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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Demonstration Of A Stabilized Hovering Platform For Undergraduate Laboratory

Camlica, Fahri Bugra 01 February 2005 (has links) (PDF)
This research work covers the design, manufacture and testing of an unmanned aerial vehicle for the purpose of testing various control systems by undergraduate students in the laboratory environment. The aerial vehicle under consideration is a four-rotor propeller powered. Aluminum rod based mechanical structure is preferred. The stabilization of the hovering vehicle in its rotational axes in the air and navigation about the yaw axis are the accomplished goals of this study. The aerial vehicle is run in real time by using Matlab 6.5 Software&rsquo / s xPc module. The linear quadratic regulator and PD controllers are utilized to stabilize the aerial vehicle in its rotation axes. To eliminate the measurement noise generated by the sensors, low-pass second order transfer function is designed and its implementation to real time experiments is discussed.
12

Att lyssna med Jämnt svävande uppmärksamhet : En studie om hur psykoterapeuter lyssnar med utgångspunkt i Freuds begrepp / To listen with Evenly hovering attention : A study on how psychotherapists listen based on Freuds term

Alsterlind-Waegle, Robert January 2021 (has links)
Inledning: Sigmund Freud omnämner 1912 för första gången i publicerad form det psykoanalytiska lyssnandets princip med begreppet Jämnt svävande uppmärksamhet (JSU) (1912/2002). Begreppet har frekvent refererats till i publikationer om psykoanalys och psykoterapi sedan Freud myntade det.  Syfte: Syftet med föreliggande studie är att ge innebörd åt och förstå mer om Freuds begrepp och hur psykodynamiska psykoterapeuter med utgångspunkt i Freuds grundregel lyssnar kliniskt idag.  Metod: Genom intervjuer med fem psykoterapeuter söks begreppets kliniska relevans och tillämpbarhet. Intervjuerna analyseras enligt en kombinerad deduktiv och induktiv Tematisk analys.  Resultat: Resultatet visar att jämnt svävande uppmärksamt lyssnande utgörs av en historiserande positionering i förhållande till berättelsen. Lyssnande som läsning utgörs av uppmärksamhet efter semantiska och vokaliserande aspekter av mänskliga erfarenheter bortom språk och begrepp. Lyssnandet i samtalets form karaktäriseras av med-lyssnande.  Diskussion: Analysen visar terapeuternas uppfattning av tillämpbarheten av JSU med hänsyn till begreppets referensvärde. Terapeuternas förståelse av och syn på dess kliniska relevans diskuteras utifrån tillgängliga forskningsresultat från studier av empatisk förståelse och kliniskt lyssnande inom psykoterapi. / Introduction: In 1912, Sigmund Freud first mentions in published form the principle of psychoanalytic listening with the concept ofEvenly Hovering Attention(EHA) (1912/2002). The term has been frequently referenced in publications on psychoanalysis and psychotherapy since Freud coined it.  Research questions: The purpose of this study is to give meaning to and understand more about Freud's concepts and how psychodynamic psychotherapists, based on Freud's groundrule, listen clinically today.  Method:Through interviews with five psychotherapists the clinical relevance and applicableness of the concept is sought. The interviews are analyzed according to a combined deductive and inductive Thematic Analysis.  Results:The results show that evenly hovering attentive listening consists of a historizing positioning in relation to thestory. Listening as readingconsists of attention aftervocalizing aspects of human experiences beyond language. Listening in the form of conversationis characterized by co-listening.  Discussion:The analysis shows the therapists' perception of the applicableness of EHAtaking into account the reference value of the term. The therapists' view of its clinical relevance is discussed based on available research results from studies of empathetic understanding and clinical listening in psychotherapy.
13

Aerodynamic Analysis of Natural Flapping Flight Using a Lift Model Based on Spanwise Flow

Alford, Lionel Devon, Jr. 05 May 2010 (has links)
No description available.
14

Unsteady Aerodynamic and Aeroelastic Analysis of Flapping Flight

Gopalalkrishnan, Pradeep 22 January 2009 (has links)
The unsteady aerodynamic and aeroelastic analysis of flapping flight under various kinematics and flow parameters is presented in this dissertation. The main motivation for this study arises from the challenges facing the development of micro air vehicles. Micro air vehicles by requirement are compact with dimensions less than 15-20 cm and flight speeds of around 10-15 m/s. These vehicles operate in low Reynolds number range of 10,000 to 100,000. At these low Reynolds numbers, the aerodynamic efficiency of conventional fixed airfoils significantly deteriorates. On the other hand, flapping flight employed by birds and insects whose flight regime coincides with that of micro air vehicles offers a viable alternate solution. For the analysis of flapping flight, a boundary fitted moving grid algorithm is implemented in a flow solver, GenIDLEST. The dynamic movement of the grid is achieved using a combination of spring analogy and trans-finite interpolation on displacements. The additional conservation equation of space required for moving grid is satisfied. The solver is validated with well known flow problems such as forced oscillation of a cylinder, a heaving airfoil, a moving indentation channel, and a hovering fruitfly. The performance of flapping flight is analyzed using Large Eddy Simulation (LES) for a wide range of Reynolds numbers and under various kinematic parameters. A spiral Leading Edge Vortex (LEV) forms during the downstroke due to the high angle of attack, which results in high force production. A strong spanwise flow of the order of the flapping velocity is observed along the core of the LEV. In addition, the formation of a negative spanwise flow is observed due to the tip vortex, which slows down the removal of vorticity from the LEV. This leads to the instability of the LEV at around mid-downstroke. Analysis with different rotation kinematics shows that a continuous rotation results in better propulsive efficiency as it generates thrust during the entire flapping cycle. Analysis with different angles of attack shows that a moderate angle of attack which results in complete shedding of the LEV offers high propulsive efficiency. The analysis of flapping flight at Reynolds numbers ranging from 100 to 100,000 shows that higher lift and thrust values are obtained for Re?100. The critical reasons are that at higher Reynolds numbers, the LEV is closer to the surface and as it sheds and convects it covers most of the upper surface. However, the Reynolds number has no or little effect on the lift and thrust as identical values are obtained for Re=10,000 and 100,000. The analysis with different tip shapes shows that tip shapes do not have a significant effect on the performance. Introduction of stroke deviation to kinematics leads to drop in average lift as wing interacts with the LEV shed during the downstroke. A linear elastic membrane model with applied aerodynamic load is developed for aeroelastic analysis. Analysis with different wing stiffnesses shows that the membrane wing outperforms the rigid wing in terms of lift, thrust and propulsive efficiency. The main reason for the increase in force production is attributed to the gliding of the LEV along the camber, which results in a high pressure difference across the surface. In addition, a high stiffness along the spanwise direction and low stiffness along the chordwise direction results in a uniform camber and high lift and thrust production. / Ph. D.
15

HoverBot : a manufacturable swarm robot that has multi-functional sensing capabilities and uses collisions for two-dimensional mapping

Nemitz, Markus P. January 2018 (has links)
Swarm robotics is the study of developing and controlling large groups of robots. Collectives of robots possess advantages over single robots such as being robust to mission failures due to single-robot errors. Experimental research in swarm robotics is currently limited by swarm robotic technology. Current swarm robotic systems are either small groups of sophisticated robots or large groups of simple robots due to manufacturing overhead, functionality-cost dependencies, and their need to avoid collisions, amongst others. It is therefore useful to develop a swarm robotic system that is easy to manufacture, that utilises its sensors beyond standard usage, and that allows for physical interactions. In this work, I introduce a new type of low-friction locomotion and show its first implementation in the HoverBot system. The HoverBot system consists of an air-levitation and magnet table, and a HoverBot agent. HoverBots are levitating circuit boards which are equipped with an array of planar coils and a Hall-effect sensor. HoverBot uses its coils to pull itself towards magnetic anchors that are embedded into a levitation table. These robots consist of a Printed Circuit Board (PCB), surface mount components, and a battery. HoverBots are easily manufacturable, robots can be ordered populated; the assembly consists of plugging in a battery to a robot. I demonstrate how HoverBot's low-cost hardware can be used beyond its standard functionality. HoverBot's magnetic field readouts from its Hall-effect sensor can be associated with successful movement, robot rotation and collision measurands. I build a time series classifier based on these magnetic field readouts, I modify and apply signal processing techniques to enable the online classification of the time-variant magnetic field measurements on HoverBot's low-cost microcontroller. This method allows HoverBot to detect rotations, successful movements, and collisions by utilising readouts from its single Hall-effect sensor. I discuss how this classification method could be applied to other sensors and demonstrate how HoverBots can utilise their classifier to create an occupancy grid map. HoverBots use their multi-functional sensing capabilities to determine whether they moved successfully or collided with a static object to map their environment. HoverBots execute an "explore-and-return-to-nest" strategy to deal with their sensor and locomotion noise. Each robot is assigned to a nest (landmark); robots leave their nests, move n steps, return and share their observations. Over time, a group of four HoverBots collectively builds a probabilistic belief over its environment. In summary, I build manufacturable swarm robots that detect collisions through a time series classifier and map their environment by colliding with their surroundings. My work on swarm robotic technology pushes swarm robotics research towards studies on collision-dependent behaviours, a research niche that has been barely studied. Collision events occur more often in dense areas and/or large groups, circumstances that swarm robots experience. Large groups of robots with collision-dependent behaviours could become a research tool to help invent and test novel distributed algorithms, to understand the dependencies between local to global (emergent) behaviours and more generally the science of complex systems. Such studies could become tremendously useful for the execution of large-scale swarm applications such as the search and rescue of survivors after a natural disaster.
16

De l'oeil élémentaire à l'oeil composé artificiel : application à la stabilisation visuelle en vol stationnaire / From elementary eye to artificial compound eye : Application to robot stabilization in hover

Juston, Raphael 25 November 2013 (has links)
La stratégie de l'équipe biorobotique est de s'inspirer de découvertes faites en biologie chez l'insecte ailé dont la vision est adaptée à la navigation autonome dans un environnement 3D inconnu. Cette inspiration donne naissance la réalisation de capteurs visuels minimalistes permettant de rendre autonomes des robots volants, pour des tâches complexes telles que : le décollage et l'atterrissage automatiques, l'évitement d'obstacles et, dans le cas de cette thèse, le vol stationnaire.Cette thèse présente la mise en œuvre des capteurs visuels minimalistes bio-inspirés qui, grâce à des algorithmes de traitement que nous avons réalisés, sont capables de localiser la position d'objets visuels en tirant partie de propriétés souvent bannies en optique : un flou, obtenu par défocalisation, associé à un micro-mouvement rétinien actif. Nous montrons que la précision en localisation ainsi obtenue est considérablement améliorée par rapport à la résolution statique définie par l'échantillonnage spatial : ces capteurs optiques bio-inspirés sont donc dotés d'hyperacuité.Cette thèse présente aussi l'œil composé artificiel miniature CurvACE (de 2,2cm3 pour 1,75g) doté d'une vision panoramique (180x60°). Cette thèse décrit la caractérisation et la mise en œuvre du capteur CurvACE sur le robot HyperRob. En fusionnant les mesures de position données par une quarantaine de pixels couvrant un grand champ visuel, l'œil CurvACE mesure sa position par rapport à un environnement visuel texturé complexe. Nous montrons aussi que le robot volant HyperRob, attaché au bout d'un bras, stabilise son roulis et sa position, dans le plan azimutal, grâce à son œil composé artificiel doté d'hyperacuité. / The biorobotics team from the Institute of Movement Sciences (Marseille, France) takes its inspiration from biological studies on flying insects which are able to navigate into unknown 3D environments with a high maneuverability. These studies led us to build minimalist optical sensors to make aerial robots autonomous for achieving complex tasks such as automatic landing and take-off, obstacle avoidance and very accurate hovering flight depicted in this doctoral thesis. This work presents several bio-inspired visual sensors implemented with different visual processing algorithms. All these sensors are able to locate visual objects (contrasting edges and bars) with unusual properties for optical sensing devices: a blur obtained by defocusing optics related with active retinal micro-movements to improve the sensor resolution. We showed that the resolution in locating contrasting objects can be improved up to 160 fold better than the static resolution defined by the pixel pitch, which means that these bio-inspired optical sensors are endowed with hyperacuity.The thesis presents a miniature artificial compound eye CurvACE (of 1.75g for 2.2cm3) with a panoramic field of view (180x60°). This thesis describes thoroughly the characterization and the implementation of the CurvACE sensor onboard an aerial robot named HyperRob. This artificial compound eye acts as a position sensing device able to measure its position relative to a complex textured scene by fusing the position measurements obtained by 40 pixels. The tethered flying robot HyperRob (a 150-g bi-rotor with a 23-cm wingspan) stabilizes its roll and its position thanks to its hyperacute artificial compound eye.
17

Creation of an Orderly Jet and Thrust Generation in Quiescent Fluid from an Oscillating Two-dimensional Flexible Foil

Shinde, Sachin Yashavant January 2012 (has links) (PDF)
In nature, many of the flapping wings and fins in swimming and flying animals have various degrees of flexibility with strong and coupled solid-fluid interactions between the structure and the fluid. In most cases, the wing structure, the flow and their interactions are complex. This thesis experimentally investigates a ‘simple’ fluid-flexible foil interaction problem: flow generated by a pitching foil with chordwise flexibility. To explore the effect of flexibility on the flow, we study the flow generated in quiescent water (the limiting case of infinite Strouhal number) by a sinusoidally pitching rigid symmetrical NACA0015 foil to which is attached a 0.05 mm thick chordwise flexible polythene flap at the trailing edge. The chordwise length of flap is 0.79 c, where c = 38 mm is the chord length of the rigid foil; span of the foil and flap is 100 mm. Detailed particle image velocimetry (PIV) and flow visualization measurements have been made for twelve cases, corresponding to three pitching amplitudes, ±10◦,± 15◦, ±20◦, and four frequencies, 1, 2, 3 and 4 Hz for each amplitude. For most of these cases, a narrow coherent jet aligned along the center-line, containing a reverse B’enard–K´arm´an vortex street, and a corresponding unidirectional thrust are generated. This thrust is similar to the upward force generated during hovering, but motion of our foil is much simpler than the complex wing kinematics found in birds and insects; also the thrust generation mechanism seems to be different. In our case, the thrust is from a coordinated pushing action of the rigid foil and the flexible flap. Control volume analysis reveals the unsteady nature of thrust generation. In this intricately coupled flow generation problem, chordwise flexibility is found to be crucial in producing the coherent jet. In this thesis, we explore in detail the physics of jet flow produced by the foil with a flexible flap, and identify the importance of flexibility in flow generation. Flap motion ensures appropriate spatial and temporal release of vortices, and also imparts them convective motion, to obtain the staggered pattern that produces the jet. To describe the fluid-flap interaction, we conveniently characterize the flap through a non-dimensional stiffness, ‘effective stiffness’ (EI)∗ of the flap, that captures the effects of both the flap properties as well as the external forcing. With the same flap by changing the pitching parameters, we cover a fairly large (EI)∗ range varying over nearly two orders of magnitude. However, we observed that only moderate (EI)∗ (~0.1 - 1) generates sustained narrow, orderly jet. We provide thrust estimates useful for the design of flapping foil thrusters/propulsors. Although this study has only indirect connections with the hovering in nature, it may be useful in understanding the role of flexibility of bird and insect wings during hovering. In contrast, a foil with a rigid trailing edge produces a weak jet whose inclination changes continually with time. This meandering is observed to be random and independent of the initial conditions over a wide range of pitching parameters.
18

Stratégies de guidage visuel bio-inspirées : application à la stabilisation visuelle d’un micro-drone et à la poursuite de cibles / Strategies for bio-inspired visual guidance : application to control an UAV and to track a target

Manecy, Augustin 22 July 2015 (has links)
Les insectes sont capables de prouesses remarquables lorsqu’il s’agit d’éviter des obstacles,voler en environnement perturbé ou poursuivre une cible. Cela laisse penser que leurs capacités de traitement, aussi minimalistes soient-elles, sont parfaitement optimisées pour le vol. A cela s’ajoute des mécanismes raffinés, comme la stabilisation de la vision par rapport au corps, permettant d’améliorer encore plus leurs capacités de vol.Ces travaux de thèse présentent l’élaboration d’un micro drone de type quadrirotor, qui ressemble fortement à un insecte sur le plan perceptif (vibration rétinienne) et reprend des points structurels clés, tels que le découplage mécanique entre le corps et le système visuel. La conception du quadrirotor (de type open-source), son pilotage automatique et son système occulo-moteur sont minutieusement détaillés.Des traitements adaptés permettent, malgré un très faible nombre de pixels (24 pixels seulement), de poursuivre finement du regard une cible en mouvement. A partir de là, nous avons élaboré des stratégies basées sur le pilotage par le regard, pour stabiliser le robot en vol stationnaire, à l’aplomb d’une cible et asservir sa position ; et ce, en se passant d’une partie des capteurs habituellement utilisés en aéronautique tels que les magnétomètres et les accéléromètres. Le quadrirotor décolle, se déplace et atterrit de façon autonome en utilisant seulement ses gyromètres, son système visuel original mimant l’oeil d’un insecte et une mesure de son altitude. Toutes les expérimentations ont été validées dans une arène de vol, équipée de caméras VICON.Enfin, nous décrivons une nouvelle toolbox qui permet d’exécuter en temps réel des modèles Matlab/Simulink sur des calculateurs Linux embarqués de façon complètement automatisée (http://www.gipsalab.fr/projet/RT-MaG/). Cette solution permet d’écrire les modèles, de les simuler, d’élaborer des lois de contrôle pour enfin, piloter en temps réel, le robot sous l’environnement Simulink. Cela réduit considérablement le "time-to-flight" et offre une grande flexibilité (possibilité de superviser l’ensemble des données de vol, de modifier en temps réel les paramètres des contrôleurs, etc.). / Insects, like hoverflies are able of outstanding performances to avoid obstacles, reject disturbances and hover or track a target with great accuracy. These means that fast sensory motor reflexes are at work, even if they are minimalist, they are perfectly optimized for the flapping flight at insect scale. Additional refined mechanisms, like gaze stabilization relative to the body, allow to increase their flight capacity.In this PhD thesis, we present the design of a quadrotor, which is highly similar to an insect in terms of perception (visual system) and implements a bio-inspired gaze control system through the mechanical decoupling between the body and the visual system. The design of the quadrotor (open-source), itspilot and its decoupled eye are thoroughly detailed. New visual processing algorithms make it possible to faithfully track a moving target, in spite of a very limited number of pixels (only 24 pixels). Using this efficient gaze stabilization, we developed new strategies to stabilize the robot above a target and finely control its position relative to the target. These new strategies do not need classical aeronautic sensors like accelerometers and magnetometers. As a result, the quadrotor is able to take off, move and land automatically using only its embedded rate-gyros, its insect-like eye, and an altitude measurement. All these experiments were validated in a flying arena equipped with a VICON system. Finally, we describe a new toolbox, called RT-MaG toolbox, which generate automatically a real-time standalone application for Linux systems from a Matlab/Simulink model (http://www.gipsalab.fr/projet/RT-MaG/). These make it possible to simulate, design control laws and monitor the robot’s flight in real-time using only Matlab/Simulink. As a result, the "time-to-flight" is considerably reduced and the final application is highly reconfigurable (real-time monitoring, parameter tuning, etc.).

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