1,721,132 research outputs found
State space model identification: from unstructured to structured models with an H-infinity approach
No full textSubspace model identification algorithms have become extremely popular in the last few
years thanks to the ease with which they can provide consistent estimates for MIMO state space models
in a non iterative way, exploiting a full parameterisation of the system matrices. The only, well known,
downside of this approach is the impossibility to impose a fixed basis to the state space representation,
and therefore the difficulties in recovering physically-motivated models. The problem considered in
this paper is the one of recovering the numerical values of the physical parameters of a structured
representation of the system starting from a fully parameterised identified model. It will be shown
that this can be achieved without explicitly constructing the similarity transformation, for linear time-
invariant systems, linear time-periodic systems and linear parameter-varying systems identified
periodic scheduling sequence. Two numerical examples are presented to illustrate the approach
Spacecraft Attitude Control based on Magnetometers and Gyros
No full textThe problem of designing attitude control laws for
a Low Earth Orbit (LEO) satellite on the basis of static feedback
from a triaxial magnetometer and a set of high precision
gyros is considered and an approach based on optimal static
output feedback for linear time-periodic system is presented.
Simulation results are used to demonstrate the feasibility of the
proposed strategy and to evaluate its performance in a realistic
setting
Identification of linear models for the dynamics of a hovering quadrotor
Full text linkAccurate dynamic modeling of helicopter aeromechanics is becoming increasingly important, as progressively stringent requirements are being imposed on rotorcraft control systems. System identification plays an important role as an effective approach to the problem of deriving or fine tuning mathematical models for purposes such as handling qualities assessment and control system design. In this paper, the problem of deriving continuous-time models for the dynamics of a small-scale quadrotor helicopter is considered. More precisely, the continuous-time predictor-based subspace identification approach is adopted and the results obtained in an experimental study are presented and discussed
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
Interactive Collision Detection for Deformable Objects in Virtual Environments
No full textWe present a new algorithm for detecting the collision of objects in a virtual environment. The algorithm which is based on an efficient data structure for evaluating collisions has been organised to support the following features: data sharing with the graphical description; representation and management of deformable objects; and quasi real-time performances for allowing interactivity in the VE. We also present an extension to the K-DOP algorithm for supporting the object deformation as it was presented by Techia (1998). The algorithm s correctness was analytically demonstrated and its preliminary performance results were verified with experiments. The algorithm was implemented in the pure forms museum research, carried out at PERCRO, which deals with full immersive virtual environment for the exploration and the fruition of digital copies of artistic works such as paintings and sculpture
- …
