Kinematics of line-plane subassemblies in Stewart platforms

Trabajo presentado al ICRA 2009 celebrado en Kobe (Japón) del 12 al 17 de mayo.When the attachments of five legs in a Stewart platform are collinear on one side and coplanar on the other, the platform is said to contain a line-plane subassembly. This paper is devoted to the kinematics analysis of this subassembly paying particular attention to the problem of moving the aforementioned attachments without altering the singularity locus of the platform. It is shown how this is always possible provided that some cross-ratios between lines - defined by points in the plane- are kept equal to other cross-ratios between points in the line. This result leads to two simple motion rules upon which complex changes in the location of the attachments can be performed. These rules have interesting practical consequences as they permit a designer to optimize aspects of a parallel robot containing the analyzed subassembly, such as its manipulability in a given region, without altering its singularity locus.This work was supported by the project 'Analysis and motion planning of complex robotic systems' (4802). This work has been partially supported by the Spanish Ministry of Education and Science, under the I+D project DPI2007-60858.Peer Reviewe

New geometric approaches to the analysis and design of Stewart-Gough platforms

In general, rearranging the legs of a Stewart-Gough platform, i.e., changing the locations of its leg attachments, modifies the platform singularity locus in a rather unexpected way. Nevertheless, some leg rearrangements have been recently found to leave singularities invariant. Identification of such rearrangements is useful not only for the kinematic analysis of the platforms, but also as a tool to redesign manipulators avoiding the implementation of multiple spherical joints, which are difficult to construct and have a small motion range. In this study, a summary of these singularity-invariant leg rearrangements is presented, and their practical implications are illustrated with several examples including well-known architectures.The authors gratefully acknowledge funding from the Generalitat de Catalunya through the Robotics group (SRG0155).Peer Reviewe

New geometric approaches to the singularity analysis of parallel platforms

Presentado al Workshop de Robótica Experimental celebrado en Sevilla del 28 al 29 de noviembre de 2011.In general, rearranging the legs of a Stewart-Gough platform, i.e., changing the locations of its leg attachments, modifies the platform singularity locus in a rather unexpected way. Nevertheless, some leg rearrangements have been recently found to leave singularities invariant. In this work, a summary of the some of such singularity-invariant leg rearrangements are presented, and their practical consequences are illustrated with several examples including well-known architectures.Peer Reviewe

Singularity-invariant leg substitutions in pentapods

6 páginas, 5 figuras, 4 tablas.-- Trabajo presentado a la IROS 2010 celebrada en Taipei (Taiwan) del 18 al 22 de Octubre.A pentapod is usually defined as a 5-degree-of-freedom fully-parallel manipulator with an axial spindle as moving platform. This kind of manipulators have revealed as an interesting alternative to serial robots handling axisymmetric tools. Their particular geometry permits that, in one tool axis, inclination angles of up to 90 degrees are possible thus overcoming the orientation limits of the classical Stewart platform.This work has been partially supported by the Spanish Ministry of Education and Innovation, under the I+D project DPI2007-60858.Peer reviewe

The octahedral manipulator revisited

Trabajo presentado al ICRA celebrado en Minnesota del 14 al 18 de mayo de 2012.In most practical implementations of the Gough-Stewart platform, the octahedral form is either taken as it stands or is approximated. The kinematics of this particular instance of the Gough-Stewart platform, commonly known as the octahedral manipulator, has been thoughtfully studied. It is well-known, for example, that its forward kinematics can be solved by computing the roots of an octic polynomial and its singularities have a simple geometric interpretation in terms of the intersection of four planes in a single point. In this paper, using a distance-based formulation, it is shown how these properties can be derived without relying neither on variable eliminations nor trigonometric substitutions. Moreover, thanks to this formulation, a family of platforms kinematically equivalent to the octahedral manipulator is obtained. Herein, two Gough-Stewart parallel platforms are said to be kinematically equivalent if there is a one-to-one correspondence between their squared leg lengths for the same configuration of their moving platforms with respect to their bases. If this condition is satisfied, it can be shown that both platforms have the same assembly modes and their singularities, in the configuration space of the moving platform, are located in the same place.Peer Reviewe

Onada migratòria: actuacions per al cribratge clínic i epidemiològic a les persones migrants que acaben d’arribar a Catalunya

Onada migratòria; Cribatge clínic; VacunacionsOla migratoria; Cribado clínico; VacunacionesMigratory wave; Clinical screening; VaccinationsEls objectius d’aquest protocol que es va impulsar inicialment amb l’onada migratòria de l’estiu 2018 són: Promoure i millorar la salut dels refugiats migrants, i d’aquells que, tot i no ser refugiats, són migrants amb especial incidència en els grups en situació de vulnerabilitat. / Prevenir malalties i detectar ràpidament qualsevol problema de salut. / Oferir en un marc general recomanacions sobre les actuacions immediates de cribratge i vacunacions que hauran d’operativitzar-se en els diferents punts del territori

Jardins per a la salut

Facultat de Farmàcia, Universitat de Barcelona. Ensenyament: Grau de Farmàcia. Assignatura: Botànica farmacèutica. Curs: 2014-2015. Coordinadors: Joan Simon, Cèsar Blanché i Maria Bosch.Els materials que aquí es presenten són el recull de les fitxes botàniques de 128 espècies presents en el Jardí Ferran Soldevila de l’Edifici Històric de la UB. Els treballs han estat realitzats manera individual per part dels estudiants dels grups M-3 i T-1 de l’assignatura Botànica Farmacèutica durant els mesos de febrer a maig del curs 2014-15 com a resultat final del Projecte d’Innovació Docent «Jardins per a la salut: aprenentatge servei a Botànica farmacèutica» (codi 2014PID-UB/054). Tots els treballs s’han dut a terme a través de la plataforma de GoogleDocs i han estat tutoritzats pels professors de l’assignatura. L’objectiu principal de l’activitat ha estat fomentar l’aprenentatge autònom i col·laboratiu en Botànica farmacèutica. També s’ha pretès motivar els estudiants a través del retorn de part del seu esforç a la societat a través d’una experiència d’Aprenentatge-Servei, deixant disponible finalment el treball dels estudiants per a poder ser consultable a través d’una Web pública amb la possibilitat de poder-ho fer in-situ en el propi jardí mitjançant codis QR amb un smartphone

Minimal information for studies of extracellular vesicles 2018 (MISEV2018):a position statement of the International Society for Extracellular Vesicles and update of the MISEV2014 guidelines

The last decade has seen a sharp increase in the number of scientific publications describing physiological and pathological functions of extracellular vesicles (EVs), a collective term covering various subtypes of cell-released, membranous structures, called exosomes, microvesicles, microparticles, ectosomes, oncosomes, apoptotic bodies, and many other names. However, specific issues arise when working with these entities, whose size and amount often make them difficult to obtain as relatively pure preparations, and to characterize properly. The International Society for Extracellular Vesicles (ISEV) proposed Minimal Information for Studies of Extracellular Vesicles (“MISEV”) guidelines for the field in 2014. We now update these “MISEV2014” guidelines based on evolution of the collective knowledge in the last four years. An important point to consider is that ascribing a specific function to EVs in general, or to subtypes of EVs, requires reporting of specific information beyond mere description of function in a crude, potentially contaminated, and heterogeneous preparation. For example, claims that exosomes are endowed with exquisite and specific activities remain difficult to support experimentally, given our still limited knowledge of their specific molecular machineries of biogenesis and release, as compared with other biophysically similar EVs. The MISEV2018 guidelines include tables and outlines of suggested protocols and steps to follow to document specific EV-associated functional activities. Finally, a checklist is provided with summaries of key points

Кераміка «terra sigillata» з с. Зимне на Волині

Стаття присвячена публікації чотирьох керамічних посудин типу «terra sigillata», знайдених на дні р. Луги у с. Зимне Володимир-Волинського району Волинської області. Попередній аналіз цих знахідок дозволяє віднести їх до Понтійського центру виробництва такого посуду. Вірогідним шляхом потрапляння цієї колекції на Волинь була готська експансія у Північне Причорномор’я

Direct Position Analysis of a Large Family of Spherical and Planar Parallel Manipulators with Four Loops

Presentado al 2nd International Workshop on: "Fundamental Issues and Future Research Directions for Parallel Mechanisms and Manipulators" celebrado en Montpellier (Francia) del 21 al 22 de septiembre de 2008.The direct position analysis (DPA) of a manipulator is the computation of the end-effector poses (positions and orientations) compatible with assigned values of the actuated-joint variables. Assigning the actuated-joint variables corresponds to considering the actuated joints locked, which makes the manipulator a structure. The solutions of the DPA of a manipulator one-to-one correspond to the assembly modes of the structure that is generated by locking the actuated-joint variables of that manipulator. Determining the assembly modes of a structure means solving the DPA of a large family of manipulators since the same structure can be generated from different manipulators. This paper provides an algorithm that determines all the assembly modes of two structures with the same topology which are generated from two families of mechanisms: one planar and the other spherical. The topology of these structures is constituted of nine links (one quaternary link, four ternary links and four binary links) connected through twelve revolute pairs to form four closed loops.This work has been partially supported by the Spanish Ministry of Education and Science, under the I+D project DPI2007-60858, by the I3P program with a short stay grant, and by funds of the Italian MIUR.Peer reviewe