Analysis and Simulation of the Leg of an Hexapod Robot for Remote Exploration

The locomotion system is determined by the terrain conditions. The aim of this paper is to introduce the characteristics and simulation of a hexapod legged robot that can be easily used for exploration of abrupt and harsh terrains, Jike the Rio Tinto environment. A walking robot seems like the best option for this kind of terrain. Some of the advantages are that they do not need continuous terrain, they have less problems with sliding and they also have greater capacity to overcome obstacles as they produce Jess harm to the environment that the scientist wants to explore on the contrary when faced with mechanical design they present a design challenge, also in the static and dynamic analysis problem of a legged robot, there is a high complexity that has to be taken into account. This paper shows how to easily cope with the analysis of hexapod robot movement based on a design developed by the Center of Astrobiology INTA-CSIC for operation in RioTinto (Huelva - Spain)

The Double Hierarchy Method: a parallel 3D contact method for the interaction of spherical particles with rigid FE boundaries using the DEM

The final publication is available at Springer via http://dx.doi.org/10.1007/s40571-016-0109-4In this work, we present a new methodology for the treatment of the contact interaction between rigid boundaries and spherical discrete elements (DE). Rigid body parts are present in most of large-scale simulations. The surfaces of the rigid parts are commonly meshed with a finite element-like (FE) discretization. The contact detection and calculation between those DE and the discretized boundaries is not straightforward and has been addressed by different approaches. The algorithm presented in this paper considers the contact of the DEs with the geometric primitives of a FE mesh, i.e. facet, edge or vertex. To do so, the original hierarchical method presented by Horner et al. (J Eng Mech 127(10):1027–1032, 2001) is extended with a new insight leading to a robust, fast and accurate 3D contact algorithm which is fully parallelizable. The implementation of the method has been developed in order to deal ideally with triangles and quadrilaterals. If the boundaries are discretized with another type of geometries, the method can be easily extended to higher order planar convex polyhedra. A detailed description of the procedure followed to treat a wide range of cases is presented. The description of the developed algorithm and its validation is verified with several practical examples. The parallelization capabilities and the obtained performance are presented with the study of an industrial application example.Peer ReviewedPostprint (author's final draft

Editorial

Editoria

Design and validation of rockfall protection systems by numerical modeling with discrete elements

Rockfall protection systems are installed in order to preserve civil infrastructures against landslides and falling rocks. For the evaluation of these systems,one of the main problems is the difficulty to develop laboratory tests, since landslides and falling rocks are unpredictable events that involve the movement of large masses of material over several meters or evenkil-ometers. For this reason, the use of numerical methods, which allows reproducing full-scale situations without the need of laboratory devices or sliding materials, has become more popular. The study presented in this document shows theapplication of the Discrete Element Method (DEM) for the analysis of the behavior of one of the most popular rockfall protection systems, flexible metallic fences.Postprint (published version

PFEM–DEM for particle-laden flows with free surface

The final publication is available at Springer via http://dx.doi.org/10.1007/s40571-019-00244-1This work proposes a fully Lagrangian formulation for the numerical modeling of free-surface particle-laden flows. The fluid phase is solved using the particle finite element method (PFEM), while the solid particles embedded in the fluid are modeled with the discrete element method (DEM). The coupling between the implicit PFEM and the explicit DEM is performed through a sub-stepping staggered scheme. This work only considers suspended spherical particles that are assumed not to affect the fluid motion. Several tests are presented to validate the formulation. The PFEM–DEM results show very good agreement with analytical solutions, laboratory tests and numerical results from alternative numerical methods.Peer ReviewedPostprint (author's final draft

Extrusion of Ingot and Powder Metallurgy Aluminum Matrix Composites Profiles

Several profiles with the same extrusion ratio were extruded from three monolithic alloys and five aluminum matrix composites (AMCs) prepared by ingot and powder metallurgy (PM). Specifically, AA6061 and AA6063 were reinforced by 10 and 25 vol.% of Al2O3 and MoSi2 intermetallic particles. To study the wear of the dies, high temperature pin-on-disk tests were performed. The results show that the composite profiles present high surface and dimensional quality and that the die steel wears slightly more against the cast composite. Maximum extrusion pressure (Pmax) depends on profile shape and increases in the following order: bar, T, L and U, and tube. It also increases as volume fraction of reinforcement increases. In general, cast materials are easier to extrude than PM ones, and MoSi2 reinforced AMCs are easier to extrude than Al2O3 ones. AMCs processed by PM have significantly higher hardness than the cast AMC and the monolithic alloys. The PM composites do not need any heat treatment to acquire maximum hardness. By adding reinforcing particles to aluminum, a significant increase in tensile strength and stiffness occur. The high tensile strength and modulus of the present PM composites, without a decrease in specific properties, makes these AMCs interesting for structural applications.Spanish project TRACE2009_0251 from MICINN, Spain, and EXTRUGASA, Galicia, Spain, are gratefully acknowledged. Thanks are also due to Amalia San Román and Miguel Acedo for their help with the experimental work.Peer reviewe

Aplicación interuniversitaria del aprendizaje basado en retos en la asignatura de Mejora Genética Animal

[EN] This paper presents the results of the first year of the inter-university implementation of challenge-based learning (CBL) in animal breeding. The challenge faced by students from the Universitat Autónoma de Barcelona, the Universidad Politécnica de Madrid and the Universitat Politècnica de València consisted of managing the genetic improvement of a cattle herd in an environment with real management and economic constraints using DCBSP software. The results obtained by the students in the challenge showed an improvement throughout the challenge, which would indicate its usefulness in learning the application of animal breeding. Regarding the students' evaluation of the challenge. The results of the surveys showed high satisfaction with this type of learning in all universities, although they indicated possible improvements in the initial explanation of the challenge. The experience during the first course of pilot application of the CBL has been very positive from the point of view of student participation and motivation, as well as with the development of critical thinking through the practical application of theoretical concepts.[ES] En este trabajo se presentan los resultados del primer año de la implementación interuniversitaria del aprendizaje basado en retos en la asignatura de Mejora Genética Animal. El reto al que se enfrentaron los alumnos de la Universitat Autònoma de Barcelona, la Universidad Politécnica de Madrid y la Universitat Politècnica de València consistió en gestionar la mejora genética de un rebaño de vacuno lechero en un entorno con limitaciones de manejo y económicas reales a través de un software informático DCBS. Los resultados obtenidos por los alumnos en el reto evidenciaron una mejoría a lo largo del mismo, lo que indicaría su utilidad en el aprendizaje de la aplicación de de la mejora genética animal. Respecto a la valoración del reto por parte de los estudiantes, los resultados de las encuestas mostraron una satisfacción elevada con este tipo de aprendizaje en todas las universidades, aunque indicaron posibles mejoras en la explicación incial del reto. La experiencia durante el primer curso de aplicación piloto del ABR ha sido muy positiva tanto desde un punto de vista de participación y motivación de los alumnos, como con el desarrollo del pensamiento crítico a través de la aplicación práctica de conceptos teóricos.Ibáñez Escriche, N.; Casto Rebollo, C.; Formoso-Rafferty Castilla, N.; González Recio, O.; Casellas Vidal, J. (2021). Aplicación interuniversitaria del aprendizaje basado en retos en la asignatura de Mejora Genética Animal. En IN-RED 2021: VII Congreso de Innovación Edicativa y Docencia en Red. Editorial Universitat Politècnica de València. 104-113. https://doi.org/10.4995/INRED2021.2021.13464OCS10411

Escalera Mecánica

Escalera mecánica, que comprende un sinfín de peldaños (1) que van montados sobre dos cadenas laterales de arrastre (2-3) y guías conductoras (4-5) y quedan limitados entre balaustradas laterales fijas. Cada peldaño está soportado por dos brazos (7-8) no alineados, que son perpendiculares a la dirección de desplazamiento de dichos peldaños y paralelos a las superficies pisables de los mismos. Estos brazos sobresalen de los peldaños, uno por cada lado, para su conexión a puntos de articulación (9- 10) de las cadenas, coincidentes con el peldaño

Four-channel self-compensating single-slope ADC for space environments

A multichannel high-resolution single-slope analogue-to-digital converter (SS ADC) is presented that automatically compensates for process, voltage and temperature variations, as well as for radiation effects, in order to be used in extreme environmental conditions. The design combines an efficient implementation by using a feedback loop that ensures an inherently monotonic and very accurate ramp generation, with high levels of configurability in terms of resolution and conversion rate, as well as input voltage range. The SS ADC was designed in a standard 0.35 μm CMOS technology. Experimental measurements of the performance and stability against radiation and temperature are presented to verify the proposed approach

A Front-End ASIC for a 3-D Magnetometer for Space Applications by Using Anisotropic Magnetoresistors

This paper presents an application-specific integrated circuit (ASIC) aimed for an alternative design of a digital 3-D magnetometer for space applications, with a significant reduction in mass and volume while maintaining a high sensitivity. The proposed system uses magnetic field sensors based on anisotropic magnetoresistances and a rad-hard mixed-signal ASIC designed in a standard 0.35 μm CMOS technology. The ASIC performs sensor-signal conditioning and analogue-to-digital conversion, and handles calibration tasks, system configuration, and communication with the outside. The proposed system provides high sensitivity to low magnetic fields, down to 3 nT, while offering a small and reliable solution under extreme environmental conditions in terms of radiation and temperature.Ministerio de Ciencia e Innovación AYA2011-29967-C05-05, AYA2009-14212-C05-04, AYA2008-06420-C04-0