Miguel Strefezza

Bio: Miguel Strefezza is an academic researcher from Simón Bolívar University. The author has contributed to research in topics: Control theory & Fuzzy logic. The author has an hindex of 6, co-authored 21 publications receiving 101 citations.

A web‐based virtual laboratory for teaching automatic control

Abstract: This paper describes a web-based virtual laboratory that improves the automatic control teaching of undergraduate courses. This is achieved by optimizing the time the students spend in the real laboratory. The virtual world or three-dimensional scenes of real laboratory plants gives the students the opportunity to “learning by doing” through web-based systems at the location they want, and at the time they like. This virtual laboratory gives the students the tools to be more prepared and therefore, use the time more efficiently and effectively when working in the real laboratory plant. The student does not require the installation of special software on his remote computer; only need a common VRML enabled browser. An example of a developed virtual laboratory of interconnected tanks is presented. © 2007 Wiley Periodicals, Inc. Comput Appl Eng Educ. 15: 192–197, 2007; Published online in Wiley InterScience (www.interscience.wiley.com); DOI 10.1002/cae.20111

Multi-objective pole placement with evolutionary algorithms

Abstract: Multi-Objective Evolutionary Algorithms (MOEA) have been succesfully applied to solve control problems. However, many improvements are still to be accomplished. In this paper a new approach is proposed: the Multi-Objective Pole Placement with Evolutionary Algorithms (MOPPEA). The design method is based upon using complex-valued chromosomes that contain information about closed-loop poles, which are then placed through an output feedback controller. Specific cross-over and mutation operators were implemented in simple but efficient ways. The performance is tested on a mixed multi-objective H2/H∞ control problem.

Una visión en la evolución de las nociones de confiabilidad y mantenimiento en la civilización occidental desde la antigüedad hasta finales de los años cuarenta del siglo XX

Abstract: Este articulo es un trabajo documental, cuyo objetivo principal es establecer que los conocimientos teorico-practico adquiridos por sociedades humanas en forma continua desde la antiguedad, han conformado el significado, aplicacion y uso de la confiabilidad y el mantenimiento, reflejandolo en disenos de infraestructuras, sistemas, equipos, componentes y procesos, asi como en modelos especificos de gestion de activos y acciones planificadas sistematicamente en el tiempo para preservar esos activos, minimizando sus fallas funcionales y mejorando sus condiciones operacionales durante los ciclos de vida esperados. La metodologia de trabajo se centro en investigar y correlacionar, el conocimiento y uso de la confiabilidad y el mantenimiento como resultado de un proceso de aprendizaje continuo y sistematico. Finalmente en los anos cuarenta del siglo XX, naciones, instituciones y organizaciones dedican recursos a formalizar, documentar y recopilar los conocimientos y aprendizajes adquiridos en el diagnostico de fallas, la valoracion de la confiabilidad y el desempeno de activos, incluyendo ademas mejoras en los modelos de gestion y administracion de recursos dedicados al mantenimiento. Se concluye que el desarrollo del conocimiento y uso de la confiabilidad y el mantenimiento, independientemente de la epoca facilitara el lograr mejoras en la productividad, minimizar riesgos y promover calidad de vida.

Fuzzy variable structure controller for a three-phase rectifier with power factor correction

Abstract: This work presents an alternative, the design of a fuzzy variable structure controller to have the line current in phase with the line voltage of a three-phase rectifier. This control strategy combines fuzzy and sliding mode control algorithms. Few fuzzy rules are used for this scheme. The fuzzy controller parameters are adjusted by using the VSC for a better response and robustness. The simulations of the three-phase rectifier with controlled current are carried out on a DSP and the result with the control scheme presented here offer higher robustness, it is easier to adjust and implement.

Virtual and remote labs in education

Abstract: Laboratory experimentation plays an essential role in engineering and scientific education. Virtual and remote labs reduce the costs associated with conventional hands-on labs due to their required equipment, space, and maintenance staff. Furthermore, they provide additional benefits such as supporting distance learning, improving lab accessibility to handicapped people, and increasing safety for dangerous experimentation. This paper analyzes the literature on virtual and remote labs from its beginnings to 2015, identifying the most influential publications, the most researched topics, and how the interest in those topics has evolved along the way. To do so, bibliographical data gathered from ISI Web of Science, Scopus and GRC2014 have been examined using two prominent bibliometric approaches: science mapping and performance analysis. Display Omitted Laboratory experimentation plays an essential role in engineering and sci-entific education.Virtual and remote labs are emerging as a valuable alternative to conven-tional hands-on labs.This paper analyzes the literature on virtual and remote labs from 1993 to 2015.4405 records retrieved from ISI Web of Science, Scopus and GRC2014 are processed.Two bibliometric approaches are applied: performance analysis and science mapping.

Decoupled control using neural network-based sliding-mode controller for nonlinear systems

Abstract: In this paper, an adaptive neural network sliding-mode controller design approach with decoupled method is proposed. The decoupled method provides a simple way to achieve asymptotic stability for a class of fourth-order nonlinear system. The adaptive neural sliding-mode control system is comprised of neural network (NN) and a compensation controller. The NN is the main regulator controller, which is used to approximate an ideal computational controller. The compensation controller is designed to compensate for the difference between the ideal computational controller and the neural controller. An adaptive methodology is derived to update weight parts of the NN. Using this approach, the response of system will converge faster than that of previous reports. The simulation results for the cart-pole systems and the ball-beam system are presented to demonstrate the effectiveness and robustness of the method. In addition, the experimental results for seesaw system are given to assure the robustness and stability of system.

Multicriteria Optimization in Engineering Design

Abstract: An engineering design optimization problem can be formulated as a search of the solution space for which the relationships among various groups of attributes are given. The search can be also conducted for a multicriteria optimization. The paper discusses three classes of problems associated with multicriteria optimization in engineering design. First, multicriteria optimization methods with a single domination relationship are reviewed. Next, such methods with many domination functions are discussed. The last part of the paper focuses on the search when the ideal solution, or solutions, are known, but they are infeasible and the solutions sought should come as close as possible.