The aim of the Master’s Thesis work is to study and develop algorithms for autonomous travel of a UGV (Unmanned Ground Vehicle). A vehicle for the mounting of sensors has been constructed in order to perform the work. Since the UGV is to be used outdoor in urban areas, GPS can be used. To improve precision and robustness, inertial navigation is used in addition to GPS, since GPS reception is likely to be diminished in such areas. The sensors used for navigation are consequently GPS, magnetometers, accelerometers, gyroscopes, tachometers and ultra sonic sensors measuring distance to be used in detection of obstacles. The system has been implemented in Matlab. Two alternative methods of navigation with sensor fusion have been developed; one is a decentralized method with Kalman filtering using an error model and the other is a centralized particle filter using an all-embracing model of the vehicle. The two methods have been evaluated and compared. Test results show that the two methods perform equivalently. The autonomous travel is undertaken between predetermined waypoints. In order to steer the vehicle a PID-controller based on the error between heading and its reference value is used. The computation of the reference value is based on position and heading in comparison to the desired path. The system has been tested using different routes and the results show an evident improvement of the precision in navigation compared to using only GPS-data. This holds for both navigation methods. Simulation of collision avoidance using virtual force fields shows satisfying results as well as terrain navigation with coordinate map referencing. / Examensarbetet är en studie i utveckling av algoritmer för autonom förflyttning av en UGV (eng Unmanned Ground Vehicle). För ändamålet har en farkost konstruerats där budgetsensorer för navigering används. Farkosten är tänkt att färdas utomhus i tätbebyggt område och GPS används. För förbättring av noggrannhet och robusthet vid dålig GPS-mottagning används även sensorer för tröghetsnavigering vilket här innebär magnetometrar, accelerometrar, gyron och tachometrar. För hinderdetektering finns avståndsmätande ultraljudssonar. Systemet som tagits fram har implementerats i realtid i Matlab. Två olika navigeringsmetoder med sensorfusion har utprovats; en decentraliserad variant med kalmanfilter som är uppbyggd kring felmodeller och en centraliserad variant med ett partikelfilter som använder en helhetsmodell för farkosten. De båda navigeringsmetoderna har utvärderats och jämförts. Resultat visar att de båda metoderna presterar likvärdigt. Den autonoma förflyttningen utförs mellan förutbestämda brytpunkter. För att styra farkosten har en PID-regulator baserad på felet mellan kurs och börvärde använts. Börvärdet på kurs baseras på nuvarande position och riktning relativt den önskade färdvägen. Olika körsituationer har testats och resultaten visar en markant förbättring av navigeringsprecisionen jämfört med endast GPS-mätningar för både kalman- och partikelfilter. Simuleringar på vektorfältsstyrning med virtuella kraftfält för att undvika hinder har utförts med goda resultat liksom simuleringar av kartreferenspositionering.

Geologically-constrained inversion of geophysical data is a powerful method for predicting geology beneath cover. The process seeks 3D physical property models that are consistent with the geology and explain measured geophysical responses. The recovered models can guide mineral explorers to prospective host rocks, structures, alteration and mineralisation. This thesis provides a comprehensive analysis of how the University of British Columbia Geophysical Inversion Facility (UBC–GIF) gravity and magnetic inversions can be applied to subsurface mapping and exploration by demonstrating the necessary approach, data types, and typical results. The non-uniqueness of inversion demands that geological information be included. Commonly available geological data, including structural and physical property measurements, mapping, drilling, and 3D interpretations, can be translated into appropriate inversion constraints using tools developed herein. Surface information provides the greatest improvement in the reliability of recovered models; drilling information enhances resolution at depth. The process used to prepare inversions is as important as the geological constraints themselves. Use of a systematic workflow, as developed in this study, minimises any introduced ambiguity. Key steps include defining the problem, preparing the data, setting inversion parameters and developing geological constraints. Once reliable physical property models are recovered they must be interpreted in a geological context. Where alteration and mineralisation occupy significant volumes, the mineralogy associated with the physical properties can be identified; otherwise a lithological classification of the properties can be applied. This approach is used to develop predictive 3D lithological maps from geologically-constrained gravity and magnetic inversions at several scales in the Agnew-Wiluna greenstone belt in Australia’s Yilgarn Craton. These maps indicate a spatial correlation between thick mafic-ultramafic rock packages and gold deposit locations, suggesting a shared structural control. The maps also identify structural geometries and relationships consistent with the published regional tectonic framework. Geophysical inversion provides a framework into which geological and geophysical data sets can be integrated to produce a holistic prediction of the subsurface. The best possible result is one that cannot be dismissed as inconsistent with some piece of geological knowledge. Such a model can only be recovered by including all available geological knowledge using a consistent workflow process.

Multi-vehicle systems offer many advantages in engineering applications such as increased efficiency and robustness. However, the disadvantage of multi-vehicle systems is that they require a high level of organization and coordination in order to successfully complete a task. Formation control is a field of engineering that addresses this issue, and provides coordination schemes to successfully implement multi-vehicle systems. Two approaches to group coordination were proposed in this work: geometric and self-organizing formations. A geometric reconfiguring formation was developed using the leader-follower method, and the self-organizing formation was developed using the velocity potential equations from fluid flow theory. Both formation controllers were first tested in simulation in MATLAB, and then implemented on the X80 mobile robot units. Various experiments were conducted to test the formations under difficult obstacle scenarios. The robots successfully navigated through the obstacles as a coordinated as a team using the self-organizing and geometric formation control approaches.

Submitted by Fernando Souza (fernandoafsou@gmail.com) on 2017-08-11T14:01:11Z No. of bitstreams: 1 arquivototal.pdf: 11420527 bytes, checksum: 9c4b07869f327f3f311a4d4c15f0210b (MD5) / Made available in DSpace on 2017-08-11T14:01:11Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 11420527 bytes, checksum: 9c4b07869f327f3f311a4d4c15f0210b (MD5) Previous issue date: 2017-02-16 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Anti-collision systems are based on sensing and estimating the mobile robot pose (coordinates and orientation), with respect to its environment. Obstacles detection, path planning and pose estimation are primordial to ensure the autonomy and safety of the robot, in order to reduce the risk of collision with objects and living beings that share the same space. For this, the use of RGB-D sensors, such as the Microsoft Kinect, has become popular in the last years, for being relative accurate and low cost sensors. In this work we propose a new 3D anti-collision algorithm based on Artificial Potential Field method, that is able to make a mobile robot pass between closely spaced obstacles, minimizing the oscillations during the cross. We develop our Unmanned Ground Vehicles (UGV) system on a ’Turtlebot 2’ platform, with which we perform the experiments. / Sistemas anti-colisão são baseados na percepção e estimação da pose do robô móvel (coordenadas e orientação), em referência ao ambiente em que ele se encontra. A detecção de obstáculos, planejamento de caminhos e estimação da pose são fundamentais para assegurar a autonomia e a segurança do robô, no intuito de reduzir o risco de colisão com objetos ou pessoas que dividem o mesmo espaço. Para isso, o uso de sensores RGB-Ds, tal como o Microsoft Kinect, vem se tornando popular nos últimos anos, por serem sensores relativamente precisos e de baixo custo. Nesse trabalho nós propomos um novo algoritmo anti-colisão 3D baseado no método de Campo Potencial Artificial, que é capaz de fazer um robô móvel passar em espaços estreitos, entre obstáculos, minimizando as oscilações, que é uma característica comum desse tipo de método, durante seu deslocamento. Foi desenvolvido um sistema para plataforma robótica ’Turtlebot 2’, o qual foi utilizado para realizar todos os experimentos.

Cette étude propose d'examiner les vestiges archéologiques de Qasr ʿAllam enfouis sous les sédiments en développant une approche géophysique adaptée aux contextes du site. La mesure du champ total à l'aide de magnétomètres vectoriels à vanne de flux permet la mise au point de dispositifs multi-capteurs qui permettent une acquisition au rapport rapidité/densité hautement modulable. Ainsi des cartes verticales et horizontales de l'anomalie de l'intensité du champ magnétique à différentes échelles sont établies. L'utilisation et le développement d'outils d'interprétation issus de la théorie du potentiel, couplés à des fouilles ciblées, permettent à la fois de d'obtenir des informations sur les sources et d'améliorer la méthode grâce aux preuves-terrain. Les résultats ainsi obtenus révèlent la présence d'un système d'irrigation complexe et étendu, d'un ensemble cultuel massif du 8e/7e siècle avant l'ère commune et d'un second ensemble plus petit postérieur de plusieurs siècles. Entre ces deux derniers un changement environnemental brutal d'un milieu humide à aride a manifestement eu lieu. Tous ces résultats permettent d'établir des cartes des vestiges pour l'étude archéologique et l'établissement d'un périmètre de protection du site. / This study proposes to investigate the archaeological remains covered by sediments in Qasr ʿAllam by developing a geophysical method adapted to the contexts of the site. The measurement of the magnetic total field with fluxgate vector magnetometers allows the design of multi-captor devices which enable an acquisition of data with a highly adjustable rapidity/density ratio. Thus, vertical and horizontal maps of the anomaly of the magnetic total field's intensity are established. The use and development of interpretative tools derived from the theory of potential fields in association with targeted excavations allow the procurement of information on the sources as well as the improvement of the method through field evidences. The results reveal the existence of a large and intricate irrigation system, of a massive cultic facility dating from the 8th/7th century before the Common Era, and of a smaller complex built a few centuries later. Evidences also show that a massive change from humid to arid environmental conditions took place during the time separating the two latter. All these results allow the establishment of maps of the remains for archaeological studies and the establishment of a perimeter of protection of the site.

Ce travail propose de nouvelles stratégies pour la planification et le contrôle des robots mobiles non-holonomes, de nouveaux algorithmes sont proposés. Tout d'abord, l'identification des différents modèles cinématiques de robot mobiles est discutée, et le problème est formulé comme l'identification en temps réel du signal de commutation d'un système singulier non-linéaire et à commutation. Deuxièmement, sur la base du modèle identifié, un algorithme de planification locale est proposé, et le contour irrégulier de l' obstacle est représenté par des segments. La trajectoire est obtenue en résolvant un problème de commande optimale avec contraintes. Troisièmement, nous appliquons un contrôleur i-PID pour contrôler le robot mobile non-holonome avec la perturbation dans les mesures. Un paramètre de commutation α est proposé en raison de la particularité du système non-holonome. En plus de notre algorithme de planification proposé, une autre approche de planification en utilisant de champs de potentiels est proposée. La nouvelle fonction de champ de potentiel est en mesure de résoudre les problèmes de minima locaux et de produire des forces lisses pour éviter les oscillations. Enfin, une approche de planification coopérative entre robots est proposée en utilisant les informations locales partagées par chaque robot. Le graphe de visibilité est utilisé pour générer une série d'objectifs intermédiaires qui assureront aux robots d’atteindre l'objectif final, et un algorithme est proposé pour étendre les obstacles et fusionner les obstacles lorsque deux obstacles s'entrecroisent / This PhD thesis is dedicated to the path planning and control strategy for non-holonomic mobile robots. After a review of the recent researches and their features, new path planning algorithms and control strategies are proposed. Firstly, the identification of different mobile robot kinematic models is discussed, robot kinematic models are formulated as a switched singular nonlinear system, and the problem becomes the real-time identification of the switching signal. Secondly, based on the identified model, a local path planning algorithm is proposed, in which the irregular contour of obstacles is represented by segments. The path planning problem is formulated as a constrained receding horizon planning problem and the trajectory is obtained by solving an optimal control problem with constraints. Thirdly, we apply an i-PID controller to control the non-holonomic mobile robot with measurement disturbance. A switching parameter α is proposed because of the particularity of the non-holonomic system. In addition to our proposed path planning algorithm, another path planning approach using potential field is proposed. The modified potential field function, which takes into account the robot orientation and angular velocity, is able to solve local minima problems and produce smooth forces to avoid oscillations. Finally, a cooperative path planning approach between robots is proposed by using the shared local information of each robot. The visibility graph is used to generate a series of intermediate objectives which will guarantee the robots reaching the final objective, and an algorithm is proposed to expand obstacles and merge obstacles when two obstacles intercross

A zone of high magnetization along the SE margin of Paleoproterozoic Laurentia in the United States is indicated by magnetic anomaly data. The SE edge corresponds to the geochemical Neodymium mantle derivation model age (TDM) boundary and the entire anomaly overlies the Paleoproterozoic Mazatzal Province. Two-dimensional gravity and magnetic models across the Nd boundary are created with Moho constrained from receiver functions with gravity, sedimentary thickness and the base of the crustal magnetization. Upper crustal magnetization does not show strong variation across this boundary and much of the strong magnetization appears to lie in the middle crust. Using magnetic modeling of several potential geologic scenarios, we estimate magnetization, depth extent, and width of this zone of high magnetization. The anomaly has variable width (~ 300 km) with amplitude of approximately 200 nT. Pre-1.55Ga Paleoproterozoic mid crustal blocks have significantly higher average effective susceptibility (0.06 SI) than those of the post-1.55Ga Mesoproterozoic (0.01 SI). In two of the three profiles, the Paleoproterozoic zone of high magnetization has the highest average susceptibility indicating the Mazatzal province is innately highly magnetic. The zone may have formed either by magmatism associated with westward subduction or from highly magnetic terranes wedging between accreting island arcs.

Geologically-constrained inversion of geophysical data is a powerful method for predicting geology beneath cover. The process seeks 3D physical property models that are consistent with the geology and explain measured geophysical responses. The recovered models can guide mineral explorers to prospective host rocks, structures, alteration and mineralisation. This thesis provides a comprehensive analysis of how the University of British Columbia Geophysical Inversion Facility (UBC–GIF) gravity and magnetic inversions can be applied to subsurface mapping and exploration by demonstrating the necessary approach, data types, and typical results. The non-uniqueness of inversion demands that geological information be included. Commonly available geological data, including structural and physical property measurements, mapping, drilling, and 3D interpretations, can be translated into appropriate inversion constraints using tools developed herein. Surface information provides the greatest improvement in the reliability of recovered models; drilling information enhances resolution at depth. The process used to prepare inversions is as important as the geological constraints themselves. Use of a systematic workflow, as developed in this study, minimises any introduced ambiguity. Key steps include defining the problem, preparing the data, setting inversion parameters and developing geological constraints. Once reliable physical property models are recovered they must be interpreted in a geological context. Where alteration and mineralisation occupy significant volumes, the mineralogy associated with the physical properties can be identified; otherwise a lithological classification of the properties can be applied. This approach is used to develop predictive 3D lithological maps from geologically-constrained gravity and magnetic inversions at several scales in the Agnew-Wiluna greenstone belt in Australia’s Yilgarn Craton. These maps indicate a spatial correlation between thick mafic-ultramafic rock packages and gold deposit locations, suggesting a shared structural control. The maps also identify structural geometries and relationships consistent with the published regional tectonic framework. Geophysical inversion provides a framework into which geological and geophysical data sets can be integrated to produce a holistic prediction of the subsurface. The best possible result is one that cannot be dismissed as inconsistent with some piece of geological knowledge. Such a model can only be recovered by including all available geological knowledge using a consistent workflow process. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Multi-vehicle systems offer many advantages in engineering applications such as increased efficiency and robustness. However, the disadvantage of multi-vehicle systems is that they require a high level of organization and coordination in order to successfully complete a task. Formation control is a field of engineering that addresses this issue, and provides coordination schemes to successfully implement multi-vehicle systems. Two approaches to group coordination were proposed in this work: geometric and self-organizing formations. A geometric reconfiguring formation was developed using the leader-follower method, and the self-organizing formation was developed using the velocity potential equations from fluid flow theory. Both formation controllers were first tested in simulation in MATLAB, and then implemented on the X80 mobile robot units. Various experiments were conducted to test the formations under difficult obstacle scenarios. The robots successfully navigated through the obstacles as a coordinated as a team using the self-organizing and geometric formation control approaches.

The use of unmanned aerial vehicles (UAV), so-called drones, has been growingrapidly in the last decade. Today, they are used for, among other things, monitoring missions and inspections of places that are difficult for people to access. Toefficiently and robustly execute these types of missions, a swarm of drones maybe used, i.e., a collection of drones that coordinate together. However, this introduces new requirements on what solutions are used for control and navigation. Two important aspects of autonomous navigation of drone swarms are formationcontrol and collision avoidance. To manage these problems, we propose four different solution algorithms. Two of them use leader-follower control to keep formation, Artificial PotentialField (APF) for path planning and Control Barrier Function (CBF)/ExponentialControl Barrier Function (ECBF) to guarantee that the control signal is safe i.e.the drones keep the desired safety distance. The other two solutions use an optimal control problem formulation of a motion planning problem to either generate open-loop or closed-loop trajectories with a linear quadratic regulator (LQR)controller for trajectory following. The trajectories are optimized in terms of timeand formation keeping. Two different controllers are used in the solutions. Oneof which uses cascade PID control, and the other uses a combination of cascadePID control and LQR control. As a way to test our solutions, a scenario is created that can show the utilityof the presented algorithms. The scenario consists of two drone swarms that willtake on different missions executed in the same environment, where the droneswarms will be on a direct collision course with each other. The implementedsolutions should keep the desired formation while smoothly avoiding collisionsand deadlocks. The tests are conducted on real UAVs, using the open sourceflying development platform Crazyflie 2.1 from Bitcraze AB. The resulting trajectories are evaluated in terms of time, path length, formation error, smoothnessand safety.  The obtained results show that generating trajectories from an optimal control problem is superior compared to using APF+leader-follower+CBF/ECBF. However, one major advantage of the last-mentioned algorithms is that decision making is done at every time step making these solutions more robust to disturbancesand changes in the environment.