1,720,992 research outputs found
MvTools, a Multivariable Systems Toolbox
No full textMvTools, (Multivariable Tools) is a toolbox for Matlab 5.3 developed within the Department of Electrical Systems and Automation (DSEA), University of Pisa, with the aim to offering to the Matlab users (especially control engineers and control engineering students) a complete toolbox for linear systems analysis and robust control synthesis. All the operations are carried out by means of a single graphical user interface, which allows the management of all the different design steps, and the comparison between the most rewarded robust control techniques. MvTools is not meant to replace the main control synthesis toolboxes, but instead it relies on them to yield a single environment in which all their best capabilities are integrated and easily achieved. A help file in HTML format is provided and is accessible within the progra
Robust control of underwater vehicles: sliding mode control vs. mu synthesis
No full textPresents the results of a controller synthesis where a robust control of an AUV is developed using two different methods. The problem statement requires the design of a position and attitude control system for the vehicle in order to achieve precise trajectory following. Firstly, a detailed nonlinear model of the vehicle was derived. Secondly an operating point for nominal design was selected, and a multivariable linear model of the vehicle was obtained by linearization around the operating point. The presence of structured uncertainties due to errors in the computation of hydrodynamic coefficients, dynamic linearization and truncation, unknown disturbances, were considered. Two robust controllers were designed, the first one linear, using standard mu analysis and synthesis techniques, and the second one nonlinear, using a sliding mode approach. The performance of the two controllers were extensively evaluated and compared in simulation with a full nonlinear model of the vehicl
Robust Control and Analysis of a Towed Underwater Vehicle
No full textThis paper presents an analysis of the dynamics and performance of a towed underwater vehicle and a study into the robust control design of such a vehicle. Firstly, the open-loop dynamical model is analysed to enhance understanding of its controllability and observability. The use of H-infinity is advocated to combat the uncertainties inherent in the complex non-linear model, the discrepancies arising between non-linear and linear models and any unknown disturbances. However, a novel procedure for automating the choice of weighting functions in the design process is introduced. This includes a performance, or quality, index dependent on user-specified parameters including time- or frequency-domain terms. The resulting controller performance is comprehensively analysed by means of both simple and complex channel commands applied to the non-linear simulation. An adaptive scheme involving a multivariable identification procedure is then proposed to improve the performance in a wide range of the trim point. A discussion of the consequences of this scheme is given
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
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