511 research outputs found
Robust curvature extrema detection based on new numerical derivation
International audienceExtrema of curvature are useful key points for different image analysis tasks. Indeed, polygonal approximation or arc decomposition methods used often these points to initialize or to improve their algorithms. Several shape-based image retrieval methods focus also their descriptors on key points. This paper is focused on the detection of extrema of curvature points for a raster-to-vector-conversion framework. We propose an original adaptation of an approach used into nonlinear control for fault-diagnosis and fault-tolerant control based on algebraic derivation and which is robust to noise. The experimental results are promising and show the robustness of the approach when the contours are bathed into a high level speckled noise
Wiener algebra for the quaternions
We define and study the counterpart of the Wiener algebra in the quaternionic
setting, both for the discrete and continuous case. We prove a Wiener-L\'evy
type theorem and a factorization theorem. We give applications to Toeplitz and
Wiener-Hopf operators
On Some Geometric Properties of Slice Regular Functions of a Quaternion Variable
The goal of this paper is to introduce and study some geometric properties of
slice regular functions of quaternion variable like univalence, subordination,
starlikeness, convexity and spirallikeness in the unit ball. We prove a number
of results, among which an Area-type Theorem, Rogosinski inequality, and a
Bieberbach-de Branges Theorem for a subclass of slice regular functions. We
also discuss some geometric and algebraic interpretations of our results in
terms of maps from to itself. As a tool for subordination we
define a suitable notion of composition of slice regular functions which is of
independent interest
Controlling the equation of telegraphy and active restoration of some signals
We are compensating the distorsion of an input signal along an electric line, which is modellised by the telegraph equation . Thi s
control synthesis, which is corroborated by several simulations, continues some previous works on the wave, the heat and th e
Euler-Bernoulli equations . It also employs operational calculus and the algebraic interpretation of controllability obtained thank s
to module theory. It extends to infinite dimensional systems the motion planning of flat nonlinear systems .On corrige la distorsion d'un signal le long d'une ligne électrique, modélisée par l'équation des télégraphistes. Cette commande, corroborée par des simulations, prolonge des travaux antérieurs sur les équations des cordes vibrantes, de la chaleur et des verges vibrantes. Elle fait appel au calcul opérationnel et à l'interprétation de la commandabilité obtenue grâce à la théorie algébrique des modules. On généralise, ainsi, à la dimension infinie la planification de trajectoires des systèmes non linéaires plats
Memory functions and Correlations in Additive Binary Markov Chains
A theory of additive Markov chains with long-range memory, proposed earlier
in Phys. Rev. E 68, 06117 (2003), is developed and used to describe statistical
properties of long-range correlated systems. The convenient characteristics of
such systems, a memory function, and its relation to the correlation properties
of the systems are examined. Various methods for finding the memory function
via the correlation function are proposed. The inverse problem (calculation of
the correlation function by means of the prescribed memory function) is also
solved. This is demonstrated for the analytically solvable model of the system
with a step-wise memory function.Comment: 11 pages, 5 figure
Robust Linear Longitudinal Feedback Control of a Flapping Wing Micro Air Vehicle
This paper falls under the idea of introducing biomimetic miniature air vehicles in ambient assisted living and home health applications. The concepts of active disturbance rejection control and flatness based control are used in this paper for the trajectory tracking tasks in the flapping-wing miniature air vehicle (FWMAV) time-averaged model. The generalized proportional integral (GPI) observers are used to obtain accurate estimations of the flat output associated phase variables and of the time-varying disturbance signals. This information is used in the proposed feedback controller in (a) approximate, yet close, cancelations, as lumped unstructured time-varying terms, of the influence of the highly coupled nonlinearities and (b) the devising of proper linear output feedback control laws based on the approximate estimates of the string of phase variables associated with the flat outputs simultaneously provided by the disturbance observers. Numerical simulations are provided to illustrate the effectiveness of the proposed approach
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