1,720,998 research outputs found
Design of nonlinear regulators from logic-based stabilizers
No full textWe focus on a class of nonlinear systems that can be stabilized at a desired compact set by means of logic-based continuous feedback and we show how to design regulators that are robust to matched exosystem-generated disturbances. The proposed design methodology, of interest also for purely continuous-time systems, combines recent advances in the field of hybrid control systems and output regulation for nonlinear systems. As an illustrative example, the problem of global stabilization of a 6-DOF rigid body affected by a force periodic disturbance of uncertain amplitude, phase and frequency, is presented
Stabilization for a class of minimum phase hybrid systems under an average dwell-time constraint
No full textWe consider the class of nonlinear systems in normal form with unitary
relative degree whose zero and output dynamics are affected by state
jumps fulfilling an average dwell-time constraint. Under a minimum-phase
assumption requiring the existence of a compact set which is globally
pre-asymptotically stable for the hybrid zero dynamics, we show how to
design continuous, global state- and semiglobal output-feedback control
laws. The proposed design methodology extends to the considered class of
hybrid systems well-known design techniques for robustly stabilizing the
class of continuous-time minimum-phase nonlinear systems having unitary
relative degree. Examples are given to show the usefulness of the technical
result
A Note About Hybrid Linear Regulation
No full textWe present some results about the problem of output regulation for a class of hybrid linear systems. We focus on the class of linear systems and exosystems whose dynamics have jumps according to the value of a clock variable, and we address the problem of designing controllers embedding an internal model of the switching exosystem to achieve the regulation objective. This will lead us to generalize concepts and tools well known in the field of output regulation for continuous-time systems, such as the concept of steady-state response, of regulator equations and the internal model property. The actual results are preliminary steps toward the development of a theory of nonlinear hybrid regulation that is under study by the authors
A note on stabilization for a class of minimum phase hybrid systems
No full textThis papers presents a result on stabilization for a class of minimum phase, relative degree one hybrid systems. The work focuses on the situation where the derivative of the output is the sum of the input and a term that vanishes everywhere on the attractor of the zero dynamics except at finite number of (nonequilibrium) points
Hybrid Output Regulation with Unmeasured Clock
No full textThis paper addresses the problem of hybrid output
regulation for linear systems in the case where the jumps of the
system and exosystem state are triggered by a clock variable
that is not measured. We extend our earlier result
by complementing the hybrid internal model-based regulator
design proposed in that paper with a hybrid clock phase
estimator yielding asymptotic regulation
Hybrid Output Regulation for Minimum Phase Linear Systems
No full textWe consider the hybrid output regulation problem
for minimum phase linear systems with relative degree
greater than one. In the hybrid output regulation problem,
the disturbances, which are assumed to be matched with the
control input, evolve through a hybrid dynamical system that
experiences jumps periodically. In constructing an output regulator
for this problem, we combine recent work on necessary
conditions for hybrid output regulation with classical ideas
related to high-gain output feedback and high-gain observers.
The output regulator we design achieves global exponential
stability of a compact set in which the output of the system is
zero
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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