Author: Alejandro Ricardo Femat Flores

A Lie-based approach to the general framework of chaotic synchronization

ALEJANDRO RICARDO FEMAT FLORES (2003)

"Diverese phenomena have been reported on the synchornization of chaotic systems. Therefore, the generalized framework of the chaotic synchronization is an actual scienti¯c debate. Here, a Lie-based geometrical approach is presented to remark some geometrical properties of the nonlinear (chaotic) systems toward their synchronization. That is, we address the general problem of ¯nding the conditions for the existence of the synchronization function y = ¸(x). The contribution is focused on the 2 and 3 dimensional (unidirectionally coupled) systems. Illustrative examples are provided along the text."

Article

CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA MATEMÁTICAS

Unveiling uncertain forces in second-order driven oscillators via internal model: a discrete-time feedback

ALEJANDRO RICARDO FEMAT FLORES (2000)

"Unveil uncertain forces acting into (or onto) systems is a very interesting and old problem. Indeed, a lot effort has been devoted to develop procedures which results in the understanding of the uncertain forces and its effects. This contribution deals with recovering of the dynamics of the uncertain forces from measurements (time series). The main idea is to construct an internal model of the nonlinear system and design a discretetime feedback in such way that the model/system differences be stabilized at origin. In principle, if the internal model tracks the trajectory of the nonlinear system, then the uncertain force is recovered by the stabilizing command."

Article

CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA MATEMÁTICAS

A note on optimization of chaos suppression via robust asymptotic feedback: accounting control cost

ALEJANDRO RICARDO FEMAT FLORES (2000)

"This paper deals with the chaos suppression for oscillators in canonical form. The underlying idea is to optimize the robust chaos supression by accounting the control cost. The robust chaos supression is attained by the robust asymptotic feedback while the optimization is solved via Riccatti ecuations. A …nite horizon is arbitrarily settled and the suppression is achieved at this time by means of optimal control problem. This scheme allows to take into account the energy that is wasted by the controller and the closed-loop performance of states. Some experimental results show the features of the approach when a High-Gain observer is added in order to have available the complete state vector."

Article

CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA MATEMÁTICAS

Feedback induction of limit cycle in a bioreactor: controlling towards scale-down

VRANI IBARRA JUNQUERA ALEJANDRO RICARDO FEMAT FLORES (2004)

"The feedback stabilization of periodic orbits (induction of limit cycle) via PI-like control is proposed as plausible tool for scale-down studies. An isothermal continuous stirred tank bioreactor (CSTB), with nonideal mixing, is studied. Kinetics is assumed to be governed by Haldane law. The Ready-to-use equations for selecting the control gains are given. Thus, osccilatory behavior with arbitrary frequency and amplitude can be induced into the PI-controlled CSTB."

Article

CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA MATEMÁTICAS

Estructura-evolución de un modelo de sistema dinámico de terremotos: análisis de correlaciones ocultas de largo alcance

VALENTINA CASTELLANOS RODRIGUEZ ALEJANDRO RICARDO FEMAT FLORES (2015)

"Este trabajo se apoya en el análisis-comparación de las series de tiempo generadas por un modelo dinámico de terremotos el cual se presenta como un sistema no lineal de tercer orden que acopla leyes de fricción y heterogeneidades del medio. El análisis-comparación de la estructura del modelo se realiza con tres métodos de análisis de series de tiempo que buscan correlaciones ocultas de largo alcance y además proporcionan información de la estructura-evolución del sistema dinámico. Las series de tiempo analizadas son las generadas por el modelo de Fricción Dieterich-Ruina-Stribeck donde ejemplica los desplazamientos relativos entre los bloques tectónicos en contacto. El primer método de análisis es la transformada ondoleta (TO) que da información de la distribución de la energía en los diferentes niveles ondoleta, el segundo método es el análisis de fuctuaciones sin tendencia (DFA por sus siglas en ingles) que da información de la estructura-comportamiento de la serie de tiempo y por último el exponente de Hurst que se utiliza para determinar la persistencia de señales además investiga el comportamiento caótico o auto-similar de series de tiempo."

Article

Modelo de fricción Dieterich-Ruina-Stribeck Wavelet transform DFA Hurst exponent CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA MATEMÁTICAS

Comparing performance on chaos control via adaptive output-feedback

ALEJANDRO RICARDO FEMAT FLORES CRESCENCIO HERNANDEZ ROSALES (2006)

"Performance of four controllers is experimentally compared and evaluated in context of chaos suppression. Four output-feedback controllers are used in experi- ments for comparison. First three schemes utilize an adaptive observer to estimate the states and parameter required for feeding back and with different techniques, which are: (i) feedback linearization, (ii) backstepping, and (iii) sliding mode. The fourth scheme is a (low-parameterized) robust adaptive feedback. A simple class of dynamical systems that exhibit chaotic behavior, called P-class, is considered as benchmark due to involves distinct chaotic systems. The need of comparison is motivated to ask: What is the suitable adaptive scheme to suppress chaos in an specific implementation? Results show a trend on different applications, are illustrated experimentally by means circuits, and are discussed in terms of control effort. This comparative study is important to select a feedback scheme in specific implementations; for example, synchronization of complex networks."

Article

Chaos suppression Adaptive observers Controlled nonlinear dynamics CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA MATEMÁTICAS

Grahp and automata in arterial vascular tree of the kidney

AURORA ESPINOZA VALDEZ ALEJANDRO RICARDO FEMAT FLORES (2009)

"The renal vascular development is not known and occurs through two mechanisms that sometimes overlap: vasculogenesis and angiogenesis. Here we only consider growth through angiogenesis, i.e., the arterial vascular tree of the kidney. There are two types of vascular angiogenesis in development: sprouting and splitting an- giogenesis. We study these processes through mathematical tools. The graphs and automatas allow modeling the vascular growth, can generated tree structures by incorporating the physiological laws of the arterial branching. That is, the graph prescribes topology of the vascular tree and the automaton can include the rule of dynamics in the phenomena of vascularization."

Article

Renal Vasculature Sprouting and Splitting Angiogenesis Graph Theory Automata CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA MATEMÁTICAS

Robust sliding mode‐based extremum‐seeking controller for reaction systems via uncertainty estimation approach

GERARDO LARA CISNEROS ALEJANDRO RICARDO FEMAT FLORES Denis Dochain (2017)

"This paper deals with the design of a robust sliding mode‐based extremum‐seeking controller aimed at the online optimization of a class of uncertain reaction systems. The design methodology is based on an input–output linearizing method with variable‐structure feedback, such that the closed‐loop system converges to a neighborhood of the optimal set point with sliding mode motion. In contrast with previous extremum‐seeking control algorithms, the control scheme includes a dynamic modelling‐error estimator to compensate for unknown terms related with model uncertainties and unmeasured disturbances. The proposed online optimization scheme does not make use of a dither signal or a gradient‐based optimization algorithm. Practical stabilizability for the closed‐loop system around to the unknown optimal set point is analyzed. Numerical experiments for two nonlinear processes illustrate the effectiveness of the proposed robust control scheme."

Article

Extremum-seeking control (Bio)chemical reactors Sliding mode control Uncertain reactionsystems CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA MATEMÁTICAS

A family of multimodal dynamic maps

Eric Campos Cantón Alejandro Ricardo Femat Flores Alexander Pisarchik (2011)

"We introduce a family of multimodal logistic maps with a single parameter. The maps domain is partitioned in subdomains according to the maximal number of modals to be generated and each subdomain contains one logistic map. The number of members of a family is equal to the maximal number of modals. Bifurcation diagrams and basins of attraction of fixed points are constructed for the family of chaotic logistic maps."

Article

Chaos Logistic map Bifurcations CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA MATEMÁTICAS MATEMÁTICAS

An analytical study of the logarithmic mean temperature difference

Estudio analítico de la media logarítmica de diferencia de temperaturas

ARTURO ZAVALA RIO ALEJANDRO RICARDO FEMAT FLORES RAUL SANTIESTEBAN COS (2005)

"La media logarítmica de diferencia de temperaturas (LMTD, por sus siglas en inglés) ha causado inconveniencias en diversas aplicaciones tales como ciertos programas de simulación de procesos. Su forma indeterminada es una de las principales causas de tales inconveniencias. Tal indeterminación es una consecuencia del procedimiento incompleto que generalmente se desarrolla para su obtención en los libros de texto. El análisis dinámico y el diseño de control de intercambiadores de calor a través de modelos de parámetros agrupados que usan la LMTD como fuerza conductora (de intercambio de calor, i.e. diferencia promedio de temperatura entre los fluidos) pueden también ser víctimas de tales inconsistencias. Este trabajo está dedicado a dar una solución a tales inconveniencias a través de un análisis matemático formal de la LMTD. Primero, un procedimiento completo para su obtención es desarrollado, dando como resultado una expresión completa bien definida. Posteriormente, diversas propiedades analíticas de la expresión resultante, tales como la continuidad y la diferenciabilidad en todo su dominio, son probadas. La utilidad de los resultados es comentada a lo largo del texto."

"The logarithmic mean temperature difference (LMTD) has caused inconveniences in several applications like equationoriented flow sheeting programs. Such inconveniences have arisen from its indeterminate form. This is a consequence of the incomplete model derivation generally developed in the textbooks. Heat exchanger dynamic analysis and control synthesis through lumped-parameter models using the LMTD as driving force (fluid mean temperature difference) may suffer from such inconsistencies too. This paper is devoted to give a solution to such inconveniences by providing a formal mathematical treatment of the LMTD. First, a complete derivation is restated resulting in a complete well-defined expression. Then, several interesting analytical properties of the resulting expression, like continuous differentiability on its domain, are proved. The usefulness of the results is highlighted throughout the text."

Article

Media logarítmica de diferencia de temperatura Intercambiadores de calor CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA MATEMÁTICAS