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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.
451

Real-time Dynamic Simulation of Constrained Multibody Systems using Symbolic Computation

Uchida, Thomas Kenji January 2011 (has links)
The main objective of this research is the development of a framework for the automatic generation of systems of kinematic and dynamic equations that are suitable for real-time applications. In particular, the efficient simulation of constrained multibody systems is addressed. When modelled with ideal joints, many mechanical systems of practical interest contain closed kinematic chains, or kinematic loops, and are most conveniently modelled using a set of generalized coordinates of cardinality exceeding the degrees-of-freedom of the system. Dependent generalized coordinates add nonlinear algebraic constraint equations to the ordinary differential equations of motion, thereby producing a set of differential-algebraic equations that may be difficult to solve in an efficient yet precise manner. Several methods have been proposed for simulating such systems in real time, including index reduction, model simplification, and constraint stabilization techniques. In this work, the equations of motion are formulated symbolically using linear graph theory. The embedding technique is applied to eliminate the Lagrange multipliers from the dynamic equations and obtain one ordinary differential equation for each independent acceleration. The theory of Gröbner bases is then used to triangularize the kinematic constraint equations, thereby producing recursively solvable systems for calculating the dependent generalized coordinates given values of the independent coordinates. For systems that can be fully triangularized, the kinematic constraints are always satisfied exactly and in a fixed amount of time. Where full triangularization is not possible, a block-triangular form can be obtained that still results in more efficient simulations than existing iterative and constraint stabilization techniques. The proposed approach is applied to the kinematic and dynamic simulation of several mechanical systems, including six-bar mechanisms, parallel robots, and two vehicle suspensions: a five-link and a double-wishbone. The efficient kinematic solution generated for the latter is used in the real-time simulation of a vehicle with double-wishbone suspensions on both axles, which is implemented in a hardware- and operator-in-the-loop driving simulator. The Gröbner basis approach is particularly suitable for situations requiring very efficient simulations of multibody systems whose parameters are constant, such as the plant models in model-predictive control strategies and the vehicle models in driving simulators.
452

Haptic control and operator-guided gait coordination of a pneumatic hexapedal rescue robot

Guerriero, Brian A. 10 July 2008 (has links)
The Compact Rescue Crawler is a pneumatic legged robot. Two legs of a hexapod were designed and built. The legs are controlled directly from operator inputs. The operator gives foot position inputs through two PHANToM haptic controllers. A PD controller with a supplementary force gain-scheduler control stroke lengths of each cylinder. The force-based position control technique allows the robot feet to track operator inputs to within 10% position error. A guided gait algorithm was developed to allow the operator to control all 6 legs simply by haptically guiding the front two. The operator records successful and collision-free trajectories and the gait coordinator plays the trajectories through the rear legs as they approach the detected obstacles. This hybrid gait algorithm allows the robot to proceed through a hazardous environment, guided by an operator, but without taxing the input capabilities of the human operator.
453

Kinematic alignment technique for total knee replacement : rational, current evidence, potential concerns / Alignement cinématique en arthroplastie totale du genou : concept, preuves scientifiques, et craintes potentielles

Rivière, Charles 15 December 2016 (has links)
La pose d’une prothèse totale de genou (PTG) se fait selon la technique d’alignement mécanique (AM) qui corrige les déformations constitutionnelles du membre pour créer un membre rectiligne. La survie à long terme des implants est excellente mais les résultats fonctionnels sont décevants avec notamment de nombreux symptômes résiduels. Une nouvelle technique chirurgicale, l’alignement cinématique (AC), vise à rétablir l’anatomie constitutionnelle pré-arthrosique du genou, et permet une amélioration des résultats fonctionnels des PTG. Cette technique est actuellement réalisée avec des implants destinés à un positionnement mécanique, et qui ont un design trochléen ne reproduisant pas l'anatomie trochléaire native. Ceci pourrait affecter la biomécanique de l’articulation patello-fémorale et donc rendre les résultats fonctionnels des PTG cinématiques non optimal. Ce travail vise à démontrer 1) les limitations de la technique mécanique, 2) la fiabilité de la technique cinématique pour le positionnement de l’implant fémoral, et 3) que les implants actuels ne permettent pas une restauration de l’anatomie trochléenne des patients. / The conventional technique for TKA, namely mechanical alignment (MA), does not preserve the constitutional limb anatomy but systematically creates a straight limb. Excellent long-term implant survivorship has been reported, but functional outcomes are disappointing. To solve this problem, an alternative technique for TKA, namely kinematic alignment (KA), has recently been promoted and aims at restoring the constitutional (pre-arthritic) knee anatomy and laxity. Mid-term outcomes have shown excellent functional outcomes with this new KA technique. However, KA technique is currently done with TKA implants designed to be mechanically inserted. Their trochlea design does not reproduce the native trochlear anatomy, which could lead to increased rate of patellar complications with KA TKA. This work aims at demonstrating technical limitations of MA technique, good reproducibility of KA technique, and inappropriateness of current implant to restore patient trochlea anatomy.
454

Effect of Lap Belt Position on Kinematics & Injuries by using 6YO PIPER child HBM : in Frontal Crash Simulations / Höftbältets påverkan på kinematiken och skador genom att använda 6åriga PIPER barnhumanmodellen vid frontalkrock

El-Mobader, Sarah Hassan January 2018 (has links)
Traffic accidents are the second leading cause of child fatality among children younger than 15 years of age. In the course of 10 years, the implementation of child restraint systems has decreased child fatality in traffic accidents with 50%, for children younger than 15 years. To gain an understanding of the kinematics and injury mechanisms of children in cars, finite element based human body models, representing higher biofidelity compared to crash test dummies, are developed. An FP7 European project, PIPER, developed a child HBM with an associated framework for scaling, morphing and positioning. The PIPER child HBM is scalable between the ages of 1.5-6YO, with scalable anthropometrics. This makes the PIPER child HBM, a powerful tool for analyzing children in vehicles.  There are insufficient analyses conducted with the PIPER child HBM, due to its recent release. The purpose is thus to study the robustness of the HBM and its sensitivity to variation of lap belts by conducting a parametric study. Injury analysis and its sensitivity to lap belt variations were in addition studied in terms of kinematics by the study of submarining, the pelvic interaction with the lap belt, and the study of injuries related to the skull, brain, kidneys and liver. A full frontal crash simulation of a 6YO PIPER child HBM, with anthropometrics, covering the 50th percentile, have been investigated. The 6YO PIPER child HBM was seated with no booster, Volvo booster cushion and Volvo highback booster, with variations of the lap belt. The hip interactions and the submarining response of the 6YO PIPER child HBM were studied, by the study of the lap belt interactions with the pelvis and abdominal organs. The abdominal organs were related to the liver and kidneys, and compared to published threshold values.  This study showed that the overall robustness of the model was questionable. With respect to kinematics, the model indicated higher robustness, however, when conducted the crash simulations with the 6YO PIPER child HBM, it was concluded that the robustness was low due to repeated premature terminations. The 6YO PIPER child HBM revealed repeated errors such as, mesh distortions, negative volume and shooting nodes. When studying the sensitivity of the 6YO PIPER child HBM, when varying the lap belt angles, as well as changing the type of boosters in addition to vehicle anchorage positions, it could be seen that the 6YO PIPER child HBM was able to capture variations with respect to lap belt positioning. Hence, the model seems to be capable of providing relevant information regarding sensitivity for lap belt variations from the kinematic perspective, in terms of being able to capture kinematic o↵set, submarining and pelvis interaction with the lap belt. However, with respect to predicted abdominal injuries and head injuries, the sensitivity was not as distinct. Some limitations were observed in which the 6YO PIPER child HBM indicated unrealistic predicted injuries related to the head, which was associated with excessive movement of the 6YO PIPER child HBM. / Trafikolyckor är den näst vanligaste orsaken till barndödlighet i världen bland barn yngre än 15 år. Inom loppet av 10 år har användning av bilbarnstolar i fordon minskat barndödligheten med 50% hos barn under 15 år. För att få en ökad förståelse om barn i bilar framtogs finita element humanmodeller som har en detaljerad anatomi samt responser liknande till människan. Ett FP7 finansierat europeiskt projekt, PIPER, skapade en barnhumanmodell med en tillhörande programvara som används för skalning, förvandling, och positionering av barnhumanmodellen. Humanmodellen är skalbar för åldrarna 1.5 år upp till 6 år, med olika antropometriska värden. Detta gör att PIPER barnhumanmodellen är ett kraftfullt verktyg att använda sig av för att studera barn i bilar. Då PIPER barnhumanmodell lanserades nyligen, finns det i dagsläget bristfällig information om humanmodellen och programmet. Syftet var därmed att undersöka hur robust modellen var samt hur dess känslighet var mot variationer av höftbältet genom en parameterstudie. Skadors känslighet studerades dessutom mot variationer av höftbältet genom att studera kinematiken i form av underglidning och höftens interaktion med höftbältet. Dessutom studerades känsligheten på skador relaterade till skallen, levern och njurarna. I denna studie har en frontalkrock med en 6 årig PIPER barnhumanmodell med antropometriska värden, som innefattar 50:e percentilen, undersökts. Den 6åriga PIPER barnhumanmodellen var placerad utan bilbarnstol, på en Volvo bälteskudde och på en Volvo bältesstol, där höftbältet sedan varierades. Höftens interaktion och PIPER barnhumanmodellens respons för variationer i höftbälte studerades. Interaktionerna med höften och bukorganen var relaterade till skador på levern och njurarna genom att jämföra med publicerad data. Denna studie påvisade att den generella robustheten av modellen kunde ifrågasättas. Modellen hade ändock högre robusthet med hänsyn på kinematiken, men på grund av de upprepande felen vid simuleringarna, kunde man konstatera att robustheten på den 6åriga PIPER barnhumanmodellen var låg. När höftbältet varierades, både när bilbarnstol varierades såväl som vinkel på höftbälte, kunde man konstatera att den 6åriga PIPER barnhumanmodellen kunde fånga skillnaderna med hänsyn på höftbältets vinkel. Modellen var dessutom kapabel till att fånga känsligheten från det kinematiska perspektivet i form av kinematisk förskjutning, underglidningen samt höftens interaktion med höftbältet. Modellen påvisade däremot ingen distinkt känslighet med hänsyn på skador relaterade till bukorganen samt huvudet. Några begränsningar observerades där den 6åriga PIPER barnhumanmodellen indikerade orealistiska skador på huvudet, som var relaterade till modellens överrörlighet. / FFI, Assessment of Passenger Safety in Future Cars
455

[en] DYNAMICS AND CONTROL OF PARALLEL MECHANISMS: CLOSED ANALYTICAL MODEL, INERTIAL TRANSDUCERS AND LINEAR ELECTRIC ACTUATORS INTEGRATION / [pt] DINÂMICA E CONTROLE DE MECANISMOS PARALELOS: INTEGRAÇÃO MODELO ANALÍTICO FECHADO, TRANSDUTORES INERCIAIS E ATUADORES ELÉTRICOS LINEARES

ALLAN NOGUEIRA DE ALBUQUERQUE 08 August 2017 (has links)
[pt] Mecanismos são essencialmente (mas não exclusivamente) compostos por vários corpos rígidos que possuem movimento relativo entre si. Cada corpo rígido está ligado através de uma junta a um ou mais corpos, sendo a sequência de corpos conectados chamada de cadeia cinemática. Cadeias cinemáticas abertas (ou em série) não têm restrições sobre uma de suas extremidades, já cadeias fechadas (ou paralelas) têm restrições em ambas as extremidades. O foco neste trabalho será dado no estudo de mecanismos com cadeias cinemáticas fechadas ou mecanismos paralelos. Assim, este trabalho apresenta a determinação da solução analítica do modelo dinâmico de um mecanismo paralelo plano com três graus de liberdade através da caracterização do fluxo de potência entre os seus componentes. A partir das relações geométricas associadas ao deslocamento dos seus graus de liberdade, as relações cinemáticas associadas às suas velocidades são determinadas. Considerando o fluxo de potência entre os graus de liberdade, e também entre estes e os elementos de atuação (atuadores lineares elétricos), as relações de equilíbrio das forças e torques são obtidas. Levando em consideração os efeitos inerciais dos componentes do sistema, a rigidez e efeitos de amortecimento, as equações de movimento ou as equações de estado são analiticamente determinadas e representadas em qualquer sistema de referência, local ou global. Além disso, as relações entre a cinemática inversa e a dinâmica direta são apresentadas. Esta abordagem adota os mesmos fundamentos, conceitos e elementos da técnica dos grafos de ligação, com a sua notação simbólica e representação gráfica. A metodologia proposta é generalizada e aplicável em qualquer tipo de mecanismo (aberto ou fechado, plano ou espacial). O modelo cinemático inverso do mecanismo de cadeia fechada, que tem uma solução fácil quando comparado com o modelo direto, pode ser desenvolvido por qualquer metodologia conhecida. Neste trabalho, a técnica da cadeia vetorial é usada para determinar o modelo geométrico inverso, e com a sua derivação, as relações cinemáticas são obtidas, e, portanto, a matriz Jacobiana inversa. Desse modo, é construída a estrutura em grafos de ligação da cinemática inversa e, a partir das relações de causa e efeito, encontra-se o modelo dinâmico direto do mecanismo. Assim, esta metodologia (grafos de ligação ou fluxo de potência) é mais eficiente e segura para determinar os modelos dinâmicos analíticos (fechados) de mecanismos paralelos. Um conjunto de simulações foi realizado para validar esta abordagem, usando os dados reais (geometria, inércia, amortecimento, forças de atuação, etc.) a partir de um mecanismo plano projetado e construído especialmente para a finalidade de comparar os resultados simulados e experimentais. Uma estratégia de controle de malha fechada usando a cinemática inversa e os modelos dinâmicos diretos é proposta. Finalmente, testes experimentais validam esta estratégia. As equações analíticas levam a um processo de simulação e controle em tempo real mais eficientes destes sistemas. / [en] Mechanisms are essentially (but not exclusively) made up of multiple rigid bodies that have relative motion between themselves. Each rigid body is connected through a joint to one or more bodies, wherein the sequence of connected bodies is called kinematic chain. Open (or serial) kinematic chains have no restrictions on one of their ends, as closed (or parallel) chains have restrictions on both ends. The focus in this work will be given on the study of mechanisms with closed kinematic chains or parallel mechanisms. Thus, this work presents the analytical form determination of the dynamic model of a parallel planar mechanism with three degrees of freedom through the characterization of the power flow between its components. From the geometrical relations associated to the displacement of their degrees of freedom, the kinematic relations associated to their speeds are determined. Considering the power flow between the degrees of freedom, and also between these and the actuating elements (linear electric actuators) the equilibrium relations of the forces and torques are obtained. Accounting for inertial effects of system components, the stiffness and damping effects, the equations of motion or the state equations are analytically determined and represented in any reference frame, local or global. Besides, the relation between the inverse kinematics and the direct dynamics is presented. This approach adopts the same fundamentals, concepts and elements of the Bond Graph Technique, with its symbolic notation and graphical representation. The proposed methodology is generalized and applicable in any type of mechanism (open or closed, planar or spatial). The inverse kinematic model of the closed chain mechanism, which has easy solution when compared to the direct model, can be developed by any known methodology. In this work, the vector loop technique is used to determine the inverse geometric model, and with its derivation, the kinematic relations are obtained, and therefore the inverse Jacobian matrix. Thereby, the inverse kinematics bond graph is built and, from the cause and effect relations, the direct dynamic model of the mechanism is found. Thus, this methodology (bond graphs or power flow) is more efficient and secure to achieve the dynamic analytical (closed) models of parallel mechanisms. A set of simulations are performed to validate this approach, using the real data (geometry, inertia, damping, actuators forces, etc.) from a planar mechanism designed and built especially for the purpose to compare the simulated and experimental results. A closed-loop control strategy using the inverse kinematic and the direct dynamic models is proposed. Finally, experimental tests validate this strategy. The analytical equations lead to a more efficient simulation process and real-time control of these systems.
456

Maintien de l'intégrité de robots mobiles en milieux naturels / Preserving the Integrity of Mobile Robots in off-road conditions

Braconnier, Jean-Baptiste 22 January 2016 (has links)
La problématique étudiée dans cette thèse concerne le maintien de l’intégrité de robots mobiles en milieux naturels. L’objectif est de fournir des lois de commande permettant de garantir l’intégrité d’un véhicule lors de déplacements autonomes en milieux naturels à vitesse élevée (5 à 7 m.s -1 ) et plus particulièrement dans le cadre de l’agriculture de précision. L’intégrité s’entend ici au sens large. En effet, l’asservissement des déplacements d’un robot mobile peut générer des consignes nuisant à son intégrité physique, ou à la réalisation de sa tâche (renversement, tête-à-queue, stabilité des commandes, maintien de la précision, etc.). De plus, le déplacement en milieux naturels amène des problématiques liées notamment à des conditions d’adhérence variables et relativement faibles (d’autant plus que la vitesse du véhicule est élevée), ce qui se traduit par de forts glissements des roues sur le sol, ou encore à des géométries de terrains non traversables par le robot. Aussi, cette thèse vise à déterminer en temps réel l’espace de stabilité en terme de commandes admissibles permettant de modérer les actions du robot. Après une présentation des modélisations existantes, et des observateurs permettant l’exploitation de ces modélisations pour la mise en place de loi de commande prédictive en braquage pour le suivi de trajectoire, une nouvelle méthode d’estimation des glissements basé sur une observation cinématique est proposée. Celle-ci permet de répondre aux problématiques de vitesse variable (et notamment du passage de la vitesse par des valeurs nulles) du véhicule et d’observation lors d’un déplacement sans trajectoire de référence. Ce nouvel observateur est primordial pour la suite des développements de cette thèse, puisque la suite des travaux s’intéresse à la modulation de la vitesse du véhicule. Ainsi, dans la suite des travaux, deux lois de commande prédictives agissant sur la vitesse du véhicule ont été mises en place. La première apporte une solution à la problématique de la saturation des actionneurs en braquage, lorsque la vitesse ou les glissements rendent la trajectoire à suivre inadmissible vis-à-vis des capacités physiques du véhicule. La deuxième répond à la problématique de la garantie de la précision du suivi de trajectoire (maintien du véhicule dans un couloir de déplacement). Dans les deux cas la stratégie de commande est similaire : on prédit l’état futur du véhicule en fonction de ses conditions d’évolution actuelle et de conditions d’évolutions futures simulées (obtenues grâce à la simulation de l’évolution d’un modèle dynamique du véhicule) afin de déterminer la valeur de la vitesse optimale pour que les variables cibles (dans un cas la valeur du braquage et dans l’autre l’écart à la trajectoire) respectent les conditions imposées (non-dépassement d’une valeur cible). Les résultats présentés dans ce mémoire ont été réalisés soit en simulations, soit en conditions réelles sur des plateformes robotiques. Il en découle que les algorithmes proposés permettent dans un cas de réduire la vitesse du véhicule pour éviter la saturation du braquage et donc les phénomènes de sur et sous virage qui en découlerait et donc permet de conserver la commandabilité du véhicule. Et dans l’autre cas de garantir que l’écart à la trajectoire reste sous une valeur cible. / This thesis focused on the issue of the preseving of the integrity of mobile robots in off-road conditions. The objective is to provide control laws to guarantee the integrity of a vehicle during autonomous displacements in natural environments at high speed (5 to 7 m.s -1 ) and more particularly in The framework of precision farming. Integrity is here understood in the broad sense. Indeed, control of the movements of a mobile robot can generate orders that affect its physical integrity, or restrains the achievement of its task (rollover, spin, control stability, maintaining accuracy , etc.). Moreover, displacement in natural environments leads to problems linked in particular to relatively variable and relatively low adhesion conditions (especially since the speed of the vehicle is high), which results in strong sliding of wheels on the ground, or to ground geometries that can not be crossed by the robot. This thesis aims to determine in real time the stability space in terms of permissible controls allowing to moderate the actions of the robot. After a presentation of the existing modelings and observers that allow the use of these modelizations for the implementation of predictive control law for trajectory tracking, a new method of estimation of side-slip angles based on a kinematic observation is proposed. It permit to address the problem of variable speed of the vehicle (and in particular the case of zero values) and also to allow the observation during a displacement without reference trajectory. This new observer is essential for the further development of this thesis, since the rest of the work is concerned with the modulation of the speed of the vehicle. So, in the further work, two predictive control laws acting on the speed of the vehicle have been set up. The first one provides a solution to the problem of the saturation of steering actuators, when the speed or side-slip angles make the trajectory inadmissible to follow with respect to the physical capacities of the vehicle. The second one adress the problem of guaranteeing the accuracy of trajectory tracking (keeping the vehicle in a corridor of displacement). In both cases, the control strategy is similar: the future state of the vehicle is predicted according to the current conditions of evolution and the simulated one for the future evolution (obtained by simulating the evolution of dynamics models of the vehicle) in order to determine the value of the optimum speed so that the target variables (in one case the value of the steering and in the other the lateral deviation from the trajectory) comply with the imposed conditions (not exceeding a target value). The results presented in this thesis were realized either in simulations or in real conditions on robotic platforms. It follows that the proposed algorithms make it possible : in one case to reduce the speed of the vehicle in order to avoid the saturation of the steering actuator and therefore the resulting over and under steering phenomena and thus make it possible to preserve the vehicle’s controllability. And in the other case, to ensure that the lateral deviation from the trajectory remains below a target value.
457

Motion Space Analysis of Smooth Objects in Point Contacts

Rama Krishna, K January 2018 (has links) (PDF)
The present work studies instantaneous motion of smooth planar and spatial objects in unilateral point contacts. The traditional first-order instantaneous kinematic analysis is found insufficient to explain many common physical scenarios. The present work looks beyond the velocity state of motion for a comprehensive understanding through higher-order kinematic analysis of the above system. The methodology proposed herein is a Euclidean space approach to second-order motion space analysis of objects in point contacts. The geometries of the objects are approximated up to second-order in the differential vicinity of the point of contact; meaning, up to curvature at the point of contact. The instantaneous motion is approximated up to second-order kinematics, i.e., up to acceleration state. The basic approach consists of impressing an instantaneous motion upon one object while holding the other fixed which is in a single point contact initially, and observing for one of the following three states: penetration, separation, and persistence of contact between the two objects. These three states are characterized by the interference between the geometries of the objects. Penetration and separation of two curves for rotation about points on the plane is geometrically studied based on the relative configuration of the osculating circles at the point of contact. It is shown that the plane is partitioned into four regions of rotation centers. Partitioning of the plane into motion space regions at a contact provided a geometrical framework compose the motion space for multiple contacts. The applications include second-order form-closure (SFC) and synthesis of kinematic pairs. To explore the consequence of a generic motion, an analytical scheme is formulated using the screw theoretic concepts of twist and twist-derivative. It is shown that the characteristics of second-order motions at a single contact depends only upon the geometric kinematic properties of the motion; meaning, the motion characteristics are time-independent. The geometric conditions for the second-order motion that will be admissible or restrained at a contact are not available in the existing literature on \second-order mobility". The classical Euler-Savary equation for enveloping curves is found to represent the condition which is both necessary and sufficient for the second-order roll-slide motion. An elegant generalized geometric characterization of second-order motions is derived. This is made use for deriving condition of immobilization of, planar mechanisms with up to 2-degrees-of-freedom (d.o.f.), with a single point contact. Illustrative examples of four-bar and 2R-mechanisms are presented. Rapid prototyped model of the four-bar mechanism is fabricated and the SFC theory is verified satisfactorily. Through a novel use of Meusnier's theorem, rotational motion characteristics of planar curves in a point contact is used to determine the patterns and distribution of admissible axes of rotation in space for two surfaces in a single point contact. In the generalized analytical method of motion space analysis, the surfaces are locally represented in Monge's form up to second-order terms and motion is represented using twist and twist-derivative. An analytical framework for the second-order motion space analysis of surfaces with multiple contacts has been developed. Using this procedure, pairs of objects are analyzed for SFC and equivalent lower kinematic pair freedom. Revolute and planar joints with two contacts, prismatic joint with three contacts, SFC of regular concave spherical tetrahedron and regular tetrahedron with four contacts are demonstrated. Although conventional first-order studies demand seven contact points for form-closure, within the context of second-order motion, the present study established that, under special geometric conditions relative immobilization of two smooth objects can be enabled with much fewer contacts. Conditions for immobilization using three and two smooth contacts have been derived. Using contact kinematics equations based on higher-order reciprocity, an instantaneous spatial higher pair to lower pair substitute-connection which is kinematically equivalent up to acceleration analysis for two smooth surfaces in persistent point contact is derived. An illustrative example of a three-link direct-contact mechanism is presented.
458

Synchronised metronome training : The effects on soccer players’ lower-limb motor dynamics and performance in a soccer-related stepping task.

McDonald, Rachel January 2015 (has links)
Good timing is important for all daily motion, even more so for athletes where the smallest movements can make the difference between a goal and miss. Despite this, there has been little research into just how timing ability is related to sport performance. Therefore the present study used a between-within groups experimental design with a sample of female elite- and semi-elite soccer players to describe the effects of a synchronised metronome training (SMT) intervention on lower-limb movement, and accuracy and speed, in a soccer-related stepping task. Participants were randomly assigned to receive SMT (n = 12) or to the control group (n = 12). The SMT group received 12 hours of Interactive Metronome (IM) training over four weeks. Pre- and post-test results showed a strong effect of SMT in improving timing and rhythmic ability. An effect of SMT on accuracy in the stepping task was seen, signifying an effect on motor planning ability. Correlational analyses showed some evident effects of IM on the kinematic parameters, as indicated by relationship between timing and rhythmicity ability with increased movement segmentation, though this did not reach significance. These results present new information and provides support for kinematic analysis to be used in future studies to address the effect of SMT. / God timing är viktig för alla dagliga rörelser, och än mer viktigt är det för idrottare där minsta lilla rörelse kan innebära skillnaden mellan mål och miss. Trots detta finns lite forskning om hur förmåga till timing kan förbättra sportsliga prestationer. Huvudsyftet med denna studie var att undersöka hur synkroniserad metronomträning (SMT) påverkade prestationen och rörelsedynamik i en fotbollsrelaterad uppgift. I studien deltog 24 aktiva fotbollsspelare från Damallsvenskan och Division 1, varav 12 fick träna med SMT under fyra veckor. Resultatet visade att SMT påverkade exaktheten i utförandet av den fotbollsrelaterade uppgiften, vilket indikera en effekt på motorplaneringsförmåga. Denna studie jämför för första gången 3D-kinematikdata från före- och efter träning med SMT samt med en kontrollgrupp, 3D-kinematikanalysen av rörelsesegmentering och kumulativ 3D-distans visade inga övertygande relationer mellan SMT och rörelsedynamiken efter IM-träning. Däremot visade korrelationen stöd för en relation mellan rörelsesegmentering och timingförmåga. Därför stödjer denna studie tidigare forskning kring timing och motorisk prestation, och det finns tillräckligt med bevis för att motivera vidare analyser av kinematiska parametrar för att studera effekten av SMT och rörelsedynamik.
459

Quantitative landslide hazard assessment with remote sensing observations and statistical modelling / Évaluation quantitative de l'aléa glissement de terrain par observations de télédétection et modèles statistiques

Schlögel, Romy 12 February 2015 (has links)
La création d’inventaires de glissements de terrain sert de base à l’évaluation quantitative de l’aléa et à la gestion du risque. Les cartes d’inventaires de mouvements gravitaires sont produites en utilisant des méthodes conventionnelles (campagnes de mesures de terrain, interprétation visuelle de photographies aériennes) et par des techniques de télédétection plus innovantes. Une des techniques les plus prometteuses pour la détection et la cartographie des glissements de terrain fait appel à la mesure de la déformation du sol par interférométrie radar satellitaire (InSAR). Cette thèse est consacrée à la constitution d’un inventaire multi-dates à partir de données multi-sources (incluant les données InSAR) en vue d’évaluer de façon quantitative l’aléa glissement de terrain. Les méthodes associent l’analyse de produits d’Observation de la Terre et des modélisations statistiques pour la caractérisation de l’aléa dans la vallée de l’Ubaye, une région rurale et montagneuse des Alpes du Sud. Elles ont été développées à l’échelle du versant (1:5.000-1:2.000) et à l’échelle régionale (1:25.000- 1:10.000). Pour la création des inventaires, cette étude propose une interprétation combinée de séries temporelles d’images SAR, de photographies aériennes, de cartes géomorphologiques, de rapports historiques et de campagnes de terrain. A l’échelle locale, une méthodologie d'interprétation guidée par la géomorphologie et utilisant l’InSAR a été proposée pour identifier les champs de déplacement des glissements de terrain et mesurer leur évolution. A l’échelle régionale, la distribution spatio-temporelle des glissements de terrain a été caractérisée et l’aléa a été calculé à partir des probabilités d’occurrence spatiale et temporelle pour une intensité donnée des phénomènes. L’occurrence spatiale est estimée grâce à un modèle multivarié (régression logistique). L’occurrence temporelle des mouvements gravitaires est évaluée grâce à un modèle de probabilité de Poisson permettant de calculer la probabilité de dépassement (incluant ou non un seuil de surface) pour plusieurs périodes de retour. Plusieurs unités d'analyse spatiale ont été utilisées pour la modélisation ; les résultats démontrent clairement leur influence sur les résultats. L’analyse de l’aléa a été réalisée sur quelques cas spécifiques. Des relations entre les (ré)activations de glissements de terrain et les facteurs déclenchants sont proposées. / The analysis of landslide inventories is the basis for quantitative hazard assessment. Landslide inventory maps are prepared using conventional methods (field surveys, visual interpretation of aerial photographs) and new remote sensing techniques. One of the most promising techniques for landslide detection and mapping is related to the measurement of the ground deformation by satellite radar interferometry (InSAR).This doctoral thesis is dedicated to the preparation of a multi-date inventory, from multi-source data, including InSAR, for a quantitative assessment of landslide hazard. The methods associate the analysis of Earth Observation products and statistical modelling for the characterization of landslide hazard in a rural and mountainous region of the South French Alps. They have been developed at the slope (1:5000-1:2000) and the regional (1:25.000-1:10.000) scales. For the creation of a multi-date inventory, this study developed a combined interpretation of time series of SAR images, aerial photographs, geomorphological maps, historical reports and field surveys. At the slope-scale, a geomorphologically-guided methodology using InSAR was proposed to identify landslide displacement patterns and measure their kinematic evolution. At regional scale, spatio-temporal distribution of landslides is characterised and hazard is assessed by computing spatial and temporal probabilities of occurrence for a given intensity of the phenomena. The spatial occurrence is evaluated using a multivariate model (logistic regression). The temporal occurrence of landslide is estimated with a Poisson probability model to compute exceedance probabilities for several return periods. Different mapping units were used in the modelling, and their influence on the results is discussed. Analysis of landslide hazard is then proposed for some particular hotspots. Relationships between landslide (re)activations and triggering factors are envisaged.
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Počítačová simulace kolapsu budovy zplastizováním kloubů / Computer simulation of building collapse due to formation of plastic hinges

Valeš, Jan January 2012 (has links)
The aim of the thesis is to create an analytical 2D model of a multi-storey building and its consequent loading until the point of collapse which occures due to formation of plastic hinges. The first part is going to present a linear analysis of the problem; it focuses on location and level of load when the plastic hinges are formed. Then a nonlinaer analysis is going to be performed by RFEM programme using postcritical analysis and dynamic relaxation. Differences between the results of mentioned types and methods of analysis are going to be compared and an impact of variables is going to be evaluated .

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