Grasping unknown objects in clutter by superquadric representation

© 20xx IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.In this paper, a quick and efficient method is presented for grasping unknown objects in clutter. The grasping method relies on real-time superquadric (SQ) representation of partial view objects and incomplete object modelling, well suited for unknown symmetric objects in cluttered scenarios which is followed by optimized antipodal grasping. The incomplete object models are processed through a mirroring algorithm that assumes symmetry to first create an approximate complete model and then fit for SQ representation. The grasping algorithm is designed for maximum force balance and stability, taking advantage of the quick retrieval of dimension and surface curvature information from the SQ parameters. The pose of the SQs with respect to the direction of gravity is calculated and used together with the parameters of the SQs and specification of the gripper, to select the best direction of approach and contact points. The SQ fitting method has been tested on custom datasets containing objects in isolation as well as in clutter. The grasping algorithm is evaluated on a PR2 robot and real time results are presented. Initial results indicate that though the method is based on simplistic shape information, it outperforms other learning based grasping algorithms that also work in clutter in terms of time-efficiency and accuracy.Peer ReviewedPostprint (author's final draft

Singularity-free computation of quaternions from rotation matrices in E4 and E3

A real orthogonal matrix representing a rotation in E4 can be decomposed into the commutative product of a left-isoclinic and a right-isoclinic rotation matrix. The double quaternion representation of rotations in E4 follows directly from this decomposition. In this paper, it is shown how this decomposition can be performed without divisions. This avoids the common numerical issues attributed to the computation of quaternions from rotation matrices. The map from the 4×4 rotation matrices to the set of double unit quaternions is a 2-to-1 covering map. Thus, this map cannot be smoothly inverted. As a consequence, it is erroneously assumed that all inversions should necessarily contain singularities that arise in the form of quotients where the divisor can be arbitrarily small. This misconception is herein clari¿ed. When particularized to three dimensions, it is shown how the resulting formulation outperforms, from the numerical point of view, the celebrated Shepperd’s method.Peer ReviewedPostprint (author's final draft

On Cayley's factorization with an application to the orthonormalization of noisy rotation matrices

The final publication is available at link.springer.comA real orthogonal matrix representing a rotation in four dimensions can be decomposed into the commutative product of a left- and a right-isoclinic rotation matrix. This operation, known as Cayley's factorization, directly provides the double quaternion representation of rotations in four dimensions. This factorization can be performed without divisions, thus avoiding the common numerical issues attributed to the computation of quaternions from rotation matrices. In this paper, it is shown how this result is particularly useful, when particularized to three dimensions, to re-orthonormalize a noisy rotation matrix by converting it to quaternion form and then obtaining back the corresponding proper rotation matrix. This re-orthonormalization method is commonly implemented using the Shepperd-Markley method, but the method derived here is shown to outperform it by returning results closer to those obtained using the Singular Value Decomposition which are known to be optimal in terms of the Frobenius norm.Peer ReviewedPostprint (author's final draft

Cosmological black holes and the direction of time

Macroscopic irreversible processes emerge from fundamental physical laws of reversible character. The source of the local irreversibility seems to be not in the laws themselves but in the initial and boundary conditions of the equations that represent the laws. In this work we propose that the screening of currents by black hole event horizons determines, locally, a preferred direction for the flux of electromagnetic energy. We study the growth of black hole event horizons due to the cosmological expansion and accretion of cosmic microwave background radiation, for different cosmological models. We propose generalized McVittie co-moving metrics and integrate the rate of accretion of cosmic microwave background radiation onto a supermassive black hole over cosmic time. We find that for flat, open, and closed Friedmann cosmological models, the ratio of the total area of the black hole event horizons with respect to the area of a radial co-moving space-like hypersurface always increases. Since accretion of cosmic radiation sets an absolute lower limit to the total matter accreted by black holes, this implies that the causal past and future are not mirror symmetric for any spacetime event. The asymmetry causes a net Poynting flux in the global future direction; the latter is in turn related to the ever increasing thermodynamic entropy. Thus, we expose a connection between four different "time arrows": cosmological, electromagnetic, gravitational, and thermodynamic.Comment: 13 pages, 2 figures in Foundations of Science (2017

COLANTA: un éxito del modelo cooperativo

El éxito de la cooperativa COLANTA es reconocido incluso a nivel internacional debido a sus resultados económicos -- El presente documento presenta un acercamiento desde la óptica administrativa para analizar su estilo gerencial y determinar su influencia en el logro de dichos resultados -- Para eso se conoce su evolución histórica y la existencia de una estrategia, que se evalúa desde la óptica de la estrategia emergente -- Para lograrlo se realiza un marco teórico que contextualiza al lector en el ámbito del modelo cooperativo, conociendo un poco de historia, su naturaleza y razón de ser, los elementos componentes y las normas que lo regulan en Colombia, tomando así una oportunidad para crear un documento de estudio útil a la comunidad estudiantil en un país donde aún falta mucha enseñanza en esta materia -- Ya en contexto, se analizan los hallazgos de múltiples entrevistas realizadas a personas que durante su vida profesional tuvieron un fuerte impacto en COLANTA, enunciando hechos históricos relevantes y las acciones que significan el desarrollo y crecimiento de la empresa hasta consolidarse como la primera lechera del país, analizando la influencia del modelo gerencial en estos resultados, evaluando la estrategia aplicada y su naturaleza hasta exponer las razones del éxito del modelo y algunos ejemplos en los que se apreci

Comunicación organizacional: Propuestas de intervención y experiencias en entornos jujeños

En este trabajo recuperamos aspectos que tuvieron que ver con el dictado del Seminario “Comunicación Institucional. Perspectivas metodológicas y revisión crítica”, impartido en la UCSE-DASS en agosto/septiembre de 2011. Su desarrollo ha sido motivador de algunas reflexiones en relación al campo específico de la comunicación organizacional en Jujuy. En ese sentido buscamos en la semiótica la forma de generar algún aporte concreto para una metodología específica en comunicación organizacional, focalizando, principalmente, los procesos de comunicación interna. Esto alineado con la idea de que el afianzamiento de la comunicación organizacional en los ámbitos jujeños depende de cómo sepamos fundamentar su valor. El trabajo pretende entonces realizar un aporte en ese sentido, planteando los beneficios que la semiótica puede ofrecer. Incluimos algunos desarrollos específicos para tener en cuenta el crecimiento de los signos en una organización, por lo que retomamos, principalmente, el concepto de signo desde los planteos de Charles Sanders Peirce. También hacemos referencia a la necesidad de considerar un conjunto de operaciones específicas para el análisis de las organizaciones, y, finalmente, la interpretación propiamente dicha. Consideramos que esta perspectiva contribuye al estudio de procesos de cambio y transformación de las organizaciones, brindando la posibilidad de incorporar la complejidad necesaria para el entendimiento global de esos procesos.Fil: González Pérez, Carlos Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Periodismo y Comunicación Social; Argentina. Universidad Nacional de Jujuy; Argentin