1,721,434 research outputs found
Automatic EKF tuning for UAS path following in turbulent air
No full textBy using two simultaneously working Extended Kalman Filters, a procedure is implemented in order to perform in a fully autonomous way the path following in turbulent air. To guarantee the robustness of the proposed algorithm, an automatic tuning procedure is proposed to determine optimal values of Process and Measurement Noise statistics. Such a procedure is based on both the characteristics of the disturbances and the desired flight path; in particular, a specific performance index is applied to tune filters. In this way control laws are adapted to the flight condition and these lead to an optimal path-following. This research represents an upload of previous papers. It allows eliminating the time expensive trial and error procedure usually employed to tune Extended Kalman Filters. Obviously, procedure results are optimal for ever flight condition
Wind component estimation for UAS flying in turbulent air
Full text linkOne of the most important problem of autonomous flight for UAS is the wind identification, especially for small scale vehicles. This research focusses on an identification methodology based on the Extended Kalman Filter (EKF). In particular authors focus their attention on.the filter tuning problem. The proposed procedure requires low computational power, so it is very useful for UAS. Besides it allows a robust wind component identification even when, as it is usually, the measurement data set is affected by noticeable noises. (C) 2019 Elsevier Masson SAS. All rights reserved
Optimal Flight Path Determination in Turbulent Air: A Modified EKF Approach
No full textBy using the Extended Kalman Filter an accurate path following in turbulent air is performed. The procedure employs
simultaneously two dierent EKFs: the rst one estimates disturbances, the second one aords to determine the necessary
controls displacements for rejecting those ones. To tune the EKFs an optimization algorithm has been designed to
automatically determine Process Noise Covariance and Measurement Noise Covariance matrices. The rst lter, by using
instrumental measurements gathered in turbulent air, estimates wind components. The second one obtains command
laws able to follow the desired
ight path. To perform this task aerodynamic coecients have been modied. Such
a procedure leads to a set of unknown stability and control parameters containing the required displacements of the
controls. The lter estimates the new set of aircraft stability derivatives by using measurements made by the desired flight path parameters. Once the unknown stability and control derivatives have been determined, the obtained control
displacements are used to perform an accurate path following in turbulent air. The obtained control laws are adaptive
and they depend by either the characteristics of the disturbance or the desired
ight path. The proposed algorithm,
using appropriate imposed constrains, permits to tune the lter without trial and error procedure
Meccanica del volo dei velivoli ad ala fissa
No full textLa meccanica del volo studia le traiettorie e le caratteristiche del moto di un aeromobile sotto l'azione delle forze aerodinamiche, propulsive e inerziali
Meccanica del volo dei velivoli ad ala rotante
No full textSi definisce elicottero un aeromobile che trae la propria sostentazione e propulsione dalla forza prodotta da uno o più rotori azionati da un motore ed aventi asse vertical
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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