Augmented Terrain-Based Navigation to Enable Persistent Autonomy for Underwater Vehicles in GPS-Denied Environments

Aquatic robots, such as Autonomous Underwater Vehicles (AUVs), play a major role in the study of ocean processes that require long-term sampling efforts and commonly perform navigation via dead-reckoning using an accelerometer, a magnetometer, a compass, an IMU and a depth sensor for feedback. However, these instruments are subjected to large drift, leading to unbounded uncertainty in location. Moreover, the spatio-temporal 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. To add to this, the interesting features are themselves spatio-temporally dynamic, and effective sampling requires a good understanding of vehicle localization relative to the sampled feature. Therefore, our work is motivated by the desire to enable intelligent data collection of complex dynamics and processes that occur in coastal ocean environments to further our understanding and prediction capabilities. The study originated from the need to localize and navigate aquatic robots in a GPS-denied environment and examine the role of the spatio-temporal dynamics of the ocean into the localization and navigation processes. The methods and techniques needed range from the data collection to the localization and navigation algorithms used on-board of the aquatic vehicles. The focus of this work is to develop algorithms for localization and navigation of AUVs in GPS-denied environments. We developed an Augmented terrain-based framework that incorporates physical science data, i.e., temperature, salinity, pH, etc., to enhance the topographic map that the vehicle uses to navigate. In this navigation scheme, the bathymetric data are combined with the physical science data to enrich the uniqueness of the underlying terrain map and increase the accuracy of underwater localization. Another technique developed in this work addresses the problem of tracking an underwater vehicle when the GPS signal suddenly becomes unavailable. The methods include the whitening of the data to reveal the true statistical distance between datapoints and also incorporates physical science data to enhance the topographic map. Simulations were performed at Lake Nighthorse, Colorado, USA, between April 25th and May 2nd 2018 and at Big Fisherman\u27s Cove, Santa Catalina Island, California, USA, on July 13th and July 14th 2016. Different missions were executed on different environments (snow, rain and the presence of plumes). Results showed that these two methodologies for localization and tracking work for reference maps that had been recorded within a week and the accuracy on the average error in localization can be compared to the errors found when using GPS if the time in which the observations were taken are the same period of the day (morning, afternoon or night). The whitening of the data had positive results when compared to localizing without whitening

AquaHet-PSO: An Informative Path Planner for a Fleet of Autonomous Surface Vehicles with Heterogeneous Sensing Capabilities based on Multi-Objective PSO

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivativesThe importance of monitoring and evaluating the quality of water resources has significantly grown over time. To achieve this effectively, an option is to employ an intelligent monitoring system capable of measuring the physical and chemical parameters of water. Surface vehicles equipped with sensors for measuring water quality parameters offer a viable solution for these missions. This work presents a novel approach called AquaHet-PSO, which addresses the challenge of simultaneously monitoring multiple water quality parameters with several peaks of contamination using a heterogeneous fleet of autonomous surface vehicles. Each vehicle in the fleet possesses a different set of sensors, such as number of sensors and sensor types, which is the definition provided by the authors for a heterogeneous fleet. The AquaHet- PSO consists of three main phases. In the initial phase, the vehicles traverse the water resource to obtain preliminary models of water quality parameters. These models are then utilized in the second phase to identify potential contamination areas and assign vehicles to specific action zones. In the final phase, the vehicles focus on a comprehensive characterization of the parameters. The proposed system combines several techniques, including Particle Swarm Optimization and Gaussian Processes, with the integration of genetic algorithm to maximize the distances between the initial positions of vehicles equipped with identical sensors, and a distributed communication system in the final phase of the AquaHet-PSO. Simulation results in the Ypacarai lake demonstrate the effectiveness and efficiency of AquaHet-PSO in generating accurate water quality models and detecting contamination peaks. The proposed method demonstrated improvements compared to the lawnmower approach. It achieved a remarkable 17% improvement, on r-squared data, in generating complete models of water quality parameters throughout the lake. In addition, it achieved a 230% improvement in accurate characterization of high pollution areas and a 24% increase in pollution peak detection specifically for heterogeneous fleets equipped with four or more identical sensors.Ministerio de Ciencia e Innovación PID2021-126921OB-C21 TED2021-131326BC21Universidad de Sevill

Experimental Investigation of a MAV-Scale Cyclocopter

The development of an efficient, maneuverable, and gust tolerant hovering concept with a multi-modal locomotion capability is key to the success of micro air vehicles (MAVs) operating in multiple mission scenarios. The current research investigated performance of two unconventional cycloidal-rotor-based (cyclocopter) configurations: (1) twin-cyclocopter and (2) all-terrain cyclocopter. The twin-cyclocopter configuration used two cycloidal rotors (cyclorotors) and a smaller horizontal edge-wise nose rotor to counteract the torque produced by the cyclorotors. The all-terrain cyclocopter relied on four cyclorotors oriented in an H-configuration. Objectives of this research include the following: (1) develop control strategies to enable level forward flight of a cyclocopter purely relying on thrust vectoring, (2) identify flight dynamics model in forward flight, (3) experimentally evaluate gust tolerance strategies, and (4) determine feasibility and performance of multi-modal locomotion of the cyclocopter configuration. The forward flight control strategy for the twin-cyclocopter used a unique combination of independent thrust vectoring and rotational speed control of the cyclorotors. Unlike conventional rotary-winged vehicles, the cyclocopter propelled in forward flight by thrust vectoring instead of pitching the entire fuselage. While the strategy enabled the vehicle to maintain a level attitude in forward flight, it was accompanied by significant yaw-roll controls coupling and gyroscopic coupling. To understand these couplings and characterize the bare airframe dynamics, a 6-DOF flight dynamics model of the cyclocopter was extracted using a time-domain system identification technique. Decoupling methods involved simultaneously mixing roll and yaw inputs in the controller. After implementing the controls mixing strategy in the closed-loop feedback system, the cyclocopter successfully achieved level forward flight up to 5 m/s. Thrust vectoring capability also proved critical for gust mitigation. Thrust vectoring input combined with flow feedback and position feedback improved gust tolerance up to 4 m/s for a twin-cyclocopter mounted on a 6-DOF test stand. Flow feedback relied on a dual-axis flowprobe attached to differential pressure sensors and position feedback was based on data recorded by the VICON motion capture system. The vehicle was also able to recover initial position for crosswind scenarios tested at various side-slip angles up to 30 degrees. Unlike existing multi-modal platforms, the all-terrain cyclocopter solely relied on its four cyclorotors as main source of propulsion, as well as wheels. Aerial and aquatic modes used aerodynamic forces generated by modulating cyclorotor rotational speeds and thrust vectors while terrestrial mode used motor torque. In aerial mode, cyclorotors operated at 1550 rpm and consumed 232 W to sustain hover. In terrestrial mode, forward translation at 2 m/s required 28 W, which was an 88% reduction in power consumption required to hover. In aquatic mode, cyclorotors operated at 348 rpm to achieve 1.3 m/s translation and consumed 19 W, a 92% reduction in power consumption. With only a modest weight addition of 200 grams for wheels and retractable landing gear, the versatile cyclocopter platform achieved sustained hover, efficient translation and rotational maneuvers on ground, and aquatic locomotion

UAS planning and trajectory generation for safe and long-duration oceanic and coastal missions.

La presente tesis doctoral, muestra el diseño de un sistema para la extensión de la duración de vuelo de sistemas autónomos no tripulados de tamaño pequeño. Este sistema fue diseñado en el contexto de misiones de vigilancia marítima y costera como parte del proyecto europeo MarineUAS. En este contexto, se han identificado tres problemas: 1) la necesidad de la estimación precisa de un campo de viento y la capacidad de identificación de fenómenos como el viento cortante o las ráfagas continuas y discretas para que puedan ser utilizadas potencialmente para la extracción de energía para mejorar la duración de vuelo. 2) La necesidad de generar trayectorias suaves para la extracción de energía considerando la dinámica de las plataformas de vuelo y 3) la habilidad de seguir dichas trayectorias. Para el primer problema, el uso de un método de computación directa permite determinar el campo de viento (velocidad y tasa de cambio de la velocidad de viento) sin la utilización de un estimador óptimo. Sin embargo, también se consideraron varios métodos y a partir de un análisis extenso se presentan diferentes comparativas de estos métodos, en el que se muestran las ventajas y desventajas de los mismos. Adicionalmente, la identificación de distintos fenómenos de viento, cómo las ráfagas, o el viento cortante, se logra a través de un innovador método que ejecuta una serie de pruebas estadísticas basadas en la distribución de Weibull y en distintos modelos dinámicos que consideran no solo la distribución del viento sino la interacción con el océano y la superficie en las respectivas capas límite. Para el segundo problema, una aproximación biomimética permitió el uso de un algoritmo complejo para la réplica de trajectorias de vuelo dinámico de aves. En dicho algoritmo se consideran observaciones presentadas por distintos científicos que permiten generar trayectorias paramétricas que consideran además restricciones cinemáticas de la plataforma en el diseño de las mismas. El tercer problema toma en consideración la curva generada y utiliza la teoría del campo de vectores para diseñar un controlador que permite seguir dicha trayectoria de manera eficiente y en tiempo real, respetando las leyes de control de bajo nivel en el autopiloto y permitiendo flexibilidad. Como complemento a este último sistema, se propone la reconfiguración dinámica de las misiones para mejorar el consumo energético durante el tiempo de vuelo considerando el viento predominante. Uno de los principales objectivos fue integrar, utilizando la metodología de ingeniería de sistemas, las distintias funciones anteriormente mencionadas en el que la ejecución de la misión fuese la prioridad. El principal logro fue haber realizado una extensa campaña experimental que permitió la validación del sistema en diferentes niveles, en el que se combinaron pruebas computacionales de alto y bajo nivel así como pruebas de campo en distintos escenarios y con distintas plataformas, lo cual permitió explorar la versatilidad del sistema. Los resultados muestran que se pueden lograr misiones más eficientes con mejoras de hasta un 20%en consumo de batería para misiones costeras. Finalmente, de los distintos análisis computacionales efectuados se concluye que el tiempo de ejecución de toda la función de extensión del vuelo es lo suficientemente pequeño para permitir la ejecución en tiempo real, lo cual, combinando con el diseño versátil en cuestión de arquitectura computacional, permiten la portabilidad del sistema así como la futura integración de funciones adicionales.In this thesis a system that aims to extend the flight duration of small Unmanned Aerial Systems (UAS) is presented. The system was designed in the context of oceanic and coastal surveillance missions as part of the MarineUAS European project. Three main problems were identified: 1) the need to accurately estimate the wind field and the capability to identify features of interest, such as, wind shear, and gusts that may be suitable to allow energy extraction to improve flight duration. 2) the need to generate smooth trajectories that extract energy, considering the UAS platform dynamics and 3) the ability to follow such paths. For the first problem, the use of a direct computation method allows determining the wind field (wind velocity and wind rate of change) without the use of an optimal estimator. Nevertheless, different wind velocity estimation methods are compared, and the pros and cons of each are exposed; in addition, the identification of features is accomplished with a novel approach that performs a real-time statistical analysis of the distribution of the wind field estimates, allowing the characterization of the shear components and also any other potential features, like continuous and discrete gusts considering complex models that take into account not only the phenomena but the interactions with the ground and ocean through their respective boundary layers. For the second problem, a biomimetic approach is presented, replicating the trajectories of soaring birds by considering observations of these birds and the replication of their swooping maneuvers using smooth parametrized curves. This allows flexibility in the curve design and also the incorporation of dynamic constraints of the platform on it. The solution of the third problem takes into account the smooth curve that was generated and among it, a type 1 Bishop moving frame is generated. Then, a novel adaptive control method based on the vector-field theory approach is proposed to calculate the error equations and the respective control law, which permits the tracking of the designed trajectory for dynamic soaring. Furthermore, an additional step was added, in which the surveillance mission is re-configured on a waypoint-to-waypoint basis for a more efficient flight considering the identified wind field. The result was that the execution of soaring trajectories would not be executed during all the mission, but only in specific legs that fulfill specific characteristics.The primary goal was to design algorithms that implement these functions and to integrate these functionalities in a systems-engineering approach, in which the mission execution is the main priority. An extensive experimental campaign was performed at different levels, in which software-in-the-loop and hardwarein- the-loop tests, together with field tests, were executed to demonstrate the efficiency of the various functions separately and integrated. The field tests and the simulations consider different scenarios and UAS platforms, showing the performance of the system in different conditions. The results showed that the system could execute a more efficient mission, with savings of up to 20% in battery consumption, with the so-called of the Flight-Duration-Enhancement-System (FDES). Finally, the computational analysis showed that the system could be executed in real-time with minimum latency despite the use of sophisticated algorithms; this, together with the chosen software and hardware architectures allows portability to other hardware components and the possibility of incorporating additional functions

Modélisation tridimensionnelle précise de l'environnement à l’aide des systèmes de photogrammétrie embarqués sur drones

Abstract : Images acquired from unmanned aerial vehicles (UAVs) can provide data with unprecedented spatial and temporal resolution for three-dimensional (3D) modeling. Solutions developed for this purpose are mainly operating based on photogrammetry concepts, namely UAV-Photogrammetry Systems (UAV-PS). Such systems are used in applications where both geospatial and visual information of the environment is required. These applications include, but are not limited to, natural resource management such as precision agriculture, military and police-related services such as traffic-law enforcement, precision engineering such as infrastructure inspection, and health services such as epidemic emergency management. UAV-photogrammetry systems can be differentiated based on their spatial characteristics in terms of accuracy and resolution. That is some applications, such as precision engineering, require high-resolution and high-accuracy information of the environment (e.g. 3D modeling with less than one centimeter accuracy and resolution). In other applications, lower levels of accuracy might be sufficient, (e.g. wildlife management needing few decimeters of resolution). However, even in those applications, the specific characteristics of UAV-PSs should be well considered in the steps of both system development and application in order to yield satisfying results. In this regard, this thesis presents a comprehensive review of the applications of unmanned aerial imagery, where the objective was to determine the challenges that remote-sensing applications of UAV systems currently face. This review also allowed recognizing the specific characteristics and requirements of UAV-PSs, which are mostly ignored or not thoroughly assessed in recent studies. Accordingly, the focus of the first part of this thesis is on exploring the methodological and experimental aspects of implementing a UAV-PS. The developed system was extensively evaluated for precise modeling of an open-pit gravel mine and performing volumetric-change measurements. This application was selected for two main reasons. Firstly, this case study provided a challenging environment for 3D modeling, in terms of scale changes, terrain relief variations as well as structure and texture diversities. Secondly, open-pit-mine monitoring demands high levels of accuracy, which justifies our efforts to improve the developed UAV-PS to its maximum capacities. The hardware of the system consisted of an electric-powered helicopter, a high-resolution digital camera, and an inertial navigation system. The software of the system included the in-house programs specifically designed for camera calibration, platform calibration, system integration, onboard data acquisition, flight planning and ground control point (GCP) detection. The detailed features of the system are discussed in the thesis, and solutions are proposed in order to enhance the system and its photogrammetric outputs. The accuracy of the results was evaluated under various mapping conditions, including direct georeferencing and indirect georeferencing with different numbers, distributions and types of ground control points. Additionally, the effects of imaging configuration and network stability on modeling accuracy were assessed. The second part of this thesis concentrates on improving the techniques of sparse and dense reconstruction. The proposed solutions are alternatives to traditional aerial photogrammetry techniques, properly adapted to specific characteristics of unmanned, low-altitude imagery. Firstly, a method was developed for robust sparse matching and epipolar-geometry estimation. The main achievement of this method was its capacity to handle a very high percentage of outliers (errors among corresponding points) with remarkable computational efficiency (compared to the state-of-the-art techniques). Secondly, a block bundle adjustment (BBA) strategy was proposed based on the integration of intrinsic camera calibration parameters as pseudo-observations to Gauss-Helmert model. The principal advantage of this strategy was controlling the adverse effect of unstable imaging networks and noisy image observations on the accuracy of self-calibration. The sparse implementation of this strategy was also performed, which allowed its application to data sets containing a lot of tie points. Finally, the concepts of intrinsic curves were revisited for dense stereo matching. The proposed technique could achieve a high level of accuracy and efficiency by searching only through a small fraction of the whole disparity search space as well as internally handling occlusions and matching ambiguities. These photogrammetric solutions were extensively tested using synthetic data, close-range images and the images acquired from the gravel-pit mine. Achieving absolute 3D mapping accuracy of 11±7 mm illustrated the success of this system for high-precision modeling of the environment.Résumé : Les images acquises à l’aide d’aéronefs sans pilote (ASP) permettent de produire des données de résolutions spatiales et temporelles uniques pour la modélisation tridimensionnelle (3D). Les solutions développées pour ce secteur d’activité sont principalement basées sur des concepts de photogrammétrie et peuvent être identifiées comme des systèmes photogrammétriques embarqués sur aéronefs sans pilote (SP-ASP). Ils sont utilisés dans plusieurs applications environnementales où l’information géospatiale et visuelle est essentielle. Ces applications incluent notamment la gestion des ressources naturelles (ex. : agriculture de précision), la sécurité publique et militaire (ex. : gestion du trafic), les services d’ingénierie (ex. : inspection de bâtiments) et les services de santé publique (ex. : épidémiologie et gestion des risques). Les SP-ASP peuvent être subdivisés en catégories selon les besoins en termes de précision et de résolution. En effet, dans certains cas, tel qu’en ingénierie, l’information sur l’environnement doit être de haute précision et de haute résolution (ex. : modélisation 3D avec une précision et une résolution inférieure à un centimètre). Pour d’autres applications, tel qu’en gestion de la faune sauvage, des niveaux de précision et de résolution moindres peut être suffisants (ex. : résolution de l’ordre de quelques décimètres). Cependant, même dans ce type d’applications les caractéristiques des SP-ASP devraient être prises en considération dans le développement des systèmes et dans leur utilisation, et ce, pour atteindre les résultats visés. À cet égard, cette thèse présente une revue exhaustive des applications de l’imagerie aérienne acquise par ASP et de déterminer les challenges les plus courants. Cette étude a également permis d’établir les caractéristiques et exigences spécifiques des SP-ASP qui sont généralement ignorées ou partiellement discutées dans les études récentes. En conséquence, la première partie de cette thèse traite des aspects méthodologiques et d’expérimentation de la mise en place d’un SP-ASP. Le système développé a été évalué pour la modélisation précise d’une gravière et utilisé pour réaliser des mesures de changement volumétrique. Cette application a été retenue pour deux raisons principales. Premièrement, ce type de milieu fournit un environnement difficile pour la modélisation, et ce, en termes de changement d’échelle, de changement de relief du terrain ainsi que la grande diversité de structures et de textures. Deuxièment, le suivi de mines à ciel ouvert exige un niveau de précision élevé, ce qui justifie les efforts déployés pour mettre au point un SP-ASP de haute précision. Les composantes matérielles du système consistent en un ASP à propulsion électrique de type hélicoptère, d’une caméra numérique à haute résolution ainsi qu’une station inertielle. La composante logicielle est composée de plusieurs programmes développés particulièrement pour calibrer la caméra et la plateforme, intégrer les systèmes, enregistrer les données, planifier les paramètres de vol et détecter automatiquement les points de contrôle au sol. Les détails complets du système sont abordés dans la thèse et des solutions sont proposées afin d’améliorer le système et la qualité des données photogrammétriques produites. La précision des résultats a été évaluée sous diverses conditions de cartographie, incluant le géoréférencement direct et indirect avec un nombre, une répartition et des types de points de contrôle variés. De plus, les effets de la configuration des images et la stabilité du réseau sur la précision de la modélisation ont été évalués. La deuxième partie de la thèse porte sur l’amélioration des techniques de reconstruction éparse et dense. Les solutions proposées sont des alternatives aux techniques de photogrammétrie aérienne traditionnelle et adaptée aux caractéristiques particulières de l’imagerie acquise à basse altitude par ASP. Tout d’abord, une méthode robuste de correspondance éparse et d’estimation de la géométrie épipolaire a été développée. L’élément clé de cette méthode est sa capacité à gérer le pourcentage très élevé des valeurs aberrantes (erreurs entre les points correspondants) avec une efficacité de calcul remarquable en comparaison avec les techniques usuelles. Ensuite, une stratégie d’ajustement de bloc basée sur l’intégration de pseudoobservations du modèle Gauss-Helmert a été proposée. Le principal avantage de cette stratégie consistait à contrôler les effets négatifs du réseau d’images instable et des images bruitées sur la précision de l’autocalibration. Une implémentation éparse de cette stratégie a aussi été réalisée, ce qui a permis de traiter des jeux de données contenant des millions de points de liaison. Finalement, les concepts de courbes intrinsèques ont été revisités pour l’appariement stéréo dense. La technique proposée pourrait atteindre un haut niveau de précision et d’efficacité en recherchant uniquement dans une petite portion de l’espace de recherche des disparités ainsi qu’en traitant les occlusions et les ambigüités d’appariement. Ces solutions photogrammétriques ont été largement testées à l’aide de données synthétiques, d’images à courte portée ainsi que celles acquises sur le site de la gravière. Le système a démontré sa capacité a modélisation dense de l’environnement avec une très haute exactitude en atteignant une précision 3D absolue de l’ordre de 11±7 mm

Optimization and Communication in UAV Networks

UAVs are becoming a reality and attract increasing attention. They can be remotely controlled or completely autonomous and be used alone or as a fleet and in a large set of applications. They are constrained by hardware since they cannot be too heavy and rely on batteries. Their use still raises a large set of exciting new challenges in terms of trajectory optimization and positioning when they are used alone or in cooperation, and communication when they evolve in swarm, to name but a few examples. This book presents some new original contributions regarding UAV or UAV swarm optimization and communication aspects