)

Hansen, Kirstin Anderson; Larsen, Ole Næsbye; Wahlberg, Magnus

2016-01-01

The underwater hearing threshold of a great cormorant (Phalacrocroax carbo sinensis) was measured at 2 kHz using psychophysical methods. Previous in-air and underwater testing suggests that cormorants have rather poor in-air hearing compared to other birds of similar size (Johansen, 2016). Prelim......The underwater hearing threshold of a great cormorant (Phalacrocroax carbo sinensis) was measured at 2 kHz using psychophysical methods. Previous in-air and underwater testing suggests that cormorants have rather poor in-air hearing compared to other birds of similar size (Johansen, 2016...

Mathematical model of unmanned aerial vehicle used for endurance autonomous monitoring

Energy Technology Data Exchange (ETDEWEB)

Chelaru, Teodor-Viorel, E-mail: teodor.chelaru@upb.ro [University POLITEHNICA of Bucharest - Research Center for Aeronautics and Space, Str. Gheorghe Polizu, no. 1, PC 011061, Sector 1, Bucharest (Romania); Chelaru, Adrian, E-mail: achelaru@incas.ro [INCAS -National Institute for Aerospace Research Elie Carafoli, B-dul Iuliu Maniu 220, 061126, Sector 6, Bucharest (Romania)

2014-12-10

The paper purpose is to present some aspects regarding the control system of unmanned aerial vehicle - UAV, used to local observations, surveillance and monitoring interest area. The calculus methodology allows a numerical simulation of UAV evolution in bad atmospheric conditions by using nonlinear model, as well as a linear one for obtaining guidance command. The UAV model which will be presented has six DOF (degrees of freedom), and autonomous control system. This theoretical development allows us to build stability matrix, command matrix and control matrix and finally to analyse the stability of autonomous UAV flight. A robust guidance system, based on uncoupled state will be evaluated for different fly conditions and the results will be presented. The flight parameters and guidance will be analysed.

Mathematical model of unmanned aerial vehicle used for endurance autonomous monitoring

International Nuclear Information System (INIS)

Chelaru, Teodor-Viorel; Chelaru, Adrian

2014-01-01

The paper purpose is to present some aspects regarding the control system of unmanned aerial vehicle - UAV, used to local observations, surveillance and monitoring interest area. The calculus methodology allows a numerical simulation of UAV evolution in bad atmospheric conditions by using nonlinear model, as well as a linear one for obtaining guidance command. The UAV model which will be presented has six DOF (degrees of freedom), and autonomous control system. This theoretical development allows us to build stability matrix, command matrix and control matrix and finally to analyse the stability of autonomous UAV flight. A robust guidance system, based on uncoupled state will be evaluated for different fly conditions and the results will be presented. The flight parameters and guidance will be analysed

Underwater television camera for monitoring inner side of pressure vessel

International Nuclear Information System (INIS)

Takayama, Kazuhiko.

1997-01-01

An underwater television support device equipped with a rotatable and vertically movable underwater television camera and an underwater television camera controlling device for monitoring images of the inside of the reactor core photographed by the underwater television camera to control the position of the underwater television camera and the underwater light are disposed on an upper lattice plate of a reactor pressure vessel. Both of them are electrically connected with each other by way of a cable to rapidly observe the inside of the reactor core by the underwater television camera. The reproducibility is extremely satisfactory by efficiently concentrating the position of the camera and image information upon inspection and observation. As a result, the steps for periodical inspection can be reduced to shorten the days for the periodical inspection. Since there is no requirement to withdraw fuel assemblies over a wide reactor core region, and the device can be used with the fuel assemblies being left as they are in the reactor, it is suitable for inspection of detectors for nuclear instrumentation. (N.H.)

Equipment and appliances for underwater operations. Pt. 2

International Nuclear Information System (INIS)

Krueger, P.

1976-01-01

The 6/75 edition of 'mt' reported on the 'ARGE underwater appliances' and the study on 'design development of appliances and equipment for underwater use' in a brief summary. One of these designs, the 'unmanned DSWS underwater appliance' was described in detail. The present article describes three further design developments mentioned in the above study and which are based on unmanned appliances connected to the mother-ship. These designs were developed by Preussag-Meerestechnik. (orig.) [de

Underwater cladding with laser beam and plasma arc welding

International Nuclear Information System (INIS)

White, R.A.; Fusaro, R.; Jones, M.G.; Solomon, H.D.; Milian-Rodriguez, R.R.

1997-01-01

Two welding processes, plasma arc (transferred arc) (PTA) and laser beam, were investigated to apply cladding to austenitic stainless steels and Inconel 600. These processes have long been used to apply cladding layers , but the novel feature being reported here is that these cladding layers were applied underwater, with a water pressure equivalent to 24 m (80 ft). Being able to apply the cladding underwater is very important for many applications, including the construction of off-shore oil platforms and the repair of nuclear reactors. In the latter case, being able to weld underwater eliminates the need for draining the reactor and removing the fuel. Welding underwater in reactors presents numerous challenges, but the ability to weld without having to drain the reactor and remove the fuel provides a huge cost savings. Welding underwater in reactors must be done remotely, but because of the radioactive corrosion products and neutron activation of the steels, remote welding would also be required even if the reactor is drained and the fuel removed. In fact, without the shielding of the water, the remote welding required if the reactor is drained might be even more difficult than that required with underwater welds. Furthermore, as shall be shown, the underwater welds that the authors have made were of high quality and exhibit compressive rather than tensile residual stresses

Underwater image mosaicking and visual odometry

Science.gov (United States)

Sadjadi, Firooz; Tangirala, Sekhar; Sorber, Scott

2017-05-01

This paper summarizes the results of studies in underwater odometery using a video camera for estimating the velocity of an unmanned underwater vehicle (UUV). Underwater vehicles are usually equipped with sonar and Inertial Measurement Unit (IMU) - an integrated sensor package that combines multiple accelerometers and gyros to produce a three dimensional measurement of both specific force and angular rate with respect to an inertial reference frame for navigation. In this study, we investigate the use of odometry information obtainable from a video camera mounted on a UUV to extract vehicle velocity relative to the ocean floor. A key challenge with this process is the seemingly bland (i.e. featureless) nature of video data obtained underwater which could make conventional approaches to image-based motion estimation difficult. To address this problem, we perform image enhancement, followed by frame to frame image transformation, registration and mosaicking/stitching. With this approach the velocity components associated with the moving sensor (vehicle) are readily obtained from (i) the components of the transform matrix at each frame; (ii) information about the height of the vehicle above the seabed; and (iii) the sensor resolution. Preliminary results are presented.

Underwater Gliders: A Review

Directory of Open Access Journals (Sweden)

Javaid Muhammad Yasar

2014-07-01

Full Text Available Underwater gliders are a type of underwater vehicle that transverse the oceans by shifting its buoyancy, during which its wings develop a component of the downward motion in the horizontal plane, thus producing a forward force. They are primarily used in oceanography sensing and data collection and play an important role in ocean research and development. Although there have been considerable developments in these gliders since the development of the first glider concept in 1989, to date, no review of these gliders have been done. This paper reviews existing underwater gliders, with emphasis on their respective working principles, range and payload capacity. All information on gliders available in the public domain or published in literature from the year 2000-2013 was reviewed. The majority of these gliders have an operational depth of 1000 m and a payload of less than 25 kg. The exception is a blend-body shape glider, which has a payload of approximately 800 kg and an operational depth around about 300 m. However, the commercialization of these gliders has been limited with only three know examples that have been successfully commercialized.

Underwater Object Segmentation Based on Optical Features

Directory of Open Access Journals (Sweden)

Zhe Chen

2018-01-01

Full Text Available Underwater optical environments are seriously affected by various optical inputs, such as artificial light, sky light, and ambient scattered light. The latter two can block underwater object segmentation tasks, since they inhibit the emergence of objects of interest and distort image information, while artificial light can contribute to segmentation. Artificial light often focuses on the object of interest, and, therefore, we can initially identify the region of target objects if the collimation of artificial light is recognized. Based on this concept, we propose an optical feature extraction, calculation, and decision method to identify the collimated region of artificial light as a candidate object region. Then, the second phase employs a level set method to segment the objects of interest within the candidate region. This two-phase structure largely removes background noise and highlights the outline of underwater objects. We test the performance of the method with diverse underwater datasets, demonstrating that it outperforms previous methods.

Localization of Energy Harvesting Empowered Underwater Optical Wireless Sensor Networks

KAUST Repository

Saeed, Nasir; Celik, Abdulkadir; Al-Naffouri, Tareq Y.; Alouini, Mohamed-Slim

2017-01-01

with insufficient battery, harvest the energy and starts communicating once it has sufficient energy storage. Network localization is carried out by measuring the RSSs of active nodes, which are modeled based on the underwater optical communication channel

Distributed flow estimation and closed-loop control of an underwater vehicle with a multi-modal artificial lateral line.

Science.gov (United States)

DeVries, Levi; Lagor, Francis D; Lei, Hong; Tan, Xiaobo; Paley, Derek A

2015-03-25

Bio-inspired sensing modalities enhance the ability of autonomous vehicles to characterize and respond to their environment. This paper concerns the lateral line of cartilaginous and bony fish, which is sensitive to fluid motion and allows fish to sense oncoming flow and the presence of walls or obstacles. The lateral line consists of two types of sensing modalities: canal neuromasts measure approximate pressure gradients, whereas superficial neuromasts measure local flow velocities. By employing an artificial lateral line, the performance of underwater sensing and navigation strategies is improved in dark, cluttered, or murky environments where traditional sensing modalities may be hindered. This paper presents estimation and control strategies enabling an airfoil-shaped unmanned underwater vehicle to assimilate measurements from a bio-inspired, multi-modal artificial lateral line and estimate flow properties for feedback control. We utilize potential flow theory to model the fluid flow past a foil in a uniform flow and in the presence of an upstream obstacle. We derive theoretically justified nonlinear estimation strategies to estimate the free stream flowspeed, angle of attack, and the relative position of an upstream obstacle. The feedback control strategy uses the estimated flow properties to execute bio-inspired behaviors including rheotaxis (the tendency of fish to orient upstream) and station-holding (the tendency of fish to position behind an upstream obstacle). A robotic prototype outfitted with a multi-modal artificial lateral line composed of ionic polymer metal composite and embedded pressure sensors experimentally demonstrates the distributed flow sensing and closed-loop control strategies.

Dynamics of underwater legged locomotion: modeling and experiments on an octopus-inspired robot.

Science.gov (United States)

Calisti, M; Corucci, F; Arienti, A; Laschi, C

2015-07-30

This paper studies underwater legged locomotion (ULL) by means of a robotic octopus-inspired prototype and its associated model. Two different types of propulsive actions are embedded into the robot model: reaction forces due to leg contact with the ground and hydrodynamic forces such as the drag arising from the sculling motion of the legs. Dynamic parameters of the model are estimated by means of evolutionary techniques and subsequently the model is exploited to highlight some distinctive features of ULL. Specifically, the separation between the center of buoyancy (CoB)/center of mass and density affect the stability and speed of the robot, whereas the sculling movements contribute to propelling the robot even when its legs are detached from the ground. The relevance of these effects is demonstrated through robotic experiments and model simulations; moreover, by slightly changing the position of the CoB in the presence of the same feed-forward activation, a number of different behaviors (i.e. forward and backward locomotion at different speeds) are achieved.

Dynamic model of an autonomous solar absorption refrigerator

International Nuclear Information System (INIS)

Ali Fellah; Tahar Khir; Ammar Ben Brahim

2009-01-01

The performance analysis of a solar absorption refrigerator operating in an autonomous way is investigated. The water/LiBr machine satisfies the air-conditioning needs along the day. The refrigerator performances were simulated regarding a dynamic model. For the solar driven absorption machines, two applications could be distinguished. The sun provides the thermal part of the useful energy. In this case, it is necessary to use additional energy as the electric one to activate the pumps, the fans and the control system. On the other hand, the sun provides all the necessary energy. Here, both photovoltaic cells and thermal concentrators should be used. The simulation in dynamic regime of the cycle requires the knowledge of the geometric characteristics of every component as the exchange areas and the internal volumes. Real characteristics of a refrigerator available at the applied thermodynamic research unit (ATRU) at the engineers' national school of Gabes are notified. The development of the thermal and matter balances in every component of the cycle has permitted to simulate in dynamic regime the performances of a solar absorption refrigerator operating with the water/LiBr couple for air-conditioning needs. The developed model could be used to perform intermittent refrigeration cycle autonomously driven. (author)

Modelling of a Hybrid Energy System for Autonomous Application

Directory of Open Access Journals (Sweden)

Yang He

2013-10-01

Full Text Available A hybrid energy system (HES is a trending power supply solution for autonomous devices. With the help of an accurate system model, the HES development will be efficient and oriented. In spite of various precise unit models, a HES system is hardly developed. This paper proposes a system modelling approach, which applies the power flux conservation as the governing equation and adapts and modifies unit models of solar cells, piezoelectric generators, a Li-ion battery and a super-capacitor. A generalized power harvest, storage and management strategy is also suggested to adapt to various application scenarios.

A Wide Area Risk Assessment Framework for Underwater Military Munitions Response

Science.gov (United States)

Holland, K. T.; Calantoni, J.

2017-12-01

Our objective was to develop a prototype statistical framework supporting Wide Area Assessment and Remedial Investigation decisions relating to the risk of unexploded ordnance and other military munitions concentrated in underwater environments. Decision making involving underwater munitions is inherently complex due to the high degree of uncertainty in the environmental conditions that force munitions responses (burial, decay, migration, etc.) and associated risks to the public. The prototype framework provides a consistent approach to accurately delineating contaminated areas at underwater munitions sites through the estimation of most probable concentrations. We adapted existing deterministic models and environmental data services for use within statistical modules that allowed the estimation of munition concentration given historic site information and environmental attributes. Ultimately this risk surface can be used to evaluate costs associated with various remediation approaches (e.g. removal, monitoring, etc.). Unfortunately, evaluation of the assessment framework was limited due to the lack of enduser data services from munition site managers. Of the 450 U.S. sites identified as having potential contamination with underwater munitions, assessment of available munitions information (including historic firing or disposal records, and recent ground-truth munitions samples) indicated very limited information in the databases. Example data types include the most probable munition types, approximate firing / disposal dates and locations, and any supportive munition survey or sampling results. However the overall technical goal to integrate trained statistical belief networks with detailed geophysical knowledge of sites, of sensors and of the underwater environment was demonstrated and should allow probabilistic estimates of the most likely outcomes and tradeoffs while managing uncertainty associated with military munitions response.

Optimal Node Placement in Underwater Wireless Sensor Networks

KAUST Repository

Felamban, M.; Shihada, Basem; Jamshaid, K.

2013-01-01

Wireless Sensor Networks (WSN) are expected to play a vital role in the exploration and monitoring of underwater areas which are not easily reachable by humans. However, underwater communication via acoustic waves is subject to several performance

A New Simple Model for Underwater Wireless Optical Channels in the Presence of Air Bubbles

KAUST Repository

Zedini, Emna

2018-01-15

A novel statistical model is proposed to characterize turbulence-induced fading in underwater wireless optical channels in the presence of air bubbles for fresh and salty waters, based on experimental data. In this model, the channel irradiance fluctuations are characterized by the mixture Exponential-Gamma distribution. We use the expectation maximization (EM) algorithm to obtain the maximum likelihood parameter estimation of the new model. Interestingly, the proposed model is shown to provide a perfect fit with the measured data under all the channel conditions for both types of water. The major advantage of the new model is that it has a simple mathematical form making it attractive from a performance analysis point of view. Indeed, the application of the Exponential-Gamma model leads to closed-form and analytically tractable expressions for key system performance metrics such as the outage probability and the average bit-error rate.

A New Simple Model for Underwater Wireless Optical Channels in the Presence of Air Bubbles

KAUST Repository

Zedini, Emna; Oubei, Hassan M.; Kammoun, Abla; Hamdi, Mounir; Ooi, Boon S.; Alouini, Mohamed-Slim

2018-01-01

A novel statistical model is proposed to characterize turbulence-induced fading in underwater wireless optical channels in the presence of air bubbles for fresh and salty waters, based on experimental data. In this model, the channel irradiance fluctuations are characterized by the mixture Exponential-Gamma distribution. We use the expectation maximization (EM) algorithm to obtain the maximum likelihood parameter estimation of the new model. Interestingly, the proposed model is shown to provide a perfect fit with the measured data under all the channel conditions for both types of water. The major advantage of the new model is that it has a simple mathematical form making it attractive from a performance analysis point of view. Indeed, the application of the Exponential-Gamma model leads to closed-form and analytically tractable expressions for key system performance metrics such as the outage probability and the average bit-error rate.

Enriching the hierarchical model of achievement motivation: autonomous and controlling reasons underlying achievement goals.

Science.gov (United States)

Michou, Aikaterini; Vansteenkiste, Maarten; Mouratidis, Athanasios; Lens, Willy

2014-12-01

The hierarchical model of achievement motivation presumes that achievement goals channel the achievement motives of need for achievement and fear of failure towards motivational outcomes. Yet, less is known whether autonomous and controlling reasons underlying the pursuit of achievement goals can serve as additional pathways between achievement motives and outcomes. We tested whether mastery approach, performance approach, and performance avoidance goals and their underlying autonomous and controlling reasons would jointly explain the relation between achievement motives (i.e., fear of failure and need for achievement) and learning strategies (Study 1). Additionally, we examined whether the autonomous and controlling reasons underlying learners' dominant achievement goal would account for the link between achievement motives and the educational outcomes of learning strategies and cheating (Study 2). Six hundred and six Greek adolescent students (Mage = 15.05, SD = 1.43) and 435 university students (Mage M = 20.51, SD = 2.80) participated in studies 1 and 2, respectively. In both studies, a correlational design was used and the hypotheses were tested via path modelling. Autonomous and controlling reasons underlying the pursuit of achievement goals mediated, respectively, the relation of need for achievement and fear of failure to aspects of learning outcomes. Autonomous and controlling reasons underlying achievement goals could further explain learners' functioning in achievement settings. © 2014 The British Psychological Society.

A new car-following model for autonomous vehicles flow with mean expected velocity field

Science.gov (United States)

Wen-Xing, Zhu; Li-Dong, Zhang

2018-02-01

Due to the development of the modern scientific technology, autonomous vehicles may realize to connect with each other and share the information collected from each vehicle. An improved forward considering car-following model was proposed with mean expected velocity field to describe the autonomous vehicles flow behavior. The new model has three key parameters: adjustable sensitivity, strength factor and mean expected velocity field size. Two lemmas and one theorem were proven as criteria for judging the stability of homogeneousautonomous vehicles flow. Theoretical results show that the greater parameters means larger stability regions. A series of numerical simulations were carried out to check the stability and fundamental diagram of autonomous flow. From the numerical simulation results, the profiles, hysteresis loop and density waves of the autonomous vehicles flow were exhibited. The results show that with increased sensitivity, strength factor or field size the traffic jam was suppressed effectively which are well in accordance with the theoretical results. Moreover, the fundamental diagrams corresponding to three parameters respectively were obtained. It demonstrates that these parameters play almost the same role on traffic flux: i.e. before the critical density the bigger parameter is, the greater flux is and after the critical density, the opposite tendency is. In general, the three parameters have a great influence on the stability and jam state of the autonomous vehicles flow.

Zebrafish model of tuberous sclerosis complex reveals cell-autonomous and non-cell-autonomous functions of mutant tuberin

Directory of Open Access Journals (Sweden)

Seok-Hyung Kim

2011-03-01

Tuberous sclerosis complex (TSC is an autosomal dominant disease caused by mutations in either the TSC1 (encodes hamartin or TSC2 (encodes tuberin genes. Patients with TSC have hamartomas in various organs throughout the whole body, most notably in the brain, skin, eye, heart, kidney and lung. To study the development of hamartomas, we generated a zebrafish model of TSC featuring a nonsense mutation (vu242 in the tsc2 gene. This tsc2vu242 allele encodes a truncated Tuberin protein lacking the GAP domain, which is required for inhibition of Rheb and of the TOR kinase within TORC1. We show that tsc2vu242 is a recessive larval-lethal mutation that causes increased cell size in the brain and liver. Greatly elevated TORC1 signaling is observed in tsc2vu242/vu242 homozygous zebrafish, and is moderately increased in tsc2vu242/+ heterozygotes. Forebrain neurons are poorly organized in tsc2vu242/vu242 homozygous mutants, which have extensive gray and white matter disorganization and ectopically positioned cells. Genetic mosaic analyses demonstrate that tsc2 limits TORC1 signaling in a cell-autonomous manner. However, in chimeric animals, tsc2vu242/vu242 mutant cells also mislocalize wild-type host cells in the forebrain in a non-cell-autonomous manner. These results demonstrate a highly conserved role of tsc2 in zebrafish and establish a new animal model for studies of TSC. The finding of a non-cell-autonomous function of mutant cells might help explain the formation of brain hamartomas and cortical malformations in human TSC.

Operational experience in underwater photogrammetry

Science.gov (United States)

Leatherdale, John D.; John Turner, D.

Underwater photogrammetry has become established as a cost-effective technique for inspection and maintenance of platforms and pipelines for the offshore oil industry. A commercial service based in Scotland operates in the North Sea, USA, Brazil, West Africa and Australia. 70 mm cameras and flash units are built for the purpose and analytical plotters and computer graphics systems are used for photogrammetric measurement and analysis of damage, corrosion, weld failures and redesign of underwater structures. Users are seeking simple, low-cost systems for photogrammetric analysis which their engineers can use themselves.

Evaluating the SCC resistance of underwater welds in sodium tetrathionate

International Nuclear Information System (INIS)

White, R.A.; Angeliu, T.M.

1997-01-01

The susceptibility of welds to stress corrosion cracking (SCC) is enhanced by the surface residual tensile stresses generated by the typical welding process. However, underwater plasma transferred arc (PTA) welding has been shown to produce compressive surface residual stresses, an encouraging result if repairs of cracked boiling water reactor (BWR) components are to be made without further endangering them to SCC. This program was designed to verify that underwater PTA welds are resistant to SCC and to determine if underwater PTA welding could mitigate SCC in potentially susceptible welds. This was achieved by exposing various welds on solution annealed (SA) and SA + thermally sensitized 304 stainless steel at 25 C in a solution of 1.5 gm/liter of sodium sulfide added to 0.05M sodium tetrathionate, titrated to a pH of 1.25 with H 2 SO 4 . The autogeneous welds were produced using gas tungsten arc (GTA) and plasma transferred arc (PTA) welding under atmospheric conditions, and PTA welding underwater. After 1 hour of sodium tetrathionate exposure, GTA and air PTA welds exhibited SCC while the underwater PTA weld heat affected zones were more resistant. Underwater PTA welds bisecting a GTA weld eliminated the cracking in the GTA weld heat affected zone under certain conditions. The lack of IG cracking in the region influenced by the underwater PTA weld is consistent with the measurement of compressive surface residual stresses inherent to the underwater welding process

Cymbal and BB underwater transducers and arrays

Energy Technology Data Exchange (ETDEWEB)

Newnham, R.E.; Zhang, J.; Alkoy, S.; Meyer, R.; Hughes, W.J.; Hladky-Hennion, A.C.; Cochran, J.; Markley, D. [Materials Research Laboratory, Penn State University, University Park, PA 16802 (United States)

2002-09-01

The cymbal is a miniaturized class V flextensional transducer that was developed for use as a shallow water sound projector and receiver. Single elements are characterized by high Q, low efficiency, and medium power output capability. Its low cost and thin profile allow the transducer to be assembled into large flexible arrays. Efforts were made to model both single elements and arrays using the ATILA code and the integral equation formulation (EQI).Millimeter size microprobe hydrophones (BBs) have been designed and fabricated from miniature piezoelectric hollow ceramic spheres for underwater applications such as mapping acoustic fields of projectors, and flow noise sensors for complex underwater structures. Green spheres are prepared from soft lead zirconate titanate powders using a coaxial nozzle slurry process. A compact hydrophone with a radially-poled sphere is investigated using inside and outside electrodes. Characterization of these hydrophones is done through measurement of hydrostatic piezoelectric charge coefficients, free field voltage sensitivities and directivity beam patterns. (orig.)

Using an autonomous Wave Glider to detect seawater anomalies related to submarine groundwater discharge - engineering challenge

Science.gov (United States)

Leibold, P.; Brueckmann, W.; Schmidt, M.; Balushi, H. A.; Abri, O. A.

2017-12-01

Coastal aquifer systems are amongst the most precious and vulnerable water resources worldwide. While differing in lateral and vertical extent they commonly show a complex interaction with the marine realm. Excessive groundwater extraction can cause saltwater intrusion from the sea into the aquifers, having a strongly negative impact on the groundwater quality. While the reverse pathway, the discharge of groundwater into the sea is well understood in principle, it's mechanisms and quantities not well constrained. We will present a project that combines onshore monitoring and modeling of groundwater in the coastal plain of Salalah, Oman with an offshore autonomous robotic monitoring system, the Liquid Robotics Wave Glider. Eventually, fluxes detected by the Wave Glider system and the onshore monitoring of groundwater will be combined into a 3-D flow model of the coastal and deeper aquifers. The main tool for offshore SGD investigation project is a Wave Glider, an autonomous vehicle based on a new propulsion technology. The Wave Glider is a low-cost satellite-connected marine craft, consisting of a combination of a sea-surface and an underwater component which is propelled by the conversion of ocean wave energy into forward thrust. While the wave energy propulsion system is purely mechanical, electrical energy for onboard computers, communication and sensors is provided by photovoltaic cells. For the project the SGD Wave Glider is being equipped with dedicated sensors to measure temperature, conductivity, Radon isotope (222Rn, 220Rn) activity concentration as well as other tracers of groundwater discharge. Dedicated software using this data input will eventually allow the Wave Glider to autonomously collect information and actively adapt its search pattern to hunt for spatial and temporal anomalies. Our presentation will focus on the engineering and operational challenges ofdetecting submarine groundwater discharges with the Wave Glider system in the Bay of Salalah

Sensor-driven area coverage for an autonomous fixed-wing unmanned aerial vehicle.

Science.gov (United States)

Paull, Liam; Thibault, Carl; Nagaty, Amr; Seto, Mae; Li, Howard

2014-09-01

Area coverage with an onboard sensor is an important task for an unmanned aerial vehicle (UAV) with many applications. Autonomous fixed-wing UAVs are more appropriate for larger scale area surveying since they can cover ground more quickly. However, their non-holonomic dynamics and susceptibility to disturbances make sensor coverage a challenging task. Most previous approaches to area coverage planning are offline and assume that the UAV can follow the planned trajectory exactly. In this paper, this restriction is removed as the aircraft maintains a coverage map based on its actual pose trajectory and makes control decisions based on that map. The aircraft is able to plan paths in situ based on sensor data and an accurate model of the on-board camera used for coverage. An information theoretic approach is used that selects desired headings that maximize the expected information gain over the coverage map. In addition, the branch entropy concept previously developed for autonomous underwater vehicles is extended to UAVs and ensures that the vehicle is able to achieve its global coverage mission. The coverage map over the workspace uses the projective camera model and compares the expected area of the target on the ground and the actual area covered on the ground by each pixel in the image. The camera is mounted on a two-axis gimbal and can either be stabilized or optimized for maximal coverage. Hardware-in-the-loop simulation results and real hardware implementation on a fixed-wing UAV show the effectiveness of the approach. By including the already developed automatic takeoff and landing capabilities, we now have a fully automated and robust platform for performing aerial imagery surveys.

Trade-off Analysis of Underwater Acoustic Sensor Networks

Science.gov (United States)

Tuna, G.; Das, R.

2017-09-01

In the last couple of decades, Underwater Acoustic Sensor Networks (UASNs) were started to be used for various commercial and non-commercial purposes. However, in underwater environments, there are some specific inherent constraints, such as high bit error rate, variable and large propagation delay, limited bandwidth capacity, and short-range communications, which severely degrade the performance of UASNs and limit the lifetime of underwater sensor nodes as well. Therefore, proving reliability of UASN applications poses a challenge. In this study, we try to balance energy consumption of underwater acoustic sensor networks and minimize end-to-end delay using an efficient node placement strategy. Our simulation results reveal that if the number of hops is reduced, energy consumption can be reduced. However, this increases end-to-end delay. Hence, application-specific requirements must be taken into consideration when determining a strategy for node deployment.

Statistical Modeling of Large-Scale Signal Path Loss in Underwater Acoustic Networks

Directory of Open Access Journals (Sweden)

Manuel Perez Malumbres

2013-02-01

Full Text Available In an underwater acoustic channel, the propagation conditions are known to vary in time, causing the deviation of the received signal strength from the nominal value predicted by a deterministic propagation model. To facilitate a large-scale system design in such conditions (e.g., power allocation, we have developed a statistical propagation model in which the transmission loss is treated as a random variable. By applying repetitive computation to the acoustic field, using ray tracing for a set of varying environmental conditions (surface height, wave activity, small node displacements around nominal locations, etc., an ensemble of transmission losses is compiled and later used to infer the statistical model parameters. A reasonable agreement is found with log-normal distribution, whose mean obeys a log-distance increases, and whose variance appears to be constant for a certain range of inter-node distances in a given deployment location. The statistical model is deemed useful for higher-level system planning, where simulation is needed to assess the performance of candidate network protocols under various resource allocation policies, i.e., to determine the transmit power and bandwidth allocation necessary to achieve a desired level of performance (connectivity, throughput, reliability, etc..

Model for Estimation of Thermal History Produced by a Single Pass Underwater Wet Weld

National Research Council Canada - National Science Library

Dill, Jay

1997-01-01

Thermal history calculations for single pass underwater wet weldments were made by solving the appropriate beat transfer equations using the three-dimensional Crank-Nicholson finite difference method...

SBMAC: Smart Blocking MAC Mechanism for Variable UW-ASN (Underwater Acoustic Sensor Network Environment

Directory of Open Access Journals (Sweden)

Soo-Hyun Park

2010-01-01

Full Text Available In this paper, several MAC scheduling methods applicable to an underwater environment are proposed. Besides, a new marine communication system model was proposed to improve the reliability of the proposed SBMAC method. The scheme minimizes transmission of control frames except for data transmission and various transmission methods and ACK methods can be used together. Simulation models are set indices and analysis of the underwater environment is established to conduct reliable simulations. Consequently, the performance improvement of the proposed method is verified with respect to delay time, data transmission rate, memory utilization, energy efficiency, etc.

Modeling an autonomous wind turbine electric pump system

Directory of Open Access Journals (Sweden)

Andreea Forcos

2009-10-01

Full Text Available Being one of the variable renewable energy sources, wind energy integration can be made using storage methods. All of these have been developed during time, but one might be more accessible than others because is using a free natural resource, water. This is pump storage. The purpose of this paper is modeling an autonomous wind turbine connected to an electric pump, in the aim of storage, and finally the determination of the efficiency.

Spatially complex distribution of dissolved manganese in a fjord as revealed by high-resolution in situ sensing using the autonomous underwater vehicle Autosub.

Science.gov (United States)

Statham, P J; Connelly, D P; German, C R; Brand, T; Overnell, J O; Bulukin, E; Millard, N; McPhail, S; Pebody, M; Perrett, J; Squire, M; Stevenson, P; Webb, A

2005-12-15

Loch Etive is a fjordic system on the west coast of Scotland. The deep waters of the upper basin are periodically isolated, and during these periods oxygen is lost through benthic respiration and concentrations of dissolved manganese increase. In April 2000 the autonomous underwater vehicle (AUV) Autosub was fitted with an in situ dissolved manganese analyzer and was used to study the spatial variability of this element together with oxygen, salinity, and temperature throughout the basin. Six along-loch transects were completed at either constant height above the seafloor or at constant depth below the surface. The ca. 4000 in situ 10-s-average dissolved Mn (Mnd) data points obtained provide a new quasi-synoptic and highly detailed view of the distribution of manganese in this fjordic environment not possible using conventional (water bottle) sampling. There is substantial variability in concentrations (600 nM) and distributions of Mnd. Surface waters are characteristically low in Mnd reflecting mixing of riverine and marine end-member waters, both of which are low in Mnd. The deeper waters are enriched in Mnd, and as the water column always contains some oxygen, this must reflect primarily benthic inputs of reduced dissolved Mn. However, this enrichment of Mnd is spatially very variable, presumably as a result of variability in release of Mn coupled with mixing of water in the loch and removal processes. This work demonstrates how AUVs coupled with chemical sensors can reveal substantial small-scale variability of distributions of chemical species in coastal environments that would not be resolved by conventional sampling approaches. Such information is essential if we are to improve our understanding of the nature and significance of the underlying processes leading to this variability.

Networking Multiple Autonomous Air and Ocean Vehicles for Oceanographic Research and Monitoring

Science.gov (United States)

McGillivary, P. A.; Borges de Sousa, J.; Rajan, K.

2013-12-01

Autonomous underwater and surface vessels (AUVs and ASVs) are coming into wider use as components of oceanographic research, including ocean observing systems. Unmanned airborne vehicles (UAVs) are now available at modest cost, allowing multiple UAVs to be deployed with multiple AUVs and ASVs. For optimal use good communication and coordination among vehicles is essential. We report on the use of multiple AUVs networked in communication with multiple UAVs. The UAVs are augmented by inferential reasoning software developed at MBARI that allows UAVs to recognize oceanographic fronts and change their navigation and control. This in turn allows UAVs to automatically to map frontal features, as well as to direct AUVs and ASVs to proceed to such features and conduct sampling via onboard sensors to provide validation for airborne mapping. ASVs can also act as data nodes for communication between UAVs and AUVs, as well as collecting data from onboard sensors, while AUVs can sample the water column vertically. This allows more accurate estimation of phytoplankton biomass and productivity, and can be used in conjunction with UAV sampling to determine air-sea flux of gases (e.g. CO2, CH4, DMS) affecting carbon budgets and atmospheric composition. In particular we describe tests in July 2013 conducted off Sesimbra, Portugal in conjunction with the Portuguese Navy by the University of Porto and MBARI with the goal of tracking large fish in the upper water column with coordinated air/surface/underwater measurements. A thermal gradient was observed in the infrared by a low flying UAV, which was used to dispatch an AUV to obtain ground truth to demonstrate the event-response capabilities using such autonomous platforms. Additional field studies in the future will facilitate integration of multiple unmanned systems into research vessel operations. The strength of hardware and software tools described in this study is to permit fundamental oceanographic measurements of both ocean

The Fluid-Solid Interaction Dynamics between Underwater Explosion Bubble and Corrugated Sandwich Plate

Directory of Open Access Journals (Sweden)

Hao Wang

2016-01-01

Full Text Available Lightweight sandwich structures with highly porous 2D cores or 3D (three-dimensional periodic cores can effectively withstand underwater explosion load. In most of the previous studies of sandwich structure antiblast dynamics, the underwater explosion (UNDEX bubble phase was neglected. As the UNDEX bubble load is one of the severest damage sources that may lead to structure large plastic deformation and crevasses failure, the failure mechanisms of sandwich structures might not be accurate if only shock wave is considered. In this paper, detailed 3D finite element (FE numerical models of UNDEX bubble-LCSP (lightweight corrugated sandwich plates interaction are developed by using MSC.Dytran. Upon the validated FE model, the bubble shape, impact pressure, and fluid field velocities for different stand-off distances are studied. Based on numerical results, the failure modes of LCSP and the whole damage process are obtained. It is demonstrated that the UNDEX bubble collapse jet local load plays a more significant role than the UNDEX shock wave load especially in near-field underwater explosion.

Filming Underwater in 3d Respecting Stereographic Rules

Science.gov (United States)

Rinaldi, R.; Hordosch, H.

2015-04-01

After an experimental phase of many years, 3D filming is now effective and successful. Improvements are still possible, but the film industry achieved memorable success on 3D movie's box offices due to the overall quality of its products. Special environments such as space ("Gravity") and the underwater realm look perfect to be reproduced in 3D. "Filming in space" was possible in "Gravity" using special effects and computer graphic. The underwater realm is still difficult to be handled. Underwater filming in 3D was not that easy and effective as filming in 2D, since not long ago. After almost 3 years of research, a French, Austrian and Italian team realized a perfect tool to film underwater, in 3D, without any constrains. This allows filmmakers to bring the audience deep inside an environment where they most probably will never have the chance to be.

FILMING UNDERWATER IN 3D RESPECTING STEREOGRAPHIC RULES

Directory of Open Access Journals (Sweden)

R. Rinaldi

2015-04-01

Full Text Available After an experimental phase of many years, 3D filming is now effective and successful. Improvements are still possible, but the film industry achieved memorable success on 3D movie’s box offices due to the overall quality of its products. Special environments such as space ("Gravity" and the underwater realm look perfect to be reproduced in 3D. "Filming in space" was possible in "Gravity" using special effects and computer graphic. The underwater realm is still difficult to be handled. Underwater filming in 3D was not that easy and effective as filming in 2D, since not long ago. After almost 3 years of research, a French, Austrian and Italian team realized a perfect tool to film underwater, in 3D, without any constrains. This allows filmmakers to bring the audience deep inside an environment where they most probably will never have the chance to be.

Wireless Underwater Monitoring Systems Based on Energy Harvestings

Directory of Open Access Journals (Sweden)

Sea-Hee HWANGBO

2013-01-01

Full Text Available One of the important research fields for aquatic exploitation and conservation is underwater wireless sensor network. Since limited energy source for underwater nodes and devices is a main open problem, in this paper, we propose wireless underwater monitoring systems powered by energy harvester which resolves the energy constraint. The target system generates renewable energy from energy harvester and shares the energy with underwater sensor nodes. For the realization of the system, key components to be investigated are discriminated as follows: acoustic modem, actuator, smart battery charge controller, energy harvester and wireless power transfer module. By developing acoustic modem, actuator and smart battery charge controller and utilizing off-the-shelf energy harvester and wireless power transfer module, we design and implement a prototype of the system. Also, we verify the feasibility of concept of target system by conducting indoor and outdoor experiments.

Low-contrast underwater living fish recognition using PCANet

Science.gov (United States)

Sun, Xin; Yang, Jianping; Wang, Changgang; Dong, Junyu; Wang, Xinhua

2018-04-01

Quantitative and statistical analysis of ocean creatures is critical to ecological and environmental studies. And living fish recognition is one of the most essential requirements for fishery industry. However, light attenuation and scattering phenomenon are present in the underwater environment, which makes underwater images low-contrast and blurry. This paper tries to design a robust framework for accurate fish recognition. The framework introduces a two stage PCA Network to extract abstract features from fish images. On a real-world fish recognition dataset, we use a linear SVM classifier and set penalty coefficients to conquer data unbalanced issue. Feature visualization results show that our method can avoid the feature distortion in boundary regions of underwater image. Experiments results show that the PCA Network can extract discriminate features and achieve promising recognition accuracy. The framework improves the recognition accuracy of underwater living fishes and can be easily applied to marine fishery industry.

Automatic stabilization of underwater robots in the time manipulation operations

International Nuclear Information System (INIS)

Filaretov, V.F.; Koval, E.V.

1994-01-01

When carrying out underwater technical works by means of an underwater vehicles having a manipulator it is desirable to perform manipulation operations in the regime of the underwater vehicle hovering above the object without durable and complicated operations up its rigid fixation. Underwater vehicle stabilization is achieved by compensation all the effects on the vehicle caused by the operating manipulator in water medium. This automatic stabilization is formed due to input of the required control signals into corresponding vehicle propellers proportional to calculated components of the generalized forces and moments. The propellers should form stops reacting against effects

Autonomic computing enabled cooperative networked design

CERN Document Server

Wodczak, Michal

2014-01-01

This book introduces the concept of autonomic computing driven cooperative networked system design from an architectural perspective. As such it leverages and capitalises on the relevant advancements in both the realms of autonomic computing and networking by welding them closely together. In particular, a multi-faceted Autonomic Cooperative System Architectural Model is defined which incorporates the notion of Autonomic Cooperative Behaviour being orchestrated by the Autonomic Cooperative Networking Protocol of a cross-layer nature. The overall proposed solution not only advocates for the inc

WODA technical guidance on underwater sound from dredging

NARCIS (Netherlands)

Thomsen, F.; Borsani, F.; Clarke, D.; Jong, C. de; Wit, P. de; Goethals, F.; Holtkamp, M.; Martin, E.S.; Spadaro, P.; Raalte, G. van; Victor, G.Y.V.; Jensen, A.

2016-01-01

The World Organization of Dredging Associations (WODA) has identified underwater sound as an environmental issue that needs further consideration. A WODA Expert Group on Underwater Sound (WEGUS) prepared a guidance paper in 2013 on dredging sound, including a summary of potential impacts on aquatic

Underwater laser imaging system (UWLIS)

Energy Technology Data Exchange (ETDEWEB)

DeLong, M. [Lawrence Livermore National Lab., CA (United States)

1994-11-15

Practical limitations with underwater imaging systems area reached when the noise in the back scattered radiation generated in the water between the imaging system and the target obscures the spatial contrast and resolution necessary for target discovery and identification. The advent of high power lasers operating in the blue-green portion of the visible spectrum (oceanic transmission window) has led to improved experimental illumination systems for underwater imaging. Range-gated and synchronously scanned devices take advantage of the unique temporal and spatial coherence properties of laser radiation, respectively, to overcome the deleterious effects of common volume back scatter.

A trajectory tracking controller for an underwater hexapod vehicle.

Science.gov (United States)

Plamondon, N; Nahon, M

2009-09-01

This paper describes work done in the modeling and control of a low speed underwater vehicle that uses paddles instead of thrusters to move in the water. A review of previously modeled vehicles and of controller designs for underwater applications is presented. Then, a method to accurately predict the thrust produced by an oscillating flexible paddle is developed and validated. This is followed by the development of a method to determine the ideal paddle motion to produce a desired thrust. Several controllers are then developed and tested using a numerical simulation of the vehicle. We found that some model-based controllers could improve the performance of the system while others showed no benefit. Finally, we report results from experimental trials performed in an open water environment comparing the performance of the controllers. The experimental results showed that all the model-based controllers outperform the simple proportional-derivative controller. The controller giving the best performance was the model-based nonlinear controller. We also found that the vehicle was able to follow a change of a roll angle of 90 degrees in 0.7 s and to precisely follow a sinusoidal trajectory with a period of 6.28 s and an amplitude of 5 degrees.

A trajectory tracking controller for an underwater hexapod vehicle

International Nuclear Information System (INIS)

Plamondon, N; Nahon, M

2009-01-01

This paper describes work done in the modeling and control of a low speed underwater vehicle that uses paddles instead of thrusters to move in the water. A review of previously modeled vehicles and of controller designs for underwater applications is presented. Then, a method to accurately predict the thrust produced by an oscillating flexible paddle is developed and validated. This is followed by the development of a method to determine the ideal paddle motion to produce a desired thrust. Several controllers are then developed and tested using a numerical simulation of the vehicle. We found that some model-based controllers could improve the performance of the system while others showed no benefit. Finally, we report results from experimental trials performed in an open water environment comparing the performance of the controllers. The experimental results showed that all the model-based controllers outperform the simple proportional-derivative controller. The controller giving the best performance was the model-based nonlinear controller. We also found that the vehicle was able to follow a change of a roll angle of 90 deg. in 0.7 s and to precisely follow a sinusoidal trajectory with a period of 6.28 s and an amplitude of 5 deg.

3D DOCUMENTATION OF ARCHEOLOGICAL REMAINS IN THE UNDERWATER PARK OF BAIAE

Directory of Open Access Journals (Sweden)

F. Bruno

2015-04-01

Full Text Available This paper presents some experimentations, which have been conducted in the submerged archeological Park of Baiae, aimed to identify the problems related to the underwater 3D documentation process. The first test has been addressed to verify if a dense stereo mapping technique, usually employed in terrestrial and aerial applications, might be employed in critical underwater conditions by assessing the influence of different factors on the results. In the second test, the accuracy of the 3D model obtained through this technique has been evaluated. The third test deals with the geo-localization of the 3D models, conducted by merging the optical and acoustic data, through a multi-resolution bathymetric map of the site as a reference.

Experimental Measurements of Temporal Dispersion for Underwater Laser Communications and Imaging

Science.gov (United States)

Cochenour, Brandon Michael

imaging sensors. Furthermore, this thesis represents one of the largest experimental data sets regarding temporal dispersion underwater. This should be of significant interest to theoreticians, who have generally lacked experimental evidence with which to verify their models.

Modeling connected and autonomous vehicles in heterogeneous traffic flow

Science.gov (United States)

Ye, Lanhang; Yamamoto, Toshiyuki

2018-01-01

The objective of this study was to develop a heterogeneous traffic-flow model to study the possible impact of connected and autonomous vehicles (CAVs) on the traffic flow. Based on a recently proposed two-state safe-speed model (TSM), a two-lane cellular automaton (CA) model was developed, wherein both the CAVs and conventional vehicles were incorporated in the heterogeneous traffic flow. In particular, operation rules for CAVs are established considering the new characteristics of this emerging technology, including autonomous driving through the adaptive cruise control and inter-vehicle connection via short-range communication. Simulations were conducted under various CAV-penetration rates in the heterogeneous flow. The impact of CAVs on the road capacity was numerically investigated. The simulation results indicate that the road capacity increases with an increase in the CAV-penetration rate within the heterogeneous flow. Up to a CAV-penetration rate of 30%, the road capacity increases gradually; the effect of the difference in the CAV capability on the growth rate is insignificant. When the CAV-penetration rate exceeds 30%, the growth rate is largely decided by the capability of the CAV. The greater the capability, the higher the road-capacity growth rate. The relationship between the CAV-penetration rate and the road capacity is numerically analyzed, providing some insights into the possible impact of the CAVs on traffic systems.

Blue-light digital communication in underwater environments utilizing orbital angular momentum

Science.gov (United States)

Baghdady, Joshua; Miller, Keith; Osler, Sean; Morgan, Kaitlyn; Li, Wenzhe; Johnson, Eric; Cochenour, Brandon

2016-05-01

Underwater optical communication has recently become the topic of much investigation as the demands for underwater data transmission have rapidly grown in recent years. The need for reliable, high-speed, secure underwater communication has turned increasingly to blue-light optical solutions. The blue-green visible wavelength window provides an attractive solution to the problem of underwater data transmission thanks to its low attenuation, where traditional RF solutions used in free-space communications collapse. Beginning with GaN laser diodes as the optical source, this work explores the encoding and transmission of digital data across underwater environments of varying turbidities. Given the challenges present in an underwater environment, such as the mechanical and optical turbulences that make proper alignment difficult to maintain, it is desirable to achieve extremely high data rates in order to allow the time window of alignment between the transmitter and receiver to be as small as possible. In this paper, work is done to increase underwater data rates through the use of orbital angular momentum. Results are shown for a range of data rates across a variety of channel types ranging in turbidity from that of a clear ocean to a dirty harbor.

Single underwater image enhancement based on color cast removal and visibility restoration

Science.gov (United States)

Li, Chongyi; Guo, Jichang; Wang, Bo; Cong, Runmin; Zhang, Yan; Wang, Jian

2016-05-01

Images taken under underwater condition usually have color cast and serious loss of contrast and visibility. Degraded underwater images are inconvenient for observation and analysis. In order to address these problems, an underwater image-enhancement method is proposed. A simple yet effective underwater image color cast removal algorithm is first presented based on the optimization theory. Then, based on the minimum information loss principle and inherent relationship of medium transmission maps of three color channels in an underwater image, an effective visibility restoration algorithm is proposed to recover visibility, contrast, and natural appearance of degraded underwater images. To evaluate the performance of the proposed method, qualitative comparison, quantitative comparison, and color accuracy test are conducted. Experimental results demonstrate that the proposed method can effectively remove color cast, improve contrast and visibility, and recover natural appearance of degraded underwater images. Additionally, the proposed method is comparable to and even better than several state-of-the-art methods.

Study of archaeological underwater finds: deterioration and conservation

Science.gov (United States)

Crisci, G. M.; La Russa, M. F.; Macchione, M.; Malagodi, M.; Palermo, A. M.; Ruffolo, S. A.

2010-09-01

This study is aimed at an assessment of the methodologies, instruments and new applications for underwater archaeology. Research focused on study of the various kinds of degradation affecting underwater finds and stone materials aged in underwater environment, efficiency evaluation of various surface cleaning methods and study and mixing of protective products with consolidating resins and antimicrobial biocides to be applied to restored underwater finds. Transmitted light optical microscopy and scanning electron microscopy (SEM) were used to study surface biofilms and the interactions with samples of different stone materials such as brick, marble and granite immersed in the submarine archaeological area of Crotone (South of Italy). Surface cleaning tests were performed with application of ion exchange resins, EDTA, hydrogen peroxide and ultrasound techniques. Capillary water absorption, simulated solar ageing and colourimetric measurements were carried out to evaluate hydrophobic and consolidant properties; to assess biocidal efficacy, heterotrophic micro-organisms ( Aspergillus niger) were inoculated on agar plates and growth inhibition was measured.

Behavioural domain knowledge transfer for autonomous agents

CSIR Research Space (South Africa)

Rosman, Benjamin S

2014-11-01

Full Text Available , and Behavior Transfer in Autonomous Robots, AAAI 2014 Fall Symposium Series, 13-15 November 2014 Behavioural Domain Knowledge Transfer for Autonomous Agents Benjamin Rosman Mobile Intelligent Autonomous Systems Modelling and Digital Science Council...

Quantifying Multiscale Habitat Structural Complexity: A Cost-Effective Framework for Underwater 3D Modelling

Directory of Open Access Journals (Sweden)

Renata Ferrari

2016-02-01

Full Text Available Coral reef habitat structural complexity influences key ecological processes, ecosystem biodiversity, and resilience. Measuring structural complexity underwater is not trivial and researchers have been searching for accurate and cost-effective methods that can be applied across spatial extents for over 50 years. This study integrated a set of existing multi-view, image-processing algorithms, to accurately compute metrics of structural complexity (e.g., ratio of surface to planar area underwater solely from images. This framework resulted in accurate, high-speed 3D habitat reconstructions at scales ranging from small corals to reef-scapes (10s km2. Structural complexity was accurately quantified from both contemporary and historical image datasets across three spatial scales: (i branching coral colony (Acropora spp.; (ii reef area (400 m2; and (iii reef transect (2 km. At small scales, our method delivered models with <1 mm error over 90% of the surface area, while the accuracy at transect scale was 85.3% ± 6% (CI. Advantages are: no need for an a priori requirement for image size or resolution, no invasive techniques, cost-effectiveness, and utilization of existing imagery taken from off-the-shelf cameras (both monocular or stereo. This remote sensing method can be integrated to reef monitoring and improve our knowledge of key aspects of coral reef dynamics, from reef accretion to habitat provisioning and productivity, by measuring and up-scaling estimates of structural complexity.

Underwater laser cutting of metallic structures

International Nuclear Information System (INIS)

Alfille, J.P.; Schildknecht, J.; Ramaswami, V.S.

1993-01-01

In the frame of an european contract, the feasibility of the underwater cutting with a CO 2 laser power is studied. The aim of this work is the dismantling metallic structures of reactors pools. The paper analyzes the general concept of the experimental device, the underwater cutting head, the experimenting vessel, examples of cuttings in dismantling situation with a 500 W CO 2 laser, and examples of cuttings with a 5 kW CO 2 laser. (author). 2 refs., 9 figs., 2 tabs

Digital sonar design in underwater acoustics principles and applications

CERN Document Server

Li, Qihu

2012-01-01

"Digital Sonar Design in Underwater Acoustics Principles and Applications" provides comprehensive and up-to-date coverage of research on sonar design, including the basic theory and techniques of digital signal processing, basic concept of information theory, ocean acoustics, underwater acoustic signal propagation theory, and underwater signal processing theory. This book discusses the general design procedure and approaches to implementation, the design method, system simulation theory and techniques, sonar tests in the laboratory, lake and sea, and practical validation criteria and methods for digital sonar design. It is intended for researchers in the fields of underwater signal processing and sonar design, and also for navy officers and ocean explorers. Qihu Li is a professor at the Institute of Acoustics, Chinese Academy of Sciences, and an academician of the Chinese Academy of Sciences.

The Trans-Contextual Model of Autonomous Motivation in Education: Conceptual and Empirical Issues and Meta-Analysis

Science.gov (United States)

Hagger, Martin S.; Chatzisarantis, Nikos L. D.

2016-01-01

The trans-contextual model outlines the processes by which autonomous motivation toward activities in a physical education context predicts autonomous motivation toward physical activity outside of school, and beliefs about, intentions toward, and actual engagement in, out-of-school physical activity. In the present article, we clarify the…

Event localization in underwater wireless sensor networks using Monitoring Courses

KAUST Repository

Debont, Matthew John Robert

2012-08-01

We propose m-courses (Monitoring Courses), a novel solution to localize events in an underwater wireless sensor network. These networks consists of surface gateways and relay nodes. GPS can localize the position of surface gateways which can then distribute their locations through the network using acoustic modems. Relay nodes are deployed to remain static, but these untethered nodes may drift due to water currents, resulting in disruption of communication links. We develop a novel underwater alarm system using a cyclic graph model. In the event of link failure, a series of alarm packets are broadcast in the network. These alarms are then captured by the underwater m-courses, which can also be used to assure network connectivity and identify node failures. M-courses also allow the network to localize events and identify network issues locally before forwarding results upwards to a Surface Gateway node. This reduces communication overhead and allows for efficient management of nodes in a mobile network. Our results show that m-course routing reduces the number of sends required to report an event to a Surface Gateway by up to 80% when compared to a naïve routing implementation.

Modeling the Turning Speed and Car Following Behaviors of Autonomous Vehicles in a Virtual World

Directory of Open Access Journals (Sweden)

Carrillo-González José Gerardo

2015-07-01

Full Text Available This article deals with mathematical models for controlling vehicles behavior in a virtual world, where two behaviors are considered: 1 curve turning and 2 car following situations, in this last is essential to provide a safety distance between the leader and the follower and at the same time keep the follower not delayed with respect to the leader, and in a curve turning the complexity is to provide a safety speed inside the curve and keep the car inside the lane. Using basic information as vehicles position, mathematical models can be developed for explaining the heading angle and the autonomous vehicles speed on curves, i.e. the controlled by the models. A model that predicts the autonomous vehicle speed on curves is developed considering previous data in other curves. Two models that control the acceleration/deceleration behavior of autonomous vehicles in a car following situation are proposed. In the first model, the parameters are calibrated with a proposed algorithm which enables accuracy in order to imitate the human behavior for accelerating and braking, and the second model provides a safety distance between the follower and the leader at sudden stops of the latter and employs the acceleration/deceleration top capabilities to follow the leader car similar to the human behavior.

WODA Technical Guidance on Underwater Sound from Dredging.

Science.gov (United States)

Thomsen, Frank; Borsani, Fabrizio; Clarke, Douglas; de Jong, Christ; de Wit, Pim; Goethals, Fredrik; Holtkamp, Martine; Martin, Elena San; Spadaro, Philip; van Raalte, Gerard; Victor, George Yesu Vedha; Jensen, Anders

2016-01-01

The World Organization of Dredging Associations (WODA) has identified underwater sound as an environmental issue that needs further consideration. A WODA Expert Group on Underwater Sound (WEGUS) prepared a guidance paper in 2013 on dredging sound, including a summary of potential impacts on aquatic biota and advice on underwater sound monitoring procedures. The paper follows a risk-based approach and provides guidance for standardization of acoustic terminology and methods for data collection and analysis. Furthermore, the literature on dredging-related sounds and the effects of dredging sounds on marine life is surveyed and guidance on the management of dredging-related sound risks is provided.

Comparison of spatial models for foreground-background segmentation in underwater videos

OpenAIRE

Radolko, Martin

2015-01-01

The low-level task of foreground-background segregation is an important foundation for many high-level computer vision tasks and has been intensively researched in the past. Nonetheless, unregulated environments usually impose challenging problems, especially the difficult and often neglected underwater environment. There, among others, the edges are blurred, the contrast is impaired and the colors attenuated. Our approach to this problem uses an efficient Background Subtraction algorithm and...

An Autonomous Connectivity Restoration Algorithm Based on Finite State Machine for Wireless Sensor-Actor Networks

Directory of Open Access Journals (Sweden)

Ying Zhang

2018-01-01

Full Text Available With the development of autonomous unmanned intelligent systems, such as the unmanned boats, unmanned planes and autonomous underwater vehicles, studies on Wireless Sensor-Actor Networks (WSANs have attracted more attention. Network connectivity algorithms play an important role in data exchange, collaborative detection and information fusion. Due to the harsh application environment, abnormal nodes often appear, and the network connectivity will be prone to be lost. Network self-healing mechanisms have become critical for these systems. In order to decrease the movement overhead of the sensor-actor nodes, an autonomous connectivity restoration algorithm based on finite state machine is proposed. The idea is to identify whether a node is a critical node by using a finite state machine, and update the connected dominating set in a timely way. If an abnormal node is a critical node, the nearest non-critical node will be relocated to replace the abnormal node. In the case of multiple node abnormality, a regional network restoration algorithm is introduced. It is designed to reduce the overhead of node movements while restoration happens. Simulation results indicate the proposed algorithm has better performance on the total moving distance and the number of total relocated nodes compared with some other representative restoration algorithms.

An Autonomous Connectivity Restoration Algorithm Based on Finite State Machine for Wireless Sensor-Actor Networks.

Science.gov (United States)

Zhang, Ying; Wang, Jun; Hao, Guan

2018-01-08

With the development of autonomous unmanned intelligent systems, such as the unmanned boats, unmanned planes and autonomous underwater vehicles, studies on Wireless Sensor-Actor Networks (WSANs) have attracted more attention. Network connectivity algorithms play an important role in data exchange, collaborative detection and information fusion. Due to the harsh application environment, abnormal nodes often appear, and the network connectivity will be prone to be lost. Network self-healing mechanisms have become critical for these systems. In order to decrease the movement overhead of the sensor-actor nodes, an autonomous connectivity restoration algorithm based on finite state machine is proposed. The idea is to identify whether a node is a critical node by using a finite state machine, and update the connected dominating set in a timely way. If an abnormal node is a critical node, the nearest non-critical node will be relocated to replace the abnormal node. In the case of multiple node abnormality, a regional network restoration algorithm is introduced. It is designed to reduce the overhead of node movements while restoration happens. Simulation results indicate the proposed algorithm has better performance on the total moving distance and the number of total relocated nodes compared with some other representative restoration algorithms.

An Autonomous Connectivity Restoration Algorithm Based on Finite State Machine for Wireless Sensor-Actor Networks

Science.gov (United States)

Zhang, Ying; Wang, Jun; Hao, Guan

2018-01-01

With the development of autonomous unmanned intelligent systems, such as the unmanned boats, unmanned planes and autonomous underwater vehicles, studies on Wireless Sensor-Actor Networks (WSANs) have attracted more attention. Network connectivity algorithms play an important role in data exchange, collaborative detection and information fusion. Due to the harsh application environment, abnormal nodes often appear, and the network connectivity will be prone to be lost. Network self-healing mechanisms have become critical for these systems. In order to decrease the movement overhead of the sensor-actor nodes, an autonomous connectivity restoration algorithm based on finite state machine is proposed. The idea is to identify whether a node is a critical node by using a finite state machine, and update the connected dominating set in a timely way. If an abnormal node is a critical node, the nearest non-critical node will be relocated to replace the abnormal node. In the case of multiple node abnormality, a regional network restoration algorithm is introduced. It is designed to reduce the overhead of node movements while restoration happens. Simulation results indicate the proposed algorithm has better performance on the total moving distance and the number of total relocated nodes compared with some other representative restoration algorithms. PMID:29316702

Where neuroscience and dynamic system theory meet autonomous robotics: a contracting basal ganglia model for action selection.

Science.gov (United States)

Girard, B; Tabareau, N; Pham, Q C; Berthoz, A; Slotine, J-J

2008-05-01

Action selection, the problem of choosing what to do next, is central to any autonomous agent architecture. We use here a multi-disciplinary approach at the convergence of neuroscience, dynamical system theory and autonomous robotics, in order to propose an efficient action selection mechanism based on a new model of the basal ganglia. We first describe new developments of contraction theory regarding locally projected dynamical systems. We exploit these results to design a stable computational model of the cortico-baso-thalamo-cortical loops. Based on recent anatomical data, we include usually neglected neural projections, which participate in performing accurate selection. Finally, the efficiency of this model as an autonomous robot action selection mechanism is assessed in a standard survival task. The model exhibits valuable dithering avoidance and energy-saving properties, when compared with a simple if-then-else decision rule.

Underwater Shock Response of Circular HSLA Steel Plates

Directory of Open Access Journals (Sweden)

R. Rajendran

2000-01-01

Full Text Available Studies on shock response of circular plates subjected to underwater explosion is of interest to ship designers. Non-contact underwater explosion experiments were carried out on air backed circular High Strength Low Alloy (HSLA steel plates of 4 mm thickness and 290 mm diameter. The experiments were carried out in two phases. In the first phase, strain gauges were fixed at intervals of 30 mm from the centre of the plate and strains were recorded for the shock intensity gradually increasing to yielding. Semi-analytical models were derived for the elastic strain prediction which showed good agreement with the experiments. Dynamic yield stress and the shock factor for yielding were established. In the second phase, individual plates were subjected to increasing shock severity until fracture and the apex bulge depth and the thickness strains were measured. Empirical models were derived to predict the plastic deformation which were validated through a fresh set of experiments. Analysis of the fractured surface by visual examination showed that there was slant fracture indicating ductile mode of failure and the same was corroborated by Scanning Electron Microscopic (SEM examination.

Photogrammetry in maritime and underwater archaeology: two marble wrecks from Sicily

Science.gov (United States)

Balletti, C.; Beltrame, C.; Costa, E.; Guerra, F.; Vernier, P.

2015-06-01

Underwater survey, compared to land archaeology, needs some specific techniques, because the application of some active 3D sensor, such as laser scanner, is obviously impossible. The necessity to produce three-dimensional survey, offering the same accuracy of classical terrestrial laserscanning or photogrammetric methods, combined with the request of low costs and rapid solutions, led the researchers to test and apply oftentimes image-based techniques. In the last two years the Ca' Foscari University and University IUAV of Venice are conducting a research on the application of integrated techniques to support underwater metric documentation, comparing them to the manual traditional one. The gained experience (and confirmed by other recently published papers) shows that the actual multiimage digital photogrammetry is a good solution for the underwater archaeology. This approach is useful both from a metric and from a recording point of view, because it achieves high quality results, such as accurate 3D models or 2D representations, offering a complete documentation of underwater sites. But photogrammetry has to be supported by a topographical survey (to acquire ground control points - GCP) to georeference all the finds in the same reference system. This paper presents the integrated survey of two roman shipwrecks, approaching differently in the GCP's acquisition just for the different morphological characteristic of the sites. The wrecks' cargos are huge marble blocks, presenting differences in quantities, layout and depths. Those characteristics determine the choice of the topographic survey. The results of the survey are two 3D polygonal textured models of the sites, which can be easily used for different analyses and reconstructive hypothesis, opening new possibilities of documentation with both specialists and the wider public. Furthermore, 3D models are the geometric base for 2D orthophoto and cross section extraction. The paper will illustrate all the phases

Feasibility of in situ beta ray measurements in underwater environment.

Science.gov (United States)

Park, Hye Min; Park, Ki Hyun; Kang, Sung Won; Joo, Koan Sik

2017-09-01

We describe an attempt at the development of an in situ detector for beta ray measurements in underwater environment. The prototype of the in situ detector is based on a CaF2: Eu scintillator using crystal light guide and Si photomultiplier. Tests were conducted using various reference sources for evaluating the linearity and stability of the detector in underwater environment. The system is simple and stable for long-term monitoring, and consumes low power. We show here an effective detection distance of 7 mm and a 2.273 MeV end-point energy spectrum of 90 Sr/ 90 Y when using the system underwater. The results demonstrate the feasibility of in situ beta ray measurements in underwater environment and can be applied for designing an in situ detector for radioactivity measurement in underwater environment. The in situ detector can also have other applications such as installation on the marine monitoring platform and quantitative analysis of radionuclides. Copyright © 2017 Elsevier Ltd. All rights reserved.

Identifying Error in AUV Communication

National Research Council Canada - National Science Library

Coleman, Joseph; Merrill, Kaylani; O'Rourke, Michael; Rajala, Andrew G; Edwards, Dean B

2006-01-01

Mine Countermeasures (MCM) involving Autonomous Underwater Vehicles (AUVs) are especially susceptible to error, given the constraints on underwater acoustic communication and the inconstancy of the underwater communication channel...

Potential role of resurfacing Subtropical Underwater in ENSO evolution

Science.gov (United States)

Qu, T.; Chi, J.

2017-12-01

Results from a model of the Estimating the Circulation and Climate of the Ocean (ECCO) have shown that the resurfacing of high salinity Subtropical Underwater contributes to the sea surface salinity variability in the equatorial Pacific. On interannual time scale, this contribution can account for as much as 25% of the surface freshwater flux anomalies and is believed to play a role in ENSO evolution. Having these results in mind, this study investigates the surface salinity budget and its primary controls in the equatorial Pacific using ECCO output for the period 1993-2016. Particular attention is paid to 2014/2015 and 2015/2016. Preliminary analyses of the model results suggest that enhanced subsurface processes and in particular enhanced entrainment of Subtropical Underwater are primarily responsible for the positive sea surface salinity anomalies in the central equatorial Pacific during 2014/2015, which represents an opposite phase of El Niño. These subsurface processes weakened during 2015/2016, diretly contributing to the development of the 2015/2016 El Niño. The mechanisms controlling these subsurface processes are discussed.

Underwater Shock Wave Research Applied to Therapeutic Device Developments

Science.gov (United States)

Takayama, K.; Yamamoto, H.; Shimokawa, H.

2013-07-01

The chronological development of underwater shock wave research performed at the Shock Wave Research Center of the Institute of Fluid Science at the Tohoku University is presented. Firstly, the generation of planar underwater shock waves in shock tubes and their visualization by using the conventional shadowgraph and schlieren methods are described. Secondly, the generation of spherical underwater shock waves by exploding lead azide pellets weighing from several tens of micrograms to 100 mg, that were ignited by irradiating with a Q-switched laser beam, and their visualization by using double exposure holographic interferometry are presented. The initiation, propagation, reflection, focusing of underwater shock waves, and their interaction with various interfaces, in particular, with air bubbles, are visualized quantitatively. Based on such a fundamental underwater shock wave research, collaboration with the School of Medicine at the Tohoku University was started for developing a shock wave assisted therapeutic device, which was named an extracorporeal shock wave lithotripter (ESWL). Miniature shock waves created by irradiation with Q-switched HO:YAG laser beams are studied, as applied to damaged dysfunctional nerve cells in the myocardium in a precisely controlled manner, and are effectively used to design a catheter for treating arrhythmia.

UTOFIA: an underwater time-of-flight image acquisition system

Science.gov (United States)

Driewer, Adrian; Abrosimov, Igor; Alexander, Jonathan; Benger, Marc; O'Farrell, Marion; Haugholt, Karl Henrik; Softley, Chris; Thielemann, Jens T.; Thorstensen, Jostein; Yates, Chris

2017-10-01

In this article the development of a newly designed Time-of-Flight (ToF) image sensor for underwater applications is described. The sensor is developed as part of the project UTOFIA (underwater time-of-flight image acquisition) funded by the EU within the Horizon 2020 framework. This project aims to develop a camera based on range gating that extends the visible range compared to conventional cameras by a factor of 2 to 3 and delivers real-time range information by means of a 3D video stream. The principle of underwater range gating as well as the concept of the image sensor are presented. Based on measurements on a test image sensor a pixel structure that suits best to the requirements has been selected. Within an extensive characterization underwater the capability of distance measurements in turbid environments is demonstrated.

Underwater photogrammetry successful in Spain and France

International Nuclear Information System (INIS)

Anon.

1988-01-01

Underwater photogrammetry has been used to measure distortions in fuel assembly alignment pins in the upper internals of the Almarez and Dampierre PWRs. Photogrammetry is a three-dimensional precision measurement method using photographic techniques for the on-site measurement phase. On the strength of the operations at the two PWRs, underwater photogrammetry is now considered as a practical and effective technique for dimensional inspection at nuclear plants. (U.K.)

OPTICAL correlation identification technology applied in underwater laser imaging target identification

Science.gov (United States)

Yao, Guang-tao; Zhang, Xiao-hui; Ge, Wei-long

2012-01-01

The underwater laser imaging detection is an effective method of detecting short distance target underwater as an important complement of sonar detection. With the development of underwater laser imaging technology and underwater vehicle technology, the underwater automatic target identification has gotten more and more attention, and is a research difficulty in the area of underwater optical imaging information processing. Today, underwater automatic target identification based on optical imaging is usually realized with the method of digital circuit software programming. The algorithm realization and control of this method is very flexible. However, the optical imaging information is 2D image even 3D image, the amount of imaging processing information is abundant, so the electronic hardware with pure digital algorithm will need long identification time and is hard to meet the demands of real-time identification. If adopt computer parallel processing, the identification speed can be improved, but it will increase complexity, size and power consumption. This paper attempts to apply optical correlation identification technology to realize underwater automatic target identification. The optics correlation identification technology utilizes the Fourier transform characteristic of Fourier lens which can accomplish Fourier transform of image information in the level of nanosecond, and optical space interconnection calculation has the features of parallel, high speed, large capacity and high resolution, combines the flexibility of calculation and control of digital circuit method to realize optoelectronic hybrid identification mode. We reduce theoretical formulation of correlation identification and analyze the principle of optical correlation identification, and write MATLAB simulation program. We adopt single frame image obtained in underwater range gating laser imaging to identify, and through identifying and locating the different positions of target, we can improve

Acoustic and Vibration Control for an Underwater Structure under Mechanical Excitation

Directory of Open Access Journals (Sweden)

Shi-Jian Zhu

2014-01-01

Full Text Available Acoustic and vibration control for an underwater structure under mechanical excitation has been investigated by using negative feedback control algorithm. The underwater structure is modeled with cylindrical shells, conical shells, and circular bulkheads, of which the motion equations are built with the variational approach, respectively. Acoustic property is analyzed by the Helmholtz integration formulation with boundary element method. Based on negative feedback control algorithm, a control loop with a coupling use of piezoelectric sensor and actuator is built, and accordingly some numerical examples are carried out on active control of structural vibration and acoustic response. Effects of geometrical and material parameters on acoustic and vibration properties are investigated and discussed.

Deep Learning Methods for Underwater Target Feature Extraction and Recognition

Directory of Open Access Journals (Sweden)

Gang Hu

2018-01-01

Full Text Available The classification and recognition technology of underwater acoustic signal were always an important research content in the field of underwater acoustic signal processing. Currently, wavelet transform, Hilbert-Huang transform, and Mel frequency cepstral coefficients are used as a method of underwater acoustic signal feature extraction. In this paper, a method for feature extraction and identification of underwater noise data based on CNN and ELM is proposed. An automatic feature extraction method of underwater acoustic signals is proposed using depth convolution network. An underwater target recognition classifier is based on extreme learning machine. Although convolution neural networks can execute both feature extraction and classification, their function mainly relies on a full connection layer, which is trained by gradient descent-based; the generalization ability is limited and suboptimal, so an extreme learning machine (ELM was used in classification stage. Firstly, CNN learns deep and robust features, followed by the removing of the fully connected layers. Then ELM fed with the CNN features is used as the classifier to conduct an excellent classification. Experiments on the actual data set of civil ships obtained 93.04% recognition rate; compared to the traditional Mel frequency cepstral coefficients and Hilbert-Huang feature, recognition rate greatly improved.

Underwater video enhancement using multi-camera super-resolution

Science.gov (United States)

Quevedo, E.; Delory, E.; Callicó, G. M.; Tobajas, F.; Sarmiento, R.

2017-12-01

Image spatial resolution is critical in several fields such as medicine, communications or satellite, and underwater applications. While a large variety of techniques for image restoration and enhancement has been proposed in the literature, this paper focuses on a novel Super-Resolution fusion algorithm based on a Multi-Camera environment that permits to enhance the quality of underwater video sequences without significantly increasing computation. In order to compare the quality enhancement, two objective quality metrics have been used: PSNR (Peak Signal-to-Noise Ratio) and the SSIM (Structural SIMilarity) index. Results have shown that the proposed method enhances the objective quality of several underwater sequences, avoiding the appearance of undesirable artifacts, with respect to basic fusion Super-Resolution algorithms.

Influence of range-gated intensifiers on underwater imaging system SNR

Science.gov (United States)

Wang, Xia; Hu, Ling; Zhi, Qiang; Chen, Zhen-yue; Jin, Wei-qi

2013-08-01

Range-gated technology has been a hot research field in recent years due to its high effective back scattering eliminating. As a result, it can enhance the contrast between a target and its background and extent the working distance of the imaging system. The underwater imaging system is required to have the ability to image in low light level conditions, as well as the ability to eliminate the back scattering effect, which means that the receiver has to be high-speed external trigger function, high resolution, high sensitivity, low noise, higher gain dynamic range. When it comes to an intensifier, the noise characteristics directly restrict the observation effect and range of the imaging system. The background noise may decrease the image contrast and sharpness, even covering the signal making it impossible to recognize the target. So it is quite important to investigate the noise characteristics of intensifiers. SNR is an important parameter reflecting the noise features of a system. Through the use of underwater laser range-gated imaging prediction model, and according to the linear SNR system theory, the gated imaging noise performance of the present market adopted super second generation and generation Ⅲ intensifiers were theoretically analyzed. Based on the active laser underwater range-gated imaging model, the effect to the system by gated intensifiers and the relationship between the system SNR and MTF were studied. Through theoretical and simulation analysis to the image intensifier background noise and SNR, the different influence on system SNR by super second generation and generation Ⅲ ICCD was obtained. Range-gated system SNR formula was put forward, and compared the different effect influence on the system by using two kind of ICCDs was compared. According to the matlab simulation, a detailed analysis was carried out theoretically. All the work in this paper lays a theoretical foundation to further eliminating back scattering effect, improving

Restoration and Enhancement of Underwater Images Based on Bright Channel Prior

Directory of Open Access Journals (Sweden)

Yakun Gao

2016-01-01

Full Text Available This paper proposed a new method of underwater images restoration and enhancement which was inspired by the dark channel prior in image dehazing field. Firstly, we proposed the bright channel prior of underwater environment. By estimating and rectifying the bright channel image, estimating the atmospheric light, and estimating and refining the transmittance image, eventually underwater images were restored. Secondly, in order to rectify the color distortion, the restoration images were equalized by using the deduced histogram equalization. The experiment results showed that the proposed method could enhance the quality of underwater images effectively.

Underwater inverse LIBS (iLIBS) for marine archaeology

Science.gov (United States)

Asmus, J.; Magde, M.; Elford, J.; Magde, D.; Parfenov, V.

2013-05-01

In recent years there have been enormous advances in nautical archaeology through developments in SONAR technologies as well as in manned and robotic submersible vehicles. The number of sunken vessel discoveries has escalated in many of the seas of the world in response to the widespread application of these and other new tools. Customarily, surviving artifacts within the debris field of a wreck are collected and then moved to laboratories, centers, or institutions for analyses and possible conservation. Frequently, the conservation phase involves chemical treatments to stabilize an artefact to standard temperature, pressure, and humidity instead of an undersea environment. Many of the artefacts encountered at an underwater site are now characterized and restored in-situ in accordance with modern trends in art conservation. Two examples of this trend are exemplified by the resting place of the wreck of the Titanic in the Atlantic and the Cancun Underwater Park in the Caribbean Sea. These two debris fields have been turned into museums for diving visitors. Several research groups have investigated the possibility of adapting the well-established analytical tool Laser Induced Breakdown Spectroscopy (LIBS) to in-situ elemental analyses of underwater cultural, historic, and archaeological artefacts where discovered, rather than as a phase of a salvage operation. As the underwater laser ablation associated with LIBS generates a "snowplough" shockwave within the aqueous matrix, the atomic emission spectrum is usually severely attenuated in escaping from the target. Consequently, probative experiments to date generally invoke a submerged air chamber or air jet to isolate water from the interaction zone as well as employ more complex double-pulse lasers. These measures impose severe logistical constraints on the examination of widely dispersed underwater artefacts. In order to overcome this constraint we report on water-immersion LIBS experiments performed with oblique

Jellyfish Identification Software for Underwater Laser Cameras (JTRACK

Directory of Open Access Journals (Sweden)

Patrizio Mariani

2018-02-01

Full Text Available Jellyfish can form erratic blooms in response to seasonal and irregular changes in environmental conditions with often large, transient effects on local ecosystem structure as well as effects on several sectors of the marine and maritime economy. Early warning systems able to detect conditions for jelly fish proliferation can enable management responses to mitigate such effects providing benefit to local ecosystems and economies. We propose here the creation of a research team in response to the EU call for proposal under the European Maritime and Fisheries Fund called “Blue Labs: innovative solutions for maritime challenges”. The project will establish a BLUELAB team with a strong cross-sectorial component that will benefit of the expertise of researchers in IT and Marine Biology, Computer Vision and embedded systems, which will work in collaboration with Industry and Policy maker to develop an early warning system using a new underwater imaging system based on Time of Flight Laser cameras. The camera will be combined to machine learning algorithm allowing autonomous early detection of jellyfish species (e.g. polyp, ephyra and planula stages. The team will develop the system and the companion software and will demonstrate its applications in real case conditions.

Low complexity lossless compression of underwater sound recordings.

Science.gov (United States)

Johnson, Mark; Partan, Jim; Hurst, Tom

2013-03-01

Autonomous listening devices are increasingly used to study vocal aquatic animals, and there is a constant need to record longer or with greater bandwidth, requiring efficient use of memory and battery power. Real-time compression of sound has the potential to extend recording durations and bandwidths at the expense of increased processing operations and therefore power consumption. Whereas lossy methods such as MP3 introduce undesirable artifacts, lossless compression algorithms (e.g., flac) guarantee exact data recovery. But these algorithms are relatively complex due to the wide variety of signals they are designed to compress. A simpler lossless algorithm is shown here to provide compression factors of three or more for underwater sound recordings over a range of noise environments. The compressor was evaluated using samples from drifting and animal-borne sound recorders with sampling rates of 16-240 kHz. It achieves >87% of the compression of more-complex methods but requires about 1/10 of the processing operations resulting in less than 1 mW power consumption at a sampling rate of 192 kHz on a low-power microprocessor. The potential to triple recording duration with a minor increase in power consumption and no loss in sound quality may be especially valuable for battery-limited tags and robotic vehicles.

Remarks on the observability of single beacon underwater navigation

DEFF Research Database (Denmark)

Jouffroy, Jerome; Ross, Andrew

This paper contributes a simple and intuitive result in the analysis of underwater navigation using a single ranging beacon. This analysis should help with the design of small and lightweight underwater vehicles by reducing the amount of instrumentation required for accurate navigation. The concept...

A Secure Communication Suite for Underwater Acoustic Sensor Networks

Directory of Open Access Journals (Sweden)

Angelica Lo Duca

2012-11-01

Full Text Available In this paper we describe a security suite for Underwater Acoustic Sensor Networks comprising both fixed and mobile nodes. The security suite is composed of a secure routing protocol and a set of cryptographic primitives aimed at protecting the confidentiality and the integrity of underwater communication while taking into account the unique characteristics and constraints of the acoustic channel. By means of experiments and simulations based on real data, we show that the suite is suitable for an underwater networking environment as it introduces limited, and sometimes negligible, communication and power consumption overhead.

Underwater Acoustic Target Tracking: A Review

Science.gov (United States)

Han, Ying; Fan, Liying

2018-01-01

Advances in acoustic technology and instrumentation now make it possible to explore marine resources. As a significant component of ocean exploration, underwater acoustic target tracking has aroused wide attention both in military and civil fields. Due to the complexity of the marine environment, numerous techniques have been proposed to obtain better tracking performance. In this paper, we survey over 100 papers ranging from innovative papers to the state-of-the-art in this field to present underwater tracking technologies. Not only the related knowledge of acoustic tracking instrument and tracking progress is clarified in detail, but also a novel taxonomy method is proposed. In this paper, algorithms for underwater acoustic target tracking are classified based on the methods used as: (1) instrument-assisted methods; (2) mode-based methods; (3) tracking optimization methods. These algorithms are compared and analyzed in the aspect of dimensions, numbers, and maneuvering of the tracking target, which is different from other survey papers. Meanwhile, challenges, countermeasures, and lessons learned are illustrated in this paper. PMID:29301318

Afocal viewport optics for underwater imaging

Science.gov (United States)

Slater, Dan

2014-09-01

A conventional camera can be adapted for underwater use by enclosing it in a sealed waterproof pressure housing with a viewport. The viewport, as an optical interface between water and air needs to consider both the camera and water optical characteristics while also providing a high pressure water seal. Limited hydrospace visibility drives a need for wide angle viewports. Practical optical interfaces between seawater and air vary from simple flat plate windows to complex water contact lenses. This paper first provides a brief overview of the physical and optical properties of the ocean environment along with suitable optical materials. This is followed by a discussion of the characteristics of various afocal underwater viewport types including flat windows, domes and the Ivanoff corrector lens, a derivative of a Galilean wide angle camera adapter. Several new and interesting optical designs derived from the Ivanoff corrector lens are presented including a pair of very compact afocal viewport lenses that are compatible with both in water and in air environments and an afocal underwater hyper-hemispherical fisheye lens.

SWARMs Ontology: A Common Information Model for the Cooperation of Underwater Robots

Science.gov (United States)

Li, Xin; Bilbao, Sonia; Martín-Wanton, Tamara; Bastos, Joaquim; Rodriguez, Jonathan

2017-01-01

In order to facilitate cooperation between underwater robots, it is a must for robots to exchange information with unambiguous meaning. However, heterogeneity, existing in information pertaining to different robots, is a major obstruction. Therefore, this paper presents a networked ontology, named the Smart and Networking Underwater Robots in Cooperation Meshes (SWARMs) ontology, to address information heterogeneity and enable robots to have the same understanding of exchanged information. The SWARMs ontology uses a core ontology to interrelate a set of domain-specific ontologies, including the mission and planning, the robotic vehicle, the communication and networking, and the environment recognition and sensing ontology. In addition, the SWARMs ontology utilizes ontology constructs defined in the PR-OWL ontology to annotate context uncertainty based on the Multi-Entity Bayesian Network (MEBN) theory. Thus, the SWARMs ontology can provide both a formal specification for information that is necessarily exchanged between robots and a command and control entity, and also support for uncertainty reasoning. A scenario on chemical pollution monitoring is described and used to showcase how the SWARMs ontology can be instantiated, be extended, represent context uncertainty, and support uncertainty reasoning. PMID:28287468

Modeling the autonomic and metabolic effects of obstructive sleep apnea: A simulation study.

Directory of Open Access Journals (Sweden)

Limei eCheng

2012-01-01

Full Text Available Long term exposure to intermittent hypoxia and sleep fragmentation introduced by recurring obstructive sleep apnea has been linked to subsequent cardiovascular disease and Type 2 diabetes. The underlying mechanisms remain unclear, but impairment of the normal interactions among the systems that regulate autonomic and metabolic function is likely involved. We have extended an existing integrative model of respiratory, cardiovascular and sleep-wake state control, to incorporate a sub-model of glucose-insulin-fatty acid regulation. This computational model is capable of simulating the complex dynamics of cardiorespiratory control, chemoreflex and state-related control of breath-to-breath ventilation, state-related and chemoreflex control of upper airway potency, respiratory and circulatory mechanics, as well as the metabolic control of glucose insulin dynamics and its interactions with the autonomic control. The interactions between autonomic and metabolic control include the circadian regulation of epinephrine secretion, epinephrine regulation on dynamic fluctuations in glucose and free-fatty acid in plasma, metabolic coupling among tissues and organs provided by insulin and epinephrine, as well as the effect of insulin on peripheral vascular sympathetic activity. These model simulations provide insight into the relative importance of the various mechanisms that determine the acute and chronic physiological effects of sleep-disordered breathing. The model can also be used to investigate the effects of a variety of interventions, such as different glucose clamps, the intravenous glucose tolerance test and the application of continuous positive airway pressure on obstructive sleep apnea subjects. As such, this model provides the foundation on which future efforts to simulate disease progression and the long-term effects of pharmacological intervention can be based.

Underwater running device

International Nuclear Information System (INIS)

Kogure, Sumio; Matsuo, Takashiro; Yoshida, Yoji

1996-01-01

An underwater running device for an underwater inspection device for detecting inner surfaces of a reactor or a water vessel has an outer frame and an inner frame, and both of them are connected slidably by an air cylinder and connected rotatably by a shaft. The outer frame has four outer frame legs, and each of the outer frame legs is equipped with a sucker at the top end. The inner frame has four inner frame legs each equipped with a sucker at the top end. The outer frame legs and the inner frame legs are each connected with the outer frame and the inner frame by the air cylinder. The outer and the inner frame legs can be elevated or lowered (or extended or contracted) by the air cylinder. The sucker is connected with a jet pump-type negative pressure generator. The device can run and move by repeating attraction and releasing of the outer frame legs and the inner frame legs alternately while maintaining the posture of the inspection device stably. (I.N.)

Smelling and Tasting Underwater.

Science.gov (United States)

Atema, Jelle

1980-01-01

Discusses differences between smell and taste, comparing these senses in organisms in aquatic and terrestrial environments. Describes the chemical environment underwater and in air, differences in chemoreceptors to receive stimuli, and the organs, brain, and behavior involved in chemoreception. (CS)

Localization of Energy Harvesting Empowered Underwater Optical Wireless Sensor Networks

KAUST Repository

Saeed, Nasir

2017-12-20

In this paper, a received signal strength (RSS) based localization technique is developed for energy harvesting underwater optical wireless sensor networks (EH-UOWSNs), where the optical noise sources and channel impairments of seawater pose significant challenges for range estimation. Energy limitation is another major problem due to the limited battery power and difficulty in replacing or recharging the battery of an underwater sensor node. In the proposed framework, sensor nodes with insufficient battery, harvest the energy and starts communicating once it has sufficient energy storage. Network localization is carried out by measuring the RSSs of active nodes, which are modeled based on the underwater optical communication channel characteristics. Thereafter, block kernel matrices are computed for the RSS based range measurements. Unlike the traditional shortest-path approach, the proposed technique reduces the shortest path estimation for each block kernel matrix. Once the complete block kernel matrices are available, a closed form localization technique is developed to find the location of every optical sensor node in the network. Furthermore, an analytical expression for Cramer Rao lower bound (CRLB) is derived as a benchmark to compare the localization performance of the proposed technique. Finally, extensive simulations show that the proposed technique outperforms the well-known network localization techniques.

Underwater Coatings for Contamination Control

International Nuclear Information System (INIS)

Julia L. Tripp; Kip Archibald; Ann-Marie Phillips; Joseph Campbell

2004-01-01

The Idaho National Engineering and Environmental Laboratory (INEEL) is deactivating several fuel storage basins. Airborne contamination is a concern when the sides of the basins are exposed and allowed to dry during water removal. One way of controlling this airborne contamination is to fix the contamination in place while the pool walls are still submerged. There are many underwater coatings available on the market that are used in marine, naval and other applications. A series of tests were run to determine whether the candidate underwater fixatives are easily applied and adhere well to the substrates (pool wall materials) found in INEEL fuel pools. The four pools considered included (1) Test Area North (TAN-607) with epoxy painted concrete walls; (2) Idaho Nuclear Technology and Engineering Center (INTEC) (CPP-603) with bare concrete walls; (3) Materials Test Reactor (MTR) Canal with stainless steel lined concrete walls; and (4) Power Burst Facility (PBF-620) with stainless steel lined concrete walls on the bottom and epoxy painted carbon steel lined walls on the upper portions. Therefore, the four materials chosen for testing included bare concrete, epoxy painted concrete, epoxy painted carbon steel, and stainless steel. The typical water temperature of the pools varies from 55 F to 80 F dependent on the pool and the season. These tests were done at room temperature. The following criteria were used during this evaluation. The underwater coating must: (1) Be easy to apply; (2) Adhere well to the four surfaces of interest; (3) Not change or have a negative impact on water chemistry or clarity; (4) Not be hazardous in final applied form; and (5) Be proven in other underwater applications. In addition, it is desirable for the coating to have a high pigment or high cross-link density to prevent radiation from penetrating. This paper will detail the testing completed and the test results. A proprietary two-part, underwater epoxy owned by S. G. Pinney and Associates

Underwater Inherent Optical Properties Estimation Using a Depth Aided Deep Neural Network

Directory of Open Access Journals (Sweden)

Zhibin Yu

2017-01-01

Full Text Available Underwater inherent optical properties (IOPs are the fundamental clues to many research fields such as marine optics, marine biology, and underwater vision. Currently, beam transmissometers and optical sensors are considered as the ideal IOPs measuring methods. But these methods are inflexible and expensive to be deployed. To overcome this problem, we aim to develop a novel measuring method using only a single underwater image with the help of deep artificial neural network. The power of artificial neural network has been proved in image processing and computer vision fields with deep learning technology. However, image-based IOPs estimation is a quite different and challenging task. Unlike the traditional applications such as image classification or localization, IOP estimation looks at the transparency of the water between the camera and the target objects to estimate multiple optical properties simultaneously. In this paper, we propose a novel Depth Aided (DA deep neural network structure for IOPs estimation based on a single RGB image that is even noisy. The imaging depth information is considered as an aided input to help our model make better decision.

Underwater Inherent Optical Properties Estimation Using a Depth Aided Deep Neural Network.

Science.gov (United States)

Yu, Zhibin; Wang, Yubo; Zheng, Bing; Zheng, Haiyong; Wang, Nan; Gu, Zhaorui

2017-01-01

Underwater inherent optical properties (IOPs) are the fundamental clues to many research fields such as marine optics, marine biology, and underwater vision. Currently, beam transmissometers and optical sensors are considered as the ideal IOPs measuring methods. But these methods are inflexible and expensive to be deployed. To overcome this problem, we aim to develop a novel measuring method using only a single underwater image with the help of deep artificial neural network. The power of artificial neural network has been proved in image processing and computer vision fields with deep learning technology. However, image-based IOPs estimation is a quite different and challenging task. Unlike the traditional applications such as image classification or localization, IOP estimation looks at the transparency of the water between the camera and the target objects to estimate multiple optical properties simultaneously. In this paper, we propose a novel Depth Aided (DA) deep neural network structure for IOPs estimation based on a single RGB image that is even noisy. The imaging depth information is considered as an aided input to help our model make better decision.

Remote Underwater Characterization System - Innovative Technology Summary Report

International Nuclear Information System (INIS)

Willis, W.D.

1999-01-01

Characterization and inspection of water-cooled and moderated nuclear reactors and fuel storage pools requires equipment capable of operating underwater. Similarly, the deactivation and decommissioning of older nuclear facilities often requires the facility owner to accurately characterize underwater structures and equipment which may have been sitting idle for years. The Remote Underwater Characterization System (RUCS) is a small, remotely operated submersible vehicle intended to serve multiple purposes in underwater nuclear operations. It is based on the commercially-available Scallop vehicle 1 , but has been modified by the Department of Energys Robotics Technology Development Program to add auto-depth control, and vehicle orientation and depth monitoring at the operator control panel. The RUCS is designed to provide visual and gamma radiation characterization, even in confined or limited access areas. It was demonstrated in August 1998 at the Idaho National Engineering and Environmental Laboratory (INEEL) as part of the INEEL Large Scale Demonstration and Deployment Project. During the demonstration it was compared in a ''head-to-head fashion with the baseline characterization technology. This paper summarizes the results of the demonstration and lessons learned; comparing and contrasting both technologies in the areas of cost, visual characterization, radiological characterization, and overall operations

Robotics Vision-based Heuristic Reasoning for Underwater Target Tracking and Navigation

OpenAIRE

Kia, Chua; Arshad, Mohd Rizal

2006-01-01

This paper presents a robotics vision-based heuristic reasoning system for underwater target tracking and navigation. This system is introduced to improve the level of automation of underwater Remote Operated Vehicles (ROVs) operations. A prototype which combines computer vision with an underwater robotics system is successfully designed and developed to perform target tracking and intelligent navigation. This study focuses on developing image processing algorithms and fuzzy inference system ...

Cardiovascular response during submaximal underwater treadmill exercise in stroke patients.

Science.gov (United States)

Yoo, Jeehyun; Lim, Kil-Byung; Lee, Hong-Jae; Kwon, Yong-Geol

2014-10-01

To evaluate the cardiovascular response during head-out water immersion, underwater treadmill gait, and land treadmill gait in stroke patients. Ten stroke patients were recruited for underwater and land treadmill gait sessions. Each session was 40 minutes long; 5 minutes for standing rest on land, 5 minutes for standing rest in water or on treadmill, 20 minutes for treadmill walking in water or on land, 5 minutes for standing rest in water or on treadmill, and 5 minutes for standing rest on land. Blood pressure (BP) and heart rate (HR) were measured during each session. In order to estimate the cardiovascular workload and myocardial oxygen demand, the rate pressure product (RPP) value was calculated by multiplying systolic BP (SBP) by HR. SBP, DBP, mean BP (mBP), and RPP decreased significantly after water immersion, but HR was unchanged. During underwater and land treadmill gait, SBP, mBP, DBP, RPP, and HR increased. However, the mean maximum increases in BP, HR and RPP of underwater treadmill walking were significantly lower than that of land treadmill walking. Stroke patients showed different cardiovascular responses during water immersion and underwater gait as opposed to standing and treadmill-walking on land. Water immersion and aquatic treadmill gait may reduce the workload of the cardiovascular system. This study suggested that underwater treadmill may be a safe and useful option for cardiovascular fitness and early ambulation in stroke rehabilitation.

Underwater sound transmission through arrays of disk cavities in a soft elastic medium.

Science.gov (United States)

Calvo, David C; Thangawng, Abel L; Layman, Christopher N; Casalini, Riccardo; Othman, Shadi F

2015-10-01

Scattering from a cavity in a soft elastic medium, such as silicone rubber, resembles scattering from an underwater bubble in that low-frequency monopole resonance is obtainable in both cases. Arrays of cavities can therefore be used to reduce underwater sound transmission using thin layers and low void fractions. This article examines the role of cavity shape by microfabricating arrays of disk-shaped air cavities into single and multiple layers of polydimethylsiloxane. Comparison is made with the case of equivalent volume cylinders which approximate spheres. Measurements of ultrasonic underwater sound transmission are compared with finite element modeling predictions. The disks provide a deeper transmission minimum at a lower frequency owing to the drum-type breathing resonance. The resonance of a single disk cavity in an unbounded medium is also calculated and compared with a derived estimate of the natural frequency of the drum mode. Variation of transmission is determined as a function of disk tilt angle, lattice constant, and layer thickness. A modeled transmission loss of 18 dB can be obtained at a wavelength about 20 times the three-layer thickness, and thinner results (wavelength/thickness ∼ 240) are possible for the same loss with a single layer depending on allowable hydrostatic pressure.

Channel coding for underwater acoustic single-carrier CDMA communication system

Science.gov (United States)

Liu, Lanjun; Zhang, Yonglei; Zhang, Pengcheng; Zhou, Lin; Niu, Jiong

2017-01-01

CDMA is an effective multiple access protocol for underwater acoustic networks, and channel coding can effectively reduce the bit error rate (BER) of the underwater acoustic communication system. For the requirements of underwater acoustic mobile networks based on CDMA, an underwater acoustic single-carrier CDMA communication system (UWA/SCCDMA) based on the direct-sequence spread spectrum is proposed, and its channel coding scheme is studied based on convolution, RA, Turbo and LDPC coding respectively. The implementation steps of the Viterbi algorithm of convolutional coding, BP and minimum sum algorithms of RA coding, Log-MAP and SOVA algorithms of Turbo coding, and sum-product algorithm of LDPC coding are given. An UWA/SCCDMA simulation system based on Matlab is designed. Simulation results show that the UWA/SCCDMA based on RA, Turbo and LDPC coding have good performance such that the communication BER is all less than 10-6 in the underwater acoustic channel with low signal to noise ratio (SNR) from -12 dB to -10dB, which is about 2 orders of magnitude lower than that of the convolutional coding. The system based on Turbo coding with Log-MAP algorithm has the best performance.

A Review of the Emerging Field of Underwater Mass Spectrometry

Directory of Open Access Journals (Sweden)

Emily Chua

2016-11-01

Full Text Available Mass spectrometers are versatile sensor systems, owing to their high sensitivity and ability to simultaneously measure multiple chemical species. Over the last two decades, traditional laboratory-based membrane inlet mass spectrometers have been adapted for underwater use. Underwater mass spectrometry has drastically improved our capability to monitor a broad suite of gaseous compounds (e.g., dissolved atmospheric gases, light hydrocarbons, and volatile organic compounds in the aquatic environment. Here we provide an overview of the progress made in the field of underwater mass spectrometry since its inception in the 1990s to the present. In particular, we discuss the approaches undertaken by various research groups in developing in situ mass spectrometers. We also provide examples to illustrate how underwater mass spectrometers have been used in the field. Finally, we present future trends in the field of in situ mass spectrometry. Most of these efforts are aimed at improving the quality and spatial and temporal scales of chemical measurements in the ocean. By providing up-to-date information on underwater mass spectrometry, this review offers guidance for researchers interested in adapting this technology as well as goals for future progress in the field.

Development of An Autonomous Underwater Glider for Observing Physical Ocean Parameters in Indonesian Seas

Science.gov (United States)

Ajie Linarka, Utoyo; Riyanto Trilaksono, Bambang; Sagala, M. Faisal; Hidayat, Egi; Sopaheluwakan, Ardhasena; Rizal, Jose; Heriyanto, Eko; Amsal Harapan, Ferdika; Eka Syahputra Makmur, Erwin

2017-04-01

Conducting a sustained monitoring and surveying of physical ocean parameters for research or operational purposes using moorings and ships would require high cost. Development of an inexpensive instrument capable to perform such tasks not only could reduce cost and risks but also increase cruising range and depth. For that reason, a prototype of underwater glider was developed, named "GaneshBlue". GaneshBlue works based on gliding principles which utilizes pitch angle and buoyancy control for moving. For one gliding movement, GaneshBlue passed through 5 phases of surface, descent, transition, ascent and back to surface. The glider is equipped with basic navigation system and remote control, programmable survey planning, temperature and salinity sampling instruments, lithium batteries for power supply, and information processing software. A field test at the shallow water showed that GaneshBule has successfully demonstrated gliding and surfacing movements with surge motion speed reaching 20 cm s-1and 20 m in depths. During the field test the glider was also equipped with three instruments, i.e. Inertial Measurement Unit (IMU) to estimate glider's speed and orientation; MiniCT to acquire temperature and conductivity data; and Altisounder to determine its distance to sea surface and to seabed. In general, all the instruments performed well but filter algorithm needs to be implemented on data collection procedure to remove data outliers.

State-of-the-Art System Solutions for Unmanned Underwater Vehicles

Directory of Open Access Journals (Sweden)

A. E. Yilmaz

2009-12-01

Full Text Available Unmanned Underwater Vehicles (UUVs have gained popularity for the last decades, especially for the purpose of not risking human life in dangerous operations. On the other hand, underwater environment introduces numerous challenges in navigation, control and communication of such vehicles. Certainly, this fact makes the development of these vehicles more interesting and engineering-wise more attractive. In this paper, we first revisit the existing technology and methodology for the solution of aforementioned problems, then we try to come up with a system solution of a generic unmanned underwater vehicles.

Toward Self-Referential Autonomous Learning of Object and Situation Models.

Science.gov (United States)

Damerow, Florian; Knoblauch, Andreas; Körner, Ursula; Eggert, Julian; Körner, Edgar

2016-01-01

Most current approaches to scene understanding lack the capability to adapt object and situation models to behavioral needs not anticipated by the human system designer. Here, we give a detailed description of a system architecture for self-referential autonomous learning which enables the refinement of object and situation models during operation in order to optimize behavior. This includes structural learning of hierarchical models for situations and behaviors that is triggered by a mismatch between expected and actual action outcome. Besides proposing architectural concepts, we also describe a first implementation of our system within a simulated traffic scenario to demonstrate the feasibility of our approach.

Isolation and biochemical characterization of underwater adhesives from diatoms.

Science.gov (United States)

Poulsen, Nicole; Kröger, Nils; Harrington, Matthew J; Brunner, Eike; Paasch, Silvia; Buhmann, Matthias T

2014-01-01

Many aquatic organisms are able to colonize surfaces through the secretion of underwater adhesives. Diatoms are unicellular algae that have the capability to colonize any natural and man-made submerged surfaces. There is great technological interest in both mimicking and preventing diatom adhesion, yet the biomolecules responsible have so far remained unidentified. A new method for the isolation of diatom adhesive material is described and its amino acid and carbohydrate composition determined. The adhesive materials from two model diatoms show differences in their amino acid and carbohydrate compositions, but also share characteristic features including a high content of uronic acids, the predominance of hydrophilic amino acid residues, and the presence of 3,4-dihydroxyproline, an extremely rare amino acid. Proteins containing dihydroxyphenylalanine, which mediate underwater adhesion of mussels, are absent. The data on the composition of diatom adhesives are consistent with an adhesion mechanism based on complex coacervation of polyelectrolyte-like biomolecules.

The aquatic tympanic ear: convergent adaptations for underwater hearing in three tetrapods

DEFF Research Database (Denmark)

Christensen-Dalsgaard, Jakob; Wahlberg, Magnus; Larsen, Ole Næsbye

pressure, low particle motion medium, and the consequence is that an efficient underwater ear is sensitive to sound pressure. It is often stated that underwater hearing can work efficiently without a middle ear apparatus by bone conduction, since sound is transmitted from water to inner ear tissue...... is modified (cartilaginous or partly cartilaginous). In all three species, the lowest threshold to underwater sound is at this peak frequency and is around 80 dB re 1 µPa. The sensitivity to sound pressure is slightly lower in water than in air, making underwater hearing much more efficient in terms of sound...

Underwater Sensor Networks: A New Energy Efficient and Robust Architecture

NARCIS (Netherlands)

Climent, Salvador; Capella, Juan Vincente; Meratnia, Nirvana; Serrano, Juan José

2012-01-01

The specific characteristics of underwater environments introduce new challenges for networking protocols. In this paper, a specialized architecture for underwater sensor networks (UWSNs) is proposed and evaluated. Experiments are conducted in order to analyze the suitability of this protocol for

Underwater methods for study of salmonids in the Intermountain West

Science.gov (United States)

Russell F. Thurow

1994-01-01

This guide describes underwater methods using snorkeling gear to study fish populations in flowing waters of the Intermountain West. It outlines procedures for estimating salmonid abundance and habitat use and provides criteria for identifying and estimating the size of fish underwater.

Underwater detection by using ultrasonic sensor

Science.gov (United States)

Bakar, S. A. A.; Ong, N. R.; Aziz, M. H. A.; Alcain, J. B.; Haimi, W. M. W. N.; Sauli, Z.

2017-09-01

This paper described the low cost implementation of hardware and software in developing the system of ultrasonic which can visualize the feedback of sound in the form of measured distance through mobile phone and monitoring the frequency of detection by using real time graph of Java application. A single waterproof transducer of JSN-SR04T had been used to determine the distance of an object based on operation of the classic pulse echo detection method underwater. In this experiment, the system was tested by placing the housing which consisted of Arduino UNO, Bluetooth module of HC-06, ultrasonic sensor and LEDs at the top of the box and the transducer was immersed in the water. The system which had been tested for detection in vertical form was found to be capable of reporting through the use of colored LEDs as indicator to the relative proximity of object distance underwater form the sensor. As a conclusion, the system can detect the presence of an object underwater within the range of ultrasonic sensor and display the measured distance onto the mobile phone and the real time graph had been successfully generated.

Symmetries and solutions of the non-autonomous von Bertalanffy equation

Science.gov (United States)

Edwards, Maureen P.; Anderssen, Robert S.

2015-05-01

For growth in a closed environment, which is indicative of the situation in laboratory experiments, autonomous ODE models do not necessarily capture the dynamics under investigation. The importance and impact of a closed environment arise when the question under examination relates, for example, to the number of the surviving microbes, such as in a study of the spoilage and contamination of food, the gene silencing activity of fungi or the production of a chemical compound by bacteria or fungi. Autonomous ODE models are inappropriate as they assume that only the current size of the population controls the growth-decay dynamics. This is reflected in the fact that, asymptotically, their solutions can only grow or decay monotonically or asymptote. Non-autonomous ODE models are not so constrained. A natural strategy for the choice of non-autonomous ODEs is to take appropriate autonomous ones and change them to be non-autonomous through the introduction of relevant non-autonomous terms. This is the approach in this paper with the focus being the von Bertalanffy equation. Since this equation has independent importance in relation to practical applications in growth modelling, it is natural to explore the deeper relationships between the introduced non-autonomous terms through a symmetry analysis, which is the purpose and goal of the current paper. Infinitesimals are derived which allow particular forms of the non-autonomous von Bertalanffy equation to be transformed into autonomous forms for which some new analytic solutions have been found.

Underwater laser cladding and seal welding for INCONEL 52

International Nuclear Information System (INIS)

Tamura, Masataka; Kouno, Wataru; Makino, Yoshinobu; Kawano, Shohei; Yoda, Masaki

2007-01-01

Recently, stress corrosion cracking (SCC) has been observed at aged components of nuclear power plants under water environment and high exposure of radiation. Toshiba has been developing both an underwater laser welding directly onto surface of the aged components as maintenance and repair techniques. This paper reports underwater laser cladding and seal welding for INCONEL 52. (author)

Autonomous Landing on Moving Platforms

KAUST Repository

Mendoza Chavez, Gilberto

2016-08-01

This thesis investigates autonomous landing of a micro air vehicle (MAV) on a nonstationary ground platform. Unmanned aerial vehicles (UAVs) and micro air vehicles (MAVs) are becoming every day more ubiquitous. Nonetheless, many applications still require specialized human pilots or supervisors. Current research is focusing on augmenting the scope of tasks that these vehicles are able to accomplish autonomously. Precise autonomous landing on moving platforms is essential for self-deployment and recovery of MAVs, but it remains a challenging task for both autonomous and piloted vehicles. Model Predictive Control (MPC) is a widely used and effective scheme to control constrained systems. One of its variants, output-feedback tube-based MPC, ensures robust stability for systems with bounded disturbances under system state reconstruction. This thesis proposes a MAV control strategy based on this variant of MPC to perform rapid and precise autonomous landing on moving targets whose nominal (uncommitted) trajectory and velocity are slowly varying. The proposed approach is demonstrated on an experimental setup.

The WODA guidance paper on underwater sound from dredging (abstract)

NARCIS (Netherlands)

Thomsen, F.; Borsani, F.; Clarke, D.; Jong, C.A.F. de; Witt, P. de; Holtkamp, M.; Goethals, F.; San Martin, E.; Spadaro, P.; Raalte, G. van; Jensen, A.

2013-01-01

The World Organisation of Dredging Associations (WODA) has identified underwater sound as an environmental issue that needs further consideration. A WODA Expert Group on Underwater Sound (WEGUS) was established to provide a guidance paper on dredging sound, impact on aquatic biota and advice on

Defect detectability of eddy current testing for underwater laser beam welding

International Nuclear Information System (INIS)

Ueno, Souichi; Kobayashi, Noriyasu; Ochiai, Makoto; Kasuya, Takashi; Yuguchi, Yasuhiro

2011-01-01

We clarified defect detectability of eddy current testing (ECT) as a surface inspection technique for underwater laser beam welding works of dissimilar metal welding (DMW) of reactor vessel nozzle. The underwater laser beam welding procedure includes groove caving as a preparation, laser beam welding in the grooves and welded surface grinding as a post treatment. Therefore groove and welded surface inspections are required in the underwater condition. The ECT is a major candidate as this inspection technique because a penetrant testing is difficult to perform in the underwater condition. Several kinds of experiments were curried out using a cross coil an ECT probe and ECT data acquisition system in order to demonstrate the ECT defect detectability. We used specimens, simulating groove and DMW materials at an RV nozzle, with electro-discharge machining (EDM) slits over it. Additionally, we performed a detection test for artificial stress corrosion cracking (SCC) defects. From these experimental results, we confirmed that an ECT was possible to detect EDM slits 0.3 mm or more in depth and artificial SCC defects 0.02 mm to 0.48 mm in depth on machined surface. Furthermore, the underwater ECT defect detectability is equivalent to that in air. We clarified an ECT is sufficiently usable as a surface inspection technique for underwater laser beam welding works. (author)

Experimental Study on the Measurement of Water Bottom Vibration Induced by Underwater Drilling Blasting

OpenAIRE

Wenbin, Gu; Jianghai, Chen; Zhenxiong, Wang; Zhihua, Wang; Jianqing, Liu; Ming, Lu

2015-01-01

Due to the lack of proper instrumentations and the difficulties in underwater measurements, the studies about water bottom vibration induced by underwater drilling blasting are seldom reported. In order to investigate the propagation and attenuation laws of blasting induced water bottom vibration, a water bottom vibration monitor was developed with consideration of the difficulties in underwater measurements. By means of this equipment, the actual water bottom vibration induced by underwater ...

Water-Depth-Based Prediction Formula for the Blasting Vibration Velocity of Lighthouse Caused by Underwater Drilling Blasting

OpenAIRE

Gu, Wenbin; Wang, Zhenxiong; Liu, Jianqing; Xu, Jinglin; Liu, Xin; Cao, Tao

2017-01-01

Lighthouses are the most important hydraulic structures that should be protected during underwater drilling blasting. Thus, the effect of blasting vibration on lighthouse should be studied. On the basis of the dimensional analysis, we deduced a revised formula for water depth based on Sodev’s empirical formula and established the linear fitting model. During the underwater reef project in the main channel of Shipu Harbor in the Ningbo–Zhoushan Port, the blasting vibration data of the lighthou...

Constrained Multi-Body Dynamics for Modular Underwater Robots — Theory and Experiments

DEFF Research Database (Denmark)

Nielsen, Mikkel Cornelius; Eidsvik, Ole Alexander; Blanke, Mogens

2018-01-01

This paper investigates the problem of modelling a system of interconnected underwater robots with highly coupled dynamics. The objective is to develop a mathematical description of the system that captures its most significant dynamics. The proposed modelling method is based on active constraint...... on a BlueROV vehicle to determine the model parameters. The applicability of the modelling approach is assessed by comparing experimental data to simulations of an equivalent model synthesised using the proposed theory....

Applicability evaluation of eddy current testing for underwater laser beam welding

International Nuclear Information System (INIS)

Kobayashi, Noriyasu; Kasuya, Takashi; Ueno, Souichi; Ochiai, Makoto; Yuguchi, Yasuhiro

2010-01-01

We clarified a defect detecting capability of eddy current testing (ECT) as a surface inspection technique for underwater laser beam welding. An underwater laser beam welding procedure includes groove caving as a preparation, laser beam welding in groove and welding surface grinding as a post treatment. Therefore groove and grinded welding surface inspections are required underwater. We curried out defect detection tests using three kinds of specimens simulated a groove, reactor vessel nozzle dissimilar metal welding materials and a laser beam welding material with a cross coil ECT probe. From experimental results, we confirmed that it is possible to detect 0.3 mm or more depth electro-discharge machining slits on machining surfaces in all specimens and an ECT has possibility as a surface inspection technique for underwater laser beam welding. (author)

Robot fish bio-inspired fishlike underwater robots

CERN Document Server

Li, Zheng; Youcef-Toumi, Kamal; Alvarado, Pablo

2015-01-01

This book provides a comprehensive coverage on robot fish including design, modeling and optimization, control, autonomous control and applications. It gathers contributions by the leading researchers in the area. Readers will find the book very useful for designing and building robot fish, not only in theory but also in practice. Moreover, the book discusses various important issues for future research and development, including design methodology, control methodology, and autonomous control strategy. This book is intended for researchers and graduate students in the fields of robotics, ocean engineering and related areas.

A Survey of Routing Issues and Associated Protocols in Underwater Wireless Sensor Networks

Directory of Open Access Journals (Sweden)

Muhammad Khalid

2017-01-01

Full Text Available Underwater wireless sensor networks are a newly emerging wireless technology in which small size sensors with limited energy and limited memory and bandwidth are deployed in deep sea water and various monitoring operations like tactical surveillance, environmental monitoring, and data collection are performed through these tiny sensors. Underwater wireless sensor networks are used for the exploration of underwater resources, oceanographic data collection, flood or disaster prevention, tactical surveillance systems, and unmanned underwater vehicles. Sensor nodes consist of a small memory, a central processing unit, and an antenna. Underwater networks are much different from terrestrial sensor networks as radio waves cannot be used in underwater wireless sensor networks. Acoustic channels are used for communication in deep sea water. Acoustic signals have many limitations, such as limited bandwidth, higher end-to-end delay, network path loss, higher propagation delay, and dynamic topology. Usually, these limitations result in higher energy consumption with a smaller number of packets delivered. The main aim nowadays is to operate sensor nodes having a smaller battery for a longer time in the network. This survey has discussed the state-of-the-art localization based and localization-free routing protocols. Routing associated issues in the area of underwater wireless sensor networks have also been discussed.

Evaluation of Underwater Image Enhancement Algorithms under Different Environmental Conditions

Directory of Open Access Journals (Sweden)

Marino Mangeruga

2018-01-01

Full Text Available Underwater images usually suffer from poor visibility, lack of contrast and colour casting, mainly due to light absorption and scattering. In literature, there are many algorithms aimed to enhance the quality of underwater images through different approaches. Our purpose was to identify an algorithm that performs well in different environmental conditions. We have selected some algorithms from the state of the art and we have employed them to enhance a dataset of images produced in various underwater sites, representing different environmental and illumination conditions. These enhanced images have been evaluated through some quantitative metrics. By analysing the results of these metrics, we tried to understand which of the selected algorithms performed better than the others. Another purpose of our research was to establish if a quantitative metric was enough to judge the behaviour of an underwater image enhancement algorithm. We aim to demonstrate that, even if the metrics can provide an indicative estimation of image quality, they could lead to inconsistent or erroneous evaluations.

Study on underwater plasma arc cutting technology

International Nuclear Information System (INIS)

Yada, Toshio; Nakamura, Uhachiro; Tomidokoro, Sakae; Fukuzawa, Mitsuo

1980-01-01

The zirconium alloy tube of the impile creep test facility had been subjected to inner pressure in the Japan Material Testing Reactor (JMTR) environment. In the near future, it will be necessary to dismantle the facility and to take out the tube for such examinations as irradiation effects on material properties. In order to establish the dismantling technology for the radioactive facility, a study on underwater plasma arc cutting has been carried out since 1977. Primarily, optimum underwater cutting sequence and conditions were studied in details for developing the remote control handling and the cutting system. Further, the amounts of particles suspended in water as well as those contained in bubbled gas were quantitatively analyzed for developing a safe removal system for contaminants which were produced by cutting the radioactive material. As a result of this study, it has been concluded that the underwater plasma arc cutting method is generally suitable and effective for dismantling such radioactive material as the impile creep test facility of the JMTR. (author)

Hydrodynamic design of an underwater hull cleaning robot and its evaluation

Directory of Open Access Journals (Sweden)

Man Hyung Lee

2012-12-01

Full Text Available An underwater hull cleaning robot can be a desirable choice for the cleaning of large ships. It can make the cleaning process safe and economical. This paper presents a hydrodynamic design of an underwater cleaning robot and its evaluation for an underwater ship hull cleaning robot. The hydrodynamic design process of the robot body is described in detail. Optimal body design process with compromises among conflicting design requirements is given. Experimental results on the hydrodynamic performance of the robot are given.

Monterey Bay ambient noise profiles using underwater gliders

OpenAIRE

Chandrayadula, Tarun K.; Miller, Chris W.; Joseph, John

2013-01-01

The article of record as published may be found at http://dx.doi.org/10.1121/1.4799131 In 2012, during two separate week-long deployments, underwater gliders outfitted with external hydrophones profiled the upper 100-200 m of the Monterey Bay. The environment contained various noises made by marine mammals, ships, winds, and earthquakes. Unlike hydrophone receivers moored to a fixed location, moving gliders measure noise variability across a wide terrain. However, underwater mobile s...

Developing national on-line services to annotate and analyse underwater imagery in a research cloud

Science.gov (United States)

Proctor, R.; Langlois, T.; Friedman, A.; Davey, B.

2017-12-01

Fish image annotation data is currently collected by various research, management and academic institutions globally (+100,000's hours of deployments) with varying degrees of standardisation and limited formal collaboration or data synthesis. We present a case study of how national on-line services, developed within a domain-oriented research cloud, have been used to annotate habitat images and synthesise fish annotation data sets collected using Autonomous Underwater Vehicles (AUVs) and baited remote underwater stereo-video (stereo-BRUV). Two developing software tools have been brought together in the marine science cloud to provide marine biologists with a powerful service for image annotation. SQUIDLE+ is an online platform designed for exploration, management and annotation of georeferenced images & video data. It provides a flexible annotation framework allowing users to work with their preferred annotation schemes. We have used SQUIDLE+ to sample the habitat composition and complexity of images of the benthos collected using stereo-BRUV. GlobalArchive is designed to be a centralised repository of aquatic ecological survey data with design principles including ease of use, secure user access, flexible data import, and the collection of any sampling and image analysis information. To easily share and synthesise data we have implemented data sharing protocols, including Open Data and synthesis Collaborations, and a spatial map to explore global datasets and filter to create a synthesis. These tools in the science cloud, together with a virtual desktop analysis suite offering python and R environments offer an unprecedented capability to deliver marine biodiversity information of value to marine managers and scientists alike.

Design, modeling and optimization of an underwater manipulator with four-bar mechanism and compliant linkage

Energy Technology Data Exchange (ETDEWEB)

Jin, Sang Ok; Kim, Ji Hoon; Bae, Jang Ho; Kim, Jong Won [School of Mechanical and Aerospace Engineering, Seoul National University, Seoul (Korea, Republic of); Seo, Tae Won [School of Mechanical Engineering, Yeungnam University, Gyeongsan (Korea, Republic of)

2016-09-15

Underwater manipulators are very important for a robot to perform a specific operation in water. Conventional robot arm manipulators have been suggested for various operations but have not been suitable for repeated motion in gathering something. This paper presents a new underwater manipulator design for gathering things such as starfish on the sea floor. The manipulator is composed of a four-bar linkage to achieve repeated motion along a loop and compliant linkages to enhance the efficiency of the gathering work. Kinematic and quasi-static analyses were performed to calculate the loop path and the reaction force at the actuation point. Based on the analysis, optimal design was performed to maximize the working distance with the height difference and the reaction moments considered as constraints. A prototype was assembled to test the performance of the manipulator, and the empirical loop path was compared to simulation results.

Design, modeling and optimization of an underwater manipulator with four-bar mechanism and compliant linkage

International Nuclear Information System (INIS)

Jin, Sang Ok; Kim, Ji Hoon; Bae, Jang Ho; Kim, Jong Won; Seo, Tae Won

2016-01-01

Underwater manipulators are very important for a robot to perform a specific operation in water. Conventional robot arm manipulators have been suggested for various operations but have not been suitable for repeated motion in gathering something. This paper presents a new underwater manipulator design for gathering things such as starfish on the sea floor. The manipulator is composed of a four-bar linkage to achieve repeated motion along a loop and compliant linkages to enhance the efficiency of the gathering work. Kinematic and quasi-static analyses were performed to calculate the loop path and the reaction force at the actuation point. Based on the analysis, optimal design was performed to maximize the working distance with the height difference and the reaction moments considered as constraints. A prototype was assembled to test the performance of the manipulator, and the empirical loop path was compared to simulation results

Energy Harvesting Hybrid Acoustic-Optical Underwater Wireless Sensor Networks Localization

Directory of Open Access Journals (Sweden)

Nasir Saeed

2017-12-01

Full Text Available Underwater wireless technologies demand to transmit at higher data rate for ocean exploration. Currently, large coverage is achieved by acoustic sensor networks with low data rate, high cost, high latency, high power consumption, and negative impact on marine mammals. Meanwhile, optical communication for underwater networks has the advantage of the higher data rate albeit for limited communication distances. Moreover, energy consumption is another major problem for underwater sensor networks, due to limited battery power and difficulty in replacing or recharging the battery of a sensor node. The ultimate solution to this problem is to add energy harvesting capability to the acoustic-optical sensor nodes. Localization of underwater sensor networks is of utmost importance because the data collected from underwater sensor nodes is useful only if the location of the nodes is known. Therefore, a novel localization technique for energy harvesting hybrid acoustic-optical underwater wireless sensor networks (AO-UWSNs is proposed. AO-UWSN employs optical communication for higher data rate at a short transmission distance and employs acoustic communication for low data rate and long transmission distance. A hybrid received signal strength (RSS based localization technique is proposed to localize the nodes in AO-UWSNs. The proposed technique combines the noisy RSS based measurements from acoustic communication and optical communication and estimates the final locations of acoustic-optical sensor nodes. A weighted multiple observations paradigm is proposed for hybrid estimated distances to suppress the noisy observations and give more importance to the accurate observations. Furthermore, the closed form solution for Cramer-Rao lower bound (CRLB is derived for localization accuracy of the proposed technique.

Energy Harvesting Hybrid Acoustic-Optical Underwater Wireless Sensor Networks Localization.

Science.gov (United States)

Saeed, Nasir; Celik, Abdulkadir; Al-Naffouri, Tareq Y; Alouini, Mohamed-Slim

2017-12-26

Underwater wireless technologies demand to transmit at higher data rate for ocean exploration. Currently, large coverage is achieved by acoustic sensor networks with low data rate, high cost, high latency, high power consumption, and negative impact on marine mammals. Meanwhile, optical communication for underwater networks has the advantage of the higher data rate albeit for limited communication distances. Moreover, energy consumption is another major problem for underwater sensor networks, due to limited battery power and difficulty in replacing or recharging the battery of a sensor node. The ultimate solution to this problem is to add energy harvesting capability to the acoustic-optical sensor nodes. Localization of underwater sensor networks is of utmost importance because the data collected from underwater sensor nodes is useful only if the location of the nodes is known. Therefore, a novel localization technique for energy harvesting hybrid acoustic-optical underwater wireless sensor networks (AO-UWSNs) is proposed. AO-UWSN employs optical communication for higher data rate at a short transmission distance and employs acoustic communication for low data rate and long transmission distance. A hybrid received signal strength (RSS) based localization technique is proposed to localize the nodes in AO-UWSNs. The proposed technique combines the noisy RSS based measurements from acoustic communication and optical communication and estimates the final locations of acoustic-optical sensor nodes. A weighted multiple observations paradigm is proposed for hybrid estimated distances to suppress the noisy observations and give more importance to the accurate observations. Furthermore, the closed form solution for Cramer-Rao lower bound (CRLB) is derived for localization accuracy of the proposed technique.

Energy Harvesting Hybrid Acoustic-Optical Underwater Wireless Sensor Networks Localization

KAUST Repository

Saeed, Nasir; Celik, Abdulkadir; Al-Naffouri, Tareq Y.; Alouini, Mohamed-Slim

2017-01-01

Underwater wireless technologies demand to transmit at higher data rate for ocean exploration. Currently, large coverage is achieved by acoustic sensor networks with low data rate, high cost, high latency, high power consumption, and negative impact on marine mammals. Meanwhile, optical communication for underwater networks has the advantage of the higher data rate albeit for limited communication distances. Moreover, energy consumption is another major problem for underwater sensor networks, due to limited battery power and difficulty in replacing or recharging the battery of a sensor node. The ultimate solution to this problem is to add energy harvesting capability to the acoustic-optical sensor nodes. Localization of underwater sensor networks is of utmost importance because the data collected from underwater sensor nodes is useful only if the location of the nodes is known. Therefore, a novel localization technique for energy harvesting hybrid acoustic-optical underwater wireless sensor networks (AO-UWSNs) is proposed. AO-UWSN employs optical communication for higher data rate at a short transmission distance and employs acoustic communication for low data rate and long transmission distance. A hybrid received signal strength (RSS) based localization technique is proposed to localize the nodes in AO-UWSNs. The proposed technique combines the noisy RSS based measurements from acoustic communication and optical communication and estimates the final locations of acoustic-optical sensor nodes. A weighted multiple observations paradigm is proposed for hybrid estimated distances to suppress the noisy observations and give more importance to the accurate observations. Furthermore, the closed form solution for Cramer-Rao lower bound (CRLB) is derived for localization accuracy of the proposed technique.

Energy Harvesting Hybrid Acoustic-Optical Underwater Wireless Sensor Networks Localization

KAUST Repository

Saeed, Nasir

2017-12-26

Underwater wireless technologies demand to transmit at higher data rate for ocean exploration. Currently, large coverage is achieved by acoustic sensor networks with low data rate, high cost, high latency, high power consumption, and negative impact on marine mammals. Meanwhile, optical communication for underwater networks has the advantage of the higher data rate albeit for limited communication distances. Moreover, energy consumption is another major problem for underwater sensor networks, due to limited battery power and difficulty in replacing or recharging the battery of a sensor node. The ultimate solution to this problem is to add energy harvesting capability to the acoustic-optical sensor nodes. Localization of underwater sensor networks is of utmost importance because the data collected from underwater sensor nodes is useful only if the location of the nodes is known. Therefore, a novel localization technique for energy harvesting hybrid acoustic-optical underwater wireless sensor networks (AO-UWSNs) is proposed. AO-UWSN employs optical communication for higher data rate at a short transmission distance and employs acoustic communication for low data rate and long transmission distance. A hybrid received signal strength (RSS) based localization technique is proposed to localize the nodes in AO-UWSNs. The proposed technique combines the noisy RSS based measurements from acoustic communication and optical communication and estimates the final locations of acoustic-optical sensor nodes. A weighted multiple observations paradigm is proposed for hybrid estimated distances to suppress the noisy observations and give more importance to the accurate observations. Furthermore, the closed form solution for Cramer-Rao lower bound (CRLB) is derived for localization accuracy of the proposed technique.

Cutting method and device underwater

International Nuclear Information System (INIS)

Takano, Genta; Kamei, Hiromasa; Beppu, Seiji

1998-01-01

A place of material to be cut is surrounded by an openable/closable box. The material to be cut is cut underwater, and materials generated in this case are removed from the cut portion by a pressurized water jet. The removed materials are sucked and recovered together with water in the box. Among the materials caused by the cutting underwater, solid materials not floating on water are caused to stay in the midway of a sucking and recovering channel. A large sucking force might be required for the entire region of the sucking and recovering channel when sucking and recovering large sized solid materials not floating on water, but even large sized materials can be recovered easily according to the present invention since they are recovered after being sucked and stayed in the midway of the sucking and recovering channel. (N.H.)

Summary of the guideline on underwater laser beam repair welding

International Nuclear Information System (INIS)

Ichikawa, Hiroya; Yoda, Masaki; Motora, Yuichi

2013-01-01

It is known that stress corrosion cracking (SCC) might occur at the weld of a reactor pressure vessel or core internals. Underwater laser beam clad welding for mitigation of SCC has been already established and the guideline 'Underwater laser beam clad welding' was published. Moreover, the guideline 'Seal welding' was also published as a repair method for SCC. In addition to these guidelines, the guideline 'Underwater laser beam repair welding' was newly published in November, 2012 for the repair welding after completely removing a SCC crack occurred in weld or base metal. This paper introduces the summary of this guideline. (author)

Application of YAG laser processing in underwater welding and cutting

Energy Technology Data Exchange (ETDEWEB)

Ohwaki, Katsura; Morita, Ichiro; Kojima, Toshio; Sato, Shuichi [Ishikawajima-Harima Heavy Industries Co. Ltd., Tokyo (Japan)

2002-09-01

The high-power YAG laser is a new fabrication tool. The laser torch is easy to combine with complex with complex mechanics because of beam delivery through optical fiber. A direct underwater laser welding technology has been developed and applied to the preservation, maintenance and removal of nuclear power plants. For subdividing or removing operations for retirement of plants, the laser cutting properties were confirmed to allow a maximum cutting thickness of 80 mm. For repairing inner surface of stainless steel tanks, an underwater laser welding system using a remote-controlled robot was developed and the high quality of underwater laser welding was confirmed. (author)

A Secure, Scalable and Elastic Autonomic Computing Systems Paradigm: Supporting Dynamic Adaptation of Self-* Services from an Autonomic Cloud

Directory of Open Access Journals (Sweden)

Abdul Jaleel

2018-05-01

Full Text Available Autonomic computing embeds self-management features in software systems using external feedback control loops, i.e., autonomic managers. In existing models of autonomic computing, adaptive behaviors are defined at the design time, autonomic managers are statically configured, and the running system has a fixed set of self-* capabilities. An autonomic computing design should accommodate autonomic capability growth by allowing the dynamic configuration of self-* services, but this causes security and integrity issues. A secure, scalable and elastic autonomic computing system (SSE-ACS paradigm is proposed to address the runtime inclusion of autonomic managers, ensuring secure communication between autonomic managers and managed resources. Applying the SSE-ACS concept, a layered approach for the dynamic adaptation of self-* services is presented with an online ‘Autonomic_Cloud’ working as the middleware between Autonomic Managers (offering the self-* services and Autonomic Computing System (requiring the self-* services. A stock trading and forecasting system is used for simulation purposes. The security impact of the SSE-ACS paradigm is verified by testing possible attack cases over the autonomic computing system with single and multiple autonomic managers running on the same and different machines. The common vulnerability scoring system (CVSS metric shows a decrease in the vulnerability severity score from high (8.8 for existing ACS to low (3.9 for SSE-ACS. Autonomic managers are introduced into the system at runtime from the Autonomic_Cloud to test the scalability and elasticity. With elastic AMs, the system optimizes the Central Processing Unit (CPU share resulting in an improved execution time for business logic. For computing systems requiring the continuous support of self-management services, the proposed system achieves a significant improvement in security, scalability, elasticity, autonomic efficiency, and issue resolving time

An acoustically controlled tetherless underwater vehicle for installation and maintenance of neutrino detectors in the deep ocean

International Nuclear Information System (INIS)

Ballou, Philip J.

1997-01-01

The task of installing and servicing high energy neutrino detectors in the deep ocean from a surface support vessel is problematic using conventional tethered systems. An array of multiple detector strings rising 500 m from the ocean floor, and forming a grid with 50 m spacing between the strings, presents a substantial entanglement hazard for equipment cables deployed from the surface. Such tasks may be accomplished with fewer risks using a tetherless underwater remotely operated vehicle that has a local acoustic telemetry link to send control commands and sensor data between the vehicle and a stationary hydrophone suspended above or just outside the perimeter of the work site. The Phase I effort involves the development of an underwater acoustic telemetry link for vehicle control and sensor feedback, the evaluation of video compression methods for real-time acoustic transmission of video through the water, and the defining of local control routines on board the vehicle to allow it to perform certain basic maneuvering tasks autonomously, or to initiate a self-rescue if the acoustic control link should be lost. In Phase II, a prototype tetherless vehicle system will be designed and constructed to demonstrate the ability to install cable interconnections within a detector array at 4 km depth. The same control technology could be used with a larger more powerful vehicle to maneuver the detector strings into desired positions as they are being lowered to the ocean floor

Optimum LED wavelength for underwater optical wireless communication at turbid water

Science.gov (United States)

Rosenkrantz, Etai; Arnon, Shlomi

2014-10-01

Underwater optical wireless communication is an emerging technology, which can provide high data rate. High data rate communication is required for applications such as underwater imaging, networks of sensors and swarms of underwater vehicles. These applications pursue an affordable light source, which can be obtained by light emitting diodes (LED). LEDs offer solutions characterized by low cost, high efficiency, reliability and compactness based on off-the-shelf components such as blue and green light emitting diodes. In this paper we present our recent theoretical and experimental results in this field.

Underwater videography and photography in Gulf of Kachchh. Sponsored by Gujarat Ecological Society, Vadodara, Gujarat

Digital Repository Service at National Institute of Oceanography (India)

Marine Archaeology Centre (MAC) has been carrying out underwater explorations and excavations of ancient ports and sunken shipwrecks to preserve underwater cultural heritage. MAC has the infrastructure facility to carry out underwater investigations...

Adaptive Backstepping Controller Design for Leveling Control of an Underwater Platform Based on Joint Space

Directory of Open Access Journals (Sweden)

Zhi-Lin Zeng

2014-01-01

Full Text Available This paper focuses on high precision leveling control of an underwater heavy load platform, which is viewed as an underwater parallel robot on the basis of its work pattern. The kinematic of platform with deformation is analyzed and the dynamics model of joint space is established. An adaptive backstepping controller according to Lyapunov's function is proposed for leveling control of platform based on joint space. Furthermore, the “lowest point fixed angle error” leveling scheme called “chase” is chosen for leveling control of platform. The digital simulation and practical experiment of single joint space actuator are carried out, and the results show high precision servo control of joint space. On the basis of this, the platform leveling control simulation relies on the hardware-in-loop system. The results indicate that the proposed controller can effectively restrain the influence from system parameter uncertainties and external disturbance to realize high precision leveling control of the underwater platform.

A curved electrode electrostatic actuator designed for large displacement and force in an underwater environment

International Nuclear Information System (INIS)

Preetham, B S; Lake, Melinda A; Hoelzle, David J

2017-01-01

There is a need for the development of large displacement ( O (10 −6 ) m) and force ( O (10 −6 ) N) electrostatic actuators with low actuation voltages (<  ±8 V) for underwater bio- MEMS applications. In this paper, we present the design, fabrication, and characterization of a curved electrode electrostatic actuator in a clamped–clamped beam configuration meant to operate in an underwater environment. Our curved electrode actuator is unique in that it operates in a stable manner past the pull-in instability. Models based on the Rayleigh–Ritz method accurately predict the onset of static instability and the displacement versus voltage function, as validated by quasistatic experiments. We demonstrate that the actuator is capable of achieving a large peak-to-peak displacement of 19.5 µ m and force of 43 µ N for a low actuation voltage of less than  ±8 V and is thus appropriate for underwater bio -MEMS applications. (paper)

Underwater nuclear power plant structure

International Nuclear Information System (INIS)

Severs, S.; Toll, H.V.

1982-01-01

A structure for an underwater nuclear power generating plant comprising a triangular platform formed of tubular leg and truss members upon which are attached one or more large spherical pressure vessels and one or more small cylindrical auxiliary pressure vessels. (author)

Analysing deterioration of marble stones exposed to underwater conditions

Science.gov (United States)

Cámara, Beatriz; Álvarez de Buergo, Mónica; Bethencourt, Manuel; Freire-Lista, David; Fort, Rafael

2016-04-01

The peculiar conditions of the marine environment make the conservation of underwater archaeological sites an extremely complex procedure. This is due to the fact that the prevailing conditions in this environment promote the development of deterioration phenomena in submerged artefacts through the synergistic action of physical, chemical and biological factors. The objective of the present investigation was to determine how petrophysical properties of cultural heritage materials can be affected by being exposed to the specific underwater conditions of the sea bottom, and so, to evaluate how this can affect, in a long term, in their durability and evolution when they part of an archaeological site. For this purpose, two types of marble (the Italian Carrara and the Spanish Macael) were subjected to an experiment consisting of exposing stone materials for one and a half year to underwater conditions. The experimental test was located in an archaeological site in the Bay of Cadiz (southern Spain), Bajo del Chapitel (recognized as Cultural Interest), which includes remains of shipwrecks from different periods. In this site, samples were submerged to 12 m depth and placed in the sea bottom simulating the different positions in which underwater archaeological objects can be found (fully exposed, half buried and covered). Petrophysical characterisation involved determination of the apparent and bulk densities, water saturation (maximum water content a material may contain), open porosity (porosity accessible to water), chromatic parameters and ultrasonic velocity. Before measuring, samples were subjected to mechanical cleaning (in those samples with biological colonization) and to removal of salt deposits. Results showed significant differences in these petrophysical properties after underwater submersion, which were directly related to the type of underwater exposure condition. Comparative analysis of petrophysical properties, like the one conducted in this study

FILMING UNDERWATER IN 3D RESPECTING STEREOGRAPHIC RULES

OpenAIRE

R. Rinaldi; H. Hordosch

2015-01-01

After an experimental phase of many years, 3D filming is now effective and successful. Improvements are still possible, but the film industry achieved memorable success on 3D movie’s box offices due to the overall quality of its products. Special environments such as space ("Gravity") and the underwater realm look perfect to be reproduced in 3D. "Filming in space" was possible in "Gravity" using special effects and computer graphic. The underwater realm is still difficult to be handled. Under...

The Trans-Contextual Model of Autonomous Motivation in Education: Conceptual and Empirical Issues and Meta-Analysis.

Science.gov (United States)

Hagger, Martin S; Chatzisarantis, Nikos L D

2016-06-01

The trans-contextual model outlines the processes by which autonomous motivation toward activities in a physical education context predicts autonomous motivation toward physical activity outside of school, and beliefs about, intentions toward, and actual engagement in, out-of-school physical activity. In the present article, we clarify the fundamental propositions of the model and resolve some outstanding conceptual issues, including its generalizability across multiple educational domains, criteria for its rejection or failed replication, the role of belief-based antecedents of intentions, and the causal ordering of its constructs. We also evaluate the consistency of model relationships in previous tests of the model using path-analytic meta-analysis. The analysis supported model hypotheses but identified substantial heterogeneity in the hypothesized relationships across studies unattributed to sampling and measurement error. Based on our meta-analysis, future research needs to provide further replications of the model in diverse educational settings beyond physical education and test model hypotheses using experimental methods.

Elasticity-dependent fast underwater adhesion demonstrated by macroscopic supramolecular assembly.

Science.gov (United States)

Ju, Guannan; Cheng, Mengjiao; Guo, Fengli; Zhang, Qian; Shi, Feng

2018-05-30

Macroscopic supramolecular assembly (MSA) is a recent progress in supramolecular chemistry to associate visible building blocks through non-covalent interactions in a multivalent manner. Although various substrates (e. g. hydrogels, rigid materials) have been used, a general design rule of building blocks in MSA systems and interpretation of the assembly mechanism are still lacking and urgently in demand. Here we design three model systems with varied modulus and correlated the MSA probability with the elasticity. Based on the effects of substrate deformability on multivalency, we have proposed an elastic-modulus-dependent rule that building blocks below a critical modulus of 2.5 MPa can achieve MSA for the used host/guest system. Moreover, this MSA rule applies well to the design of materials applicable for fast underwater adhesion: Soft substrates (0.5 MPa) can achieve underwater adhesion within 10 s with one magnitude higher strength than that of rigid substrates (2.5 MPa). © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.