Porta Pleite, Josep M.
Total activity: 46
Research group
ROBiri - IRI Robotics Group
Institute
Institute of Robotics and Industrial Informatics
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portairi.upc.edu
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    Planning singularity-free paths on closed-chain manipulators  Open access

     Bohigas Nadal, Oriol; Henderson, Michael E.; Ros Giralt, Lluis; Manubens Ferriol, Montserrat; Porta Pleite, Josep M.
    IEEE transactions on robotics
    Date of publication: 2013
    Journal article

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    This paper provides an algorithm for computing singularity-free paths on closed-chain manipulators. Given two non-singular configurations of the manipulator, the method attempts to connect them through a path that maintains a minimum clearance with respect to the singularity locus at all points, which guarantees the controllability of the manipulator everywhere along the path. The method can be applied to non-redundant manipulators of general architecture, and it is resolution-complete. It always returns a path whenever one exists at a given resolution, or determines path non-existence otherwise. The strategy relies on defining a smooth manifold that maintains a one-to-one correspondence with the singularity-free C-space of the manipulator, and on using a higher-dimensional continuation technique to explore this manifold systematically from one configuration, until the second configuration is found. If desired, the method can also be used to compute an exhaustive atlas of the whole singularity-free component reachable from a given configuration, which is useful to rapidly resolve subsequent planning queries within such component, or to visualize the singularity-free workspace of any of the manipulator coordinates. Examples are included that demonstrate the performance of the method on illustrative situations.

    Postprint (author’s final draft)

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    Grasp optimization under specific contact constraints  Open access

     Rosales Gallegos, Carlos; Porta Pleite, Josep M.; Ros Giralt, Lluis
    IEEE transactions on robotics
    Date of publication: 2013
    Journal article

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    This paper presents a procedure for synthesizing high-quality grasps for objects that need to be held and manipulated in a specific way, characterized by a prespecified set of contact constraints to be satisfied. Due to the multimodal nature of typical grasp quality measures, approaches that resort to local optimization methods are likely to get trapped into local extrema on such a problem. An additional difficulty is that the set of feasible grasps is a highly dimensional manifold, implicitly defined by a system of nonlinear equations. The proposed procedure finds a way around these issues by focusing the exploration on a relevant subset of grasps of lower dimension and tracing this subset exhaustively using a higher-dimensional continuation technique. A detailed atlas of the subset is obtained as a result, on which the highest quality grasp, according to any desired criterion, or a combination of criteria, can be readily identified. Examples are included that illustrate the application of the method to a three-fingered planar hand and to the Schunk anthropomorphic hand grasping different objects, using several quality indices.

    This paper presents a procedure to synthesize highquality grasps for objects that need to be held and manipulated in a specific way, characterized by a pre-specified set of contact constraints to be satisfied. Due to the multi-modal nature of typical grasp quality measures, approaches that resort to local optimization methods are likely to get trapped into local extrema on such problem. An additional difficulty of the problem is that the set of feasible grasps is a highly-dimensional manifold, implicitly defined by a system of non-linear equations. The proposed procedure finds a way around these issues by focusing the exploration on a relevant subset of grasps of lower dimension, and tracing this subset exhaustively using a higher-dimensional continuation technique. A detailed atlas of the subset is obtained as a result, on which the highest-quality grasp according to any desired criterion, or a combination of criteria, can be readily identified. Examples are included that illustrate the application of the method to a three-fingered planar hand and to the Schunk anthropomorphic hand grasping several objects, using several quality indices.

    Postprint (author’s final draft)

  • Exploring the energy landscapes of flexible molecular loops using higher-dimensional continuation

     Porta Pleite, Josep M.; Jaillet, Leonard Georges
    Journal of computational chemistry
    Date of publication: 2013
    Journal article

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  • Path planning under kinematic constraints by rapidly exploring manifolds

     Jaillet, Leonard Georges; Porta Pleite, Josep M.
    IEEE transactions on robotics
    Date of publication: 2013
    Journal article

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    The situation arising in path planning under kinematic constraints, where the valid configurations define a manifold embedded in the joint ambient space, can be seen as a limit case of the well-known narrow corridor problem. With kinematic constraints, the probability of obtaining a valid configuration by sampling in the joint ambient space is not low but null, which complicates the direct application of sampling-based path planners. This paper presents the AtlasRRT algorithm, which is a planner especially tailored for such constrained systems that builds on recently developed tools for higher-dimensional continuation. These tools provide procedures to define charts that locally parametrize a manifold and to coordinate the charts, forming an atlas that fully covers it. AtlasRRT simultaneously builds an atlas and a bidirectional rapidly exploring random tree (RRT), using the atlas to sample configurations and to grow the branches of the RRTs, and the RRTs to devise directions of expansion for the atlas. The efficiency of AtlasRRT is evaluated in several benchmarks involving high-dimensional manifolds embedded in large ambient spaces. The results show that the combined use of the atlas and the RRTs produces a more rapid exploration of the configuration space manifolds than existing approaches.

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    A singularity-free path planner for closed-chain manipulators  Open access

     Bohigas Nadal, Oriol; Henderson, Michael E; Ros Giralt, Lluis; Porta Pleite, Josep M.
    IEEE International Conference on Robotics and Automation
    Presentation's date: 2012
    Presentation of work at congresses

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    This paper provides an algorithm for computing singularity-free paths on non-redundant closed-chain manipulators. Given two non-singular configurations of the manipulator, the method attempts to connect them through a configuration space path that maintains a minimum clearance with respect to the singularity locus at all points. The method is resolutioncomplete, in the sense that it always returns a path if one exists at a given resolution, or returns “failure” otherwise. The path is computed by defining a new manifold that maintains a oneto- one correspondence with the singularity-free configuration space of the manipulator, and then using a higher-dimensional continuation technique to explore this manifold systematically from one configuration, until the second configuration is found. Examples are included that demonstrate the performance of the method on illustrative situations.

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    Numerical computation of manipulator singularities  Open access

     Bohigas Nadal, Oriol; Zlatanov, Dimiter; Ros Giralt, Lluis; Manubens Ferriol, Montserrat; Porta Pleite, Josep M.
    IEEE International Conference on Robotics and Automation
    Presentation's date: 2012
    Presentation of work at congresses

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    This paper provides a method to compute all types of singularities of non-redundant manipulators with non-helical lower pairs and designated instantaneous input and output speeds. A system of equations describing each singularity type is given. Using a numerical method based on linear relaxations, the configurations in each type are computed independently. The method is general and complete: it can be applied to manipulators with arbitrary geometry; and will isolate singu- larities with the desired accuracy. As an example, the entire singularity set and its complete classification are computed for a two-degree-of-freedom mechanism. The complex partition of the configuration space by various singularities is illustrated by three-dimensional projections.

    Postprint (author’s final draft)

  • Asymptotically-optimal path planning on manifolds

     Jaillet, Leonard Georges; Porta Pleite, Josep M.
    Robotics: Science and Systems
    Presentation's date: 2012
    Presentation of work at congresses

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  • Randomized path planning on manifolds based on higher-dimensional continuation

     Porta Pleite, Josep M.; Jaillet, Leonard Georges; Bohigas Nadal, Oriol
    International journal of robotics research
    Date of publication: 2012
    Journal article

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

     Rojas Libreros, Nicolás Enrique
    Defense's date: 2012-06-20
    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-

  • Rigid-CLL: Avoiding constant-distance computations in cell linked-lists algorithms

     Ruiz de Angulo Garcia, Vicente; Cortés, Juan; Porta Pleite, Josep M.
    Journal of computational chemistry
    Date of publication: 2012-01-30
    Journal article

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  • EG-RRT: Environment-guided random trees for kinodynamic motion planning with uncertainty and obstacles

     Jaillet, Leonard Georges; Hoffman, Judy; van den Berg, Jur; Abbeel, Pieter; Porta Pleite, Josep M.; Goldberg, Ken
    IEEE/RSJ International Conference on Intelligent Robots and Systems
    Presentation's date: 2011
    Presentation of work at congresses

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  • Probabilistic simultaneous pose and non-rigid shape recovery

     Moreno Noguer, Francesc d'Assis; Porta Pleite, Josep M.
    IEEE Conference on Computer Vision and Pattern Recognition
    Presentation's date: 2011
    Presentation of work at congresses

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  • Path planning in belief space with Pose SLAM

     Valencia Carreño, Rafael; Andrade Cetto, Juan; Porta Pleite, Josep M.
    IEEE International Conference on Robotics and Automation
    Presentation's date: 2011
    Presentation of work at congresses

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    The probabilistic belief networks that result from standard feature-based simultaneous localization and map building cannot be directly used to plan trajectories. The reason is that they produce a sparse graph of landmark estimates and their probabilistic relations, which is of little value to find collision free paths for navigation. In contrast, we argue in this paper that Pose SLAM graphs can be directly used as belief roadmaps. We present a method that devises optimal navigation strategies by searching for the path in the pose graph with lowest accumulated robot pose uncertainty, independently of the map reference frame. The method shows improved navigation results when compared to shortest paths both over synthetic data and real datasets.

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    Global optimization of robotic grasps  Open access

     Rosales Gallegos, Carlos; Porta Pleite, Josep M.; Ros Giralt, Lluis
    Robotics: Science and Systems
    Presentation's date: 2011
    Presentation of work at congresses

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    This paper presents a procedure to optimize the quality of robotic grasps for objects that need to be held and manipulated in a specific way, characterized by a number of tight contact constraints. The main difficulties of the problem include that the set of feasible grasps is a manifold implicitly defined by a system of non-linear equations, the high dimension of this manifold, and the multi-modal nature of typical grasp quality indices, which make local optimization methods get trapped into local extrema. The proposed procedure finds a way around these difficulties by focussing the exploration on a relevant subset of grasps of lower dimension, which is traced out exhaustively using higher-dimensional continuation techniques. Using these techniques, a detailed atlas of the subset is obtained, on which the highest quality grasp according to any desired criterion can be readily identified. Experiments on a 3-finger planar hand and on the Schunk anthropomorphic hand validate the approach.

    Postprint (author’s final draft)

  • Singularity-invariant leg rearrangements in stewart-gouch platforms

     Borras Sol, Julia
    Defense's date: 2011-04-15
    Institute of Industrial and Control Engineering (IOC), Universitat Politècnica de Catalunya
    Theses

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  • Map-based Localization for Urban Service Mobile Robotics  Open access

     Corominas Murtra, Andreu
    Defense's date: 2011-09-23
    Institute of Industrial and Control Engineering (IOC), Universitat Politècnica de Catalunya
    Theses

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    Mobile robotics research is currently interested on exporting autonomous navigation results achieved in indoor environments, to more challenging environments, such as, for instance, urban pedestrian areas. Developing mobile robots with autonomous navigation capabilities in such urban environments supposes a basic requirement for a upperlevel service set that could be provided to an users community. However, exporting indoor techniques to outdoor urban pedestrian scenarios is not evident due to the larger size of the environment, the dynamism of the scene due to pedestrians and other moving obstacles, the sunlight conditions, and the high presence of three dimensional elements such as ramps, steps, curbs or holes. Moreover, GPS-based mobile robot localization has demonstrated insufficient performance for robust long-term navigation in urban environments. One of the key modules within autonomous navigation is localization. If localization supposes an a priori map, even if it is not a complete model of the environment, localization is called map-based. This assumption is realistic since current trends of city councils are on building precise maps of their cities, specially of the most interesting places such as city downtowns. Having robots localized within a map allows for a high-level planning and monitoring, so that robots can achieve goal points expressed on the map, by following in a deliberative way a previously planned route. This thesis deals with the mobile robot map-based localization issue in urban pedestrian areas. The thesis approach uses the particle filter algorithm, a well-known and widely used probabilistic and recursive method for data fusion and state estimation. The main contributions of the thesis are divided on four aspects: (1) long-term experiments of mobile robot 2D and 3D position tracking in real urban pedestrian scenarios within a full autonomous navigation framework, (2) developing a fast and accurate technique to compute on-line range observation models in 3D environments, a basic step required by the real-time performance of the developed particle filter, (3) formulation of a particle filter that integrates asynchronous data streams and (4) a theoretical proposal to solve the global localization problem in an active and cooperative way, defining cooperation as either information sharing among the robots or planning joint actions to solve a common goal.

    Actualment, la recerca en robòtica mòbil té un interés creixent en exportar els resultats de navegació autònoma aconseguits en entorns interiors cap a d'altres tipus d'entorns més exigents, com, per exemple, les àrees urbanes peatonals. Desenvolupar capacitats de navegació autònoma en aquests entorns urbans és un requisit bàsic per poder proporcionar un conjunt de serveis de més alt nivell a una comunitat d'usuaris. Malgrat tot, exportar les tècniques d'interiors cap a entorns exteriors peatonals no és evident, a causa de la major dimensió de l'entorn, del dinamisme de l'escena provocada pels peatons i per altres obstacles en moviment, de la resposta de certs sensors a la il.luminació natural, i de la constant presència d'elements tridimensionals tals com rampes, escales, voreres o forats. D'altra banda, la localització de robots mòbils basada en GPS ha demostrat uns resultats insuficients de cara a una navegació robusta i de llarga durada en entorns urbans. Una de les peces clau en la navegació autònoma és la localització. En el cas que la localització consideri un mapa conegut a priori, encara que no sigui un model complet de l'entorn, parlem d'una localització basada en un mapa. Aquesta assumpció és realista ja que la tendència actual de les administracions locals és de construir mapes precisos de les ciutats, especialment dels llocs d'interés tals com les zones més cèntriques. El fet de tenir els robots localitzats en un mapa permet una planificació i una monitorització d'alt nivell, i així els robots poden arribar a destinacions indicades sobre el mapa, tot seguint de forma deliberativa una ruta prèviament planificada. Aquesta tesi tracta el tema de la localització de robots mòbils, basada en un mapa i per entorns urbans peatonals. La proposta de la tesi utilitza el filtre de partícules, un mètode probabilístic i recursiu, ben conegut i àmpliament utilitzat per la fusió de dades i l'estimació d'estats. Les principals contribucions de la tesi queden dividides en quatre aspectes: (1) experimentació de llarga durada del seguiment de la posició, tant en 2D com en 3D, d'un robot mòbil en entorns urbans reals, en el context de la navegació autònoma, (2) desenvolupament d'una tècnica ràpida i precisa per calcular en temps d'execució els models d'observació de distàncies en entorns 3D, un requisit bàsic pel rendiment del filtre de partícules a temps real, (3) formulació d'un filtre de partícules que integra conjunts de dades asíncrones i (4) proposta teòrica per solucionar la localització global d'una manera activa i cooperativa, entenent la cooperació com el fet de compartir informació, o bé com el de planificar accions conjuntes per solucionar un objectiu comú.

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    Synthesizing grasp configurations with specified contact regions  Open access

     Rosales Gallegos, Carlos; Ros Giralt, Lluis; Porta Pleite, Josep M.; Suarez Feijoo, Raul
    International journal of robotics research
    Date of publication: 2011
    Journal article

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    This paper presents a new method to solve the configuration problem on robotic hands:deter- mine how a hand should be configured so as to grasp a given object in a specific way, characterized by a number of hand-object contacts to be satisfied. In contrast to previous algorithms given for the same purpose, the one presented here allows specifing such contacts between free-form regions on the hand and object surfaces, and always returns a solution whenever one exists. The method is based on formulating the problem as a system of polynomial equations of special form, and then exploiting this form to isolate the solutions, using a numerical technique based on linear relaxations. The approach is general, in the sense that it can be applied to any grasping mechanism involving lower-pair joints, and it can accommodate as many hand-object contacts as required. Experi- ments are included that illustrate the performance of the method in the particular case of the Schunk Anthropomorphic hand.

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    Amortized constant time estimation in Pose SLAM and hierarchical SLAM using a mixed Kalman-information filter  Open access

     Ila, Viorela Simona; Porta Pleite, Josep M.; Andrade Cetto, Juan
    Robotics and autonomous systems
    Date of publication: 2011
    Journal article

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    The computational bottleneck in all information-based algorithms for simultaneous localization and mapping (SLAM) is the recovery of the state mean and covariance. The mean is needed to evaluate model Jacobians and the covariance is needed to generate data association hypotheses. In general, recovering the state mean and covariance requires the inversion of a matrix with the size of the state, which is computationally too expensive in time and memory for large problems. Exactly sparse state representations, such as that of Pose SLAM, alleviate the cost of state recovery either in time or in memory, but not in both. In this paper, we present an approach to state estimation that is linear both in execution time and in memory footprint at loop closure, and constant otherwise. The method relies on a state representation that combines the Kalman and the information-based approaches. The strategy is valid for any SLAM system that maintains constraints between marginal states at different time slices. This includes both Pose SLAM, the variant of SLAM where only the robot trajectory is estimated, and hierarchical techniques in which submaps are registered with a network of relative geometric constraints.

  • Exploring ambiguities for monocular non-rigid shape estimation

     Moreno Noguer, Francesc d'Assis; Porta Pleite, Josep M.; Fua, Pascal
    European Conference on Computer Vision
    Presentation's date: 2010
    Presentation of work at congresses

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  • Path planning on manifolds using randomized higher-dimensional continuation

     Porta Pleite, Josep M.; Jaillet, Leonard Georges
    International Workshop on the Algorithmic Foundations of Robotics
    Presentation's date: 2010
    Presentation of work at congresses

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    Path planning with pose SLAM  Open access

     Valencia Carreño, Rafael; Andrade Cetto, Juan; Porta Pleite, Josep M.
    Date: 2010
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    The probabilistic belief networks that result from standard feature-based simultaneous localization and map building (SLAM) approaches cannot be directly used to plan trajectories. The reason is that they produce a sparse graph of landmark estimates and their probabilistic relations, which is of little value to find collision free paths for navigation. In contrast, we argue in this paper that Pose SLAM graphs can be directly used as belief roadmaps (BRMs). The original BRM algorithm assumes a known model of the environment from which probabilistic sampling generates a roadmap. In our work, the roadmap is built on-line by the Pose SLAM algorithm. The result is a hybrid BRM-Pose SLAM method that devises optimal navigation strategies on-line by searching for the path with lowest accumulated uncertainty for the robot pose. The method is validated over synthetic data and standard SLAM datasets.

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    Information-based compact Pose SLAM  Open access

     Ila, Viorela Simona; Porta Pleite, Josep M.; Andrade Cetto, Juan
    IEEE transactions on robotics
    Date of publication: 2010
    Journal article

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    Pose SLAMis the variant of simultaneous localization and map building (SLAM) is the variant of SLAM, in which only the robot trajectory is estimated and where landmarks are only used to produce relative constraints between robot poses. To reduce the computational cost of the information filter form of PoseSLAM and, at the same time, to delay inconsistency as much as possible, we introduce an approach that takes into account only highly informative loop-closure links and nonredundant poses. This approach includes constant time procedures to compute the distance between poses, the expected information gain for each potential link, and the exact marginal covariances while moving in open loop, as well as a procedure to recover the state after a loop closure that, in practical situations, scales linearly in terms of both time and memory. Using these procedures, the robot operates most of the time in open loop, and the cost of the loop closure is amortized over long trajectories. This way, the computational bottleneck shifts to data association, which is the search over the set of previously visited poses to determine good candidates for sensor registration. To speed up data association, we introduce a method to search for neighboring poses whose complexity ranges from logarithmic in the usual case to linear in degenerate situations. The method is based on organizing the pose information in a balanced tree whose internal levels are defined using interval arithmetic. The proposed Pose-SLAM approach is validated through simulations, real mapping sessions, and experiments using standard SLAM data sets.

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    Amortized constant time state estimation in SLAM using a mixed Kalman-information filter  Open access

     Ila, Viorela Simona; Porta Pleite, Josep M.; Andrade Cetto, Juan
    European Conference on Mobile Robots
    Presentation's date: 2009
    Presentation of work at congresses

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    The computational bottleneck in all informationbased algorithms for SLAM is the recovery of the state mean and covariance. The mean is needed to evaluate model Jacobians and the covariance is needed to generate data association hypotheses. Recovering the state mean and covariance requires the inversion of a matrix of the size of the state. Current state recovery methods use sparse linear algebra tools that have quadratic cost, either in memory or in time. In this paper, we present an approach to state estimation that is worst case linear both in execution time and in memory footprint at loop closure, and constant otherwise. The approach relies on a state representation that combines the Kalman and the information-based state representations. The strategy is valid for any SLAM system that maintains constraints between robot poses at different time slices. This includes both Pose SLAM, the variant of SLAM where only the robot trajectory is estimated, and hierarchical techniques in which submaps are registered with a network of relative geometric constraints.

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    Concise proof of Tienstra's formula  Open access

     Porta Pleite, Josep M.; Thomas Arroyo, Federico
    Journal of surveying engineering (ASCE)
    Date of publication: 2009
    Journal article

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    The resection problem consists in finding the location of an observer by measuring the angles sub-tended by lines of sight from this observer to three known stations. Many researchers and practitioners recognize that Tienstra’s formula provides the most compact and elegant solution to this problem. Un- fortunately, all available proofs for this remarkable formula are intricate. This paper shows how, by using barycentric coordinates for the observer in terms of the locations of the stations, a neat and short proof is straightforwardly derived.

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    A linear relaxation technique for the position analysis of multiloop linkages  Open access

     Porta Pleite, Josep M.; Ros Giralt, Lluis; Thomas Arroyo, Federico
    IEEE transactions on robotics
    Date of publication: 2009
    Journal article

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    This paper presents a new method to isolate all configurations that a multiloop linkage can adopt. The problem is tackled by means of formulation and resolution techniques that fit particularly well together. The adopted formulation yields a system of simple equations (only containing linear, bilinear, and quadratic monomials, and trivial trigonometric terms for the helical pair only) whose 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, irrespective of whether the linkage is rigid or mobile.

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    Reduced state representation in delayed-state SLAM  Open access

     Ila, Viorela Simona; Porta Pleite, Josep M.; Andrade Cetto, Juan
    IEEE/RSJ International Conference on Intelligent Robots and Systems
    Presentation's date: 2009-10-11
    Presentation of work at congresses

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    This paper introduces an approach that reduces the size of the state and maximizes the sparsity of the information matrix in exactly sparse delayed-state SLAM. We propose constant time procedures to measure the distance between a given pair of poses, the mutual information gain for a given candidate link, and the joint marginals required for both measures. Using these measures, we can readily identify non redundant poses and highly informative links and use only those to augment and to update the state, respectively. The result is a delayed-state SLAM system that reduces both the use of memory and the execution time and that delays filter inconsistency by reducing the number of linearization introduced when adding new loop closure links. We evaluate the advantage of the proposed approach using simulations and data sets collected with real robots.

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    Finding all valid hand configurations for a given precision grasp  Open access

     Rosales Gallegos, Carlos; Porta Pleite, Josep M.; Suarez Feijoo, Raul; Ros Giralt, Lluis
    IEEE International Conference on Robotics and Automation
    Presentation's date: 2008
    Presentation of work at congresses

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    Planning a precision grasp for a robot hand is usually decomposed into two main steps. First, a set of contact points over the object surface must be determined, ensuring they allow a stable grasp. Second, the inverse kinematics of the robot hand must be solved to verify whether the contact points can actually be reached. Whereas the first problem has been largely solved in a general posing, the second one has only been tackled with local convergence methods. These methods only provide one solution to the problem, even if many are possible, and depending on the initial estimation they use, they may fail to converge, which results in grasp re-planning in situations where it could be avoided. This paper overcomes both issues by providing a complete method to solve the kinematics of human-like hands. The method is able to find all possible configurations that reach the specified contact points, even when positive-dimensional sets of such configurations are possible.

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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.

  • Complete maps of molecular-loop conformational spaces

     Porta Pleite, Josep M.; Ros, L; Thomas, F; Corcho Sanchez, Francisco Jose; Canto Silva, Josep; Perez Gonzalez, Juan Jesus
    Journal of computational chemistry
    Date of publication: 2007-10
    Journal article

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    Complete maps of molecular-loop conformational spaces  Open access

     Porta Pleite, Josep M.; Ros Giralt, Lluis; Thomas Arroyo, Federico; Corcho Sanchez, Francisco Jose; Canto Silva, Josep; Perez Gonzalez, Juan Jesus
    Journal of computational chemistry
    Date of publication: 2007-01
    Journal article

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    This paper presents a numerical method to compute all possible conformations of distance-constrained molecular loops, i.e., loops where some interatomic distances are held fixed, while others can vary. The method is general (it can be applied to single or multiple intermingled loops of arbitrary topology) and complete (it isolates all solutions, even if they form positive-dimensional sets). Generality is achieved by reducing the problem to finding all embeddings of a set of points constrained by pairwise distances, which can be formulated as computing the roots of a system of Cayley-Menger determinants. Completeness is achieved by expressing these determinants in Bernstein form and using a numerical algorithm that exploits such form to bound all root locations at any desired precision. The method is readily parallelizable, and the current implementation can be run on single- or multiprocessor machines. Experiments are included that show the method's performance on rigid loops, mobile loops, and multiloop molecules. In all cases, complete maps including all possible conformations are obtained, thus allowing an exhaustive analysis and visualization of all pseudo-rotation paths between different conformations satisfying loop closure.

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    Box approximations of planar linkage configuration spaces  Open access

     Porta Pleite, Josep M.; Ros Giralt, Lluis; Creemers, T; Thomas Arroyo, Federico
    Journal of mechanical design
    Date of publication: 2007-01
    Journal article

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    This paper presents a numerical method able to compute all possible configurations of planar linkages. The procedure is applicable to rigid linkages (i.e., those that can only adopt a finite number of configurations) and to mobile ones (i.e., those that exhibit a continuum of possible configurations). The method is based on the fact that this problem can be reduced to finding the roots of a polynomial system of linear, quadratic, and hyperbolic equations, which is here tackled with a new strategy exploiting its structure. The method is conceptually simple and easy to implement, yet it provides solutions of the desired accuracy in short computation times. Experiments are included that show its performance on the double butterfly linkage and on larger linkages formed by the concatenation of basic patterns.

  • Point-based value iteration for continuous POMDPs

     Porta Pleite, Josep M.; Vlassis, N; Spaan, Mtj; Poupart, P
    Journal of machine learning research
    Date of publication: 2006-11
    Journal article

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  • Planificador de trayectorias para sistemas robotizados de arquitectura arbitraria.

     Ros Giralt, Lluis; Creemers, Tom Lambert; Ruiz de Angulo Garcia, Vicente; Torras, Carme; Canto Silva, Josep; Sabater Pruna, Maria Assumpta; Corcho Sanchez, Francisco Jose; Porta Pleite, Josep M.
    Participation in a competitive project

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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
    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
    Presentation of work at congresses

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  • Reactive free-gait generation to follow arbitrary trajectories with a hexapod robot

     Porta Pleite, Josep M.; Celaya Llover, Enric
    Robotics and autonomous systems
    Date of publication: 2004-07
    Journal article

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  • BAHAVOIR-BASED ROBOTS AND REINFORCEMENT LEARNING. A CASE STUDY ON LEGGED-ROBOTS

     Porta Pleite, Josep M.
    Defense's date: 2001-10-09
    Department of Software, Universitat Politècnica de Catalunya
    Theses

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  • Efficient Gait Generation Using Reinforcement Learning

     Porta Pleite, Josep M.; Celaya Llover, Enric
    4th International Conference on Climbing and Walking robots
    Presentation of work at congresses

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  • Learning in categorizable environments

     Porta Pleite, Josep M.; Celaya Llover, Enric
    Sixth. Int. Conf. on Simulation of Adaptive Behavior
    Presentation of work at congresses

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  • Reinforcement Learning and Automatic Categorization

     Porta Pleite, Josep M.; Celaya Llover, Enric
    IEEE International Conference on Emerging Technologies and Factory Automation
    Presentation of work at congresses

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  • Navigation of a walking robot in natural environments

     Celaya Llover, Enric; Porta Pleite, Josep M.
    2nd International Conference on Climbing and Walking Robots CLAWAR'99
    Presentation of work at congresses

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  • Reactive gait generation for varying speed and direction

     Celaya Llover, Enric; Porta Pleite, Josep M.; Ruiz de Angulo Garcia, Vicente
    First International Symposium On Climbing And Walking Robots, CLAWAR'98
    Presentation's date: 1998-11-26
    Presentation of work at congresses

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  • A Control Structure for the Locomotion of a Legged Robot on Difficult Terrain

     Celaya Llover, Enric; Porta Pleite, Josep M.
    IEEE robotics and automation magazine
    Date of publication: 1998-06
    Journal article

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  • GAIT ANALYSIS FOR SIX-LEGGED ROBOTS

     Porta Pleite, Josep M.; Celaya Llover, Enric
    Date: 1998-06
    Report

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  • Walking in Unstructured Natural Environments

     Porta Pleite, Josep M.; Celaya Llover, Enric
    European Workshop on Hazardous Environment Robotics (HEROS'96)
    Presentation of work at congresses

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  • Control of a Six-Legged Robot Walking on Abrupt Terrain

     Celaya Llover, Enric; Porta Pleite, Josep M.
    IEEE International Conference on Robotics and Automation
    Presentation of work at congresses

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