Fredy Martínez

Universidad Distrital Francisco José de Caldas | UDISTRITAL · Electric Engineering

Currently, there are saturated frequency bands that affect the quality of service for new users. Cognitive radio provides an alternative solution to this problem through dynamic spectrum access. However, the solutions proposed in the current literature are focused on a centralized network and do not allow demonstrating the behavior in a multi-user...

The professional training model in Colombia is moving from a competency-based approach to learning outcomes. This path is enriched with contributions both at the level of national policies and each institution, as well as the teaching experiences and interests of the students. In this environment, this research presents the impact on the motivation...

The primary goal of this research study is to develop an integrated emotion recognition system for domestic service robots. To build and train the model, this study uses the Dense Convolutional Network (DenseNet) and the Ryerson Audio-Visual Database of Emotional Speech and Song (RAVDESS). The recognition system is composed of two emotion recogniti...

span>Computer simulations are without a doubt a useful methodology that allows to explore research queries and develop prototypes at lower costs and timeframes than those required in hardware processes. The simulation tools used in cognitive radio networks (CRN) are undergoing an active process. Currently, there is no stable simulator that enables...

This research study aims to assess the performance of two predictive spectral decision models (Naïve Bayes and logistic regression) by analyzing interference and prediction quality levels. Real spectral occupancy data are used in two types of scenarios (low traffic and high traffic), based on five metrics: 1) number of total handoffs, 2) number of...

Autonomous mobility remains an open research problem in robotics. This is a complex problem that has its characteristics according to the type of task and environment intended for the robot’s activity. Service robotics has in this sense problems that have not been solved satisfactorily. These robots must interact with human beings in environments d...

The rapid spread of the SARS-CoV-2 virus has highlighted many social interaction problems that favor the spread of disease, particularly airborne spread, which can be addressed by adjusting existing systems. Of particular interest are places where large numbers of people interact, as they become a focus for the spread of these diseases. This paper...

Background: The academic activity of students and professors constitutes the basis of professional training in engineering. Training in electrical engineering has always been of less interest to university students compared to other professional training programs. However, in recent years, this interest has decreased beyond previous trends, an effe...

This paper proposes a minimalist strategy of agent coordination in a multi-robot system with flocking behavior intended for the development of search tasks in dynamic and unknown environments. The minimalist design principle seeks the ability to implement the strategy on small low-cost robots, with hardware limitations, and with small functional va...

A thermal combustion process involves three variables: the fuel (which oxidizes and gives off heat), the comburent (which accelerates combustion), and the heat source. The proportion of these three variables determines the behavior of the process, and in the case of industrial production, their control is fundamental to guarantee continuity, quanti...

Traditionally, power electronics has been a complex training field for undergraduate students in the electrical area of the Universidad Distrital Francisco José de Caldas. In this course, multiple theories and concepts are difficult to assimilate due to the distance from other program courses and the complexity of conceptualizing abstract elements....

Banana cultivation is an important source of economic income for several developing countries, with economies heavily dependent on their agricultural production. Such is the case of Colombia, a banana export country in which much of its production is still carried out by small peasant families without a high degree of modernization. The plant is qu...

Este libro presenta los avances en la investigación de los potenciales energéticos de la biomasa en Colombia, como recurso proveniente de actividades de origen agropecuario y de los residuos sólidos urbanos, que son susceptibles de ser transformados en bioenergía; por tanto, se considera a la biomasa, no como un residuo sino como un subproducto con...

Sign languages (or signed languages) are languages that use visual techniques, primarily with the hands, to transmit information and enable communication with deaf-mutes people. This language is traditionally only learned by people with this limitation, which is why communication between deaf and non-deaf people is difficult. To solve this problem...

Online education was the alternative used worldwide to provide continuity with training processes in higher education institutions during the confinement generated by the Covid-19 pandemic. The objective of this work is to analyze and identify the characteristics of connectivity and the level of acceptance linked to online learning by students of t...

Service robots are characterized by autonomously performing indoor tasks in unstructured environments, this condition of the environment prevents the prior programming of the map, which requires reactive behavior. These robots require real-time and cost-effective identification of obstacles in the environment, which includes not only distance infor...

This paper proposes a solution for the problem of continuous prediction in real-time of the emotional state of a human user from the identification of characteristics in facial expressions. In robots whose main task is the care of people (children, sick or elderly people) is important to maintain a close relationship man-machine, anld a rapid respo...

This paper evaluates the performance of the Neural Architecture Search Network (NASNet) in the automatic detection of COVID-19 (Coronavirus Disease 2019) from chest x-ray images. COVID-19 is a disease caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) that produces in patients fever, cough, shortness of breath, muscle pain, sput...

This paper presents a low cost strategy for real-time estimation of the position of obstacles in an unknown environment for autonomous robots. The strategy was intended for use in autonomous service robots, which navigate in unknown and dynamic indoor environments. In addition to human interaction, these environments are characterized by a design c...

Cognitive radio networks emerge as a solution to fixed allocation issues and spectrum scarcity through the dynamic access to spectrum. In cognitive networks, users must make intelligent decisions based on spectrum variation and actions taken by other users. Under this dynamic, cooperative systems can significantly improve quality of service paramet...

This paper proposes a strategy for the coordination of a swarm of robots in an unknown environment. The basic idea is to achieve the autonomous movement of the group from an initial region to a target region avoiding obstacles. We use a behavior model similar to bacterial Quorum Sensing (QS) as a technique for the coordination of robots. This behav...

This work deals with a smart visual assisted manipulation algorithm, for an assistant robot. The algorithm is divided in two parts: Object visual position feedback, and whole body motion computation. The object position feedback is based on image analysis to define coordinates in R3 space, and provide a reference to the robot about the object local...

The objective of this article is to present a review of techniques based on artificial intelligence for the decision-making process in cognitive radio networks. The cognitive radio networks emerged as a solution to solve the problems of fixed allocation and scarcity of spectrum, work with a management model called the cognitive cycle. Decision maki...

This paper uses K-means clustering as a strategy to determine the minimum, average and maximum reactive power ranges required by an industrial plant for the design of its power factor (PF) solution. The strategy calculates three cluster points in the sensed power data set. The analysis is carried out by comparing the consumption of reactive power a...

The level of autonomy and intelligence of a robot is a fundamental characteristic of tasks related to service robotics, particularly due to its interaction with human environments. These environments tend to change constantly over time (dynamic environments) so a mapping turns out to be inefficient in the long run. A service robot must be able to p...

A direct data-driven path planner for small autonomous robots is a desirable feature of robot swarms that would allow each agent of the system to directly produce control actions from sensor readings. This feature allows to bring the artificial system closer to its biological model, and facilitates the programming of tasks at the swarm system level...

Path planning is a very important problem in robotics, especially in the development of Automatic Guided Vehicles (AGVs). These problems are usually formulated as search problems, so many search algorithms with a high level of intelligence are evaluated to solve them. We propose a navigation algorithm based on bacterial swarming from a simplified m...

This paper proposes a navigation scheme for robots in indoor environments which uses real-time analysis of raw data captured by an infra-red sensor. The infra-red sensor captures distance data in real time producing a large database that the robot analyzes according to previous experiences to directly define its movement strategy. Observing the dep...

Objectives: To design and implement a totally-functional 4-bit didactic processor, in order to be applied as a tool for improving the learning process of students of microprocessors courses, and to be used as a base for future applications. Methods/Analysis: This work was reached through the application of a final course project in microprocessor a...

Context: The control and navigation systems of autonomous robots constitute a dynamic field of research in robotics. The possible solutions to problems are often evaluated with laboratory prototypes in order to determine their real performance. We propose in this paper an architecture for the design and development of robotic systems (particularly...

Contexto: Los sistemas de control y navegación de robots autónomos constituyen un dinámico campo de investigación en robótica. Los esquemas y estrategias propuestos como posible solución a problemas se evalúan siempre sobre prototipos de laboratorio a fin de determinar su desempeño real. Se propone en este artículo una arquitectura para el diseño y...

This article shows the implementation of the cryptographic algorithm "Present" in both software and hardware embedded platforms, for which measurements of the performance results of the implementation of the algorithm are performed on the different microcontrollers and also on FPGA type programmable logic devices. Encryption and decryption function...

Context: Electric power generation systems designed as a point solution to supply needs away from the power grid typically make use of the energy resources available in the area. These systems are custom designed to supply a specific need, and with high efficiency criteria in mind. A fundamental element in these systems are the batteries charge and...

Similarity distance measures are used to study the similarity between patterns. We propose the use of similarity measures between images to estimate the quality of combustion in a furnace designed for carbonization processes in the production of activated carbon. Broadly speaking, the production of activated carbon requires two thermal processes: c...

InvestIgacIón RESUMEN Contexto: El sistema visual del ser humano es ca-paz de un elevado nivel de procesamiento de imá-genes y extracción de información; por otro lado, muchos procesos de toma de decisiones se soportan en el análisis visual como herramienta primaria. Se propone, por lo tanto, un esquema de segmentación de imágenes de acuerdo al col...

This paper shows the results of the automatic design of a generic heat sink, through a morphogenesis algorithm done in Matlab. This algorithm is based on two-dimensional fractal images, generated by Lindenmayer systems, which create the heat sink shape. Those shapes iteratively evolve through a genetic algorithm in order to maximize their heat diss...

Professional training in engineering is traditionally deductive. Under this approach, curriculum and its development are designed to start with a first stage of theoretical foundation, then, and progressively interact with the application of that theory. However, given the high labor requirements in terms of specific knowledge and skills, and the d...

In the technological formation of students, specially for Technology and Electronic Engineering at the District University Francisco José de Caldas of Colombia, South America, it is required that students in addition of the theorical bases and the use of tools possess skills in implementation of real applications, where the use of mathematics in da...

This paper shows the use of an embedded robotic platform of low cost and high performance, hand in hand with problem-based learning strategies, to professional training in Electrical Engineering at the District University Francisco José de Caldas (Colombia). These technical training and research tools involves several innovations, among which stand...

Contexto: La asignación de espectro en las redes de radio cognitiva es un aspecto clave para reducir la latencia, incrementar la tasa de datos, aumentar el ancho de banda, mejorar la capacidad y cobertura, y optimizar el uso del espectro, garantizando la calidad de servicio necesaria para aplicaciones de tiempo-real y mejor-esfuerzo. Objetivo: Este...

Context: Spectrum allocation in cognitive radio networks is a key aspect to reduce latency, increase data rate, increase bandwidth, improve capacity and coverage, and optimize the use of the spectrum, guaranteeing the quality of service required applications and best-effort and real-time.Objective: This paper aims to present a review of the algorit...

Se presenta un modelo para el estudio, análisis, diseño y evaluación de navegación colectiva multi-agente para robots autónomos basado en comportamientos observados en bacterias. El sistema consiste de un conjunto de agentes sencillos (bacterias artificiales), los cuales a través de lecturas e interacciones locales se auto-organizan para navegar a...

We present a model for the study, analysis, design and evaluation of collective multi-agent navigation for autonomous robots based on behaviors observed in bacteria. The system consists of a set of simple agents (artificial bacteria), which through readings and local interaction are self-organized to navigate along the environment. Given the parall...

For the further research on passive/active walking control, an anthropomorphic mechanical prototype for a bipedal robot consisting of 10 DOF (degree of freedom) is represented in this article. Based on the concept that a robot that works and interacts with humans must interact with environments designed for humans, we propose a biped robot mechanic...

We present a grasp control scheme for an anthropomorphic multi-fingered robotic hand (kinematic structure similar to the human hand) with five fingers and 15 DOF that use different control surfaces according to the system state and the expected response. The responses of each surface are combined into a single structure using a fuzzy control scheme...

InvestIgacIón Resumen Este artículo propone como solución para el meca-nizado de materiales metálicos, una fuente eléctrica resonante, la cual se emplea en el proceso denomi-nado mecanizado por descarga eléctrica (EDM). La fuente se compone de tres etapas: una de alimenta-ción DC, un inversor resonante y un circuito eléctri-co que emula la descarga...

In robotics, one of multiplies problems in the last few years has been the study of the strategies to find the navigation path (path planning) of the mobile robots in statics and observable conditions. This is an open problem without predefined rules (Non Heuristic), which requiring measuring of the environment, found useful information, and to use...

InvestIgacIón Resumen Para la futura investigación sobre el control de la marcha pasiva/activa, se representa en este artículo un prototipo mecánico de un robot antropomórfico bípedo que consta de 10 DOF (grado de libertad). Partiendo del concepto de que un robot que trabaje e interactúe con el ser humano debe interactuar con ambientes diseñados pa...

This paper proposes a technique and an algorithm used to build a device for people identification through the processing of a low resolution camera image. The infrared channel is the only information needed, sensing the blood reaction with the proper wave length, and getting a preliminary snapshot of the vascular map of the back side of the hand. T...

One of most worked issues in the last years in robotics has been the study of strategies to path planning for mobile robots in static and observable conditions. This is an open problem without pre-defined rules (non-heuristic), which needs to measure the state of the environment, finds useful information, and uses an algorithm to select the best pa...

This article details the development and evaluation of an autonomous acoustic localization system for robots based on Time Delay Estimation (TDE) and signal intensity, principally aimed at robotic service applications. Time Delay Estimation is carried out through an arrangement of two microphones. The time delay criteria are supported with the sign...

Se expone un estudio realizado en el municipio de Icononzo (Colombia), que evalúa la viabilidad técnica y económica de utilizar energías alternativas para el suministro de energía eléctrica en el hospital de dicho municipio. La investigación se centra en la comparación de los recursos renovables (solar y eólico), determinando la energía aprovechab...

The visual tracking is a feature of great importance for an artificial autonomous system that interfaces with the environment. It is also an open research problem of great activity in the field of computer vision. In this paper a minimalist tracking system for autonomous robots, designed primarily for navigation tasks, is proposed. The concept of m...

In recent years, much research has been devoted to the analysis, modeling and design of multi-agent robotic systems. Such systems are composed of a set of simple agents that self-organize to perform a task. Given the parallel structure, also happens to be a very robust solution. This paper focuses on the development of a behavioral model of each ag...

This paper proposes a geometric strategy for generating optimal navigation paths for robots in static and observable environments. As design principles for the algorithm, robustness, simplicity and low computational cost were established. The algorithm uses image segmentation into regions as architecture support. These regions are constructed from...

Resumen The navigation system of mobile robot should have the capability of environment cognition, action decision, motion control, and state monitoring. This paper proposes a prediction algorithm route based on Voronoi diagrams, applicable for mobile robots with range sensors operating in indoor and unknown environments. The proposed control law...

p>Este artículo de investigación ataca el problema de la navegación robótica autónoma basada en sistemas de visión artificial en tiempo real. Como una primera aproximación a un sistema de visión artificial que permita la navegación del robot, se ha desacoplado el módulo sensor e implementado como una unidad independiente sobre un pequeño robot dife...