Arbetet undersöker vilken militär nytta en obemannad autonom undervattensfarkost med syntetisk apertursonar tillför vid sökning efter sjöminor. Genom systemanalys jämförs obemannad autonom undervattensfarkost och syntetisk apertursonar mot ett referenssystem för minsökning som finns i försvarsmakten. Referenssystemet är en fjärrstyrd undervattensfarkost med minjaktsonar. Resultatet med arbetet redovisas som slutsatser och rekommendationer utifrån de grundläggande förmågorna; verkan, uthållighet, rörelse och skydd samt systemets effektivitet vid minsökning. / This thesis studies the military benefits of autonomous underwater vehicle equipped with synthetic aperture sonar conducting mine reconnaissance. The autonomous underwater vehicle and synthetic aperture sonar are compared through system analysis using a reference system within the Swedish Armed Forces. The reference system is a remote operated underwater vehicle with mine hunting sonar. The result is presented as conclusions and recommendations based on the basic capabilities; effect, mobility, endurance, protection as well as the theoretical effectiveness of the system conducting mine reconnaissance.

Approved for public release; distribution is unlimited / This thesis centers around actual field operations and post-mission analysis of data acquired using a REMUS AUV operated by the Naval Postgraduate School Center for Autonomous Underwater Vehicle Research. It was one of many platforms that were utilized for data collection during AOSN II, (Autonomous Oceanographic Sampling Network II), an ONR sponsored exercise for dynamic oceanographic data taking and model based analysis using adaptive sampling. The vehicle's ability to collect oceanographic data consisting of conductivity, temperature, and salinity during this experiment is assessed and problem areas investigated. Of particular interest are the temperature and salinity profiles measured fromlong transect runs of 18 Km. length into the southern parts of Monterey Bay. Experimentation with the REMUS as a mine detection asset was also performed. The design and development of the mine hunting experiment is discussed as well as its results and their analysis. Of particular interest in this portion of the work is the issue relating to repeatability and precision of contact localization, obtained from vehicle position and sidescan sonar measurements. / Lieutenant, United States Navy

Les travaux présentés s'inscrivent dans le cadre des architectures logicielles de contrôle des AUV (Autonomous Underwater Vehicle). La commande d'un AUV est basée sur un ensemble de ressources informatiques embarquées et un ensemble de capteurs/actionneurs qui peut changer selon le type de mission confiée au robot (modification de la charge utile). Le robot est comparable à un "porte charge" adaptable à différentes tâches et par conséquent évoluant au grés des progrès technologiques et de l'apparition de nouvelles applications scientifiques.<br /><br />De plus, le besoin d'autonomie dans un environnement (milieu sous-marin) en constante évolution et souvent inconnu requiert de la part du véhicule d'être capable, à chaque moment, d'évaluer son état et l'état de son environnement afin de prendre les décisions cohérentes pour exécuter sa mission. La réalisation d'un tel véhicule autonome requiert une méthodologie de conception de son architecture logicielle/matérielle.<br /><br />Ici, nous présentons l'architecture développée au LIRMM pour l'AUV Taipan. Cette architecture est construite en respectant certains critères tels que la modularité, l'évolutivité et la réutilisabilité.<br /><br />L'architecture est construite à partir de composants indépendants appelés "modules". Ces modules possèdent un ensemble de ports entrée/sortie qui vont permettre l'établissement dynamique de flux de données/contrôle. Il est alors possible de programmer les modules séparément, de les modifier et de les tester avant de les assembler.<br /><br />L'architecture mixte proposée repose sur deux niveaux hiérarchiques: un niveau décisionnel comprenant un Superviseur Global et des Superviseurs Locaux (un pour chaque mode: autonome, téléopération, coopération) et un niveau exécutif basé sur un ordonnanceur et des modules.<br /><br />Un vocabulaire basé sur trois types de termes: les objectifs, les sous-objectifs et les modules est utilisé au sein de l'architecture pour exprimer l'intention (objectifs), les capacités du système (modules) et la manière dont les intentions vont être réalisées grâce aux capacités du robot (sous-objectifs).<br /><br />Le plus haut niveau, le superviseur global, est en charge de la gestion de la mission à un niveau stratégique. Les décisions relatives aux tâches robotiques à lancer à des dates précises, la planification de ces tâches sont prises à ce niveau. Il décompose la mission reçue de l'opérateur en une séquence d'objectifs envoyés au superviseur local. Le superviseur local vérifie la disponibilité des ressources, réagit aux événements immédiats (e.g. évitement d'obstacle). Il subdivise chaque objectif en sous-objectifs avant de les envoyer au niveau exécutif. Le niveau exécutif fonctionne de manière périodique. Plusieurs modules dans ce niveau sont coordonnés pour configurer les capteurs, calculer les lois de commandes et gérer les conflits liés à l'instrumentation. Pour assurer le respect des contraintes bas niveau (e.g. capteurs acoustiques interférents) un ordonnanceur est en charge de gérer en ligne l'activité des modules bas niveau.<br /><br />Pour illustrer les principaux aspects de notre approche, un exemple d'application a été développé et testé sur l'AUV Taipan.

<p>The purpose of this master thesis, performed at FOI, was to evaluate a range gated underwater camera, for the application identification of bottom objects. The master thesis was supported by FMV within the framework of “arbetsorder Systemstöd minjakt (Jan Andersson, KC Vapen)”. The central part has been field trials, which have been performed in both turbid and clear water. Conclusions about the performance of the camera system have been done, based on resolution and contrast measurements during the field trials. Laboratory testing has also been done to measure system specific parameters, such as the effective gate profile and camera gate distances.</p><p>The field trials shows that images can be acquired at significantly longer distances with the tested gated camera, compared to a conventional video camera. The distance where the target can be detected is increased by a factor of 2. For images suitable for mine identification, the increase is about 1.3. However, studies of the performance of other range gated systems shows that the increase in range for mine identification can be about 1.6. Gated viewing has also been compared to other technical solutions for underwater imaging.</p>

Underwater Acoustic Sensor Networks (UW-ASNs) have the potential to enable many applications such as environmental monitoring, undersea exploration and distributed tactical surveillance. In order to realize the potential gains of these applications, it is essential that the sensor nodes can be accurately located in a three dimensional underwater sensor network topology. Although many localization protocols have been proposed recently for terrestrial sensor networks, the unique characteristics of the underwater acoustic communication channel, such as high and variable propagation delay, necessitate new localization protocols. In order to address this need, a localization protocol for UW-ASN, Three-Dimensional Underwater Localization (3DUL), is presented in this thesis. 3DUL achieves network-wide robust 3D localization by using a distributed and iterative algorithm. Importantly, 3DUL exploits only three surface buoys for localization. The sensor nodes leverage the low speed of sound to accurately determine the inter-node distances. We show through simulation experiments that the localization accuracy does not degrade significantly with an increase in the number of nodes, making 3DUL scalable.

The proposed project is the simulation of a system to search for air vehicles which have splashed-down in the ocean. The system comprises a group of 10+ autonomous underwater vehicles, which cooperate in order to locate the aircraft. The search algorithm used in this system is based on a quadratic Newton method and was developed at Sandia National Laboratories. The method has already been successfully applied to several two dimensional problems at Sandia. The original 2D algorithm was converted to 3D and tested for robustness in the presence of sensor error, position error and navigational error. Treating the robots as point masses, the system was found to be robust for all such errors. Several real-life adaptations were necessary. A round-robin communication strategy was implemented on the system to properly simulate the dissemination of information throughout the group. Time to convergence is delayed but the system still functioned adequately. Once simulations for the point masses had been exhausted, the dynamics of the robots were included. The robot equations of motion were described using Kane's equations. Path-planning was investigated using optimal control methods. The Variational Calculus approach was attempted using a line search tool "fsolve" found in Matlab and a Genetic Algorithm. A dynamic programming technique was also investigated using a method recently developed by Sandia National Laboratories. The Dynamic Programming with Interior Points (DPIP) method was a very effcient method for path planning and performed well in the presence of system constraints. Finally all components of the system were integrated. The motion of the robot exactly matched the motion of the particles, even when subjected to the same robustness tests carried out on the point masses. This thesis provides exciting developments for all types of cooperative projects.

L'utilisation de correcteur discret à période d'échantillonnage variable peut être intéressante dans plusieurs cas, par exemple lorsque la mesure, bien qu'envoyée de façon périodique, est reçue à intervalle variable. C'est le cas en milieu marin lorsque la mesure d'altitude est effectuée avec un capteur à ultrason (la durée du trajet du signal dans l'eau dépend de la distance par rapport au fond). Le délai variable entre deux réceptions de mesures, peut être vu comme une variation de période d'échantillonnage pour le contrôleur. La synthèse de lois de commande discrète à période d'échantillonnage variable a déjà été étudiée pour des systèmes stationnaires. On se propose ici d'étendre cette méthode pour des systèmes Linéaires à Paramètres Variants (LPV), qui permettent de conserver des paramètres importants d'un système non-linéaire en temps que paramètres d'un système linéaires. La synthèse de contrôleur repose sur le méthodologie H∞, appliquée aux systèmes LPV. En particulier, on s'intéressera à deux approches existantes dans la littérature : l'approche polytopique (où le paramètre variant évolue dans un volume convexe) et la Représentation Linéaire Fractionnelle (LFR). La méthode proposée est appliquée au contrôle d'un AUV (Autonomous Underwater Vehicle), qui est système difficile à contrôler du fait d'importantes non-linéarités. Des résultats de simulations permettront de montrer l'intérêt de la méthode pour le contrôle d'altitude d'un AUV, et notamment les améliorations apportées par l'ajout de paramètres issus du système non-linéaire au modèle utilisé pour la synthèse des régulateurs.

In this thesis we present a suitable way of calibrating and debugging an autonomous underwater vehicle (AUV). The issues that occur when working with an AUV are the inconvenient way of having to constantly recompile the software to change the behavior of the AUV and the lack of feedbacksreceived. If the vehicle does not behave as it should the information needed to be able to trace and fix the problems that occur isin general difficult to retrieve. To tackle this problem a literature study was made on logging libraries, communication protocols as well as AUVs in general. This resulted in identifying a set of existing logging libraries and possible communication protocols. From testing and analyzing these results, Zlog was chosen as the logging library and UDP as the communication protocol. Zlog has then been used in the AUV application to log relevant information on the AUV and UDP allows establishing a connection between the AUV and a desktop program created for Windows to send this logging information to. The desktop program also allows filtering of any incoming logs with the use of a parser. This has been an essential part of the solution to be able to identify specific logging data and help presenting this in a convenient way. To be able to change the format of the log file, the parser has been given a grammar which can be adjusted to adapt to a different log file. Additionally, the desktop application has the ability to send commands to the AUVapplication via the UDP connection to change the behavior of the AUV live.

No description available.

Scleractinian cold-water corals are widely distributed in seaways and basins of the North Atlantic Ocean, including the Straits of Florida. These corals can form extensive biogenic mounds, which are biodiversity hotspots in the deep ocean. The processes that lead to the genesis of such cold-water coral mounds and control their distribution and morphology are poorly understood. This work uses an innovative mapping approach that combines 130 km2 of high resolution geophysical and oceanographic data collected using an Autonomous Underwater Vehicle (AUV) from five cold-water coral habitats in the Straits of Florida. These AUV data, together with ground-truthing observations from eleven submersible dives, are used to investigate fine-scale mound parameters and their relationships with environmental factors. Based on these datasets, automated methods are developed for extracting and analyzing mound morphometrics and coral cover. These analyses reveal that mound density is 14 mound/km2 for the three surveyed sites on the toe-of-slope of Great Bahama Bank (GBB); this density is higher than previously documented (0.3 mound/km2) in nearby mound fields. Morphometric analyses further indicate that mounds vary significantly in size, from a meter to up to 110 m in relief, and 81 to 600,000 m2 in footprint area. In addition to individual mounds, cold-water corals also develop in some areas as elongated low-relief ridges that are up to 25 m high and 2000 m long. These ridges cover approximately 60 and 70% of the mapped seafloor from the sites at the center of the Straits and at the base of the Miami Terrace, respectively. Morphometrics and current data analyses across the five surveyed fields indicate that mounds and ridges are not in alignment with the dominant current directions. These findings contradict previous studies that described streamlined mounds parallel to the northward Florida Current. In contrast, this study shows that the sites dominated by coral ridges are influenced by unidirectional flowing current, whereas the mounds on the GBB slope are influenced by tidal current regime. The GBB mounds also experience higher sedimentation rates relative to the sites away from the GBB slope. Sub-surface data document partially or completely buried mounds on the GBB sites. The sediments burying mounds are off-bank material transported downslope by mass gravity flow. Mass gravity transport creates complex slope architecture on the toe-of-slope of GBB, with canyons, slump scars, and gravity flow deposits. Cold-water corals use all three of these features as location for colonization. Coral mounds growing on such pre-existing topography keep up with off-bank sedimentation. In contrast, away from the GBB slope, off-bank sedimentation is absent and coral ridges grow independently of antecedent topography. In the sediment-starved Miami Terrace site, coral ridge initiation is related to a cemented mid-Miocene unconformity. In the center of the Straits, coral ridges and knobs develop over an unconsolidated sand sheet at the tail of the Pourtales drift. Coral features at the Miami Terrace and center of the Straits have intricate morphologies, including waveform and chevron-like ridges, which result from asymmetrical coral growth. Dense coral frameworks and living coral colonies grow preferentially on the current-facing ridge sides in order to optimize food particle capture, whereas coral rubble and mud-sized sediments accumulate in the ridge leesides. Finally, this study provides a method using solely acoustic data for discriminating habitats in which cold-water corals are actively growing. Results from this method can guide future research on and management of cold-water coral ecosystems. Taken together, spatial quantitative analyses of the large-scale, high-resolution integrated surveys indicate that cold-water coral habitats in the Straits of Florida: (1) are significantly more diverse and abundant than previously thought, and (2) can be influenced in their distribution and development by current regime, sedimentation, and/or antecedent topography.