External localization system for mobile robotics

We present a fast and precise vision-based software intended for multiple robot localization. The core component of the proposed localization system is an efficient method for black and white circular pattern detection. The method is robust to variable lighting conditions, achieves sub-pixel precision, and its computational complexity is independent of the processed image size. With off-the-shelf computational equipment and low-cost camera, its core algorithm is able to process hundreds of images per second while tracking hundreds of objects with millimeter precision. We propose a mathematical model of the method that allows to calculate its precision, area of coverage, and processing speed from the camera’s intrinsic parameters and hardware’s processing capacity. The correctness of the presented model and performance of the algorithm in real-world conditions are verified in several experiments. Apart from the method description, we also publish its source code; so, it can be used as an enabling technology for various mobile robotics problems

Nonparametric Edge Detection in Speckled Imagery

We address the issue of edge detection in Synthetic Aperture Radar imagery. In particular, we propose nonparametric methods for edge detection, and numerically compare them to an alternative method that has been recently proposed in the literature. Our results show that some of the proposed methods display superior results and are computationally simpler than the existing method. An application to real (not simulated) data is presented and discussed.Comment: Accepted for publication in Mathematics and Computers in Simulatio

WhyCon: an efficient, marker-based localization system

We present an open-source marker-based localization system intended as a low-cost easy-to-deploy solution for aerial and swarm robotics. The main advantage of the presented method is its high computational efficiency, which allows its deployment on small robots with limited computational resources. Even on low-end computers, the core component of the system can detect and estimate 3D positions of hundreds of black and white markers at the maximum frame-rate of standard cameras. The method is robust to changing lighting conditions and achieves accuracy in the order of millimeters to centimeters. Due to its reliability, simplicity of use and availability as an open-source ROS module (http://purl.org/robotics/whycon), the system is now used in a number of aerial robotics projects where fast and precise relative localization is required

Monte Carlo localization for teach-and-repeat feature-based navigation

This work presents a combination of a teach-and-replay visual navigation and Monte Carlo localization methods. It improves a reliable teach-and-replay navigation method by replacing its dependency on precise dead-reckoning by introducing Monte Carlo localization to determine robot position along the learned path. In consequence, the navigation method becomes robust to dead-reckoning errors, can be started from at any point in the map and can deal with the `kidnapped robot' problem. Furthermore, the robot is localized with MCL only along the taught path, i.e. in one dimension, which does not require a high number of particles and significantly reduces the computational cost. Thus, the combination of MCL and teach-and-replay navigation mitigates the disadvantages of both methods. The method was tested using a P3-AT ground robot and a Parrot AR.Drone aerial robot over a long indoor corridor. Experiments show the validity of the approach and establish a solid base for continuing this work

Habilidades sociais, isolamento e comportamento antissocial em adolescentes em contextos de pobreza

O trabalho explora as habilidades sociais e a presença de comportamentos antissociais, isolamento social e sentimentos de solidão em adolescentes de nível socioeconômico baixo de Tucumán, Argentina. Tratou-se de um estudo descritivo-correlacional, com mostra intencional formado por 106 mulheres e homens escolarizados de 5° e 6° grado. Os instrumentos utilizados foram o BAS-3, o CC-A (Martorell e González, 1992), o CAS (Casullo, 1996) e uma pesquisa sociodemográfica. A análise dos dados realizou-se com o pacote PAWS Statistics 18. Observou-se a prevalência de comportamentos de Consideração pelos demais (M=10.84; DE=2.62), Autocontrole (M=8.74; DE=2.50) e Liderança (M=7.50; DE=2.66) sobre os comportamentos de Isolamento social (M=6.25; DE=2.50) e Retraimento (M=4.38; DE=2.14). Em quanto ao gênero, se encontraram diferenças significativas em Liderança, sendo mais alto em mulheres que em homens (t=2.46, p=0.05).El trabajo explora las habilidades sociales y la presencia de comportamientos antisociales, aislamiento social y sentimientos de soledad en adolescentes de nivel socioeconómico bajo de Tucumán, Argentina. Se trató de un estudio descriptivo-correlacional, con muestreo intencional formado por 106 mujeres y varones escolarizados de 5° y 6° grado. Los instrumentos utilizados fueron el BAS-3, el CC-A (Martorell y González, 1992), el CAS (Casullo, 1996) y una encuesta sociodemográfica. El análisis de los datos se realizó con el paquete PAWS Statistics 18. Se observó la prevalencia de comportamientos de consideración por los demás (M=10.84; DE=2.62), Autocontrol (M=8.74; DE=2.50) y Liderazgo (M=7.50; DE=2.66) sobre los comportamientos de Aislamiento social (M=6.25; DE=2.50) y Retraimiento (M=4.38; DE=2.14). En cuanto al género, se hallaron diferencias significativas en Liderazgo, siendo más alta en mujeres que en varones (t=2.46, p=0.05).The paper explores social skills and the presence of anti-social behavior, social isolation and feelings of loneliness in adolescents of low socioeconomic status from Tucumán, Argentina. It was a descriptive-correlational study using an intentional sampling consisting of 106 school girls and boys from 5° and 6°grade. The instruments used were the BAS-3, the CC-A (Gonzalez & Martorell, 1992), the CAS (Casullo, 1996) and a demographic survey. Data were analyzed with the statistical package PAWS Statistics 18. Results showed the prevalence of behaviors of Consideration for others (M=10.84; S=2.62), Self-control (M=8.74; S=2.50) and Leadership (M=7.50; S=2.66), compared with the social isolation behavior (M=6.25; S=2.50) and withdrawal (M=4.38; S=2.14). Regarding gender, significant differences were found in Leadership, being higher in women than in men (t=2.46, p=0.05)

A simple visual navigation system for an UAV

We present a simple and robust monocular camera-based navigation system for an autonomous quadcopter. The method does not require any additional infrastructure like radio beacons, artificial landmarks or GPS and can be easily combined with other navigation methods and algorithms. Its computational complexity is independent of the environment size and it works even when sensing only one landmark at a time, allowing its operation in landmark poor environments. We also describe an FPGA based embedded realization of the method’s most computationally demanding phase

La distribución G0A en el modelado y análisis de imágenes de radar de apertura sintética

Los datos provenientes de un sistema de iluminación por radiación coherente, como lo son los datos de radar de apertura sintética - SAR (Synthetic Aperture Radar), pueden modelarse con el modelo multiplicativo. Este modelo es muy conveniente para explicar las características estadísticas de estos datos. El retorno multilook en formato amplitud se modela como una variable aleatoria que es el producto de otras dos variables aleatorias independientes. Estas variables aleatorias corresponden al backscatter y al ruido speckle. El modelo para el segundo, para el formato aquí considerado, es universalmente aceptado como la distribución Raiz Cuadrada de Gamma. Por otro lado, el modelo a utilizar para el backscatter solamente dependerá, idealmente, de algunos parámetros que representarán la información disponible a cerca de la rugosidad y de la textura de la imagen. Se pueden utilizar diferentes distribuciones para modelar el backscatter. Esta elección dependerá del grado de homogeneidad presente en las imágenes. Las distribuciones K han sido muy utilizadas para modelar datos que han sido generados por un sistema de iluminación coherente, en particular para imágenes SAR . El modelo multiplicativo clásico postula que el retorno en amplitud de áreas no homogéneas obedece un tipo de distribución K llamado KA. Si el área es homogénea la distribución Γ½ modelará bien los datos y, por ser ésta un caso particular de la anterior, se preserva la validez del modelo KA. Sin embargo, las distribuciones KA no modelan bien los datos provenientes de áreas muy heterogéneas. Se ha propuesto el uso de las llamadas distribuciones Gº, para el modelado de áreas extremamente heterogéneas. En este trabajo se estudia la factibilidad de substituir la distribución KA por la distribución GºA en el ajuste de datos. Con este fin se propondrá una aproximación entre ambas distribuciones. Se verificará que la aproximación de la distribución KA por la distribución GºA tiene sentido práctico, concluyendo que se debe adoptar como verdadero modelo a la distribución GºA

Agresividad y habilidades sociales

La adolescencia ha sido un tema siempre presente en los estudios de las ciencias sociales. Pero en este siglo XXI ha adquirido un progresivo protagonismo. Desde las políticas públicas en Latinoamérica se reconocen avances en salud y educación, aunque persisten desafíos como la prevención de la violencia y comportamientos vinculados a esta, como la agresividad. La agresi- vidad y las habilidades sociales constituyeron el objeto de estudio de este trabajo. Los objetivos fueron: a) Describir las habilidades sociales y el comportamiento agresivo en adolescentes escolarizados de San Miguel de Tucumán (Argentina) de 12 a 17 años, residentes en zona urbana de nivel socio económico bajo. b) Comparar las habilidades sociales y el comportamien- to agresivo según edad, sexo y tipo de familia. Método: se trata de una investigación descriptiva, de tipo no experimental, transversal, con adolescentes de escuelas públicas urbanas de San Miguel de Tucumán (Argentina). La mues- tra estuvo conformada por de 752 casos, seleccionada de manera no probabilística incidental. Los Instrumentos utilizados fueron: Batería de Socialización para adolescentes (BAS-3, Silva y Martorell), Cuestionario de Conducta Antisocial (CC-A, Adaptación Casullo) y una encuesta socio-demográfica. A partir de los resultados se argumenta que es esperable relacionar estilos  de habilidades sociales y una de sus disfunciones, la agresividad, con variables contextuales como sexo, edad y tipo de familia. Los resultados aportan datos para encarar programas de intervención que prevengan comportamientos agresivos, valorando la capacidad para controlar los impulsos y el respeto por las normas sociales. Ello asegurará modos de relación interpersonal saludables que faciliten la inclusión del adolescente en su grupo de referencia.Adolescence has always been a subject of study in the field of social sciences and it has gained increasing importance in the 21st century. Great progress has been acknowledged in the fields of health and education as a result of public policies; however, the prevention of violence and related behaviour, such as aggressiveness, remains a challenge. Aggressiveness and social skills were the object of study of this work. The aims were: a) to describe social skills and aggressive behaviour in 12-to-17-year-old adolescents who attend school in San Miguel de Tucumán (Ar- gentina) and who live in low socioeconomic status urban areas; and b) to compare social skills and aggressive behavior according to age, sex and family type. Method: this is a descriptive, non-experimental and cross-sectional research with adolescents who attend urban state schools from San Miguel de Tucumán (Argentina). The sample consisted of 752 cases, selected in a non-probabilistic and incidental fashion. The instruments used were the Socialization Battery for adolescents (BAS-3, Silva and Martorell), the Antisocial Behavior Questionnaire (CC-A, Casullo Adaptation) and a sociodemographic survey. The results indicate that we can relate social skills’ styles and one of its dysfunctions, aggressiveness, to contextual variables such as sex, age and family type. The results provide information to run intervention programmes that prevent aggressive behaviour, by assessing the ability to control impulses and respect for social norms. This will guarantee ways of healthy interpersonal relations; and therefore, will enable the adolescent’s inclusion in the reference group

Seguimiento de objetos en video usando contornos activos y bounding boxes

El seguimiento de objetos en forma automática a lo largo de una secuencia de imágenes tiene aplicaciones en áreas tan diversas como robótica, animación, sistemas de seguridad o diagnóstico médico. El algoritmo de seguimiento utilizado en este trabajo comienza con la definición de una curva B-Spline que es el área inicial de búsqueda del contorno de un objeto. Luego se consideran una serie de segmentos de rectas normales a esta curva y se aplica algún método de detección de bordes para hallar puntos sobre el contorno a lo largo de las rectas. Para que el algoritmo de seguimiento del objeto sea exitoso es necesario que la estimación inicial sea muy precisa. En este trabajo se presenta un nuevo método estable y eficiente para evitar errores de parametrización al ajustar el contorno del objeto con una curva B-Spline al comienzo del método de seguimiento. Se utiliza una estructura de aceleración para evitar conflictos al estimar el contorno del objeto. El algoritmo modificado se prueba en videos reales y se observan excelentes resultados.The automatic tracking of objects along a sequence of images has applications in different areas as robotics, animation, security systems or medical diagnosis. The tracking algorithm used in this paper starts fitting the contour of an object, using a B-Spline curve as the initial search region. The next step is to sample normal vectors at regularly-spaced points along this curve and to detect points on the border of the object by applying some image-processing filter along the curve normals. A good initial estimate is required for the tracking algorithm to be successful. This paper presents a method to avoid parametrization errors when fitting the outline of the object at the beginning of the tracking. It has the advantage of being simple and efficient. Conflicts when fitting the contour of the object are avoided using an acceleration structure. The modified algorithm is tested against real videos with excellent results.V Workshop de Computación Gráfica, Imágenes Y VisualizaciónRed de Universidades con Carreras en Informática (RedUNCI

A practical multirobot localization system

We present a fast and precise vision-based software intended for multiple robot localization. The core component of the software is a novel and efficient algorithm for black and white pattern detection. The method is robust to variable lighting conditions, achieves sub-pixel precision and its computational complexity is independent of the processed image size. With off-the-shelf computational equipment and low-cost cameras, the core algorithm is able to process hundreds of images per second while tracking hundreds of objects with a millimeter precision. In addition, we present the method's mathematical model, which allows to estimate the expected localization precision, area of coverage, and processing speed from the camera's intrinsic parameters and hardware's processing capacity. The correctness of the presented model and performance of the algorithm in real-world conditions is verified in several experiments. Apart from the method description, we also make its source code public at \emph{http://purl.org/robotics/whycon}; so, it can be used as an enabling technology for various mobile robotic problems