1,721,080 research outputs found
Development and implementation of a tensegrity-based formation controller
Full text linkThe formation control or cooperative work of multiple unmanned vehicles has proved to be
more effective in terms of time consumption and overall performance in a wide variety of
applications. This project aims to review some of the research which has been done up to date and in the subsequent chapters a tensegrity-based formation controller is developed and implemented to assess its global behaviour. This development starts with the design of the heading angle control of a vessel based on the first order Nomoto model which is later transformed into a waypoint problem. Later on, a globally decentralised formation topology and the tensegrity concept is introduced in the context of formation control where a sliding mode controller, a linear-quadratic regulator servo controller and a conventional
proportional-integral-derivative controller are designed and simulated to regulate the elongation of a virtual spring-mass-damper system which connects two vehicles. This is done by applying a force to this system which, from the point of view of the reference vehicle, can be regarded as a repelling force if the formation distance is smaller than the reference and attracting otherwise. The results obtained are satisfactory proving stability and feasibility of the proposed strategy and the limitations and drawbacks of each control technique used are described. However, it is observed that the LQR servo controller yields a better balance between performance and robustness. Afterwards, the tensegrity concept is implemented on a leader-light-guided-follower formation topology using the LEGO® Mindstorms NXT platform. The distance keeping evolution between the follower and the leader is assessed positively for both cases, a PID and LQR servo controller, however, this latter with better tracking while the leader is moving.Outgoin
Development and implementation of a tensegrity-based formation controller
No full textThe formation control or cooperative work of multiple unmanned vehicles has proved to be
more effective in terms of time consumption and overall performance in a wide variety of
applications. This project aims to review some of the research which has been done up to date and in the subsequent chapters a tensegrity-based formation controller is developed and implemented to assess its global behaviour. This development starts with the design of the heading angle control of a vessel based on the first order Nomoto model which is later transformed into a waypoint problem. Later on, a globally decentralised formation topology and the tensegrity concept is introduced in the context of formation control where a sliding mode controller, a linear-quadratic regulator servo controller and a conventional
proportional-integral-derivative controller are designed and simulated to regulate the elongation of a virtual spring-mass-damper system which connects two vehicles. This is done by applying a force to this system which, from the point of view of the reference vehicle, can be regarded as a repelling force if the formation distance is smaller than the reference and attracting otherwise. The results obtained are satisfactory proving stability and feasibility of the proposed strategy and the limitations and drawbacks of each control technique used are described. However, it is observed that the LQR servo controller yields a better balance between performance and robustness. Afterwards, the tensegrity concept is implemented on a leader-light-guided-follower formation topology using the LEGO® Mindstorms NXT platform. The distance keeping evolution between the follower and the leader is assessed positively for both cases, a PID and LQR servo controller, however, this latter with better tracking while the leader is moving.Outgoin
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
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
Concepts in Electric Circuits - eBooks and textbooks from bookboon.com
No full textThis book covers fundamental aspects of electric circuits that form the core of many engineering disciplines. In particular, basic circuit elements and their characteristics are presented when connected in an electric network. In addition, techniques to analyse and solve electric circuits are explained in a simple manner and examples are shown to demonstrate each strategy. DC as well as AC circuit analysis is provided with a brief account of filters in the end. Difficult electric circuit concepts such as sinusoids and phasors are explicated in an effective way so that basic understanding can be properly achieved
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