Artículos de conferencia

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1-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.
27-level converter for electric vehicles using only one power supply
(IEEE, 2010) Dixon Rojas, Juan; Pereda Torres, Javier Eduardo
The 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 â€œone-sourceâ€ multilevel system.
3-D CNC trajectory interpolation using Bresenham's algorithm
(IEEE, 1994) Chiang Sánchez, Luciano Eduardo
This article describes a 3D extension of Bresenham's algorithm and its implementation in the linear trajectory interpolation of CNC paths. The resulting algorithm has been successfully applied to a CNC milling machine that uses stepper motors as actuators, resulting in minimal contour errors for a given step motor resolution. A numerical control system that uses the algorithm implementation has been built as part of a wider effort which is to test the feasibility of building or retrofitting machine tools with CNC capabilities at an affordable price tag for a developing country.<>
A 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.
A Blind Calibration Scheme for Switched-Capacitor Pipeline Analog-to-Digital Converters
(IEEE, 2020) Bozzo Jiménez Juan Andrés; Abusleme Hoffman, Ángel Christian; Martinez, J. S.
A foreground calibration algorithm is proposed to digitally self-calibrate a switched-capacitor (SC), pipelined, analog-to-digital converter (ADC). Static errors resulting from capacitor mismatch, charge transfer loss (from limited amplifier dc gain) and variance in Multiplying DAC (MDAC) voltages are estimated and compensated for. The proposed algorithm reuses the electrical components of the pipeline stages to instantiate Î”Î£ converters in the stages' interfaces. By feeding to those converters self-generated input signals and storing the output stream of codes, the algorithm is able to infer the electrical parameters of the reused elements. The algorithm does not require external stimulus or specialized circuitry to be used as true ground but depends on the stages sub-ADC threshold levels precision, diminishing its performance in circuits where error is dominated by sub-ADC input offset. A number of 10-bit ADC's with a mean uncalibrated Effective Number Of Bits (ENOB) of 6.3 bits where simulated, and a resolution improvement between 2.5 bits, for the best case, and 1 bit for the worst, were observed.
A comparison of gradient versus color and texture analysis for lane detection and tracking
(IEEE, 2009) Tapia Espinoza, Rodolfo Antonio; Torres Torriti, Miguel Attilio
Accurate lane detection in real-time is a critical task in autonomous vehicle guidance and lane departure warning for driver assistance. Existing vision-based approaches rely mostly on some analysis of the spatial gradient of the image. However, if the road structure is not regular and well delimited, edges may not be easy to extract and other features must be employed. This paper evaluates the use of color and textural features as a way to improve the standard gradient-based lane detection. Textural features are generated using a bank of Gabor filters. A benefit of using color and texture is that the sky regions of the image, as well as side elements, can be detected. The results obtained from testing the approaches on city roads show that color and texture analysis yields a more accurate road segmentation.
A Comparison of Path Planning Algorithms for Omni-Directional Robots in Dynamic Environments
(IEEE, 2006) Haro, F.; Torres Torriti, Miguel Attilio
The 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
A Container-based IoT-oriented Programmable Logical Controller
(IEEE, 2020) Mellado Aceitón, Jacob Enrique; Núñez Retamal, Felipe Eduardo
The programmable-logical-controller (PLC) has been the key building block of industrial control systems throughout the whole automation revolution, where its role has been mainly to command low-level regulatory feedback control loops. Modernized versions of PLCs aim at facilitating its integration with cloud-based solutions, in the context of the Industrial Internet of Things (IIoT) paradigm. This work is a step forward in this direction and presents a container-based formulation of an IoT-oriented programmable controller, named IoT-PLC, in which each functionality works within a separate container. This IoT-PLC device has regulatory control capabilities, fog-computing functionalities as filtering and field data storage, and multiple wireless interfaces managed independently by individual containers. A virtual device model is used as an abstraction method to represent real entities, and OPC-UA is available for straightforward compatibility with the upper control layers.
A CSP-theoretic Framework of Checking Conformance of Business Processes
(IEEE, 2012) Roy, S.; Bihary, S.; Corso Laos, José Alfonso
In 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.
A customizable collaborative virtual environment on the Web
(IEEE, 1999) Portugal Portugal, Roberto Carlos; Guerrero, Luis A.; Fuller Padilla, David Alfredo
Collaborative 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.
A 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 Walter
There 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.
A Deep Learning Based Behavioral Approach to Indoor Autonomous Navigation
(IEEE, 2018) Sepulveda Villalobos, Gabriel Andres; Niebles, Juan Carlos; Soto Arriaza, Álvaro Marcelo
We 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.
A density-based approach for effective pedestrian counting at bus stops
(IEEE, 2009) García Bunster, Guillermo; Torres Torriti, Miguel Attilio
Accurately counting people waiting at bus stops is essential for automated bus fleet scheduling and dispatch. Estimating the passenger demand in regular open bus stops is a nontrivial problem because of the varying conditions, such as illumination, crowdedness, people poses, to name a few. This paper presents a simple, but very effective approach to estimate the passenger count using people density estimates. People density is obtained from foreground segmentation using a Gaussian mixture background model. A linear model, which is employed to correct the densities due to perspective scaling for people far from the camera position, yields the final people count estimates. The approach is compared to the well-know Viola-Jones detector and shown to yield better people count estimates despite its simplicity, because it is more robust to occlusions, pose changes, and due to the fact that it does not attempt to find body parts. The proposed method is general and can be employed to count people in other public spaces, such as buildings.
A Digital Memristor Emulator for FPGA-Based Artificial Neural Networks
(IEEE, 2016) Vourkas, Ioannis; Abusleme Hoffman, Ángel Christian; Ntinas, Vasileios; Sirakoulis, Georgios C.; Rubio, Antonio
FPGAs 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.
A full compensating system for general loads, based on a combination of thyristor binary compensator, and a PWM-IGBT active power filter
(IEEE, 2001) Dixon Rojas, Juan, 1948-; Del Valle, Yamille; Orchard, Marcos; Ortúzar Dworsky, Micah Etan; Morán, Luis; Maffrand, Carlos
A full compensating system for distribution networks which is able to eliminate harmonics, correct unbalanced loads and generate or absorb reactive power is presented. The system is based on a combination of a thyristor binary compensator (TBC), and a PWM-IGBT active power filter (APF) connected in cascade. The TBC compensates the fundamental reactive power and balances the load connected to the system. The APF eliminates the harmonics and compensates the small amounts of load unbalances or power factor that the TBC cannot eliminate due to its binary condition. The TBC is based on a chain of binary-scaled capacitors and one inductor per phase. This topology allows, with an adequate number of capacitors, a soft variation of reactive power compensation and a negligible generation of harmonics. The capacitors are switched on when the line voltage reaches its peak value, avoiding inrush currents generation. The inductor helps to balance the load, and absorbs reactive power when required. The APF works by measuring the source currents, forcing them to be sinusoidal. The two converters (TBC and APF) work independently, making the control of the system simpler and more reliable. The system is able to respond to many kinds of transient perturbations in no more than a couple of cycles. The paper analyzes the circuit proposed, the way it works and the results obtained under operation with different types of loads.
A 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, Roberto
An 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.<>
A Logarithmic X-Ray Imaging Model for Baggage Inspection: Simulation and Object Detection
(IEEE, 2017) Mery Quiroz, Domingo Arturo; A. K. Katsaggelos
In the last years, many computer vision algorithms have been developed for X-ray testing tasks. Some of them deal with baggage inspection, in which the aim is to detect automatically target objects. The progress in automated baggage inspection, however, is modest and very limited compared to what is needed because X-ray screening systems are still being manipulated by human inspectors. In this work, we present an X-ray imaging model that can separate foreground from background in baggage screening. The model can be used in two main tasks: i) Simulation of new X-ray images, where simulated images can be used in training programs for human inspectors, or can be used to enhance datasets for computer vision algorithms. ii) Detection of (threat) objects, where new algorithms can be employed to perform automated baggage inspection or to aid an user in the inspection task showing potential threats. In our model, rather than a multiplication of foreground and background, that is typically used in X-ray imaging, we propose the addition of logarithmic images. This allows the use of linear strategies to superimpose images of threat objects onto X-ray images and the use of sparse representations in order to segment target objects. In our experiments, we simulate new X-ray images of handguns, shuriken and razor blades, in which it is impossible to distinguish simulated and real X-ray images. In addition, we show in our experiments the effective detection of shuriken, razor blades and handguns using the proposed algorithm outperforming some alternative state-of- the-art techniques.
A Methodology to Obtain a Synthetic Driving Cycle through GPS Data for Energy Analysis
(IEEE, 2015) Naranjo Lourido, W.; Munoz, L. E.; Pereda Torres, Javier Eduardo
This paper proposes a methodology to obtain a synthetic driving cycle by using GPS data as input. The aim is to obtain a driving cycle that is representative of a given condition when used for energy consumption studies. The methodology begins with a data acquisition phase, where an adequate sampling frequency is proposed. Velocity raw data are processed and clustered to capture a mobility global pattern. A synthetic driving cycle is generated from the clustered information using a two level energy model optimization. For a case study, a representative synthetic driving cycle was determined for a Bus Rapid Transit (BRT) route.
A 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.
A Mobile Robotics Course for Undergraduate Students in Computer Science
(IEEE, 2006) Soto Arriaza, Alvaro; Espinace Ronda, Pablo Andrés; Mitnik Asun, Ruben Felipe
A 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

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