http://hdl.handle.net/2117/2249 2013-05-21T15:11:55Z http://hdl.handle.net/2117/19254 Title: Spatiotemporal descriptor for wide-baseline stereo reconstruction of non-rigid and ambiguous scenes Authors: Trulls Fortuny, Eduard; Sanfeliu Cortés, Alberto; Moreno-Noguer, Francesc Abstract: This paper studies the use of temporal consistency to match appearance descriptors and handle complex ambiguities when computing dynamic depth maps from stereo. Previous attempts have designed 3D descriptors over the spacetime volume and have been mostly used for monocular action recognition, as they cannot deal with perspective changes. Our approach is based on a state-of-the-art 2D dense appearance descriptor which we extend in time by means of optical flow priors, and can be applied to wide-baseline stereo setups. The basic idea behind our approach is to capture the changes around a feature point in time instead of trying to describe the spatiotemporal volume. We demonstrate its effectiveness on very ambiguous synthetic video sequences with ground truth data, as well as real sequences. 2013-05-15T13:55:05Z http://hdl.handle.net/2117/19206 Title: Negotiation and learning in distributed MPC of large scale systems Authors: Javalera Rincón, Valeria; Morcego Seix, Bernardo; Puig Cayuela, Vicenç Abstract: A key issue in distributed MPC control of Large Scale Systems (LSS) is how shared variables among the different MPC controller in charge of controlling each system partition (subsystems) are handled. When these connections represent control variables, the distributed control has to be consistent for both subsystems and the optimal value of these variables will have to accomplish a common goal. In order to achieve this, the present work combines ideas from Distributed Artificial Intelligence (DAI), Reinforcement Learning (RL) and Model Predictive Control (MPC) in order to provide an approach based on negotiation, cooperation and learning techniques. Results of the application of this approach to a small drinking water network show that the resulting trajectories of the levels in tanks (control variables) can be acceptable compared to the centralized solution. The application to a real network (the Barcelona case) is currently under development. 2013-05-14T12:34:16Z http://hdl.handle.net/2117/19009 Title: Experimental analysis of a degraded open-cathode PEM fuel cell stack Authors: Strahl, Stephan; Gasamans Rodríguez, Noemí; Llorca Piqué, Jordi; Husar, Attila Peter Abstract: The well-known challenges to be overcome in PEM fuel cell research are their relatively low durability and high costs for the platinum catalysts. Thus, this work focuses on factors that impact durability and the links to the fuel cell performance. Therefore a degraded, open-cathode, 20-cell, PEM fuel cell stack, which was used in a laboratory test station for characterization experiments, was analyzed experimentally. Voltage transients during external perturbations, such as changing temperature, humidity and stoichiometries show that degradation affects individual cells quite differently throughout the lifetime of the stack. Electrochemical impedance spectroscopy (EIS) data presents non-reversible catalyst layer and membrane degradation of several cells. X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) are in progress in order to validate the results of the electrical analysis and elucidate catalyst and membrane degradation. 2013-04-26T12:04:59Z http://hdl.handle.net/2117/18767 Title: POMDP approach to robotized clothes separation Authors: Monsó Purtí, Pol; Alenyà Ribas, Guillem; Torras, Carme Abstract: Rigid object manipulation with robots has mainly relied on precise, expensive models and deterministic sequences. Given the great complexity of accurately modeling deformable objects, their manipulation seems to call for a rather different approach. This paper proposes a probabilistic planner, based on a Partially Observable Markov Decision Process (POMDP), targeted at reducing the inherent uncertainty of deformable object sorting. It is shown that a small set of unreliable actions and inaccurate perceptions suffices to accomplish the task, provided faithful statistics on both of them are collected beforehand. The planner has been applied to a clothes sorting task in a real case context with a depth and color sensor and a robotic arm. Experimental results show the promise of the approach since more than 95% certainty of having isolated a piece of clothing is reached in an average of four steps for quite entangled initial clothing configurations. 2013-04-11T11:16:20Z http://hdl.handle.net/2117/18447 Title: Diseño de un convertidor CC-CC doble boost acoplado Authors: González, Sergio; Puleston, Paul; Fossas Colet, Enric Abstract: El convertidor de CC a CC doble boost acoplado (C2B) es de interés en aplicaciones emergentes que demandan alto rendimiento y alta relación de conversión, evitando valores extremos del ciclo de trabajo de la llave. El C2B consta de dos convertidores boost en cascada, operando con una sola llave y acoplados magnéticamente a través de sus inductores. Este acoplamiento condiciona fuertemente la relación de conversión del convertidor, dada su dependencia con la corriente de carga. Se analiza su principio de funcionamiento distinguiendo cuatro modos de operación. A través de un modelo general de gran señal es posible conocer el comportamiento de la relación de conversión del convertidor con cambios de carga en diferentes puntos de operación. Estos resultados son volcados al diseño de un prototipo, legitimando el análisis en un prototipo experimental. 2013-03-20T17:35:55Z http://hdl.handle.net/2117/18424 Title: Application of predictive control strategies to the management of complex networks in the urban water cycle Authors: Ocampo-Martínez, Carlos; Puig Cayuela, Vicenç; Cembrano Gennari, Gabriela; Quevedo Casín, Joseba Jokin Abstract: The management of the urban water cycle (UWC) is a subject of increasing interest because of its social, economic, and environmental impact. The most important issues include the sustainable use of limited resources and the reliability of service to consumers with adequate quality and pressure levels, as well as the urban drainage management to prevent flooding and polluting discharges to the environment. 2013-03-19T18:02:56Z http://hdl.handle.net/2117/18423 Title: Characterization of textile grasping experiments Authors: Alenyà Ribas, Guillem; Ramisa Ayats, Arnau; Moreno-Noguer, Francesc; Torras, Carme Abstract: Grasping highly deformable objects, like textiles, is an emerging area of research that involves both percep- tion and manipulation abilities. As new techniques appear, it becomes essential to design strategies to compare them. However, this is not an easy task, since the large state-space of textile objects explodes when coupled with the variability of grippers, robotic hands and robot arms performing the manipulation task. This high variability makes it very difficult to design experiments to evaluate the performance of a system in a repeatable way and compare it to others. We propose a framework to allow the comparison of different grasping methods for textile objects. Instead of measuring each component separately, we there- fore propose a methodology to explicitly measure the vision- manipulation correlation by taking into account the throughput of the actions. Perceptions of deformable objects should be grouped into different clusters, and the different grasping actions available should be tested for each perception type to obtain the action-perception success ratio. This characterization potentially allows to compare very different systems in terms of specialized actions , perceptions or widely useful actions , along with the cost of performing each action. We will also show that this categorization is useful in manipulation planning of deformable objects. 2013-03-19T17:57:49Z http://hdl.handle.net/2117/18378 Title: Stochastic exploration of ambiguities for nonrigid shape recovery Authors: Moreno-Noguer, Francesc; Fua, Pascal Abstract: Recovering the 3D shape of deformable surfaces from single images is known to be a highly ambiguous problem because many different shapes may have very similar projections. This is commonly addressed by restricting the set of possible shapes to linear combinations of deformation modes and by imposing additional geometric constraints. Unfortunately, because image measurements are noisy, such constraints do not always guarantee that the correct shape will be recovered. To overcome this limitation, we introduce a stochastic sampling approach to efficiently explore the set of solutions of an objective function based on point correspondences. This allows to propose a small set of ambiguous candidate 3D shapes and then use additional image information to choose the best one. As a proof of concept, we use either motion or shading cues to this end and show that we can handle a complex objective function without having to solve a difficult non-linear minimization problem. The advantages of our method are demonstrated on a variety of problems including both real and synthetic data. 2013-03-18T18:31:33Z http://hdl.handle.net/2117/18285 Title: Water transport study in high temperature fuel cell stack Authors: Bezmalinovic, Dario; Husar, Attila Peter Abstract: This work presents analysis of water transport phenomena in the 120 Wel high temperature PEM fuel cell stack. Phosphoric acid doped PBI membranes are known for their abilities to work with dry gases; however water in the electrolyte still plays an integral role in the proton conduction mechanism. The presence of water in the membrane increases proton conductivity, however at high operating temperatures in the anhydrous environment phosphoric acid can dehydrate consequently lowering its conductivity. Therefore, understanding of water transport in the PBI- H3PO4 membranes is important as it can explain certain phenomena inside the cell. Tests have shown that water transport from cathode to anode due to water accumulation rises almost linearly with current density while decreases with cathode stoichiometry. Water transport seems to be independent of operating temperature. Also, in some cases, reverse flow water transport (from anode to cathode) appears to take place near the outlet. Ohmic resistance was also found to decrease slightly with an increase in current density and lower stoichiometries. 2013-03-13T17:52:15Z http://hdl.handle.net/2117/18284 Title: Diseño e implementación de un control supervisor para sistemas híbridos de generación basado en pilas de combustible Authors: More, J.J.; Puleston, Paul; Kunusch, Cristian; Riera Colomer, Jordi Abstract: En el presente artículo se muestra el desarrollo, implementación y resultados experimentales de un control supervisor para un sistema híbrido de generación de energía eléctrica basado en una pila de combustible tipo PEM. El núcleo de este sistema está formado por una pila de combustible tipo PEM y un banco de supercapacitores. La primera se encuentra vinculada a un bus de corriente continua mediante un convertidor DC/DC unidireccional, mientras que los supercapacitores están conectados al bus mediante un convertidor bidireccional. E l sistema se completa mediante un módulo de energía alternativa, en este caso una turbina eólica, junto con un electrolizador que genera el hidrógeno a ser utilizado por la pila de combustible. El control supervisor diseñando gestiona el flujo de energía garantizando que la carga conectada al bus siempre se encuentre correctamente alimentada. Por otro lado, debe asegurarse, de ser posible, de mantener cargados los supercapacitores, así como el reservorio de hidrógeno. Con estos objetivos el control supervisor es responsable de generar las referencias de potencia para cada subsistema, las cuales deben ser oportunamente satisfechas por controladores dedicados en cada uno de ellos. El esquema propuesto es implementado y evaluado experimentalmente en una estación de ensayo híbrida bajo condiciones extremas de funcionamiento. 2013-03-13T17:38:29Z http://hdl.handle.net/2117/18283 Title: Online human-assisted learning using random ferns Authors: Villamizar Vergel, Michael Alejandro; Garrell Zulueta, Anais; Sanfeliu Cortés, Alberto; Moreno-Noguer, Francesc Abstract: We present an Online Random Ferns (ORFs) classifier that progressively learns and builds enhanced models of object appearances. During the learning process, we allow the human intervention to assist the classifier and discard false positive training samples. The amount of human intervention is minimized and integrated within the online learning, such that in a few seconds, complex object appearances can be learned. After the assisted learning stage, the classifier is able to detect the object under severe changing conditions. The system runs at a few frames per second, and has been validated for face and object detection tasks on a mobile robot platform. We show that with minimal human assistance we are able to build a detector robust to viewpoint changes, partial occlusions, varying lighting and cluttered backgrounds. 2013-03-13T17:23:20Z http://hdl.handle.net/2117/18243 Title: Design of non-anthropomorphic robotic hands for anthropomorphic tasks Authors: Simo Serra, Edgar; Moreno-Noguer, Francesc; Pérez Gracia, Alba Abstract: In this paper, we explore the idea of designing non- anthropomorphic multi-fingered robotic hands for tasks tha t replicate the motion of the human hand. Taking as input data a finite set of rigid-body positions for the five fingertips, we de- velop a method to perform dimensional synthesis for a kinema tic chain with a tree structure, with five branches that share thr ee common joints. We state the forward kinematics equations of relative dis- placements for each serial chain expressed as dual quaterni ons, and solve for up to five chains simultaneously to reach a numbe r of positions along the hand trajectory. This is done using a h y- brid global numerical solver that integrates a genetic algo rithm and a Levenberg-Marquardt local optimizer. Although the number of candidate solutions in this problem is very high, the use of the genetic algorithm allows us to per form an exhaustive exploration of the solution space to obtain a s et of solutions. We can then choose some of the solutions based on t he specific task to perform. Note that these designs match the ta sk exactly while generally having a finger design radically dif ferent from that of the human hand. 2013-03-12T18:21:39Z http://hdl.handle.net/2117/18241 Title: Robust non-rigid registration of 2D and 3D graphs Authors: Serradell, Eduard; Glowacki, Przemyslaw; Jan, Kybic; Moreno-Noguer, Francesc; Fua, Pascal Abstract: We present a new approach to matching graphs embedded in R2 or R3. Unlike earlier methods, our approach does not rely on the similarity of local appearance features, does not require an initial alignment, can handle partial matches, and can cope with non-linear deformations and topological differences. To handle arbitrary non-linear deformations, we represent them as Gaussian Processes. In the absence of appearance information, we iteratively establish correspondences between graph nodes, update the structure accordingly, and use the current mapping estimate to find the most likely correspondences that will be used in the next iteration. This makes the computation tractable. We demonstrate the effectiveness of our approach first on synthetic cases and then on angiography data, retinal fundus images, and microscopy image stacks acquired at very different resolutions. 2013-03-12T18:06:06Z http://hdl.handle.net/2117/18240 Title: Asymptotically-optimal path planning on manifolds Authors: Jaillet, Leonard Georges; Porta Pleite, Josep Maria Abstract: This paper presents an approach for optimal path planning on implicitly-defined configuration spaces such as those arising, for instance, when manipulating an object with two arms or with a multifingered hand. In this kind of situations, the kinematic and contact constraints induce configuration spaces that are manifolds embedded in higher dimensional ambient spaces. Existing sampling-based approaches for path planning on manifolds focus on finding a feasible solution, but they do not optimize the quality of the path in any sense. Thus, the returned paths are usually not suitable for direct execution. Recently, RRT* and other similar asymptotically-optimal path planners have been proposed to generate high-quality paths in the case of globally parametrizable configuration spaces. In this paper, we propose to use higher dimensional continuation tools to extend RRT* to the case of implicitly-defined configuration spaces. Experiments in different problems validate the proposed approach. 2013-03-12T17:56:02Z http://hdl.handle.net/2117/18239 Title: External force estimation for textile grasp detection Authors: Colomé Figueras, Adrià; Pardo Ayala, Diego Esteban; Alenyà Ribas, Guillem; Torras, Carme Abstract: Our current work on external force estimation without end-effector force sensor is resented.To verify if a grasp of a textile has been successful, the external wrench applied on the robot is computed online, with a state observer based on a LWPR [3] model of a task. 2013-03-12T17:45:58Z