1,721,160 research outputs found
A non-square sector condition and its application in deferred-action anti-windup compensator design
Full text linkA sector condition for two connected deadzone nonlinearities is provided. By introducing an additional non-square operator which exploits their connectivity, a more general set of sector-like matrix inequalities is obtained. This “non-square” matrix inequality condition is applied to an anti-windup (AW) problem in which the AW compensator is not activated until the unconstrained control signal reaches a well-defined level beyond that of the physical actuator limits. The non-square sector condition allows such “deferred-action” AW synthesis to be performed in a manner much closer to traditional (“immediate”) sector-based AW with either lowered conservatism or decreased computational effort in contrast to recent work. The non-square condition is applicable to other AW problems
Anticipatory Anti-Windup: An Alternative Construction
No full textAnticipatory anti-windup compensation involves activation of the anti-windup compensator before the physical saturation limits on the control signals are reached; the antiwindup compensator is activated in anticipation of actuatorsaturation occurring. Existing studies, which have used a pseudo-LPV representation for compensator synthesis, have proposed convex but somewhat complicated and opaque synthesis routines. This paper offers an alternative method of synthesising anticipatory anti-windup compensators, involvingthe exploitation of a “non-square” sector condition associated with a combination of deadzone nonlinearities. This method leads to an anticipatory compensator synthesis routine which is close to that associated with standard immediately activated anti-windup compensators. A numerical example and comments on the use of anticipatory anti-windup are also given
An alternative approach to anti-windup in anticipation of actuator saturation
Full text linkTraditionally, an anti-windup compensator is activated when control signal saturation occurs. An alternative approach is to activate the compensator at a level below that of the physical control constraints: the antiwindup compensator is activated in anticipation of actuator saturation. Recent studies have proposed systematic methods for the construction of such anticipatory anti-windup compensators, but a pseudo-LPV representation of the saturated system has been central to these results. This paper approaches the anticipatory anti-windup problem for open-loop stable plants using a ”non-square” sector condition which is associated with a combination of deadzone nonlinearities. The advantage of this approach is that it leads to synthesis routines which bear a close resemblance to those associated with traditional immediately activated anti-windup compensators. A by-product of this approach also appears to be that the arising compensators are better numerically conditioned. Some simulation examples illustrating the effectiveness of anticipatory anti-windup compensators and some comments on their wider use complete the paper
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
Cooperative Robot Manipulator Control with human `pinning' for robot assistive task execution.
No full textThis paper presents the use of a multi-agent controller in application to a human-robot cooperative task where the human is the lead and two robotic manipulators act as agents allowing for physical assistance of the human in a lifting task: the human aids in providing direction for two synchronized robot arms placing a tray with a water glass in a human-robot interaction experiment.Novel adaptive multi-agent theory is exploited to achieve precise coordination between the arms, while being lead by the human. A novel finite-time adaptation scheme aids changing structures, such as the removal of the leading agent, so that consensus and synchronisation is retained. This is permitted by the decentralized control structure, where each agent is supported by an agent-specific controller and information exchanged between the agents is limited to position and velocity of each manipulator. Thus, the controller is robust to structural changes in the multi-agent network, e.g. the removal of the pinning agent
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
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