Caracterización, Modelado y Diseño de Sensores Táctiles Piezorresistivos

Un sensor táctil es un dispositivo con el que se obtiene información del entorno mediante el contacto con él. Su implementación se basa en distribuir una serie de unidades sensoriales de fuerza, a las que denominamos tácteles, de forma matricial; de modo que al contactar con un objeto se detecta la distribución de fuerzas, su forma, su orientación, etc. El campo de aplicación de estos sensores es muy amplio, por ejemplo en medicina, robótica, o tele-presencia, siendo especialmente necesarios en entornos complejos, no estructurados o peligros. En el presente trabajo se proponen diferentes sensores basados en polímeros piezorresistivos, cuya estructura se basa en una matriz flexible de electrodos sobre la que se coloca una lámina de un material electro-activo que disminuye su resistencia con el aumento de la presión aplicada. Se analizan y caracterizan los sensores, que están orientados a aplicaciones de gran área con tecnologías de bajo coste. Para la elaboración de las matrices de electrodos se utilizan dos tecnologías: una placa de circuito impreso sobre un sustrato flexible (tecnología PCB), y técnicas de serigrafía sobre un sustrato plástico (tecnología screen-printing). Los sensores fabricados se caracterizan desde el punto de vista de su respuesta, evaluando parámetros como la sensibilidad, la linealidad, la histéresis, el tiempo de respuesta, la deriva y la dispersión; y analizando también la influencia que ciertos factores de diseño, como el tamaño y geometría de los electrodos, o la conductividad del material activo, tienen sobre estas características. Para los sensores fabricados con la tecnología de screen-printing (construidos mediante la superposición de capas de diferentes materiales) se propone un método de control de la sensibilidad y rango en base a la constante elástica de dos de las capas. Para explicar los resultados experimentales se hace uso de una herramienta de análisis de elementos finitos y del modelo de Winkler, que permite modelar las rugosidades en la interfaz de contacto entre los electrodos y el material piezorresistivo. Por otro lado, se proponen, diseñan y fabrican dos estructuras que superpuestas a los sensores anteriores les dotan de la capacidad de detectar fuerzas tanto normales como tangenciales. Las componentes de las fuerzas tangenciales se obtienen del desequilibrio de fuerzas que registran los tácteles del sensor que hace de base. Ambas propuestas se analizan con una herramienta de análisis de elementos finitos. Además, se muestran resultados experimentales de los prototipos fabricados para ilustrar su viabilidad. Por último, se describe un trabajo concreto de fabricación de un sensor de gran área para cubrir el brazo de un robot de rescate haciendo uso de elementos discretos de fuerza comerciales (FSR). En él se proponen, implementan y evalúan algunas estrategias de diseño que mejoran la respuesta de los FSR. De todo el trabajo desarrollado, se adquiere un conocimiento acerca de cómo abordar el diseño de este tipo de sensores táctiles y de aquellos realizados con tecnologías similares, extrayendo conclusiones y reglas de diseño básicas. Así mismo, se describen las diversas plataformas de test para los sensores táctiles que han sido fabricadas y que en su conjunto constituyen una infraestructura automatizada de caracterización, muy útil para futuros trabajos

Two proposals to simplify resistive sensor readout based on Resistance-to-Time-to-Digital conversion

Direct Interface Circuits (DICs) are simple circuits used in readouts for all types of sensors. For resistive sensors, all DICs perform a resistance-to-time-to-digital conversion using just the sensor, some calibration resistors, one or two capacitors, and a Digital Processor. These circuits require a variable number of charging and discharging cycles of a capacitor to estimate the sensor resistance, Rx, increasing both acquisition time and power consumption. This paper presents two resistive DICs capable of estimating Rx by means of a single charging-discharging process, simplifying the readout process. Furthermore, this is achieved without increasing hardware requirements. Only two time measurements are used to obtain Rx. Despite the simplicity of the new circuits, the experimental results show that relative errors of estimating Rx can be below 0.8 %, and this in a wide range of resistances of over 40 dB. Moreover, acquisition time and energy consumption can be reduced by up to 75 %.Funding for open access charge: Universidad de Málaga / CBUA. This work was supported by the Spanish Government under contract PID2021-125091OB-I0

Three Realizations and Comparison of Hardware for Piezoresistive Tactile Sensors

Tactile sensors are basically arrays of force sensors that are intended to emulate the skin in applications such as assistive robotics. Local electronics are usually implemented to reduce errors and interference caused by long wires. Realizations based on standard microcontrollers, Programmable Systems on Chip (PSoCs) and Field Programmable Gate Arrays (FPGAs) have been proposed by the authors for the case of piezoresistive tactile sensors. The solution employing FPGAs is especially relevant since their performance is closer to that of Application Specific Integrated Circuits (ASICs) than that of the other devices. This paper presents an implementation of such an idea for a specific sensor. For the purpose of comparison, the circuitry based on the other devices is also made for the same sensor. This paper discusses the implementation issues, provides details regarding the design of the hardware based on the three devices and compares them.This work has been partially funded by the Spanish Government under contracts TEC2006-12376 and TEC2009-14446

A Large Area Tactile Sensor Patch Based on Commercial Force Sensors

This paper reports the design of a tactile sensor patch to cover large areas of robots and machines that interact with human beings. Many devices have been proposed to meet such a demand. These realizations are mostly custom-built or developed in the lab. The sensor of this paper is implemented with commercial force sensors. This has the benefit of a more foreseeable response of the sensor if its behavior is understood as the aggregation of readings from all the individual force sensors in the array. A few reported large area tactile sensors are also based on commercial sensors. However, the one in this paper is the first of this kind based on the use of polymeric commercial force sensing resistors (FSR) as unit elements of the array or tactels, which results in a robust sensor. The paper discusses design issues related to some necessary modifications of the force sensor, its assembly in an array, and the signal conditioning. The patch has 16 × 9 force sensors mounted on a flexible printed circuit board with a spatial resolution of 18.5 mm. The force range of a tactel is 6 N and its sensitivity is 0.6 V/N. The array is read at a rate of 78 frames per second. Finally, two simple application examples are also carried out with the sensor mounted on the forearm of a rescue robot that communicates with the sensor through a CAN bus

Three Realizations and Comparison of Hardware for Piezoresistive Tactile Sensors

Tactile sensors are basically arrays of force sensors that are intended to emulate the skin in applications such as assistive robotics. Local electronics are usually implemented to reduce errors and interference caused by long wires. Realizations based on standard microcontrollers, Programmable Systems on Chip (PSoCs) and Field Programmable Gate Arrays (FPGAs) have been proposed by the authors for the case of piezoresistive tactile sensors. The solution employing FPGAs is especially relevant since their performance is closer to that of Application Specific Integrated Circuits (ASICs) than that of the other devices. This paper presents an implementation of such an idea for a specific sensor. For the purpose of comparison, the circuitry based on the other devices is also made for the same sensor. This paper discusses the implementation issues, provides details regarding the design of the hardware based on the three devices and compares them

DESARROLLO MODULAR DE UN MODELO GENÉRICO PARA LA DOMÓTICA MEDIANTE COMUNICACIÓN INALÁMBRICA BASADA EN EL PROTOCOLO ZIGBEE

ResumenEn este artículo se presenta el desarrollo y los resultados de un proyecto de investigación aplicada, vigente en el Departamento de Ingeniería Eléctrica y Electrónica del Instituto Tecnológico de Oaxaca.El proyecto consiste en integrar componentes de hardware y software para crear un sistema en domótica, que gestione los sensores y actuadores de manera inalámbrica mediante una red de equipos basados en el protocolo ZigBee perteneciente al grupo de Estándares del IEEE 802.15.4 en el área de redes inalámbricas personales(WPAN), utilizando la frecuencia de 2.4 GHz, en este se utilizan distintas herramientas tecnológicas para su implementación, digitalización, cuantificación, y transmisión; hasta llevar esos datos a un controlador que tiene la capacidad de generar el monitoreo y seguridad en nuestros hogares. El modelo de la arquitectura del proyecto corresponde a una topología estrella, en esta se establece el coordinador de la red, el cual con la instalación de sensores configurados con Arduino se manipularán con los dispositivos XBee, permitiendo así la creación de los circuitos y programación de los sensores.Palabras Claves: automatización, control, coordinador, monitoreo, señales. AbstractThis article describes the development and the results of a research project applied force at the Department of Electrical and Electronic Engineering Institute of Technology of Oaxaca.The project is to integrate hardware and software to create a system in home automation, which manages the sensors and actuators wirelessly through a network based on ZigBee protocol equipment belonging to the group of IEEE 802.15.4 standars in equipment wireless personal area networks (WPAN) using the 2.4 Ghz frequency in which various technological tools for implementation, digitization, quantification, and transmission are used; to bring that data to a controller that has the ability to generate monitoring and safety in our homes. The model of the project architecture corresponds to a star topology, where the network coordinator, which with installing configured with Arduino will be handled with XBee sensor devices is established, enabling the creation of circuits and programming sensors.Keywords: automation, control, coordinator, monitoring, signals

Tactile Sensors Based on Conductive Polymers

This paper presents results from a selection of tactile sensors that have been designed and fabricated. These sensors are based on a common approach that consists in placing a sheet of piezoresistive material on the top of a set of electrodes. We use a thin film of conductive polymer as the piezoresistive mate¬rial. Specifically, a conductive water-based ink of this polymer is deposited by spin coating on a flexible plastic sheet, giving it a smooth, homogeneous and conducting thin film. The main interest in this procedure is that it is cheap and it allows the fabrication of flexible and low cost tactile sensors. In this work we present results from sensors made using two technologies. Firstly, we have used a flexible Printed Circuit Board (PCB) technology to fabricate the set of electrodes and addressing tracks. The result is a simple, flexible tactile sensor. In addition to these sensors on PCB, we have proposed, designed and fabricated sensors with screen printing technology. In this case, the set of electrodes and addressing tracks are made by printing an ink based on silver nanoparticles. The intense characterization provides us insights into the design of these tactile sensors.This work has been partially funded by the spanish government under contract TEC2006-12376-C02

Acondicionamiento sostenible de la vivienda de interés social, como medio saludable para los habitantes. Caso de estudio Urbanización Tierra Tayrona en Bosa, Bogotá D.C.

Trabajo de InvestigaciónLa vivienda como el espacio de mayor permanencia de las personas, se configura como el lugar en donde el cuerpo es mas vulnerable a enfermedades, en la sostenibilidad se identifican estrategias que mejoran los espacios construidos, como herramienta de transformación a partir del concepto de Biofilia; Permitir procesos y elementos naturales en el entorno construido genera un mejor estado de salud.INTRODUCCIÓN 1. GENERALIDADES 2. ESTADO DEL ARTE 3. MARCO TEÓRICO 4. METODOLOGÍA 5. RESULTADOS 6. ANÁLISIS DE RESULTADOS 7. CONCLUSIONES BIBLIOGRAFÍAMaestríaMagíster en Diseño Sostenibl

Oral Anticoagulation and Risk of Symptomatic Hemorrhagic Transformation in Stroke Patients Treated With Mechanical Thrombectomy: Data From the Nordictus Registry

Introduction: We aimed to evaluate if prior oral anticoagulation (OAC) and its type determines a greater risk of symptomatic hemorrhagic transformation in patients with acute ischemic stroke (AIS) subjected to mechanical thrombectomy. Materials and Methods: Consecutive patients with AIS included in the prospective reperfusion registry NORDICTUS, a network of tertiary stroke centers in Northern Spain, from January 2017 to December 2019 were included. Prior use of oral anticoagulants, baseline variables, and international normalized ratio (INR) on admission were recorded. Symptomatic intracranial hemorrhage (sICH) was the primary outcome measure. Secondary outcome was the relation between INR and sICH, and we evaluated mortality and functional outcome at 3 months by modified Rankin scale. We compared patients with and without previous OAC and also considered the type of oral anticoagulants. Results: About 1.455 AIS patients were included, of whom 274 (19%) were on OAC, 193 (70%) on vitamin K antagonists (VKA), and 81 (30%) on direct oral anticoagulants (DOACs). Anticoagulated patients were older and had more comorbidities. Eighty-one (5.6%) developed sICH, which was more frequent in the VKA group, but not in DOAC group. OAC with VKA emerged as a predictor of sICH in a multivariate regression model (OR, 1.89 [95% CI, 1.01–3.51], p = 0.04) and was not related to INR level on admission. Prior VKA use was not associated with worse outcome in the multivariate regression model nor with mortality at 3 months. Conclusions: OAC with VKA, but not with DOACs, was an independent predictor of sICH after mechanical thrombectomy. This excess risk was associated neither with INR value by the time thrombectomy was performed, nor with a worse functional outcome or mortality at 3 months

Application of the Generalized Normal Distribution Optimization Algorithm to the Optimal Selection of Conductors in Three-Phase Asymmetric Distribution Networks

This article addresses the problem of the optimal selection of conductors in asymmetric three-phase distribution networks from a combinatorial optimization perspective, where the problem is represented by a mixed-integer nonlinear programming (MINLP) model that is solved using a master-slave (MS) optimization strategy. In the master stage, an optimization model known as the generalized normal distribution optimization (GNDO) algorithm is proposed with an improvement stage based on the vortex search algorithm (VSA). Both algorithms work with discrete-continuous coding that allows us to represent the locations and gauges of the different conductors in the electrical distribution system. For the slave stage, the backward/forward sweep (BFS) algorithm is adopted. The numerical results obtained in the IEEE 8- and 27-bus systems demonstrate the applicability, efficiency, and robustness of this optimization methodology, which, in comparison with current methodologies such as the Newton metaheuristic algorithm, shows significant improvements in the values of the objective function regarding the balanced demand scenario for the 8- and 27-bus test systems (i.e., 10.30% and 1.40% respectively). On the other hand, for the unbalanced demand scenario, a reduction of 1.43% was obtained in the 27-bus system, whereas no improvement was obtained in the 8-bus grid. An additional simulation scenario associated with the three-phase version of the IEEE33-bus grid under unbalanced operating conditions is analyzed considering three possible load profiles. The first load profile corresponds to the yearly operation under the peak load conduction, the second case is associated with a daily demand profile, and the third operation case discretizes the demand profile in three periods with lengths of 1000 h, 6760 h, and 1000 h with demands of 100%, 60% and 30% of the peak load case. Numerical results show the strong influence of the expected demand behavior on the plan’s total costs, with variations upper than USD/year 260,000.00 between different cases of analysis. All implementations were developed in the MATLAB® programming environment