1,721,030 research outputs found
Design of unknown input observers for nonlinear systems with full and partial information
No full textThe problem of designing Unknown Input Observers (UIOs) for nonlinear systems is approached in this paper, in the cases of full and partial information. In the former, it is shown that the construction hinges upon the solution of a system of first-order Partial Differential Equations (PDEs). Such system admits a trivial solution that however renders the observer completely insensitive to disturbances as well as additional control inputs, which is a rather undesirable property in the application of UIOs to the context of Fault Detection. Therefore, we propose an alternative design methodology that allows to extend the set of solutions to the above PDEs by relying merely on the solution of ordinary differential equations, namely by exploiting the Theory of Characteristics. Then, in the partial information scenario, it is shown that introducing a suitable change of coordinates and considering reduced-order observers permit the decomposition of the primary task of disturbance decoupling with that of asymptotic stability, hence providing more intuitive conditions for the observer design
Asymptotic tracking for linear and nonlinear systems: a two-point boundary value formulation
Full text linkL2-Gain for hybrid linear systems with periodic jumps: A game theoretic approach for analysis and design
No full textIn this paper, the disturbance attenuation problem is formulated and solved for a class of linear hybrid systems in the presence of periodic jumps. The results are achieved, both in the finite and infinite horizon cases, by borrowing ideas from the theory of dynamic games. In the considered formulation, independent disturbances affecting the continuous-time and the discrete-time components of the hybrid system are allowed. Moreover, the analysis is carried out by introducing easily verifiable conditions, involving the definition of a Monodromy Riccati Equation , i.e., a classical Riccati equation defined for the one-period discrete-time equivalent model. Interestingly, as a by-product, the main statements essentially characterize the solution of zero-sum noncooperative dynamic games for periodic linear hybrid systems, which is of interest per se
On polynomial feedback Nash equilibria for two-player scalar differential games
No full textIn this paper, two-player scalar differential games are thoroughly studied, in the presence of polynomial dynamics and focusing on the notion of solution provided by polynomial feedback Nash equilibria. It is well-known that such strategies are related to the solution of coupled partial differential equations, namely the so-called Hamilton–Jacobi–Isaacs equations. Herein, we firstly prove a somewhat negative result, stating that, for a generic choice of the parameters, two-player scalar polynomial differential games do not admit polynomial Nash equilibria. Then, we focus on the class of Linear–Quadratic (LQ) games and we propose an algorithm that, by borrowing techniques from algebraic geometry, allows to recast the problem of computing all stabilizing Nash feedback strategies into that of finding the zero of a single polynomial function in a scalar variable. This permits a comprehensive characterization–in terms of number and values–of the set of solutions to the associated game
An algebraic geometry approach for the computation of all linear feedback Nash equilibria in LQ differential games
No full textIn this paper, Linear-Quadratic (LQ) differential games are studied, focusing on the notion of solution provided by linear feedback Nash equilibria. It is well-known that such strategies are related to the solution of coupled algebraic Riccati equations, associated to each player. Herein, we propose an algorithm that, by borrowing techniques from algebraic geometry, allows to recast the problem of computing all stabilizing Nash strategies into that of finding the zeros of a single polynomial function in a scalar variable, regardless of the number of players and the dimension of the state variable. Moreover, we show that, in the case of a scalar two-player differential game, the proposed approach permits a comprehensive characterization - in terms of number and values - of the set of solutions to the associated game
Hamiltonian-Based Clustering: Algorithms for Static and Dynamic Clustering in Data Mining and Image Processing
No full textThe large amount of data available for analysis and management raises the need for defining, determining, and extracting meaningful information from the data. Hence in scientific, engineering, and economics studies, the practice of clustering data arises naturally when sets of data have to be divided into subgroups with the aim of possibly deducting common features for data belonging to the same subgroup. For instance, the innovation scoreboard [1] (see Figure 1) allows for the classification of the countries into four main clusters corresponding to the level of innovation defining the "leaders," the "followers," the "trailing," and the "catching up" countries. Many other disciplines may require or take advantage of a clustering of data, from market research [2] to gene expression analysis [3], from biology to image processing [4][7]. Therefore, several clustering techniques have been developed (for details see "Review of Clustering Algorithms"). © 1991-2012 IEEE
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
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