1,720,963 research outputs found
Implementation of Coordinated Complex Dynamic Behaviors in Multirobot Systems
No full textDecentralized control strategies for multirobot systems have been extensively studied over the past few years. Typically, these strategies aim at exploiting local interaction rules to regulate the overall state of the multirobot system toward a desired configuration, thus generating some desired coordinated behaviors, such as synchronization, swarming, deployment, or formation control. However, when considering the real-world application of multirobot systems, more complex cooperative dynamic behaviors are desirable. Along these lines, in this paper, we propose a methodology to control a multirobot system for cooperatively tracking arbitrarily defined periodic setpoint trajectories. This objective is fulfilled partitioning the multirobot system into independent robots (that can provide control inputs) and dependent robots (that are controlled through local interaction). The motion of the independent robots is then defined in such a way that, exploiting local interactions, the dependent robots are controlled to track the desired trajectories. The proposed control strategy is validated by means of simulations and experiments on real robots
Implementation of arbitrary periodic dynamic behaviors in networked systems
No full textDecentralized control of networked systems has been
widely investigated in the literature, with the aim
of regulating the overall state of the system to
some desired configuration, thus obtaining
coordinated emerging behaviors
(e.g. synchronization, swarming, coverage, formation
control) by means of local interaction. In this
paper we introduce a methodology to solve a tracking
problem, that is defining a decentralized control
strategy for making a networked system follow an
arbitrarily defined periodic setpoint function. The
most suitable interconnection topology is defined
together with the control law as the solution of a
constrained optimization problem, in order to ensure
asymptotic tracking. Simulations are provided for
validating the proposed control strateg
Coordinated dynamic behaviors in multi-robot systems with time-varying topologies
No full textA control strategy for the execution of coordinated complex dynamic behaviors in multi-robot systems is introduced in this paper. In particular, considering a dependent-independent robot partitioning of a multi-robot system, we introduce a methodology for controlling the independent robots in such a way that, exploiting local interaction, the dependent robots are driven to track desired periodic setpoint trajectories. The control strategy is designed taking explicitly into account variations in the interconnection topology, due to relative movements among the robots
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Rétroactions non linéaires et hybrides avec systèmes linéaires à temps continu
No full textIn this thesis we study linear time-invariant systems feedback interconnected with three specific nonlinear blocks; a play/stop operator, a switching-reset mechanism, and an adaptive dead-zone. This setup resembles the Lure problem studied in the absolute stability framework, but the types of nonlinearities considered here do not satisfy (in general) a sector condition. These nonlinear blocks give rise to a whole range of interesting phenomena, such as compact sets of equilibria, hybrid omega-limit sets, and state constraints. Throughout the thesis, we use the hybrid systems formalism to describe these phenomena and to analyze these loops. We obtain sharp stability conditions that can be formulated as linear matrix inequalities, thus verifiable with numerically efficient solvers. Finally, we apply the theoretical findings to two automotive applications.Dans cette thèse, nous étudions la rétroaction de systèmes linéaires invariants dans le temps reliés entre eux par trois blocs non linéaires spécifiques : un opérateur de lecture/arrêt, un mécanisme de réinitialisation de commutation et une zone morte adaptative. Cette configuration ressemble au problème de Lure étudié dans le cadre de stabilité absolue, mais les types de non-linéarités considérés ici ne satisfont pas (en général) une condition sectorielle. Ces blocs non linéaires donnent lieu à toute une série de phénomènes intéressants, tels que des ensembles compacts d’équilibres, des ensembles hybrides oméga-limites et des contraintes d’état. Tout au long de la thèse, nous utilisons le formalisme des systèmes hybrides pour décrire ces phénomènes et analyser ces boucles. Nous obtenons des conditions de stabilité très précises qui peuvent être formulées sous forme d’inégalités matricielles linéaires, donc vérifiables avec des solveurs numériques efficaces. Enfin, nous appliquons les résultats théoriques à deux applications automobiles
Nonlinear and Hybrid Feedbacks with Continuous-Time Linear Systems
Full text linkIn this thesis we study linear time-invariant systems feedback interconnected with three specific nonlinear blocks; a play/stop operator, a switching-reset mechanism, and an adaptive dead-zone. This setup resembles the Lure problem studied in the absolute stability framework, but the types of nonlinearities considered here do not satisfy
(in general) a sector condition. These nonlinear blocks give rise to a whole range of interesting phenomena, such as compact sets of equilibria, hybrid omega-limit sets, and state constraints. Throughout the thesis, we use the hybrid systems formalism to describe these
phenomena and to analyze these loops. We obtain sharp stability conditions that can be formulated as linear matrix inequalities, thus verifiable with numerically efficient solvers.
Finally, we apply the theoretical findings to two automotive applications
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
- …
