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1
Bautin, Antoine. "Stratégie d'exploration multirobot fondée sur le calcul de champs de potentiels." Thesis, Université de Lorraine, 2013. http://www.theses.fr/2013LORR0261/document.
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Cette thèse s'inscrit dans le cadre du projet Cart-O-Matic mis en place pour participer au défi CAROTTE (CArtographie par ROboT d'un TErritoire) organisé par l'ANR et la DGA. Le but de ce défi est de construire une carte en deux et trois dimensions et de localiser des objets dans un environnement inconnu statique de type appartement. Dans ce contexte, l'utilisation de plusieurs robots est avantageuse car elle permet d'augmenter l'efficacité en temps de la couverture. Cependant, comme nous le montrons, le gain est conditionné par le niveau de coopération entre les robots. Nous proposons une stratégie de coopération pour une cartographie multirobot efficace. Une difficulté est la construction d'une carte commune, nécessaire, afin que chaque robot puisse connaître les zones de l'environnement encore inexplorées. Pour obtenir une bonne coopération avec un algorithme simple nous proposons une technique de déploiement fondée sur le choix d'une cible par chaque robot. L'algorithme proposé cherche à distribuer les robots vers différentes directions. Il est fondé sur le calcul partiel de champs de potentiels permettant à chaque robot de calculer efficacement son prochain objectif. En complément de ces contributions théoriques, nous décrivons le système robotique complet mis en oeuvre au sein de l'équipe Cart-O-Matic ayant permis de remporter la dernière édition du défi CAROTTEThis thesis is part of Cart-O-Matic project set up to participate in the challenge CARROTE (mapping of a territory) organized by the ANR and the DGA. The purpose of this challenge is to build 2D and 3D maps of a static unknown 'apartment-like' environment. In this context, the use of several robots is advantageous because it increases the time efficiency to discover fully the environment. However, as we show, the gain is determined by the level of cooperation between robots. We propose a cooperation strategy for efficient multirobot mapping. A difficulty is the construction of a common map, necessary so that each robot can know the areas of the environment which remain unexplored.For a good cooperation with a simple algorithm we propose a deployment technique based on the choice of a target by each robot. The proposed algorithm tries to distribute the robots in different directions. It is based on calculation of the partial potential fields allowing each robot to compute efficiently its next target. In addition to these theoretical contributions, we describe the complete robotic system implemented in the Cart-O-Matic team that helped win the last edition of the CARROTE challenge
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Bautin, Antoine. "Stratégie d'exploration multirobot fondée sur le calcul de champs de potentiels." Electronic Thesis or Diss., Université de Lorraine, 2013. http://www.theses.fr/2013LORR0261.
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Cette thèse s'inscrit dans le cadre du projet Cart-O-Matic mis en place pour participer au défi CAROTTE (CArtographie par ROboT d'un TErritoire) organisé par l'ANR et la DGA. Le but de ce défi est de construire une carte en deux et trois dimensions et de localiser des objets dans un environnement inconnu statique de type appartement. Dans ce contexte, l'utilisation de plusieurs robots est avantageuse car elle permet d'augmenter l'efficacité en temps de la couverture. Cependant, comme nous le montrons, le gain est conditionné par le niveau de coopération entre les robots. Nous proposons une stratégie de coopération pour une cartographie multirobot efficace. Une difficulté est la construction d'une carte commune, nécessaire, afin que chaque robot puisse connaître les zones de l'environnement encore inexplorées. Pour obtenir une bonne coopération avec un algorithme simple nous proposons une technique de déploiement fondée sur le choix d'une cible par chaque robot. L'algorithme proposé cherche à distribuer les robots vers différentes directions. Il est fondé sur le calcul partiel de champs de potentiels permettant à chaque robot de calculer efficacement son prochain objectif. En complément de ces contributions théoriques, nous décrivons le système robotique complet mis en oeuvre au sein de l'équipe Cart-O-Matic ayant permis de remporter la dernière édition du défi CAROTTEThis thesis is part of Cart-O-Matic project set up to participate in the challenge CARROTE (mapping of a territory) organized by the ANR and the DGA. The purpose of this challenge is to build 2D and 3D maps of a static unknown 'apartment-like' environment. In this context, the use of several robots is advantageous because it increases the time efficiency to discover fully the environment. However, as we show, the gain is determined by the level of cooperation between robots. We propose a cooperation strategy for efficient multirobot mapping. A difficulty is the construction of a common map, necessary so that each robot can know the areas of the environment which remain unexplored.For a good cooperation with a simple algorithm we propose a deployment technique based on the choice of a target by each robot. The proposed algorithm tries to distribute the robots in different directions. It is based on calculation of the partial potential fields allowing each robot to compute efficiently its next target. In addition to these theoretical contributions, we describe the complete robotic system implemented in the Cart-O-Matic team that helped win the last edition of the CARROTE challenge
3
Frazier, Cameron. "Re-Active Vector Equilibrium: A Novel Method of Autonomous Vehicle Navigation using Artificial Potential Fields." Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/32270.
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The use of potential field based navigation schemes in robotics has been limited by inherent local minima issues. Local minima traps, small passages, unstable motion, and targets positioned near objects all pose major concerns when using potential fields for local vehicle control. This work proposes a new algorithm, "Re-Active Vector Equilibrium" (RAVE) that mitigates many of these issues. The vehicle representation model is expanded to use multiple points subject to potential calculation and the addition of two forces, a velocity dependent "risk force" (F_rsk) and a velocity and direction dependent "tangential force" (F_tan). The vehicle representation model is also expanded from a single reactive point to a series of points that define the vehicle body, providing better and simpler vehicle control. This has the effect of simplifying the required calculations at the cost of increasing the calculation count. The risk force, F_rsk, allows for dynamic adaptation to the immediate environment by acting in opposition to the net obstacle force, and is inversely proportional to the vehicle speed. The tangential force, F_tan, encourages better wall-following behaviour and provides a biasing mechanism to resolve obstacle aligned with target local minima issues.
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Kamm, Jochen. "Inversion and Joint Inversion of Electromagnetic and Potential Field Data." Doctoral thesis, Uppsala universitet, Geofysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-215673.
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In this thesis, four inversion problems of different scale and difficulty are solved. Two of them are electromagnetic inverse problems. Two more are joint inversion problems of potential field data and other types of data. First, a linear approximation, which is a generalization of the low-induction-number approximation standard in slingram dual-loop interpretation is developed and used for rapid two and three dimensional inversion. The approximation takes induction within a background half-space into account and can thus be applied in conductive scenarios, where otherwise a rigorous electromagnetic modeling would be required. Second, a three-dimensional inversion of airborne tensor very-low-frequency data with a rigorous forward modeling at its core is developed. For dealing with the large scale of the forward problem, a nested fast-Fourier-transform-based integral equation method is introduced, wherein electromagnetic interactions are arranged according to their range and larger ranges are treated with less accuracy and effort. The inversion improves the traditional interpretation through data derived maps by providing a conductivity model, thus constraining the upper few hundred meters of the crust down to the shallowest conductor and allowing the study of its top in three dimensions. The third inversion problem is the the joint inversion of refraction and geoelectric data. By requiring the velocity and resistivity models to share a common, laterally variable layered geometry, easily interpretable models, which are reasonable in many geological near surface situations (e.g., groundwater exploration in Quaternary sediments), are produced directly from the joint inversion. Finally, a joint inversion of large scale potential field data from a gabbro intrusion is presented. Gravity and magnetic data are required to abide to a petrophysical constraint, which is derived from extensive field sampling. The impact of the constraint is maximized under the provision that both data sets are explained equally well as they would be through individual inversions. This leads to a simple and clearly defined intrusion geometry, consistent for both the density and magnetic susceptibility distribution. In all presented inversion problems, field data sets are successfully inverted, the results are appraised through synthetic tests and, if available, through comparison with independent data.Diese Arbeit hat die Lösung von vier geophysikalischen Umkehraufgaben, sogenannten Inversionsproblemen, zum Gegenstand. Zwei dieser Aufgaben befassen sich mit der Inversion elektromagnetischer Daten, zwei weitere sind Probleme der kombinierten Inversion von Datensätzen aus unterschiedlichen geophysikalischen Messverfahren. Im ersten Problem wird die für die Auswertung elektromagnetischer Zweispulensystemdaten typische lineare Näherung der kleinen Induktionszahlen als Bornsche Näherung verallgemeinert, ihre Anwendbarkeit durch exakte Berücksichtigung der Induktionsvorgänge in einem beliebigen homogenen Halbraum von schlechtleitenden auf gutleitende Untergründe ausgedehnt und schließlich zur zwei- und dreidimensionalen Inversion eingesetzt. Dadurch kann auch im leitfähigen Untergrund eine aufwändige exakte Modellierung vermieden werden. Im zweiten Problem wird eine dreidimensionale Inversion von flugzeuggestützten Längstwellenmessungen entwickelt und als ihre Grundlage eine exakte elektromagnetische Rechnung erdacht. Damit wird traditionelle kartengestützte Dateninterpretation durch ein dreidimensionales Leitfähigkeitsmodell ergänzt, welches die oberen hundert bis dreihundert Meter der Erdkruste bis hin zur Tiefe des obersten Leiters abbildet, so dass dessen Oberflächenform erkundet werden kann. Die enorme Problemgröße wird durch eine Fouriertransformationsmethode bewältigt, welche die elektromagnetischen Wechselwirkungen nach ihrer Reichweite einteilt, die Fernwirkungen mit entsprechend verringerter Genauigkeit behandelt und dadurch eine erhebliche Anzahl an Rechnungen einspart. Im dritten Problem werden refraktionsseismische und geoelektrische Messungen kombiniert, indem sowohl das Geschwindigkeits- als auch das Widerstandsmodell mit einer gemeinsamen, lateral veränderlichen und durch beide Datensätze bestimmten Schichtstruktur versehen werden. Ein solches, durch Schichten definiertes Inversionsergebnis, stellt in vielen oberflächennahen Anwendungen, beispielsweise im Grundwasserbereich, ein sinnvolles Abbild der Erde dar. Im vierten Problem werden Schweremessungen und Magnetfeldmessungen, die über einer Gabbrointrusion aufgenommen wurden, mittels einer empirischen petrophysikalischen Beziehung vereinigt, welche aus Labormessungen an einer großen Anzahl von Gesteinsproben abgeleitet wurde. Hierbei wird der Einfluss dieser Modellkopplung solange maximiert, wie beide Datensätze mit derjenigen Genauigkeit angepasst werden können, welche vorher in Einzelinversionen erreicht wurde. Das Ergebnis ist ein einfaches, geometrisch konsistentes Modell der Verteilungen von Dichte und magnetischer Suszeptibilität. In allen vier Aufgaben wurden erfolgreich reale Felddaten invertiert. Die Güte der Ergebnisse wurde mittels synthetischer Experimente untersucht und, so vorhanden, mit unabhängigen Informationen verglichen.
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Uusitalo, Tim. "A first approach in applying Artificial Potential Fields in Car Games." Thesis, Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-2480.
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In car racing simulation games, finishing first is the main goal. To reach that goal, it is required to go around a racing track, competing against other cars aiming for the same goal. Implementing a bot for doing so may have its difficulties, although using a technique called multi-agent systems combined with artificial potential field, let- ting the agents take care of subtasks like keeping the car on the track, minimize how much the car turns in a curvature and basics in navigation around the track, has showed that artificial potential fields very well fit the problem of driving a car in simulated car racing in a competitive way.Mobiltelefon: 0707422666
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Sheffer, Megan Rae. "Forward modelling and inversion of streaming potential for the interpretation of hydraulic conditions from self-potential data." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/235.
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The self-potential method responds to the electrokinetic phenomenon of streaming potential and has been applied in hydrogeologic and engineering investigations to aid in the evaluation of subsurface hydraulic conditions. Of specific interest is the application of the method to embankment dam seepage monitoring and detection. This demands a quantitative
interpretation of seepage conditions from the geophysical data.
To enable the study of variably saturated flow problems of complicated geometry, a three-dimensional finite volume algorithm
is developed to evaluate the self-potential distribution resulting from subsurface fluid flow. The algorithm explicitly calculates
the distribution of streaming current sources and solves for the self-potential given a model of hydraulic head and prescribed distributions of the streaming current cross-coupling conductivity and electrical resistivity. A new laboratory apparatus is developed to measure the streaming potential coupling coefficient
and resistivity in unconsolidated soil samples. Measuring both of these parameters on the same sample under the same conditions
enables us to properly characterize the streaming current cross-coupling conductivity coefficient. I present the results of a laboratory investigation to study the influence of soil and fluid parameters on the cross-coupling coefficient, and characterize this property for representative well-graded embankment soils. The streaming potential signals associated with preferential seepage through the core of a synthetic embankment dam model are studied using the forward modelling algorithm and measured electrical properties to assess the sensitivity of the self-potential method in detecting internal erosion. Maximum self-potential anomalies are shown to be linked to large localized
hydraulic gradients that develop in response to piping, prior to any detectable increase in seepage flow through the dam. A linear
inversion algorithm is developed to evaluate the three-dimensional distribution of hydraulic head from self-potential data, given a known distribution of the cross-coupling coefficient and electrical resistivity. The inverse problem is solved by
minimizing an objective function, which consists of a data misfit that accounts for measurement error and a model objective function that incorporates a priori information. The algorithm is suitable
for saturated flow problems or where the position of the phreatic surface is known.
7
Hoffbauer, Cole. "MULTI-USER REDIRECTED WALKING AND RESETTING UTILIZING ARTIFICIAL POTENTIAL FIELDS." Miami University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=miami1530629793552698.
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Morgan, David C. "A Gaussian approximation to the effective potential." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/26500.
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This thesis investigates some of the properties of a variational approximation to scalar field theories: a trial wavefunctional which has a gaussian form is used as a ground state ansatz for an interacting scalar field theory - the expectation value of the Hamiltonian in this state is then minimized. This we call the Gaussian Approximation; the resulting effective potential we follow others by calling the Gaussian Effective Potential (GEP). An equivalent but more general finite temperature formalism is then reviewed and used for the calculations of the GEP in this thesis. Two scalar field theories are described: ϕ⁴ theory in four dimensions (ϕ⁴₄) and ϕ⁶ theory in three dimensions (ϕ⁶₃). After showing what the Gaussian Approximation does in terms of Feynman diagrams, renormalized GEP's are calculated for both theories. Dimensional Regularization is used in the renormalization and this this is especially convenient for the GEP in ϕ⁶₃ theory because it becomes trivially renor-malizable. It is noted that ϕ⁶₃ loses its infrared asymptotic freedom in the Gaussian Approximation. Finally, it is shown how a finite temperature GEP can be calculated by finding low and high temperature expansions of the temperature terms in ϕ⁶₃ theory.Science, Faculty of
Physics and Astronomy, Department of
Graduate
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Capito, Ruiz Linda J. "Optical Flow-based Artificial Potential Field Generation for Gradient Tracking Sliding Mode Control for Autonomous Vehicle Navigation." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1555599397128602.
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Malik, Waqar Ahmad. "Motion planning of mobile robot in dynamic environment using potential field and roadmap based planner." Texas A&M University, 2003. http://hdl.handle.net/1969/338.
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Blommé, Johan. "Evaluation of biometric security systems against artificial fingers." Thesis, Linköping University, Department of Electrical Engineering, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-1145.
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Verification of users’ identities are normally carried out via PIN-codes or ID- cards. Biometric identification, identification of unique body features, offers an alternative solution to these methods.
Fingerprint scanning is the most common biometric identification method used today. It uses a simple and quick method of identification and has therefore been favored instead of other biometric identification methods such as retina scan or signature verification.
In this report biometric security systems have been evaluated based on fingerprint scanners. The evaluation method focuses on copies of real fingers, artificial fingers, as intrusion method but it also mentions currently used algorithms for identification and strengths and weaknesses in hardware solutions used.
The artificial fingers used in the evaluation were made of gelatin, as it resembles the surface of human skin in ways of moisture, electric resistance and texture. Artificial fingers were based on ten subjects whose real fingers and artificial counterpart were tested on three different fingerprint scanners. All scanners tested accepted artificial fingers as substitutes for real fingers. Results varied between users and scanners but the artificial fingers were accepted between about one forth and half of the times.
Techniques used in image enhancement, minutiae analysis and pattern matching are analyzed. Normalization, binarization, quality markup and low pass filtering are described within image enhancement. In minutiae analysis connectivity numbers, point identification and skeletonization (thinning algorithms) are analyzed. Within pattern matching, direction field analysis and principal component analysis are described. Finally combinations of both minutiae analysis and pattern matching, hybrid models, are mentioned.
Based on experiments made and analysis of used techniques a recommendation for future use and development of fingerprint scanners is made.
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Bott, M. P. "A new, robust, and generic method for the quick creation of smooth paths and near time-optimal path tracking." Thesis, University of St Andrews, 2011. http://hdl.handle.net/10023/2095.
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Robotics has been the subject of academic study from as early as 1948. For much of this time, study has focused on very specific applications in very well controlled environments. For example, the first commercial robots (1961) were introduced in order to improve the efficiency of production lines. The tasks undertaken by these robots were simple, and all that was required of a control algorithm was speed, repetitiveness and reliability in these environments. Now however, robots are being used to move around autonomously in increasingly unpredictable environments, and the need for robotic control algorithms that can successfully react to such conditions is ever increasing. In addition to this there is an ever-increasing array of robots available, the control algorithms for which are often incompatible. This can result in extensive redesign and large sections of code being re-written for use on different architectures. The thesis presented here is that a new generic approach can be created that provides robust high quality smooth paths and time-optimal path tracking to substantially increase applicability and efficiency of autonomous motion plans. The control system developed to support this thesis is capable of producing high quality smooth paths, and following these paths to a high level of accuracy in a robust and near time-optimal manner. The system can control a variety of robots in environments that contain 2D obstacles of various shapes and sizes. The system is also resilient to sensor error, spatial drift, and wheel-slip. In achieving the above, this system provides previously unavailable functionality by generically creating and tracking high quality paths so that only minor and clear adjustments are required between different robots and also be being capable of operating in environments that contain high levels of perturbation. The system is comprised of five separate novel component algorithms in order to cater for five different motion challenges facing modern robots. Each algorithm provides guaranteed functionality that has previously been unavailable in respect to its challenges. The challenges are: high quality smooth movement to reach n-dimensional goals in regions without obstacles, the navigation of 2D obstacles with guaranteed completeness, high quality smooth movement for ground robots carrying out 2D obstacle navigation, near time-optimal path tracking, and finally, effective wheel-slip detection and compensation. In meeting these challenges the algorithms have tackled adherence to non-holonomic constraints, applicability to a wide range of robots and tasks, fast real-time creation of paths and controls, sensor error compensation, and compensation for perturbation. This thesis presents each of the above algorithms individually. It is shown that existing methods are unable to produce the results provided by this thesis, before detailing the operation of each algorithm. The methodology employed is varied in accordance with each of the five core challenges. However, a common element of methodology throughout the thesis is that of gradient descent within a new type of potential field, which is dynamic and capable of the simultaneous creation of high-quality paths and the controls required to execute them. By relating global to local considerations through subgoals, this methodology (combined with other elements) is shown to be fully capable of achieving the aims of the thesis. It is concluded that the produced system represents a novel and significant contribution as there is no other system (to the author’s knowledge) that provides all of the functionality given. For each component algorithm there are many control systems that provide one or more of its features, but none that are capable of all of the features. Applications for this work are wide ranging as it is comprised of five component algorithms each applicable in their own right. For example, high quality smooth paths may be created and followed in any dimensionality of space if time optimality and obstacle avoidance are not required. Broadly speaking, and in summary, applications are to ground-based robotics in the areas of smooth path planning, time optimal travel, and compensation for unpredictable perturbation.
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Weidig, Tom. "Classical and quantum aspects of topological solitons (using numerical methods)." Thesis, Durham University, 1999. http://etheses.dur.ac.uk/4277/.
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In Introduction, we review integrable and topological solitons. In Numerical Methods, we describe how to minimize functionals, time-integrate configurations and solve eigenvalue problems. We also present the Simulated Annealing scheme for minimisation in solitonic systems. In Classical Aspects, we analyse the effect of the potential term on the structure of minimal- energy solutions for any topological charge n. The simplest holomorphic baby Skyrme model has no known stable minimal-energy solution for n > 1. The one-vacuum baby Skyrme model possesses non-radially symmetric multi-skyrmions that look like 'skyrmion lattices' formed by skyrmions with n = 2. The two-vacua baby Skyrme model has radially symmetric multi- skyrmions. We implement Simulated Annealing and it works well for higher order terms. We find that the spatial part of the six-derivative term is zero. In Quantum Aspects, we find the first order quantum mass correction for the Ф(^4) kink using the semi-classical expansion. We derive a trace formula which gives the mass correction by using the eigenmodes and values of the soliton and vacuum perturbations. We show that the zero mode is the most important contribution. We compute the mass correction of Ф(^4) kink and Sine-Gordon numerically by solving the eigenvalue equations and substituting into the trace formula.
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East, Jackie R. "NATURAL PHENOMENA AS POTENTIAL INFLUENCE ON SOCIAL AND POLITICAL BEHAVIOR: THE EARTH’S MAGNETIC FIELD." UKnowledge, 2014. http://uknowledge.uky.edu/polysci_etds/11.
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Researchers use natural phenomena in a number of disciplines to help explain human behavioral outcomes. Research regarding the potential effects of magnetic fields on animal and human behavior indicates that fields could influence outcomes of interest to social scientists. Tests so far have been limited in scope. This work is a preliminary evaluation of whether the earth’s magnetic field influences human behavior it examines the baseline relationship exhibited between geomagnetic readings and a host of social and political outcomes. The emphasis on breadth of topical coverage in these statistical trials, rather than on depth of development for any one model, means that evidence is only suggestive – but geomagnetic readings frequently covary with social and political variables in a fashion that seems inexplicable in the absence of a causal relationship. The pattern often holds up in more-elaborate statistical models. Analysis provides compelling evidence that geomagnetic variables furnish valuable information to models. Many researchers are already aware of potential causal mechanisms that link human behavior to geomagnetic levels and this evidence provides a compelling case for continuing to develop the line of research with in-depth, focused analysis.
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Morais, Carlos Eduardo Silva. "Um Sistema Anticolisão 3D baseado no método de Campo Potencial Artificial para um robô móvel." Universidade Federal da Paraíba, 2017. http://tede.biblioteca.ufpb.br:8080/handle/tede/9243.
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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.
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Stetkiewicz, Stacia Serreze. "Interdisciplinary assessment of the potential for improving Integrated Pest Management practice in Scottish spring barley." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/28959.
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Integrated Pest Management (IPM) has long been promoted as a means of reducing reliance on pesticide inputs as compared to conventional farming systems. Reduced pesticide application could be beneficial due to the links between intensive pesticide use and negative impacts upon biodiversity and human health as well as the development of pesticide resistance. Work assessing the potential of IPM in cereal production is currently limited, however, and previous findings have generally covered the subject from the perspective of either field trial data or social science studies of farmer behaviour. This thesis attempts to help to address this knowledge gap by providing a more holistic assessment of IPM in Scottish spring barley production (selected because of its dominance in Scotland’s arable production systems), in relation to three of its most damaging fungal pathogens: Rhynchosporium commune, Blumeria graminis f.sp. hordei, and Ramularia collo-cygni. Several IPM techniques of potential relevance to the sector were identified, and the prospects of three in particular – crop rotation, varietal disease resistance, and forecasting disease pressure – were assessed in several ways. Preliminary analysis of experimental field trial data collected from 2011 – 2014 across Scotland found that the majority of spring barley trials in this period (65%) did not show a statistically significant impact of fungicide treatment on yield, with the average yield increase due to fungicide application being 0.62 t/ha. This initial analysis was expanded upon using stepwise regressions of long-term (1996 – 2014) field trial data from the same dataset. Here, the difference between treated and untreated yields could be explained by disease resistance, average seasonal rainfall (whereby wetter seasons saw an increased impact of fungicide use on yield), and high combined disease severity. Stakeholder surveying provided information about current practice and attitudes towards the selected IPM techniques amongst a group of 43 Scottish spring barley farmers and 36 agronomists. Stakeholders were broadly open to taking up IPM measures on farm; sowing of disease resistant varieties was most frequently selected as the best technique in terms of both practicality and cost, though individual preference varied. However, a disparity was seen between farmer perception of their uptake of IPM and actual, self-reported uptake for both varietal disease resistance and rotation. Farmers and agronomists also overestimated the impact of fungicide use as compared with the field trials results – the majority of stakeholders believed fungicide treatment to increase yields by 1 - 2 t/ha, while the majority of 2011 – 2014 field trials had a yield difference of under 1 t/ha. The reasons behind these differences between perception and practice are not currently known. Finally, an annual survey of commercial crops, gathered from 552 farms across Scotland (from 2009 – 2015), highlighted two gaps where IPM practice could be improved upon. Firstly, relatively few of the varieties listed in the commercial crops database were highly resistant to the three diseases – 26.1% were highly resistant to Ramularia, 14.2% to Rhynchosporium, and 58.1% to mildew. Secondly, 71% of the farms included in the database had planted barley in at least two consecutive seasons, indicating that crop rotation practices could be improved. The overarching finding of this project is that there is scope for IPM uptake to be improved upon and fungicide use to be reduced while maintaining high levels of yield in Scottish spring barley production. Incorporating experimental field data, stakeholder surveying, and commercial practice data offered a unique view into the potential for IPM in this sector, and provided insights which could not have been gained through the lens of a single discipline.
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Pruner, Elisha. "Control of Self-Organizing and Geometric Formations." Thèse, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/30491.
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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.
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Yalim, Mehmet S. "An artificial compressibility analogy approach for compressible ideal MHD: application to space weather simulation." Doctoral thesis, Universite Libre de Bruxelles, 2008. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210427.
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Ideal magnetohydrodynamics (MHD) simulations are known to have problems in satisfying the solenoidal constraint (i.e. the divergence of magnetic field should be equal to zero, $ablacdotvec{B} = 0$). The simulations become unstable unless specific measures have been taken.
In this thesis, a solenoidal constraint satisfying technique that allows discrete satisfaction of the solenoidal constraint up to the machine accuracy is presented and validated with a variety of test cases. Due to its inspiration from Chorin's artificial compressibility method developed for incompressible CFD applications, the technique was named as \
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished
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Taormina, Bastien. "Potential impacts of submarine power cables from marine renewable energy projects on benthic communities A review of potential impacts of submarine power cables on the marine environment: Knowledge gaps, recommendations and future directions, in Renewable and Sustainable Energy Reviews 96, November 2018 Optimizing image-based protocol to monitor macroepibenthic communities colonizing artificial structures, in ICES Journal of marine science 77(2), March 2020." Thesis, Brest, 2019. http://theses-scd.univ-brest.fr/2019/These-2019-SML-Ecologie_marine-TAORMINA_Bastien.pdf.
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Dans un contexte de développement rapide des projets d’énergies marines renouvelables, le but de cette thèse était d’améliorer les connaissances sur les impacts potentiels des câbles électriques sous-marins sur les écosystèmes benthiques côtiers. En se focalisant sur la phase de fonctionnement, ce travail était essentiellement dédié à la caractérisation de l’effet récif généré par ces câbles et leurs structures associées (protection, stabilisation) sur les communautés épibenthiques fixées et la mégafaune mobile. L’étude était principalement basée sur l’utilisation d’images sous-marines (photo et vidéo) prises in situ par des plongeurs. Ce travail a mené à des réflexions méthodologiques sur la manière la plus efficace d’analyser ce genre de données afin d’appréhender pleinement la dynamique de colonisation des structures artificielles et leur rôle d’habitat pour des espèces commerciales. Outre cet effet récif, certains organismes se retrouvent exposés à des champs magnétiques émis par les câbles électriques. Ceci m’a conduit à mesurer expérimentalement l’impact de champs magnétiques artificiels sur le comportement du homard Européen (Homarus gammarus) au stade juvénile. Finalement, nous avons étudié in situ les potentiels bénéfices pour la macrofaune benthique de l’exclusion d’activités anthropiques autour de la route de câbles électriques. Le couplage d’approches in situ et ex situ m’a permis de mieux appréhender les impacts environnementaux associés aux câbles électriques sous-marins. Ces résultats permettront d’améliorer l’évaluation de l’empreinte écologique des futurs raccordements électriquesIn a global context of rapid development of marine renewable energy projects, the aim of this PhD thesis was to better characterise the potential impacts of submarine power cables on coastal benthic ecosystems. The work specifically focused on the impacts associated with the operational phase. The major part of this work was dedicated to the reef effect created by these cables and their protective and stabilising structures on sessile epibenthic communities and mobile megafauna. This work was mainly based on underwater imagery, either video or photo collected in situ by divers. The challenge of working with underwater imagery has led me to optimise image analyses so as to effectively monitor benthic colonisation and to quantify artificial reef habitat provision to commercial species.In addition to this reef effect, colonising organisms are exposed to magnetic fields generated by the power cables. Thus, I designed an experimental study to assess the impact of realistic magnetic fields on the behaviour of juvenile European lobsters (Homarus gammarus). Finally, we explored the ecological impacts of excluding anthropogenic activity from the cables routes and potential benefits for benthic macrofauna. By coupling both in situ and ex situ approaches, my PhD research better characterises the environmental impacts associated with submarine power cables. These results will help to assess the ecological footprint of future power grid connections
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Shetti, Rohan [Verfasser], Martin [Akademischer Betreuer] Wilmking, Achim [Gutachter] Bräuning, and Martin [Gutachter] Wilmking. "Potential of shrubs in the evolving field of Arctic and Alpine dendroecology : methods in shrub dendro-ecology: understanding the processes influencing shrub growth in the Arctic and Alpine ecosystems / Rohan Shetti ; Gutachter: Achim Bräuning, Martin Wilmking ; Betreuer: Martin Wilmking." Greifswald : Ernst-Moritz-Arndt-Universität, 2018. http://d-nb.info/1173322779/34.
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MELCHIORRE, MATTEO. "Real-time trajectory planning for human-friendly collaborative robotics." Doctoral thesis, Politecnico di Torino, 2021. http://hdl.handle.net/11583/2932747.
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Gavazzi, Bruno. "Méthode magnétique multi-échelle à trois dimensions appliquée à l'étude archéologique du site de Qasr 'Allam, oasis de Bahariya, Egypte." Thesis, Strasbourg, 2015. http://www.theses.fr/2015STRAG029/document.
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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 siteThis 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
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Le, Maire Pauline. "Caractérisation des anomalies magnétiques, approches théoriques et expérimentales : applications à des objets anthropiques et géologiques." Thesis, Strasbourg, 2017. http://www.theses.fr/2017STRAH006/document.
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L’objectif de ce travail est d’améliorer la caractérisation des sources à l’origine d’anomalies magnétiques, par le biais de développements théoriques et expérimentaux. Pour des structures invariantes dans une direction horizontale (structures à 2D), l’idée de Nabighian (1972) a été généralisée, ce qui implique une nouvelle façon d’étudier les méthodes potentielles à 2D. Ces développements ont permis de proposer une nouvelle approche théorique et de nouvelles représentations dans le plan complexe des fonctions magnétiques. La deuxième approche de ce travail est expérimentale. Une étude y est faite par le biais de données et de cas synthétiques, afin d’estimer l’apport d’acquisitions magnétiques à différentes altitudes pour caractériser une source. Dans un troisième temps, les développements théoriques et expérimentaux sont mis en œuvre pour deux exemples : des anomalies magnétiques en domaine océanique de type Vine et Mathews et une cartographie pour l’archéologieMagnetic anomalies recorded outside bodies provide high quality information relative to buried structures. By using theoretical and experimental developments, this thesis aims to improve the characterization of the source inducing the magnetic anomaly. Firstly, some properties of three dimensional magnetic functions are presented, for example the presence of several maxima of the analytic signal operator (3D) is demonstrated. The Nabighian (1972) equation is generalized, which imply a new process to study potential method in two dimensions. These developments enable a new visualization of the anomaly in the complex field. The second approach is experimental. Synthetic cases are used to estimate the contribution of different configurations of magnetic data acquisitions at different altitudes to characterize the magnetic source. Theoretical and experimental developments are finally applied to two field examples: oceanic magnetic anomalies and archaeological magnetic prospection
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Winkler, Alexander. "Sensorgeführte Bewegungen stationärer Roboter." Doctoral thesis, Universitätsbibliothek Chemnitz, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-197679.
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Den Kern der vorliegenden Arbeit bilden sog. sensorgeführte Roboterbewegungen, d. h. die Nutzung von Informationen externer Sensoren zur Regelung des Roboters. Da gängige Industrierobotersysteme üblicherweise positionsgeregelt sind und seitens der Robotersteuerung lediglich der Zugriff zu den Sollwerten der Lageregelkreise erlaubt wird, kann auch der Regelkreis der sensorgeführten Roboterbewegung nur über den Lageregelkreis geschlossen werden. Aus diesem Grunde werden hier nur positionsbasierte Regelungsansätze verfolgt. Die Kraft-/ Momentregelung gilt als eine der wichtigsten Varianten sensorgeführter Roboterbewegungen. Dementsprechend widmet sich auch ein großer Teil dieser Arbeit dem Thema, mit dem Ziel durch innovative und übersichtliche Regelalgorithmen die Akzeptanz der Kraft-/ Momentregelung in industriellen Produktionsprozessen zu erhöhen. Beginnend mit der eindimensionalen Kraftregelung führt der Weg dabei über Konzepte zur Konturenverfolgung und kraft-/ momentgeregelten Montageaufgaben hin zur Kooperation von Robotern. In einem weiteren Teil wird ein Konzept zur Kollisionsvermeidung zwischen Robotern und Hindernissen präsentiert. Es basiert auf dem Ansatz der virtuellen Potential- bzw. Kraftfelder. Dabei ruft das künstliche Feld eine Bewegung des Roboters hervor, die vom Hindernis weg führt. Um das Feld zu erzeugen, wird die Methode der künstlichen Punktladungen entwickelt. Diese werden auf der Oberfläche eines Hindernisses platziert und generieren dann das virtuelle Kraftfeld. Die Platzierung kann z. B. mithilfe der CAD-Daten des Hindernisses erfolgen. Bei bewegten Objekten müssen alle Ladungspositionen ständig aktualisiert werden. Für Lehr- und Präsentationszwecke ist das sog. inverse Pendel eine oft genutzte Regelstrecke. Sein Aufrichten und Stabilisieren ist auch mit Hilfe eines Industrieroboters möglich. Dazu beschäftigt sich ein Kapitel dieser Arbeit mit Fragen zur Modellbildung der Kombination inverses Pendel und Industrieroboter und mit Regelungskonzepten für das Aufschwingen und Balancieren. Letztendlichen wird in diesem Zusammenhang noch ein Visual-Servoing System präsentiert, dass den Neigungswinkel des Pendels mit einer Kamera bestimmt. Alle hier vorgestellten Konzepte und Algorithmen werden Anhand von praktischen Experimenten verifiziertThis work deals with so-called sensor guided robot motions, which means using the data of external sensors to control the robot. The control loop of the sensor guided robot motion can be only closed around the position control loop, because industrial robot systems usually work position controlled and only access to the desired positions is enabled. For this reason here only position based control approaches are regarded. Force/torque control is a very important type of sensor guided robot motions. According to this, a good portion of this work deals with the subject of force/torque control. Thus, the acceptance of force/torque control in industrial production processes should be increased, by using innovative and clear control algorithms. For this purpose force control in one degree of freedom, contour-following, force/torque controlled assembling tasks and the cooperation between robots are discussed here in different chapters. Thereafter, a concept to collision avoidance between robots and obstacles is presented. It uses the approach of virtual potential/force fields. In this case the artificial field induces a robot motion away from the obstacle. The method of artificial charges is developed to generate this field. For this purpose virtual charges are placed on the surface of the obstacles. Placing of the charges can be performed using e.g. CAD data of the obstacles. Having moving obstacles charge positions must be updated continuously. The inverted pendulum is commonly used teaching students in control theory. The swinging up and the stabilization of the pendulum also can be performed by an industrial robot. One chapter of this work deals with modelling of the robot mounted inverted pendulum and control algorithms for its swinging up and its stabilization. Finally, in combination with the inverted pendulum a visual-servoing system is presented, which measures the pendulum inclination angle by camera. All concepts introduced in this work are verified by practical experiments
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Tran, Ngo Quoc Huy. "Planification de mouvement pour les systèmes dynamiques multi-agents dans un environnement variable." Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAT099.
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Cette thèse propose des solutions de commande basées sur la planification optimale de trajectoires pour des systèmes dynamiques multi-agents fonctionnant dans un environnement variable (avec obstacles statiques ou mobiles et des perturbations variables dans le temps).Cette planification de trajectoires repose sur l'utilisation combinée de la théorie des ensembles (en particulier des ensembles convexes bornés), de la commande prédictive non-linéaire (NMPC), du calcul de champs de potentiel et des méthodes basées sur des graphes. Elle se base sur la construction de champs de potentiel répulsifs associés à des fonctions de barrière marche-arrêt (on-off barrier functions) qui décrivent et activent ou désactivent les trajectoires libres (sans collision) calculées au préalable par une commande de type NMPC distribuée. Ces constructions sont ensuite utilisées pour maintenir la connectivité dans le groupe d'agents, tout en assurant le suivi du chemin pré-généré. En outre, un observateur pour l'estimation de perturbations non linéaires est intégré dans le schéma de commande afin de les rejeter.Les résultats théoriques obtenus sont validés en simulation, par des comparaisons avec des approches utilisant la programmation mixte en nombres entiers, à l'aide de données numériques réelles provenant d'une plateforme de navigation sécurisée pour les véhicules de surface non habités dans le fjord de Trondheim (Norvège)This thesis proposes optimization-based control solutions for the motion planning of multi-agent dynamical systems operating in a variable environment (with static/mobile obstacles and time-varying environmental disturbances).Collision-free paths are planned for the agents through the combined use of set theory (particularly, bounded convex sets), non(-linear) Model Predictive Control (MPC), Potential Field (PF) and graph-based methods. The contributions build on the proposal of repulsive potential field constructions together with on-off barrier functions which describe and, respectively, activate/deactivate the collision-free conditions introduced in a distributed NMPC framework. These constructions are further used for connectivity maintenance conditions among the group of agents while ensuring the tracking of the a priori generated path. Furthermore, a nonlinear disturbance observer is integrated within the control scheme for environmental disturbance rejection.Finally, the results are validated in simulation through comparisons with mixed-integer approaches and over a benchmark for the safe navigation of Unmanned Surface Vehicles (USVs) in the Trondheim fjord, Norway, using real numerical data
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Winkler, Alexander. "Sensorgeführte Bewegungen stationärer Roboter." Doctoral thesis, Universitätsverlag der Technischen Universität Chemnitz, 2014. https://monarch.qucosa.de/id/qucosa%3A20403.
Full textAbstract:
Den Kern der vorliegenden Arbeit bilden sog. sensorgeführte Roboterbewegungen, d. h. die Nutzung von Informationen externer Sensoren zur Regelung des Roboters. Da gängige Industrierobotersysteme üblicherweise positionsgeregelt sind und seitens der Robotersteuerung lediglich der Zugriff zu den Sollwerten der Lageregelkreise erlaubt wird, kann auch der Regelkreis der sensorgeführten Roboterbewegung nur über den Lageregelkreis geschlossen werden. Aus diesem Grunde werden hier nur positionsbasierte Regelungsansätze verfolgt.
Die Kraft-/ Momentregelung gilt als eine der wichtigsten Varianten sensorgeführter Roboterbewegungen. Dementsprechend widmet sich auch ein großer Teil dieser Arbeit dem Thema, mit dem Ziel durch innovative und übersichtliche Regelalgorithmen die Akzeptanz der Kraft-/ Momentregelung in industriellen Produktionsprozessen zu erhöhen. Beginnend mit der eindimensionalen Kraftregelung führt der Weg dabei über Konzepte zur Konturenverfolgung und kraft-/ momentgeregelten Montageaufgaben hin zur Kooperation von Robotern.
In einem weiteren Teil wird ein Konzept zur Kollisionsvermeidung zwischen Robotern und Hindernissen präsentiert. Es basiert auf dem Ansatz der virtuellen Potential- bzw. Kraftfelder. Dabei ruft das künstliche Feld eine Bewegung des Roboters hervor, die vom Hindernis weg führt. Um das Feld zu erzeugen, wird die Methode der künstlichen Punktladungen entwickelt. Diese werden auf der Oberfläche eines Hindernisses platziert und generieren dann das virtuelle Kraftfeld. Die Platzierung kann z. B. mithilfe der CAD-Daten des Hindernisses erfolgen. Bei bewegten Objekten müssen alle Ladungspositionen ständig aktualisiert werden.
Für Lehr- und Präsentationszwecke ist das sog. inverse Pendel eine oft genutzte Regelstrecke. Sein Aufrichten und Stabilisieren ist auch mit Hilfe eines Industrieroboters möglich. Dazu beschäftigt sich ein Kapitel dieser Arbeit mit Fragen zur Modellbildung der Kombination inverses Pendel und Industrieroboter und mit Regelungskonzepten für das Aufschwingen und Balancieren. Letztendlichen wird in diesem Zusammenhang noch ein Visual-Servoing System präsentiert, dass den Neigungswinkel des Pendels mit einer Kamera bestimmt.
Alle hier vorgestellten Konzepte und Algorithmen werden Anhand von praktischen Experimenten verifiziert.This work deals with so-called sensor guided robot motions, which means using the data of external sensors to control the robot. The control loop of the sensor guided robot motion can be only closed around the position control loop, because industrial robot systems usually work position controlled and only access to the desired positions is enabled. For this reason here only position based control approaches are regarded. Force/torque control is a very important type of sensor guided robot motions. According to this, a good portion of this work deals with the subject of force/torque control. Thus, the acceptance of force/torque control in industrial production processes should be increased, by using innovative and clear control algorithms. For this purpose force control in one degree of freedom, contour-following, force/torque controlled assembling tasks and the cooperation between robots are discussed here in different chapters. Thereafter, a concept to collision avoidance between robots and obstacles is presented. It uses the approach of virtual potential/force fields. In this case the artificial field induces a robot motion away from the obstacle. The method of artificial charges is developed to generate this field. For this purpose virtual charges are placed on the surface of the obstacles. Placing of the charges can be performed using e.g. CAD data of the obstacles. Having moving obstacles charge positions must be updated continuously. The inverted pendulum is commonly used teaching students in control theory. The swinging up and the stabilization of the pendulum also can be performed by an industrial robot. One chapter of this work deals with modelling of the robot mounted inverted pendulum and control algorithms for its swinging up and its stabilization. Finally, in combination with the inverted pendulum a visual-servoing system is presented, which measures the pendulum inclination angle by camera. All concepts introduced in this work are verified by practical experiments.
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ZHENG, DONG-ZE, and 鄭東澤. "Modified Artificial Potential Field Method for Manipulator Path Planning and Obstacle Avoidance." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/jkaw25.
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碩士逢甲大學
自動控制工程學系
107
In the past, the manipulator was manually planned to make the path planning method when moving. However, in a complicated environment, the manual planning could not satisfy the actual needs. Therefore, let the manipulator search for the path by itself, can economize manpower and satisfy real-time obstacle avoidance. In this paper, the two-degree-of-freedom manipulator of plane motion and the three-degree-of-freedom manipulator of three-dimensional motion are taken as research objects, and kinematics analysis and motion equation are respectively derived. Then, using the artificial potential field method to do path planning, in the traditional artificial potential field method, the parameters of the attractive potential field function are usually found by try and error, and some scholars find through by the genetic algorithm. But these methods require a lot of calculations, wich are not east to find, and the repulsive potential field let the obstacle as a point, which is not in line with the actual situation. Therefore, in this paper, the traditional artificial potential field method is modified, and the parameters of the attractive potential field function can be obtained by setting the damping ratio and the settling time, which can greatly reduce the calculation, the obstacle in repulsive potential field function is also modified to change from a point to spherical. And the controller is designed by the method of the partition control scheme and the modified artificial potential field method. The designed controller is robust,even if the specifications of the manipulator change, the planned path will not change. Finally, by adding virtual target points to improve the local minimum problem, it can avoid the obstacles and reach the required position accurately, and simulate in MATLAB.
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Shun-MinWang and 王舜民. "Research on Autonomous Underwater Vehicle Collision Avoidance and Navigation Based on H∞ Controller and Artificial Potential Field Method." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/655nz7.
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博士國立成功大學
系統及船舶機電工程學系
105
This dissertation proposes integrating an H∞ controller with an artificial potential field method (APFM) to solve collision avoidance and navigation issues in an autonomous underwater vehicle (AUV). We applied APFM in designing three types of control algorithms—altitude, depth, and heading; the AUV used the proposed control algorithms to navigate in unknown three-dimensional static environment and avoid collisions with obstacles. The depth-control algorithm involved a safe altitude above the seafloor to prevent the AUV from colliding with the seafloor or vertical obstacles. The altitude-control algorithm involved a maximum safe depth below the surface to prevent the AUV from following terrain beyond the maximum pressure of vessel strength. The heading-control algorithm was based on an improved APFM to solve the local minimum problem; it combined APFM with an obstacle boundary following method (OBFM) to solve the problems of the AUV falling into the U-shaped trap and repetition path hovering. For simulation analysis, we modeled a self-developed National Cheng Kung University Autonomous Underwater Vehicle (NCKU-AUV) as a device under test. Using a planar motion mechanism (PMM) test, we obtained the hydrodynamic force coefficient of the vehicle. We applied the system simulation parameters for building the mathematical model used to design the H∞ controller. We used the loop shaping method to adjust the weight function, obtaining the optimal controller. The simulation results showed that the controller had robustness and anti-interference properties, met system performance requirements, and provided stability. Additionally, we tested the control algorithms for altitude, depth, and heading, simulating seafloor with different depths, different terrain, and various types of obstacles; the simulation results showed that the proposed collision avoidance algorithm was effective and guided the NCKU-AUV to avoid the underwater obstacles safely and correctly. Using the simulated H∞ controller, the simulated NCKU-AUV was able to accurately navigate to the appointed target. For practical testing, physical sensors including a Doppler velocity log, depth gauge, altimeter, and inertia measurement unit were installed on the physical NCKU-AUV to measure its velocity, altitude, depth, and attitude angle. In particular, five sonar sensors were installed at the bow end of the vehicle to detect horizontal and vertical obstacles; these sonar sensors were able to measure the distances between the vehicle and obstacles. AUV trials were carried out in the towing tank at NCKU. Obstacles were placed at the bottom of the towing tank, and the walls of the tank acted as a horizontal U-shaped obstacle. All control tests (fixed altitude, fixed depth, and navigation) were conducted and completed successfully. Preliminary results of the towing tank test validated the feasibility and effectiveness of the proposed H∞ controller with APFM; real sea testing could be conducted in future to prove the practicality of this system.
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Gautam, Vishal. "Some studies on different navigation techniques of mobile robot." Master's thesis, 2018. http://hdl.handle.net/10316/97059.
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Documentos apresentados no âmbito do reconhecimento de graus e diplomas estrangeirosNow a day’s mobile robots are vastly used in many industries for performing different activities such as, manufacturing, security, automated transportation systems, material handling, warehouse management, packet distribution and arrangement ,and in working in accessible and dangerous sites ,etc. The goal of mobile robot is to reach a prescribed destination by using optimal path from all the paths available , and in least time, with certain precision and accuracy. To achieve this goal Navigation becomes one of the most important part for mobile robots. The problem of mobile robot navigation is very wide and complex. In the past years, there has been a tremendous progress in the area of autonomous robot navigation and a large variety of robots ,robot navigation algorithms have been developed who demonstrated robust navigation capabilities indoors and non-urban outdoor environments. In this thesis , we present simulation of different kind of navigation techniques for mobile robots designed to operate in static obstacles environments. We are using math works (MATLAB) software for simulation of navigation techniques . Problem of navigation of mobile robots can be sub divided into subparts i.e. mapping of environment ,localization of mobile robot in its environment, obstacle avoidance, path planning from present position to final (Goal) position. In this work we first describe the technique that is used to generate map of real world. After that we use object recognition technique in MATLAB ,to solve the localization problem of mobile robot.Then we describe and do simulation on different maps of real world environment and using different software, for four different kinds of navigation techniques which are most popular among mobile robots.
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Zhao, Shengkai. "Chebyshev spectral methods for potential field computation." Thesis, 1993. http://hdl.handle.net/2429/2110.
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We investigate Chebyshev spectral methods for solving Poisson's equation and the generalized Poisson's equations and apply them to 3-D gravity and DC resistivity modeling. When we approximate a function by a finite sum of Chebyshev polynomials, there are two kinds of errors: truncation and aliasing. We present a cell-average discretization scheme to reduce the aliasing error. Both theoretical analysis and numerical examples show that when there are discontinuities in a function, the cell-average discretization is better than the point injection discretization. We use both the r and collocation methods to solve Poisson's equation V2u = f. We solve the discrete systems by a matrix-diagonalization method. The speed and accuracy of collocation methods are better than those of the r method. For the generalized Poisson's equation V • (oVu) = f, we present a new iterative method. We rewrite the equation in the form of a Poisson's equation, V2u = (f —Va•Vu)la. At each iteration we compute the right hand-side term from the current value of u first. Then we solve the resultant Poisson’s equation by the collocation method. Numerical results show that the convergence rate of the new method is much faster than that of the spectral multi grid method. When there are discontinuities in the source function f and/or the conductivity o, the single-domain Chebyshev spectral method does not converge exponentially. In this case we use the multi-domain Chebyshev spectral method to solve the problem. We divide the whole domain into a number of subdomains so that in each subdomain the function is infinitely differentiable. Then we approximate the function by a separate Chebyshev series in each subdomain. We determine the relations between the Chebyshev polynomials in adjacent subdomains by the interface conditions. In this way we can achieve exponential convergence.
In 3-D gravity modeling, we present a method to realize 2-D and 3-D point-injection and cell-average discretizations, use a multi pole expansion to compute the approximate
boundary conditions and solve the equations by both single-domain and multi-domain Chebyshev spectral methods. We also extend Okabe's analytic formulation for the gravitational field of a homogeneous, polyhedral body to the potential. Numerical results show that the accuracy of the cell-average discretization is better than that of the point injection discretization. The multi-domain solution is the best. We apply the multi-domain Chebyshev spectral method to 3-D DC resistivity modeling. We discuss the singularity removal and present a modified finite-difference method for comparison. For a two-layered model, the multi-domain Chebyshev spectral solution is far more accurate than the finite-difference solution. For piecewise-constant and piecewise-smooth models the solutions obtained by both methods agree with each other quite well. However, the Chebyshev spectral method is more efficient than the finite-difference method.
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Yung-Lun, Lin. "Distributed Formation Control of Multi-Robot Systems Using Potential Field Methods." 2005. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-1307200511400500.
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Lin, Yung-Lun, and 林雍倫. "Distributed Formation Control of Multi-Robot Systems Using Potential Field Methods." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/26922146879021380981.
Full textAbstract:
碩士國立臺灣大學
電機工程學研究所
93
The research topics of multi-robot systems have attracted much attention in recent years. Due to the ability of cooperation of robots, multiple robots can perform more difficult and complex tasks than one robot can perform. However, formation control problem is an important topic because multiple robots can perform tasks efficiently if the robots are in formation. Some specific formations can be formed by the multiple robots by planning trajectories of all robots. Moreover, when there are some obstacles in the real environment, the trajectories of the robots must be planned to navigate all robots for avoiding the obstacles and forming specific formations in the real environment. In the trajectory planning problems of multi-robot systems, potential field methods are used widely in the past. Artificial forces related to the potential field are used as the controllers of the robots. There are many kinds of the artificial forces proposed previously. One is the inverse power force. However, the coefficients of the inverse power force are designed intuitively in previous research. Moreover, there is another potential field method which is stream function method used to navigate a robot to avoid the obstacles in the environment. In this thesis, the trajectory planning problem of multi-robot systems is focused. The formations of multi-robot systems are defined firstly for the formation control problems. Secondly, the potential field methods and the artificial inverse power forces used in this thesis are defined. Thirdly, a case of three-robot system in is analyzed mathematically. There are two analysis methods used in thesis, that is, Lyapunov’s method and Linearization method. The convergence of these three robots is analyzed by Lyapunov’s method. The relationship between the stability of the formations which formed by these there robots and the coefficients of the artificial inverse power force are analyzed by the linearization method. The analysis results act as a design criterion when using inverse power forces in multi-robot systems. Moreover, the stream function method is combined with the artificial power forces to navigate these three robots to avoid obstacles and move to goal. Furthermore, some simulations demonstrate the analysis results in this thesis.
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Yang, Chen-Ning, and 楊甄寧. "On the Implementation of Collision Avoidance of a Wheeled-robot using Artificial Potential Field Approach." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/08076170982018604163.
Full textAbstract:
碩士國立清華大學
動力機械工程學系
101
The objective of this thesis is performing path planning to avoid obstacles by Artificial Potential Field Method. The experimental system consists of a wheeled robot, a scanning laser range finder, and a notebook. In Artificial Potential Field Method, the mobile robot is viewed as a particle, and the environment as a virtual potential field. In the moving area, obstacles produce repulsive force, and the target produces attractive force to the mobile robot. According to the environment information obtaining from scanning data, we can determine whether the obstacle is moving or not, and also calculate the resultant force of all obstacles in setting range and the target by Artificial Potential Field Method. By analyzing the resultant force calculated by Artificial Potential Field Method and choosing step size by Steepest Descend Method, we can control the motion of the robot so that the mobile robot can avoid obstacles and moving toward the target. In this thesis, the robot can determine the status of obstacles and following the motion strategy safely avoid obstacles, and move toward the target. After reaching the target, the robot moves toward the preset U-shaped object (charger place) by alignment and being recharged automatically.
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Chou, Si Yu, and 周思妤. "The Implementation of a Dynamic Obstacle Avoidance System for a Mobile Robot Using Artificial Potential Field." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/54007626593303099936.
Full textAbstract:
碩士國立清華大學
動力機械工程學系
104
This thesis applied artificial potential field to avoid obstacles for wheeled mobile robot. This system implements by using microcontroller and a laser range finder to obtain environment information. The artificial potential field approach constructs a virtual potential field for robot, obstacles and target. It introduces an attractive potential field at target and a repulsive potential field at obstacle to determine the moving path and speed for the mobile robot moving to target without collision. However, there are some defects, when avoiding moving-obstacles, the mobile robot may cause collisions due to small rotation angle or slow moving speed. As the solution, this thesis improves the repulsive potential field, having relative speed between obstacles and the mobile robot into consideration, to make robot avoid obstacles smoothly. In the experiment, the mobile robot can avoid obstacles and make to the target, then park in the garage by identifying the feature of U-garage. In addition, we use Class-E power amplifier to realize wireless power transfer. The purpose of Class-E circuit is making the switch of MOSFET in the state of “Zero-Voltage Switching, ZVS”, in order to reduce the power loss when switching, we implement the circuit by the resonance between inductors and capacitors. Use quartz oscillator to control the frequency of MOSFET switch, and simplify the switching circuit. Besides, the resonant tank is combined with resonance capacitor and resonance inductor to transfer the power.
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Harmer, Gregory Peter. "Stochastic processing for enhancement of artificial insect vision / by Gregory P. Harmer." Thesis, 2001. http://hdl.handle.net/2440/21783.
Full textAbstract:
"November, 2001"Includes bibliographical references (leaves 229-246)
xxiv, 254 leaves : ill. (col.) ; 30 cm.
Thesis (Ph.D.)--University of Adelaide, Dept. of Electrical and Electronic Engineering, 2002
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Harmer, Gregory Peter. "Stochastic processing for enhancement of artificial insect vision / by Gregory P. Harmer." 2001. http://hdl.handle.net/2440/21783.
Full textAbstract:
"November, 2001"Includes bibliographical references (leaves 229-246)
xxiv, 254 leaves : ill. (col.) ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
Thesis (Ph.D.)--University of Adelaide, Dept. of Electrical and Electronic Engineering, 2002
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Lew, Wei-Zhen, and 劉瑋禎. "The Effect of Static Magnetic Field on the Proliferation And Differentiation Potential of Dental Pulp Stem Cells Isolated From Different Methods." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/f5qnu8.
Full textAbstract:
碩士臺北醫學大學
牙醫學系碩博士班
102
Dental pulp stem cells (DPSCs) can be an alternative resource for clinical cell therapy and tissue engineering. DPSCs are superior to bone marrow stem cells in clinical trials and future therapies because of several advantages. However, the extensive proliferation in vitro without loss of their differentiative capacity is an important issue. Static magnetic fields (SMFs) was reported to significantly promote osteogeneration. However, the positive effect of static magnetic fields on DPSCs is seldom discussed. Also, different isolation method can give rise different stem cells populations. Therefore, the aim of this study was to evaluate whether 0.4-Tesla SMF can enhance the proliferation of dental pulp cells (DPCs) and DPSCs in vitro. In methodology, different handling methods of DPCs and DPSCs were cultured with 0.4T SMF exposure. The MTT assay was used to determine the proliferation rate of the cells. Cell membrane anisotropy was monitored by TMA-DPH or DPH fluorescent dye to evaluate the structure change of cell when cultured under SMF. To identify the stem cell’s characteristics after SMF exposure, a set of surface antigens were labeled by fluorescent conjugated antibodies and analyzed by flow cytometry. Multilineage differential stimuli were performed to investigate whether the differential potential of the SMF-exposed cells were influenced by SMF. Our results demonstrated that DPSCs exposed to SMF exhibited a higher proliferation rate than control cells, especially in DPSCs group. Fluorescent anisotropy assay showed that the cell membrane fluidity was decrease when exposed to SMF. In addition, DPSCs cultured in SMF environment has no adverse effect on the CD marker expression and differential potential. According to these results, we found that an in vitro 0.4T SMF stimulation is positive for the proliferation rate of DPSCs without adverse effect on its differential potential. This effects is more prominent to DPSCs than DPCs.
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Whitehead, Robert. "Interpretation of aeromagnetic data from the Kuruman Military Area, Northern Cape, South Africa - through the use of structural index independent methods: a description of three depth and structural index inversion techniques for application to potential field data." Thesis, 2016. http://hdl.handle.net/10539/19305.
Full textAbstract:
A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science. Johannesburg, 2015Three new methods for determining the structural index and source distance for magnetic field data are presented. These methods require only the calculation of the first and second order analytic signal amplitudes of the total field and are applicable to both profile and gridded data. The three methods are first tested on synthetic data and then on two real datasets to test for applicability and repeatability. It was found that each method had different strengths and weaknesses and thus one method cannot be favoured over the others. Cooper (2014) describes how to calculate the distance to source over both profile and gridded data given a user defined structural index. Often however, particularly in the case of real data, the structural index is not known or varies over the surveyed area. These three new methods however do not require any user input since the structural index is calculated thus making them more applicable to regions of unknown geology. It was found that the first of the three new methods, the multi-distance inversion method, was best used as an edge-detection filter, since the use of higher order derivatives resulted in increased noise levels in the distance to source calculation. The third of these new methods, the unconstrained inversion method, discussed in Chapter 7, not only solves for the structural index but also determines the depth of the source. In that particular case, the structural index is used as a rejection filter, whereby, depth solutions associated with structural index values outside of the expected range are deemed to be invalid. Unlike the third new method, the first two methods require the distance to source to be calculated via the approach described by Cooper (2014) (which requires the user to define the structural index), the results of which are later rescaled by the calculated structural index to yield what is termed a rescaled distance to source. All three of the new methods are fully automatic and require no user control. The techniques were first tested on both profile and gridded theoretical data over sources with known structural index values. All of the methods were able to estimate the structural index of each of the particular sources and give depth estimates that varied from the true depth by less than 20 percent (with deeper sources being more inaccurate). Noise was also added to the theoretical data in an attempt to assess how the methods can be expected to perform with real data. It was found that when applied to noisy data, these methods performed equally well to slightly worse, than when the method developed by Cooper (2014) was used. As a real world case study these three new methods were tested on aeromagnetic data collected over the Kuruman Military Area, Northern Cape, South Africa. Regional deformations as well as later intrusive dykes and cross cutting faults were imaged by the chosen depth determination procedures. The dolerite dykes in the area were found to occur between 20 to 60 m deep. While the sand cover was estimated to be between 30 to 40 m thick. Overall, the techniques yield distance to source estimates that differ by less than 15 m, over sources, to the results obtained by using the source distance method (Cooper, 2014). To test for repeatability a second aeromagnetic dataset, collected over a dyke swarm within the Bushveld Complex, South Africa was considered. Again comparable (less than 15 m over sources) depth estimates were made between the unconstrained and constrained inversions. Since the distance to source estimates produced by these new unconstrained inversion methods are comparable to those produced by constrained inversion (Cooper, 2014) the project can be deemed successful.