Search

Quienes conocimos a Emiliana de Zubeldía en el desarrollo de su vida laboral en la Universidad de Sonora, fuimos testigos de su entrega total. Su trabajo no decayó durante los últimos años de su vida. En esta biografía testimonial hemos recopilado las voces del pasado; no solamente de quienes fueron sus alumnos sino también las de sus hermanos y de quienes escucharon sus conciertos desde América del Sur hasta llegar a México a integrar una historia que es parte de la universidad misma, lugar que Emiliana eligió para trabajar casi cuarenta años de su vida, dedicada a la enseñanza de la música, a la formación de concertistas y a promover actividades que elevaran el nivel cultural de la comunidad universitaria, de la ciudad de Hermosillo y el de las diferentes entidades que visitó con sus pianistas y su coro. Entre tantas voces destaca la voz de la propia Emiliana vertida en sus escritos y en los documentos de trabajo en los que plasmó sus programas de enseñanza musical y las teorías pedagógicas de sus maestros: Blanche Selva y Désiré Pâque. También contribuyó a la creación de la música contemporánea mexicana al componer obras basadas en el Sistema natural de la música, desarrollado por Augusto Novaro. Decía Emiliana: Cuando una persona sabe ver lo bello, tiene el camino allanado; y si lo bello no existe [cerca suyo], entonces tiene que crearlo con su fantasía. En esto coincide con la afirmación central de la destacada filósofa María Zambrano, contemporánea y coetánea suya quien, en su libro Claros del bosque, define la belleza como una necesidad fundamental del ser humano para realizarse en plenitud.

This paper pursues the construction of a valid strong Lyapunov function for second-order sliding mode algorithms, usually employed for control, observation, and differentiation purposes. The developed solution is based on combining convex representations of such algorithms with the direct Lyapunov method, which leads to stability conditions expressed in the form of linear matrix inequalities. The proposed methodology enlarges the set of gains for which the algorithms are guaranteed stable in prior literature.

Chitosan fibers were prepared by wet spinning in three stages. Initially, a polymer solution of chitosan and polyvinyl alcohol (PVA) was solidified in a mixture of potassium hydroxide and ethanol. The polymers were then crosslinked with sodium tripolyphosphate (TPP) or glutaraldehyde, and finally dried in methanol or acetone. The effect of these conditions was evaluated based on scanning electron microscopy images, water-holding capacity, and swelling and mechanical properties. The miscibility of the mixture was evaluated using Fourier Transform Infrared spectroscopy and differential scanning calorimetry. The results obtained showed that chitosan fibers containing 45% (v/v) PVA and crosslinked using TPP have properties similar to those of commercial sutures prepared using other biomaterials.

This paper deals with the design of robust regulation for both angular speed stability enhancement and voltage in synchronous generator machines with an excitation control system. The designed controller is based on the block control technique combined with a sliding-mode (SM) control approach. The block control is used to design a nonlinear sliding manifold with the desired stability property. In order to attenuate the chattering effect which can appear in the presence of the exciter's unmodeled dynamics, a high-order SM algorithm and a robust exact differentiator are employed. The efficiency of the proposed controller, i.e., robustness and high accuracy, is verified via simulations.

In this paper, a control strategy is proposed for robust stabilization of nonlinear perturbed plants in the presence of actuator unmodeled dynamics. The block control technique is applied to design a nonlinear SM manifold for achieving the error tracking, and High Order Sliding Mode (HOSM) algorithm is implemented to ensure finite time convergence of the state vector to the designed SM manifold. A robust exact differentiator is designed to obtain the estimates of the sliding variable and its derivatives. The proposed method is applied to design robust controllers for a power electric system in the presence of the exciter system unmodeled dynamics.

The problem of angular velocity of rotor and voltage control in synchronous generator machines is considered. As a robust solution of this problem the block control technique with sliding mode is proposed. The physical implementations of the proposed control law for the real synchronous machines results in chattering due to the presence of exciter unmodelled dynamics. In order to reduce the chattering effect we design high order sliding mode controllers and exact sliding mode differentiators, ensuring the robustness of the closed-loop system.

This paper presents a novel sliding surface design for uncertain linear systems. The proposed approach is twofold inspired: on the one hand, it acknowledges the increasing interest of the sliding control community to formulate their problems in terms of linear matrix inequalities since they are efficiently solved via convex optimization techniques; on the other hand, it incorporates recent developments based on Finsler's Lemma for Lyapunov-based design. It is shown that former results are included as particular cases of the new approach. Illustrative examples are provided.

This paper extends to H ∞ performance design a recent local approach for non-quadratic stabilization of continuous-time Takagi-Sugeno (TS) models based on the fuzzy Lyapunov function (FLF). The main obstacle for using FLFs altogether with TS models consists in handling the time-derivatives of the membership functions (MFs). By reducing global stability goals via local considerations, the aforementioned impediment has been removed leading to stabilization domains where H ∞ disturbance rejection is guaranteed. Conditions are expressed as linear matrix inequalities (LMIs), thus enabling systematic and efficient solutions which are solved by convex optimization techniques.

The dynamics of the most of the industrial plants (for example electric power system, electromechanical system, electro-hydraulic system and so on) are highly nonlinear and, moreover, include actuator dynamics which increase the relative degree of the complete system. To stabilize the plant dynamics it is naturally to applied some feedback linearization (FL) technique: block control [18], backstepping [14] or input-output linearization [11], since the model of these plants can be presented in the nonlinear block controllable form or (the same) strict-feedback one. All these control techniques require to calculate the time derivatives of the plant dynamics vector fields (Lie derivatives), results in a computationally expensive control algorithm, and moreover, the closed-loop system is susceptible to plant parameter variations and disturbances. To simplify the control algorithm the actuator fast dynamics are usually skipped, and to overcome the robust problem the sliding mode (SM) control [25] in combination with FL technique [18], [17] can be can be applied. However, the presence of the actuator unmodeled fast dynamics can destroy the desired behavior of the SM control systems causing lost of robustness and accuracy and provoking the chattering effect [25], [8]. Therefore, the problem of control design for the systems with unmodeled actuator dynamics becomes to be a big challenge.

The synchronous generators have a natural different time scale dynamics. That is why for modeling and control design in such systems the methods of singular perturbations are widely used. In this paper the possibilities of sliding mode control design for synchronous generators are analyzed. With this aim the concept of singular perturbation is revised in order to use it for relay control system with a discontinuous slow-motion integral manifold. Obtained results are used for variable structure control of synchronous generator.

The synchronous generators have a natural different time scale dynamics. That is why for modeling and control design in such systems the methods of singular perturbations are widely used. In this paper the possibilities of sliding mode control design for synchronous generators are analyzed. With this aim the concept of singular perturbation is revised in order to use it for relay control system with a discontinuous right hand side. The obtained results are used for variable structure control of synchronous generator.