Colecciones Institucionales
Permanent URI for this community
Browse
Browsing Colecciones Institucionales by browse.metadata.fuente "IEEE"
Now showing 1 - 20 of 313
Results Per Page
Sort Options
- Item1-D memristor-based cellular automaton for pseudo-random number generation(IEEE, 2017) Karamani, Rafailia Eleni; Ntinas, Vasileios; Vourkas, Ioannis; Sirakoulis, Georgios C.Cellular Automata (CAs) is a well-known parallel, bio-inspired, computational model. It is based on the capability of simpler, locally interacting units, i.e. the CAs cells, to evolve in time, giving rise to emergent computation, suitable to model physical system behavior, prediction of natural phenomena and multi-dimensional problem solutions. Moreover, at the same time CAs constitute a promising computing platform, beyond the von Neumann architecture. In this paper, a memristor device is considered to be the basic module of a CA cell circuit implementation, performing as a combined memory and processing element to implement CA-based circuits, able to model sufficiently systems and applications as mentioned above, targeting tentatively to a more energy efficient design compared to the conventional electronics. In particular and as a proof of concept, the results of elementary CAs modeling and simulation for the generation of pseudo-random numbers are presented using a 1-D memristor-based CAs array to illustrate the robustness and the efficacy of the proposed computing approach.
- Item23-Level Inverter for Electric Vehicles Using a Single Battery Pack and Series Active Filters(IEEE, 2012) Pereda Torres, Javier Eduardo; Dixon, JuanCascaded H-bridge (CHB) multilevel inverters have been conceived as an alternative to reduce total harmonic distortion (THD) in medium-voltage drives. The reduced THD makes them useful for electric vehicle (EV) applications, but the main problem with the CHB is the large amount of isolated power sources required to feed each of the H-bridges. An improved variant known as the asymmetrical CHB (ACHB) inverter uses H-bridges of different sizes and then needs fewer isolated power sources than the CHB. However, in battery-powered EVs, only one power supply (fuel cell or battery pack) is desirable. This work presents a solution to solve the problem, operating some of the small H-bridges (Aux-bridges) as series active filters and using a small high-frequency link (HFL). With this solution, only one dc source is required to feed the inverter, and if the control is adjusted to work at particular switching points, more than 98% of power is transferred through the larger H-bridges (MAIN bridges). The proposed ACHB topology can produce any number of levels, and the M AIN bridges always commutate at fundamental frequency. As the number of levels must remain constant for all output voltages, a variable dc source is required to control the amplitude of the motor voltage. This work shows some simulations and experiments on a 2-kW 27-level ACHB working with only 23 levels. The concept is being implemented in a small EV with an ACHB drive of 18 kW.
- Item27-level converter for electric vehicles using only one power supply(IEEE, 2010) Dixon Rojas, Juan; Pereda Torres, Javier EduardoThe main advantage of asymmetrical multilevel inverters is the optimization of levels with a minimum number of power supplies. However, this optimized multilevel system still needs a large number of isolated and floating DC supplies, which makes these converters complicated to implement in electric vehicles (EVs), because the system will require many independent battery packs. In this paper, a very simple scheme, based on a small and cheap high frequency link (HFL), allows the utilization of only one power supply for the complete multilevel inverter drive, with an inherent regulation of the voltages supplied among the H-bridges. It also allows voltage control with full number of levels if the DC power supply is of variable voltage characteristic. This work is focused on a 27-level asymmetric inverter but the strategy, using only one power supply, can be applied to converters with any number of levels. In particular, an asymmetrical 27-level converter needs nine isolated power supplies and the proposed system reduces these nine sources to only one: the battery car. The topology also permits full regenerative braking working as a three-level converter. The proposed system is intended for application in electric vehicles from power ratings up to 150 kW. Simulations and experimental results show the feasibility to implement this “one-source†multilevel system.
- Item3D Quantification of Wall Shear Stress and Oscillatory Shear Index Using a Finite-Element Method in 3D CINE PC-MRI Data of the Thoracic Aorta(2016) Sotelo Parraguez, Julio Andrés; Urbina, Jesus; Valverde, Israel; Tejos Nunez, Cristian Andres; Irarrázaval Mena, Pablo; Andia Kohnenkampf, Marcelo Edgardo; Uribe Arancibia, Sergio A.; Hurtado Sepúlveda, DanielSeveral 2D methods have been proposed to estimate WSS and OSI from PC-MRI, neglecting the longitudinal velocity gradients that typically arise in cardiovascular flow, particularly on vessel geometries whose cross section and centerline orientation strongly vary in the axial direction. Thus, the contribution of longitudinal velocity gradients remains understudied. In this work, we propose a 3D finite-element method for the quantification of WSS and OSI from 3D-CINE PC-MRI that accounts for both in-plane and longitudinal velocity gradients. We demonstrate the convergence and robustness of the method on cylindrical geometries using a synthetic phantom based on the Poiseuille flow equation. We also show that, in the presence of noise, the method is both stable and accurate. Using computational fluid dynamics simulations, we show that the proposed 3D method results in more accurate WSS estimates than those obtained from a 2D analysis not considering out-of-plane velocity gradients. Further, we conclude that for irregular geometries the accurate prediction of WSS requires the consideration of longitudinal gradients in the velocity field. Additionally, we compute 3D maps of WSS and OSI for 3D-CINE PC-MRI data sets from an aortic phantom and sixteen healthy volunteers and two patients. The OSI values show a greater dispersion than WSS, which is strongly dependent on the PC-MRI resolution. We envision that the proposed 3D method will improve the estimation of WSS and OSI from 3D-CINE PC-MRI images, allowing for more accurate estimates in vessels with pathologies that induce high longitudinal velocity gradients, such as coarctations and aneurisms.
- ItemA baseline restorer for charge-sensitive amplifiers in a 500-nm CMOS process(IEEE, 2018) Abusleme Hoffman, Ángel Christian; Barraza Altamirano, Renzo Ignacio; Kuleshov, S.Charge-sensitive amplifiers (CSAs), widely used as front-ends in pulse processors for capacitive detectors, require a feedback network to set the operation point, deal with leakage currents and restore the baseline voltage upon the arrival of signals. Passive feedback networks are simple and reliable solutions that accomplish the task, but cannot modify the operation point in order to accommodate an input with different polarity, and do not offer sufficient flexibility to deal with a wide range of leakage current or input rates. The Krummenacher feedback solves these drawbacks at the cost of a large compensation capacitor, which is required for stability purposes. In this work, a novel configurable feedback network is presented. Based on the same principle as the Krummenacher network, this circuit relies on the design parameters to ensure stability. This work shows analysis, design and test results from a recent implementation in a 500-nm CMOS process.
- ItemA Compact Answer Set Programming Encoding of Multi-Agent Pathfinding(IEEE, 2021) Gómez Araya, Rodrigo Nicolás Teófilo; Hernández, Carlos; Baier Aranda, Jorge AndrésMulti-agent pathfinding (MAPF) is the problem of finding k non-colliding paths connecting k given initial positions with k given goal positions on a given map. In its sum-of-costs variant, the total number of moves and wait actions performed by agents before they definitely reach the goal is minimized. Not surprisingly, since MAPF is combinatorial, a number of compilations to Boolean Satisfiability (SAT) and Answer Set Programming (ASP) exist. In this article, we describe in detail the first family of compilations to ASP that solve sum-of-costs MAPF over 4-connected grids. Compared to existing ASP compilations, a distinguishing feature of our compilation is that the number of total clauses (after grounding) grow linearly with the number of agents, while existing compilations grow quadratically. In addition, the optimization objective is such that its size after grounding does not depend on the size of the grid. In our experimental evaluation, we show that our approach outperforms search-based sum-of-costs MAPF solvers when grids are congested with agents. We also show that our approach is competitive with a SAT-based approach when follow conflicts are taken into account. We also explore the potential of our solver when finding makespanoptimal solutions, in which makespan is minimized first and then cost is minimized. Our results show that makespan-optimal solutions are slightly suboptimal in most benchmarks. Moreover, our MAPF solver, when run in that mode, is faster and scales better.
- ItemA Comparison of Path Planning Algorithms for Omni-Directional Robots in Dynamic Environments(IEEE, 2006) Haro, F.; Torres Torriti, Miguel AttilioThe scope of this paper is to analyze and compare three path planning methods for omni-directional robots, which are based on a) the bug algorithm, b) the potential fields algorithm, and c) the A* algorithm for minimum cost path with multiresolution grids. The approaches are compared in terms of computational costs and the resulting path lengths. Results obtained indicate that the bug algorithm is a suitable choice for this type of application as its computational cost is lower than that of the other methods. Furthermore, minor modifications of the standard bug algorithm, such as the tangent following modification, allow the path planner to handle well the situations encountered in typical multi-robot environments
- ItemA CSP-theoretic Framework of Checking Conformance of Business Processes(IEEE, 2012) Roy, S.; Bihary, S.; Corso Laos, José AlfonsoIn this paper, we tackle the problem of conformance checking which verifies if the event logs (observed) match/fit the reference (arbitrary) process. We use concepts from Communicating Sequential Processes (CSP), which facilitates automated analysis using PAT toolkit. By this technique one can identify all the logs which cannot be properly replayed on the process. We illustrate our approach with an example. Finally, we introduce some metrics based on conformance checking. They are related to fitness, closeness, and appropriateness of the event logs vis-a-vis reference process models.
- ItemA customizable collaborative virtual environment on the Web(IEEE, 1999) Portugal Portugal, Roberto Carlos; Guerrero, Luis A.; Fuller Padilla, David AlfredoCollaborative virtual environments (CVE) support the collaboration, communication and social interaction among users in virtual spaces. We present a customizable CVE implemented on top of the Web that allows for the creation of various interactive environments. This CVE is designed mainly, from the perspective of the desk, rooms and hall metaphors. The architecture of our CVE is based on design patterns and integrates a group of tools in order to support interaction among users in both synchronous and asynchronous ways.
- ItemA DAC reconstruction filter for narrowband long distance Communications(IEEE, 2014) Aldunate Varela, Joaquín Pablo; Feres Ducci, Carlos Jose; Vlahoyiannatos, Spyros; Oberli Graf, Christian Robert; de Villers-Grandchamps Zaldivar, Jean-Paul Idesbald; Guarini Hermann, Marcelo WalterThere are applications that require long-range, low data rate and low power consumption communications that could be implemented with wireless sensor networks equipped with multiple antennas. We are implementing a transceiver for that purpose. The transceiver requires a specific reconstruction filter which isn't commercially available for our target technology, XFAB XH018. An integrated active DAC reconstruction filter was designed and implemented on the target technology using Synopsys design tools. This document present the design, implementation and testing of the reconstruction filter. The filter achieved the design requirements.
- ItemA Deep Learning Based Behavioral Approach to Indoor Autonomous Navigation(IEEE, 2018) Sepulveda Villalobos, Gabriel Andres; Niebles, Juan Carlos; Soto Arriaza, Álvaro MarceloWe present a semantically rich graph representation for indoor robotic navigation. Our graph representation encodes: semantic locations such as offices or corridors as nodes, and navigational behaviors such as enter office or cross a corridor as edges. In particular, our navigational behaviors operate directly from visual inputs to produce motor controls and are implemented with deep learning architectures. This enables the robot to avoid explicit computation of its precise location or the geometry of the environment, and enables navigation at a higher level of semantic abstraction. We evaluate the effectiveness of our representation by simulating navigation tasks in a large number of virtual environments. Our results show that using a simple sets of perceptual and navigational behaviors, the proposed approach can successfully guide the way of the robot as it completes navigational missions such as going to a specific office. Furthermore, our implementation shows to be effective to control the selection and switching of behaviors.
- ItemA Digital Memristor Emulator for FPGA-Based Artificial Neural Networks(IEEE, 2016) Vourkas, Ioannis; Abusleme Hoffman, Ángel Christian; Ntinas, Vasileios; Sirakoulis, Georgios C.; Rubio, AntonioFPGAs are reconfigurable electronic platforms, well-suited to implement complex artificial neural networks (ANNs). To this end, the compact hardware (HW) implementation of artificial synapses is an important step to obtain human brain-like functionalities at circuit-level. In this context, the memristor has been proposed as the electronic analogue of biological synapses, but the price of commercially available samples still remains high, hence motivating the development of HW emulators. In this work we present the first digital memristor emulator based upon a voltage-controlled threshold-type bipolar memristor model. We validate its functionality in low-cost yet powerful FPGA families. We test its suitability for complex memristive circuits and prove its synaptic properties in a small associative memory via a perceptron ANN.
- ItemA Framework for Transmission Expansion Planning: A Complex Problem Clouded by Uncertainty(IEEE, 2016) Velásquez Guerino, Constantin Sebastián Klaus; Watts Casimis, David; Rudnick van de Wyngard, Hugh; Bustos Sölch, Cristián PabloTransmission Expansion Planning (TEP), a complex problem that is vital to ensure the proper functioning of restructured electricity markets, is clouded by uncertainties. Timely and cost-effective transmission expansion is necessary for providing secure and reliable electricity service to customers, enhancing competition, and ensuring market efficiency in electricity markets. Given the irreversibility and long lifetimes of transmission investments, TEP requires addressing uncertainties on future system conditions several years ahead. Because of these fundamental properties of transmission, the importance of developing tools and models to assist power system planning under uncertainty has long been recognized. As any decision under uncertainty is made before the uncertainty is revealed, addressing uncertainties allows hedging against risks caused by the outcomes of decisions taken under uncertainty.
- ItemA fuzzy logic based model computes cardiac output from the radial arterial pressure waveform(IEEE, 1994) Urzua Urzua, Jorge; Guarini Hermann, Marcelo Walter; Cipriano, Aldo; Matus Acuña, Marcelo Enrique; Lee, J.; Salinas, C.; Olmedo Hidalgo, Juan Carlos; Lema F., Guillermo; Canessa, RobertoAn interactive scheme for the development of a fuzzy logic based model has been implemented and applied to build a model that is able to determine cardiac output from radial arterial pressure. It was built using as input radial pressure waveforms from patients in whom cardiac output was simultaneously measured by thermodilution. The scheme was programmed in C language in an Apollo workstation under Unix. Input variables were area under the curve, ratio between systolic and diastolic pressure, and pulse frequency. To determine fuzzy sets and membership functions the authors used 149 pressure waveforms. To test the model, the authors used 6 waveforms not used in building the model. Correlation between predicted cardiac output with measured flow was 0.98.<>
- ItemA fuzzy-controlled active front-end rectifier with current harmonic filtering characteristics and minimum sensing variables(1999) Dixon Rojas, Juan; Contardo, J. M.; Morán, L. A.A control strategy which allows conventional voltage-source current-controlled (VSCC) pulsewidth modulation (PWM) rectifiers to work simultaneously as active power filters is presented. The proposed control strategy also allows compensating the system power factor and compensating unbalanced loads. The measurement and/or calculation of the harmonics and reactive power are not required, making the proposed control scheme very simple. The active front-end rectifier acts directly on the mains line currents, forcing them to be sinusoidal and in phase with the mains voltage supply. To improve the dynamic of the system, the amplitude of the current is controlled by a fuzzy system, which adjusts the DC-link voltage of the PWM rectifier. The strategy is based on connecting all the polluting loads between the PWM rectifier and their input current sensors. The main advantages of this approach are the following: (1) there is no need to install a specially dedicated active power filter; (2) it also works simultaneously as a power factor compensator; and (3) no special and complicated calculations are required for harmonic elimination. The viability of the proposed active front-end rectifier is proved by simulation and with experimental results obtained from a 2 kVA PWM prototype.
- ItemA low-cost altitude control system for the Kadet Senior radio-controlled airplane(2003) Abusleme Hoffman, Ángel Christian; Cipriano, Aldo; Guarini Hermann, Marcelo WalterIn automatic control education, real examples always improve students' learning and motivation. Considering this fact, a hardware-in-the-loop, low-cost altitude control system for a radio-controlled (RC) airplane has been developed to improve automatic control education. This system constitutes a high-impact demonstrator for teaching automatic control topics, applied to a real-life problem. The airplane has an altitude sensor; students can safely remotely control this variable in a computer real-time environment. This paper addresses the system analysis and description, controller design, and real demonstrations. This device was tested in a basic automatic control course for undergraduate electrical engineering students and received good results; students reacted with curiosity and enthusiasm and encouraged the lecturers to design more experiences like this one.
- ItemA Mobile Cloud Shared Workspace to Support Lessons-Learned in Construction Companies(IEEE, 2014) Nuñez, D.; Neyem, A.; Sepúlveda Cárdenas, Marcos Daniel; Serpell, A.; Ferrada, X.Construction is a project-based industry, and for each project, companies have to cope with specific challenges. Nevertheless, most of these challenges are similar to each other and share many common elements. Thus, projects are an important source of expert know-how and organizational knowledge, but lessons learned in each one are not systematically incorporated into the design and construction phases of subsequent projects. Typically, construction companies do not have effective tools to make an appropriate transfer of this valuable knowledge for future projects. Therefore, shared workspaces could play an important role to do this by increasing communication among workers, organizing work more efficiently, reducing the coordination cost, and keeping an updated overview of the project. This paper presents a mobile cloud shared workspace to support knowledge management along each project. The platform is the result of the research and development work conducted by the authors, supported by a construction company, during the last two years.
- ItemA Mobile Robotics Course for Undergraduate Students in Computer Science(IEEE, 2006) Soto Arriaza, Alvaro; Espinace Ronda, Pablo Andrés; Mitnik Asun, Ruben FelipeA first generation of mobile robots able to cope with the high uncertainty of natural environments is starting to emerge. As a consequence, there is an increasing need for theoretical and practical courses that can formally teach the state of the art of the technology. This paper describes our experience teaching a mobile robotics course as part of our computer science curriculum for undergraduate students. The course has a strong experimental part, where the goal is to provide the students with a set of hand-on experiences using real mobile robots. In particular, we show how using a simple differential drive mobile platform and a low cost visual sensor, it is possible to teach the topics that are currently most relevant to the area of mobile robot programming for autonomous navigation. The course starts by illustrating low level control routines, such as locomotion, and simple behaviors, such as obstacle avoidance and target tracking in non-structured environments. Then, as the course moves to higher level tasks such as localization and mapping, the real world becomes too complex and a more structured world is needed. A structured world, called MazeWorld is then presented where we are able to illustrate high level topics using limited perception capabilities. In addition to the main parts of the class, we also describe the perception algorithms that we developed to achieve autonomous navigation in non-structured environments and in MazeWorld. Our experience indicates that the course is highly motivating for the students. They are able to reinforce several topics from the computer science curriculum and they learn the basis for advanced coursework, research, and the development of applications in robotics and related fields, such as, artificial intelligence and computer perception
- ItemA model based fault detection and diagnosis system for rolling mill equipments(IEEE, 2001) Orchard, M. C.; Cipriano, A. M.; Cipriano, Aldo; Viale, M.; Vigliocco, A.In this paper, the implementation of a Model Based Fault Detection and Diagnosis System, that uses fuzzy logic to determinate the nature of the detected faults in rolling mill equipments is presented. The system is built with 4 components which work independently. An Identification module estimates the parameters of a continuous domain second order transfer function model for the process by analyzing the step response. A Predictive model module generates the controlled variable residual which is statistically analyzed in a Detection module. The results of the statistical analysis are fuzzified and processed in a Diagnosis module to determine detected fault's nature. The system is tested using real operation data of a main motor process in order to detect and classify abnormalities into Operation Point Change (OPC) or Process Fault (PF) alarms.
- ItemA model of internal control may improve the response time of an automatic arterial pressure controller(IEEE, 2000) Urzua Urzua, Jorge; Sauma Santis, Enzo Enrique; Cipriano, Aldo; Guarini Hermann, Marcelo WalterA simplified model for the arterial pressure control system was implemented on a personal computer using Matlab Simulink(R). Model responses to variations of systemic vascular resistance were comparable to those predicted by physiology. Computer simulation suggested that including this model of the internal pressure control system within the design of an external controller would achieve better arterial pressure control and faster response than previous systems.