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    A bilinear formulation for the motion planning of non-holonomic parallel orienting platforms  Open access

     Grosch Obregon, Patrick John; Thomas Arroyo, Federico
    IEEE/RSJ International Conference on Intelligent Robots and Systems
    p. 953-958
    DOI: 10.1109/IROS.2013.6696465
    Presentation's date: 2013
    Presentation of work at congresses

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    This paper deals with the motion planning problem for parallel orienting platforms with one non-holonomic joint and two prismatic actuators which can maneuver to reach any three-degree-of-freedom pose of the moving platform. Since any system with two inputs and up to four generalized coordinates can always be transformed into chained form, this path planning problem can be solved using well-established procedures. Nevertheless, the use of these procedures requires a good understanding of Lie algebraic methods whose technicalities have proven a challenge to many practitioners who are not familiar with them. As an alternative, we show how by (a) properly locating the actuators, and (b) representing the platform orientation using Euler parameters, the studied path planning problem admits a closed-form solution whose derivation requires no other tools than ordinary linear algebra.

    Postprint (author’s final draft)

  • Computational Kinematics 2013 (CK2013)

     Thomas Arroyo, Federico
    Competitive project

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  • Honorable mention, ASME Mechanisms and Robotics Committee Best Paper Award

     Thomas Arroyo, Federico; Rojas, Nicolas
    Award or recognition

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  • Distance-Based Formulations For The Position Analysis Of Kinematic Chains  Open access

     Rojas Libreros, Nicolás Enrique
    Institute of Industrial and Control Engineering (IOC), Universitat Politècnica de Catalunya
    Theses

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    This thesis addresses the kinematic analysis of mechanisms, in particular, the position analysis of kinematic chains, or linkages, that is, mechanisms with rigid bodies (links) interconnected by kinematic pairs (joints). This problem, of completely geometrical nature, consists in finding the feasible assembly modes that a kinematic chain can adopt. An assembly mode is a possible relative transformation between the links of a kinematic chain. When an assignment of positions and orientations is made for all links with respect to a given reference frame, an assembly mode is called a configuration. The methods reported in the literature for solving the position analysis of kinematic chains can be classified as graphical, analytical, or numerical. The graphical approaches are mostly geometrical and designed to solve particular problems. The analytical and numerical methods deal, in general, with kinematic chains of any topology and translate the original geometric problem into a system of kinematic analysis of all the Assur kinematic chains resulting from replacing some of its revolute joints by slider joints. Thus, it is concluded that the polynomials of all fully-parallel planar robots can be derived directly from that of the widely known 3-RPR robot. In addition to these results, this thesis also presents an efficient procedure, based on distance and oriented area constraints, and geometrical arguments, to trace coupler curves of pin-jointed Gr¨ubler kinematic chains. All these techniques and results together are contributions to theoretical kinematics of mechanisms, robot kinematics, and distance plane geometry. equations that defines the location of each link based, mainly, on independent loop equations. In the analytical approaches, the system of kinematic equations is reduced to a polynomial, known as the characteristic polynomial of the linkage, using different elimination methods —e.g., Gr¨obner bases or resultant techniques. In the numerical approaches, the system of kinematic equations is solved using, for instance, polynomial continuation or interval-based procedures. In any case, the use of independent loop equations to solve the position analysis of kinematic chains, almost a standard in kinematics of mechanisms, has seldom been questioned despite the resulting system of kinematic equations becomes quite involved even for simple linkages. Moreover, stating the position analysis of kinematic chains directly in terms of poses, with or without using independent loop equations, introduces two major disadvantages: arbitrary reference frames has to be included, and all formulas involve translations and rotations simultaneously. This thesis departs from this standard approach by, instead of directly computing Cartesian locations, expressing the original position problem as a system of distance-based constraints that are then solved using analytical and numerical procedures adapted to their particularities. In favor of developing the basics and theory of the proposed approach, this thesis focuses on the study of the most fundamental planar kinematic chains, namely, Baranov trusses, Assur kinematic chains, and pin-jointed Gr¨ubler kinematic chains. The results obtained have shown that the novel developed techniques are promising tools for the position analysis of kinematic chains and related problems. For example, using these techniques, the characteristic polynomials of most of the cataloged Baranov trusses can be obtained without relying on variable eliminations or trigonometric substitutions and using no other tools than elementary algebra. An outcome in clear contrast with the complex variable eliminations require when independent loop equations are used to tackle the problem. The impact of the above result is actually greater because it is shown that the characteristic polynomial of a Baranov truss, derived using the proposed distance-based techniques, contains all the necessary and sufficient information for solving the position

    Esta tesis aborda el problema de análisis de posición de cadenas cinemáticas, mecanismos con cuerpos rígidos (enlaces) interconectados por pares cinemáticos (articulaciones). Este problema, de naturaleza geométrica, consiste en encontrar los modos de ensamblaje factibles que una cadena cinemática puede adoptar. Un modo de ensamblaje es una transformación relativa posible entre los enlaces de una cadena cinemática. Los métodos reportados en la literatura para la solución del análisis de posición de cadenas cinemáticas se pueden clasificar como gráficos, analíticos o numéricos. Los enfoques gráficos son geométricos y se diseñan para resolver problemas particulares. Los métodos analíticos y numéricos tratan con cadenas cinemáticas de cualquier topología y traducen el problema geométrico original en un sistema de ecuaciones cinemáticas que define la ubicación de cada enlace, basado generalmente en ecuaciones de bucle independientes. En los enfoques analíticos, el sistema de ecuaciones cinemáticas se reduce a un polinomio, conocido como el polinomio característico de la cadena cinemática, utilizando diferentes métodos de eliminación. En los métodos numéricos, el sistema se resuelve utilizando, por ejemplo, la continuación polinomial o procedimientos basados en intervalos. En cualquier caso, el uso de ecuaciones de bucle independientes, un estándar en cinemática de mecanismos, rara vez ha sido cuestionado a pesar de que el sistema resultante de ecuaciones es bastante complicado, incluso para cadenas simples. Por otra parte, establecer el análisis de la posición de cadenas cinemáticas directamente en términos de poses, con o sin el uso de ecuaciones de bucle independientes, presenta dos inconvenientes: sistemas de referencia arbitrarios deben ser introducidos, y todas las fórmulas implican traslaciones y rotaciones de forma simultánea. Esta tesis se aparta de este enfoque estándar expresando el problema de posición original como un sistema de restricciones basadas en distancias, en lugar de directamente calcular posiciones cartesianas. Estas restricciones son posteriormente resueltas con procedimientos analíticos y numéricos adaptados a sus particularidades. Con el propósito de desarrollar los conceptos básicos y la teoría del enfoque propuesto, esta tesis se centra en el estudio de las cadenas cinemáticas planas más fundamentales, a saber, estructuras de Baranov, cadenas cinemáticas de Assur, y cadenas cinemáticas de Grübler. Los resultados obtenidos han demostrado que las técnicas desarrolladas son herramientas prometedoras para el análisis de posición de cadenas cinemáticas y problemas relacionados. Por ejemplo, usando dichas técnicas, los polinomios característicos de la mayoría de las estructuras de Baranov catalogadas se puede obtener sin realizar eliminaciones de variables o sustituciones trigonométricas, y utilizando solo álgebra elemental. Un resultado en claro contraste con las complejas eliminaciones de variables que se requieren cuando se utilizan ecuaciones de bucle independientes. El impacto del resultado anterior es mayor porque se demuestra que el polinomio característico de una estructura de Baranov, derivado con las técnicas propuestas, contiene toda la información necesaria y suficiente para resolver el análisis de posición de las cadenas cinemáticas de Assur que resultan de la sustitución de algunas de sus articulaciones de revolución por articulaciones prismáticas. De esta forma, se concluye que los polinomios de todos los robots planares totalmente paralelos se pueden derivar directamente del polinomio característico del conocido robot 3-RPR. Adicionalmente, se presenta un procedimiento eficaz, basado en restricciones de distancias y áreas orientadas, y argumentos geométricos, para trazar curvas de acoplador de cadenas cinemáticas de Grübler. En conjunto, todas estas técnicas y resultados constituyen contribuciones a la cinemática teórica de mecanismos, la cinemática de robots, y la geometría plana de distancias. Barcelona 13-

  • Simplified Voronoi diagrams for motion planning of quadratically-solvable Gough-Stewart platforms

     Vaca Alzate, Ruben Hernando; Aranda López, Juan; Thomas Arroyo, Federico
    International Symposium on Advances in Robot Kinematics
    p. 157-164
    DOI: 10.1007/978-94-007-4620-6_20
    Presentation's date: 2012
    Presentation of work at congresses

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    Motion planning for parallel robots with non-holonomic joints  Open access

     Tchon, Krzysztof; Jakubiak, Janusz; Grosch Obregon, Patrick John; Thomas Arroyo, Federico
    International Symposium on Advances in Robot Kinematics
    p. 115-122
    DOI: 10.1007/978-94-007-4620-6_15
    Presentation's date: 2012
    Presentation of work at congresses

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    Designing a robot manipulator with fewer actuators than the dimension of its configuration space —to reduce bulk, weight and cost— becomes feasible by introducing mechanical elements that lead to non-holonomic constraints. Unfortunately, the mechanical advantages of these non-holonomic designs are usually darkened by the complexity of their control. This paper deals with motion planning for parallel robots with non-holonomic joints shedding new light on their control strategies. As a case study, the motion planning problem is solved for a 3-˘UPU parallel robot,where ˘U stands for a non-holonomic joint whose instantaneous kinematics are equivalent to that of a universal joint. It is thus shown how the three prismatic actuators can maneuver to reach any six-degree-of-freedompose of the moving platform. The motion planning has been addressed as a control problem in the control system representation of the robot’s kinematics and a motion planning algorithm has been devised based on a Jacobian inversion of the end-point map of the representation. Performance of the algorithm is illustrated with numeric computations.

  • The octahedral manipulator revisited

     Rojas Libreros, Nicolás Enrique; Borras Sol, Julia; Thomas Arroyo, Federico
    IEEE International Conference on Robotics and Automation
    p. 2293-2298
    DOI: 10.1109/ICRA.2012.6224908
    Presentation's date: 2012
    Presentation of work at congresses

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  • Superficies programables

     Rull Sanahuja, Aleix; Pérez Gracia, María Alba; Grosch Obregon, Patrick John; Thomas Arroyo, Federico
    Competitive project

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  • Singularity-invariant leg rearrangements in stewart-gouch platforms

     Borras Sol, Julia
    Institute of Industrial and Control Engineering (IOC), Universitat Politècnica de Catalunya
    Theses

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  • Desplegament de l'exposició RSME imaginari a Catalunya. Fase 2011

     Xambó Descamps, Sebastian; Plans Berenguer, Bernat; Borras Sol, Julia; Barja Yañez, Miguel Angel; Thomas Arroyo, Federico; Quer Bosor, Jordi; Torras, Carme; Alberich Carramiñana, Maria
    Competitive project

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  • A coordinate-free approach to tracing the coupler curves of pin-jointed linkages  awarded activity

     Rojas Libreros, Nicolás Enrique; Thomas Arroyo, Federico
    ASME International Design Engineering Technical Conferences
    p. 417-426
    DOI: 10.1115/DETC2011-48147
    Presentation's date: 2011
    Presentation of work at congresses

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    In general, high-order coupler curves of plane mechanisms cannot be properly traced by standard predictor-corrector algorithms due to drifting problems and the presence of singularities. Instead of focusing on finding better algorithms for tracing curves, a simple coordinate-free method that first traces these curves in a distance space and then maps them onto the mechanism workspace is proposed. Tracing a coupler curve in the proposed distance space is much simpler because (a) the equation of this curve in this space can be straightforwardly obtained from a sequence of bilaterations; and (b) the curve in this space naturally decomposes into branches in which the signs of the oriented areas of the triangles involved in the aforementioned bilaterations remain constant. A surjective mapping permits to map the thus traced curves onto the workspace of the mechanism. The advantages of this two-step method are exemplified by tracing the coupler curves of a double butterfly linkage, curves that can reach order 48.

    Honorable mention, ASME Mechanisms and Robotics Committee Best Paper Award

  • New geometric approaches to the singularity analysis of parallel platforms

     Borras Sol, Julia; Thomas Arroyo, Federico; Torras, Carme
    Workshop Español de Robótica
    p. 173-180
    Presentation's date: 2011
    Presentation of work at congresses

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  • DESPLEGAMENT DE L'EXPOSICIÓ RSME-IMAGINARY A CATALUNYA - FASE 2010

     Xambó Descamps, Sebastian; Borras Sol, Julia; Quer Bosor, Jordi; Plans Berenguer, Bernat; Barja Yañez, Miguel Angel; Thomas Arroyo, Federico; Torras, Carme; Alberich Carramiñana, Maria
    Competitive project

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  • Factories del futur pel sector manufacturer a Catalunya (manucat)

     Casado Lopez, Ramon; Rodriguez Sendra, Rosa Maria; Buj Corral, Irene; Gomà Ayats, Joan Ramon; Fenollosa Artes, Felip; Napoles Alberro, Amelia Emelina; Martinez Miralles, Jordi Ramon; Fruitos Bickham, Oscar Alejandro; Travieso Rodríguez, José Antonio; Maspoch Ruldua, Maria Lluïsa; Martinez Velasco, Antonio Benito; Tort-Martorell Llabres, Javier; Vivancos Calvet, Joan; Roure Fernandez, Francisco; Puigjaner Corbella, Luis; Espuña Camarasa, Antonio; Thomas Arroyo, Federico; Pastor Artigues, M. Magdalena; Minguella Canela, Joaquim
    Competitive project

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  • GARNICS: Gardening with a Cognitive System (FP7-ICT-247947)

     Moreno Noguer, Francesc d'Assis; Torras, Carme; Agostini, Alejandro Gabriel; Husain, Syed Farzad; Dellen, Babette Karla Margarete; Alenyà Ribas, Guillem; Jimenez Schlegl, Pablo; Thomas Arroyo, Federico; Rozo Castañeda, Leonel; Foix Salmeron, Sergi
    Competitive project

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    A one-motor full-mobility 6-PUS manipulator  Open access

     Grosch Obregon, Patrick John; Di Gregorio, Silvana; Thomas Arroyo, Federico
    CISM-IFToMM Symposium on Robot Design, Dynamics and Control
    p. 49-56
    DOI: 10.1007/978-3-7091-0277-0_5
    Presentation's date: 2010
    Presentation of work at congresses

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    This paper presents the feasibility study of an under-actuated parallel manipulator with 6-PUS topology, destined to handle work-tables in CNC machine tools. The proposed device exploits the fact that, in such an application, the path between the initial and final poses of the mobile platform is not assigned to reduce the number of actuators to only one.

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    Singularity-invariant leg rearrangements in doubly-planar Stewart-Gough platforms  Open access

     Borras Sol, Julia; Thomas Arroyo, Federico; Torras, Carme
    Robotics: Science and Systems
    p. 1-8
    Presentation's date: 2010
    Presentation of work at congresses

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    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 but, unfortunately, these rearrangements are only valid for Stewart-Gough platforms containing rigid components. In this work, the authors go a step further presenting singularity-invariant leg rearrangements that can be applied to any Stewart-Gough platform whose base and platform attachments are coplanar. The practical consequences of the presented theoretical results are illustrated with several examples including well-known architectures.

    Postprint (author’s final draft)

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    Singularity-invariant leg rearrangements in Stewart-Gough platforms  Open access

     Borras Sol, Julia; Thomas Arroyo, Federico; Torras, Carme
    International Symposium on Advances in Robot Kinematics
    p. 421-428
    DOI: 10.1007/978-90-481-9262-5_45
    Presentation's date: 2010
    Presentation of work at congresses

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    A family of quadratically-solvable 5-SPU parallel robots  Open access

     Borras Sol, Julia; Thomas Arroyo, Federico; Torras, Carme
    IEEE International Conference on Robotics and Automation
    p. 4703-4708
    DOI: 10.1109/ROBOT.2010.5509965
    Presentation's date: 2010
    Presentation of work at congresses

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    A 5-SPU robot with collinear universal joints is well suited to handling an axisymmetric tool, since it has 5 controllable DoFs and the remaining one is a free rotation around the tool. The kinematics of such a robot having also coplanar spherical joints has previously been studied as a rigid subassembly of a Stewart-Gough platform, it being denoted a line-plane component. It was shown that this component has 8 assembly modes corresponding to the roots of a bi-quartic polynomial. Here we identify a whole family of these 5-SPU robots having only 4 assembly modes, which are obtained by solving two quadratic equations. This family is defined by a simple proportionality constraint relating the coordinates of the base and platform attachments. A geometric interpretation of the architectural singularities of this type of robots in terms of conics is provided, which facilitates their avoidance at the design stage. Parallel singularities obey also a neat geometric structure, which permits deriving a cell decomposition of configuration space. Two practical features of these quadratically-solvable robots are the large maneuverability within each connected component and the fact that, for a fixed orientation of the tool, the singularity locus reduces to a plane. Index Terms—Parallel manipulators, Stewart-Gough platforms, robot kinematics, kinematics singularities.

    Postprint (author’s final draft)

  • A distance-based formulation of the octahedral manipulator kinematics

     Rojas Libreros, Nicolás Enrique; Borras Sol, Julia; Thomas Arroyo, Federico
    IFToMM Symposium on Mechanism Design for Robotics
    p. 1-12
    Presentation's date: 2010
    Presentation of work at congresses

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    A robust forward kinematics analysis of 3-RPR planar platforms  Open access

     Rojas, Nicolás; Thomas Arroyo, Federico
    International Symposium on Advances in Robot Kinematics
    p. 23-32
    DOI: 10.1007/978-90-481-9262-5_3
    Presentation's date: 2010
    Presentation of work at congresses

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    The standard forward kinematics analysis of 3-RPR planar parallel platforms boils down to computing the roots of a sextic polynomial. There are many different ways to obtain this polynomial but all of them include exceptions for which the formulation is not valid. Unfortunately, near these exceptions the corresponding polynomial exhibits numerical instabilities. In this paper, we provide a way around this inconvenience by translating the forward kinematics problem to be solved into an equivalent problem fully stated in terms of distances. Using constructive geometric arguments, an alternative sextic —which is not linked to a particular reference frame— is straightforwardly obtained without the need of variable eliminations nor tangent-half-angle substitutions. The presented formulation is valid, without any modification, for any planar 3-RPR parallel platform, including the special architectures and configurations —which ultimately lead to numerical instabilities— that cannot be directly handled by previous formulations.

    Postprint (author’s final draft)

  • Singularity-invariant leg substitutions in pentapods

     Borras Sol, Julia; Thomas Arroyo, Federico
    IEEE/RSJ International Conference on Intelligent Robots and Systems
    p. 2766-2771
    DOI: 10.1109/IROS.2010.5652202
    Presentation's date: 2010
    Presentation of work at congresses

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    Motion planning for a novel reconfigurable parallel manipulator with lockable revolute joints  Open access

     Grosch Obregon, Patrick John; Di Gregorio, Silvana; López, Javier; Thomas Arroyo, Federico
    IEEE International Conference on Robotics and Automation
    p. 4697-4702
    DOI: 10.1109/ROBOT.2010.5509305
    Presentation's date: 2010
    Presentation of work at congresses

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    This paper introduces a class of reconfigurable parallel robots consisting of a fixed base and a moving platform connected by serial chains having RRPS (Revolute-Revolute-Prismatic-Spherical) topology. Only the prismatic joint is actuated and the first revolute joint in the chain can be locked or released online. The introduction of these lockable joints allow the prismatic actuators to maneuver to approximate 6-DoF motions for the moving platform. An algorithm for generating these maneuvers is first described. Then, a motion planner, based on the generation of a Probabilistic RoadMap (PRM) whose nodes are connected using the described maneuvers, is presented. The generated trajectories avoid singularities and possible collisions between legs. (See accompanying video)

    Postprint (author’s final draft)

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    "Adaptive Neural Control of Nonlinear Systems"  Open access

     Thomas Arroyo, Federico; Baruch, I; Flores, JM; Garrido, R
    DOI: 10.1007/978-3-642-02172-5_18
    Date of publication: 2009-06-12
    Book chapter

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    The present paper addresses pedestrian detection using local boosted features that are learned from a small set of training images. Our contribution is to use two boosting steps. The first one learns discriminant local features corresponding to pedestrian parts and the second one selects and combines these boosted features into a robust class classifier. In contrast of other works, our features are based on local differences over Histograms of Oriented Gradients (HoGs). Experiments carried out to a public dataset of pedestrian images show good performance with high classification rates

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    Straightening-free algorithm for the singularity analysis of Stewart-Gough platforms with collinear/coplanar attachments  Open access

     Borras Sol, Julia; Thomas Arroyo, Federico; Torras, Carme
    Computational Kinematics
    p. 359-366
    Presentation's date: 2009-05-08
    Presentation of work at congresses

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    An algorithm to derive the pure condition of any double-planar Stewart-Gough platform in a standard form suitable for comparison is presented. By applying the multilinear properties of brackets directly to the superbracket encoding of the pure condition, no straightening is required. It is then shown that any 3-3 platform has a corresponding 6-6 platform having its same superbracket, meaning that they have identical singularity loci. In general, the superbracket of any doubleplanar platform can be written as a linear combination of the superbrackets of 3-3 platforms, leading to a direct singularity assessment by inspecting the resulting decomposition.

    Postprint (author’s final draft)

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    Kinematics of line-plane subassemblies in Stewart platforms  Open access

     Borras Sol, Julia; Thomas Arroyo, Federico
    IEEE International Conference on Robotics and Automation
    p. 4094-4099
    Presentation's date: 2009
    Presentation of work at congresses

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    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.

  • Generation of under-actuated parallel robots with non-holonomic joints and kinetostatic analysis of a case-study

     Grosch Obregon, Patrick John; Di Gregorio, Silvana; Thomas Arroyo, Federico
    ASME International Design Engineering Technical Conferences
    p. 1-8
    Presentation's date: 2009
    Presentation of work at congresses

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    It will be shown how to generate under-actuated manipulators by substituting non-holonomic spherical pairs (nS pairs) for (holonomic) spherical pairs (S pairs) in fully-parallel manipulators (FPMs). Through this pair substitution, an under-actuated manipulator, previously proposed by one of the authors, will be demonstrated to be generated from an inversion of the 6-3 FPM. Moreover, the kinetostatic analysis of this manipulator will be reconsidered to obtain a simple and compact formulation. This reformulated analysis can be used both in the design of the underactuated manipulator, and in its control.

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    A reconfigurable 5-DoF 5-SPU parallel platform  Open access

     Borras Sol, Julia; Thomas Arroyo, Federico; Ottaviano, Erika; Ceccarelli, Marco
    ASME/IFToMM International Conference on Reconfigurable Mechanisms and Robots
    p. 617-623
    Presentation's date: 2009
    Presentation of work at congresses

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    This paper presents a 5-SPU platform whose base leg attachments can be easily reconfigured, statically or dynamically, without altering its singularity locus. This permits to adapt the platform’s geometry to particular tasks without increasing the complexity of its control. The allowed reconfigurations permit to reduce the risk of collisions between legs, or even improving the stiffness of the platform, in a given region of its configuration space. It is also shown that no architectural singularities are introduced by the proposed reconfigurations.

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    A linear relaxation technique for the position analysis of multi-loop linkages  Open access

     Porta Pleite, Josep M.; Ros Giralt, Lluis; Thomas Arroyo, Federico
    Date: 2008-01
    Report

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    This report presents a new method able to isolate all configurations that a multi-loop linkage can adopt. We tackle the problem by providing formulation and resolution techniques that fit particularly well together. The adopted formulation yields a system of simple equations (only containing linear and bilinear terms, and trivial trigonometric functions for the helical pair exclusively) whose special structure is later exploited by a branch-and-prune method based on linear relaxations. The method is general, as it can be applied to linkages with single or multiple loops with arbitrary topology, involving lower pairs of any kind, and complete, as all possible solutions get accurately bounded, irrespectively of whether the linkage is rigid or mobile.

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    A wrench-sensitive touch pad based on a parallel structure  Open access

     Frigola Alcalde, Roger; Ros Giralt, Lluis; Roure Fernandez, Francisco; Thomas Arroyo, Federico
    IEEE International Conference on Robotics and Automation
    p. 3449-3459
    DOI: 10.1109/ROBOT.2008.4543738
    Presentation's date: 2008
    Presentation of work at congresses

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    Many different robotic in-parallel structures have been conceived as six-component force sensors. In general, they perform well for most applications but, when accuracy is a must, two main limitations arise. First, in most designs, the legs are connected to the base and the platform through ball-and-socket joints. Although the dry friction in each of these joints can be individually neglected, the integrated effect of twelve such elements becomes noticeable. Second, dynamical measurements might not be very accurate because the natural resonance frequency of the used structures is quite low even for relatively small dimensions. This dynamical response can be obviously modified with a proper mechanical design, but this increases the complexity of the sensor. This paper discusses the design and implementation of a touch pad based on a 6-axis force sensor and shows how the above limitations degrade its behavior. Moreover, it is shown how using a tensegrity structure both problems could be alleviated because ball-and-socket joints can be substituted by point contacts and the resonance frequency of the structure can be controlled by adjusting the static tensions of the tendons.

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    Analysing the singularities of 6-SPS parallel robots using virtual legs  Open access

     Borras Sol, Julia; Thomas Arroyo, Federico; Torras, Carme
    International Workshop on Fundamental Issues and Future Research Directions for Parallel Mechanisms and Manipulators
    p. 145-150
    Presentation's date: 2008
    Presentation of work at congresses

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    A virtual leg in a 6-SPS parallel robot is defined as a leg whose length is determined by the lengths of a subset of the actual legs of the robot. This necessarily implies that this subset of legs defines a rigid subassembly. In this paper, we consider four different rigid subassemblies, and show how the singularities of a robot containing one or several of these subassemblies are modified when substituting its actual legs by virtual legs.

  • Architecture singularities in flagged parallel manipulators

     Borras Sol, Julia; Thomas Arroyo, Federico; Torras, Carme
    IEEE International Conference on Robotics and Automation
    p. 3844-3850
    DOI: 10.1109/ROBOT.2008.4543801
    Presentation's date: 2008
    Presentation of work at congresses

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  • Wire-based tracking using mutual information

     Andrade Cetto, Juan; Thomas Arroyo, Federico
    10th International symposium on advances in robot kinematics
    p. 3-14
    Presentation of work at congresses

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  • Distance Constraints Solved Geometrically

     Thomas Arroyo, Federico; Ros Giralt, Lluis; Porta Pleite, Josep M.
    9th International Symposium on Advances in Robot Kinematics
    p. 31-40
    Presentation of work at congresses

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  • Isolating Self-Motion Manifolds on a Playstation

     Thomas Arroyo, Federico; Ros Giralt, Lluis; Porta Pleite, Josep M.
    9th International Symposium on Advances in Robot Kinematics
    p. 123-132
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  • Geometric methods in robotics

     Ros Giralt, Lluis; Porta Pleite, Josep M.; Torras, Carme; Ruiz Miera, Vicente; Creemers, Tom Lambert; Canto Silva, Josep; Corcho Sanchez, Francisco Jose; Thomas Arroyo, Federico; Sabater Pruna, Maria Assumpta
    Jornada de Recerca en Automàtica, Visió i Robòtica
    p. 33-41
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  • Solving Geometric Constraints by Iterative Projections and Backprojections

     Thomas Arroyo, Federico
    IEEE International Conference on Robotics and Automation
    p. 1
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  • Fast skeletonization of volumetric objects

     Rodriguez Rojas, Jorge Ernesto; Ros Giralt, Lluis; Ayala Vallespi, M. Dolors; Thomas Arroyo, Federico
    XIII Congreso Español de Informática Gràfica
    p. 115-128
    Presentation's date: 2003-07
    Presentation of work at congresses

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  • Identificación de pigmentos en biofilms fototróficos mediante espectofotometría confocal

     Roldan, M; Thomas Arroyo, Federico; Castel, S; Quesada, A; Hernández-Mariné, M
    XIV Simposio de Botánica Criptogámica
    p. 1
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  • Coordinate-free Formulation of a 3-2-1 Wire based Tracking System using Cayley-Menger Determinants

     Thomas Arroyo, Federico; Ros Giralt, Lluis
    IEEE International Conference on Robotics and Automation
    p. 255-263
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  • On the Reconstruction of an Image from its Moments

     Thomas Arroyo, Federico
    IEEE International Conference on Image Processing
    p. 217-221
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  • Efficient Computation od 3D Skeletons by Extreme Vertex Encoding

     Rodríguez, J; Thomas Arroyo, Federico; Ayala Vallespi, M. Dolors; Ros Giralt, Lluis
    11th International Conference on Discrete Geometry for Computer Imagery
    p. 338-347
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  • A branch-and-prune algorithm for solving systems of distance constraints

     Thomas Arroyo, Federico; Ros Giralt, Lluis; Torras, Carme
    IEEE International Conference on Robotics and Automation
    p. 342-348
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  • An Integrated-Plus-State Neural Control of Mechanical Systems

     Thomas Arroyo, Federico
    2003 IEEE Conference on Control Applications (CCA 2003)
    p. 342-348
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  • Singular Configurations of a 6-Wire Parallel Architecture

     Thomas Arroyo, Federico
    12th International Workshop on Robotics in Alpe-Adria-Danube Region
    p. 1
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  • "Solving Multi-Loop Linkages by Iterating 2D Clippings"

     Ros Giralt, Lluis; Thomas Arroyo, Federico; Torras, Carme; Ros L, JM
    Date of publication: 2002-10-31
    Book chapter

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  • "Uncertainty Model and Singularities of a 3-2-1 Wire-Based Tracking Systems"

     Thomas Arroyo, Federico; Ros Giralt, Lluis; Ottaviano, E; Ceccarelli, M
    Date of publication: 2002-10-31
    Book chapter

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  • Local Characterization of the Configuration Space

     STAFFETI, ERNESTO
    Institute of Industrial and Control Engineering (IOC), Universitat Politècnica de Catalunya
    Theses

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  • "Shape Representation using Trihedral Mesh Projections"

     Thomas Arroyo, Federico; Ros, L; Sugihara, K
    Date of publication: 2002-04
    Book chapter

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