http://hdl.handle.net/2117/3755 2013-05-25T22:00:16Z http://hdl.handle.net/2117/19349 Title: Segmentation robust to the vignette effect for machine vision systems Authors: Karatzas, D; Rusiñol, Marçal; Antens, Coen; Ferrer Sumsi, Miquel Abstract: The vignette effect (radial fall-off) is commonly encountered in images obtained through certain image acquisition setups and can seriously hinder automatic analysis processes. In this paper we present a fast and efficient method for dealing with vignetting in the context of object segmentation in an existing industrial inspection setup. The vignette effect is modelled here as a circular, non-linear gradient. The method estimates the gradient parameters and employs them to perform segmentation. Segmentation results on a variety of images indicate that the presented method is able to successfully tackle the vignette effect. 2013-05-17T14:48:37Z http://hdl.handle.net/2117/19347 Title: Combination of OCR engines for page segmentation based on performance evaluation Authors: Ferrer Sumsi, Miquel; Valveny, Ernest Abstract: In this paper we present a method to improve the performance of individual page segmentation engines based on the combination of the output of several engines. The rules of combination are designed after analyzing the results of each individual method. This analysis is performed using a performance evaluation framework that aims at characterizing each method according to its strengths and weaknesses rather than computing a single performance measure telling which is the "best" segmentation method. 2013-05-17T14:31:18Z http://hdl.handle.net/2117/19344 Title: An iterative algorithm for approximate median graph computation Authors: Ferrer Sumsi, Miquel; Bunke, Horst Abstract: Recently, the median graph has been shown to be a good choice to obtain a representative of a given set of graphs. It has been successfully applied to graph-based classification and clustering. In this paper we exploit a theoretical property of the median, which has not yet been utilized in the past, to derive a new iterative algorithm for approximate median graph computation. Experiments done using five different graph databases show that the proposed approach yields, in four out of these five datasets, better medians than two of the previous existing methods. 2013-05-17T14:07:48Z http://hdl.handle.net/2117/19342 Title: An approximate algorithm for median graph computation using graph embedding Authors: Ferrer Sumsi, Miquel; Valveny, Ernest; Serratosa Casanelles, Francesc; Riesen, Kaspar; Bunke, Horst Abstract: Graphs are powerful data structures that have many attractive properties for object representation. However, some basic operations are difficult to define and implement, for instance, how to obtain a representative of a set of graphs. The median graph has been defined for that purpose, but existing algorithms are computationally complex and have a very limited applicability. In this paper we propose a new approach for the computation of the median graph based on graph embedding in vector spaces. Experiments on a real database containing large graphs show that we succeed to compute good approximations of the median graph. We have also applied the median graph to perform some basic classification tasks achieving reasonable good results. 2013-05-17T13:58:08Z 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/2117/18631 Title: LPV model for PV cell and fractional control of DC-DC converter for photovoltaic systems Authors: Martínez González, Rubén; Bolea Monte, Yolanda; Grau Saldes, Antoni; Martínez García, Herminio Abstract: This paper deals with the fractional modelling of a DC-DC converter, suitable in solar-powered electrical generation systems, and the design of a fractional controller for the aforementioned switching converter. A new model for PV cells is proposed in order to obtain a linear equation for V-I characteristic via scheduling dependence of temperature and irradiance. Due to the fractional nature of the ultracapacitors this kind of controller gives a suitable and good performance. 2013-04-05T08:37:19Z 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/2117/18325 Title: Probabilistic invariant image representation and associated distance measure Authors: Scandaliaris, Jorge; Sanfeliu Cortés, Alberto 2013-03-15T07:46:59Z 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/2117/18253 Title: Current-mode one-cycle control applied to linear–assisted DC/DC converters Authors: Martínez García, Herminio; Grau Saldes, Antoni; Bolea Monte, Yolanda Abstract: This article shows the proposal of a current-mode one-cycle control for linear-assisted DC/DC converters. Linear-assisted DC/DC converters are structures that allow to take advantages of the two classic alternatives in the design of power supply systems: voltage linear regulators (classic NPN topology or LDO –low dropout–) and switching DC/DC converters. The current-mode onecycle control technique is proposed in order to obtain the duty cycle of the linear-assisted converter switch. The proposed structure can provide an output with suitable load and line regulations. Thus, the paper shows the design and simulation results of the proposed currentmode one-cycle linear-assisted converter. 2013-03-13T10:28:34Z 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/2117/18132 Title: Buck–Boost DC-DC converter with fractional control Authors: Martínez García, Herminio; Grau Saldes, Antoni; Bolea Monte, Yolanda; Martínez González, Rubén Abstract: This paper deals with the fractional modeling of a DC-DC buck-boost converter, suitable in solar-powered electrical generation systems, and the design of a fractional controller for the aforementioned switching converter. Although the modeling and design of the controller is carried out for this particular DC-DC converter, it can be easily extended to other kind of switching converter. In addition, the comparison between integer-order plant/controller and fractional-order plants/controller is carried out. The article also shows that, under the same design conditions, the fractional-order controller has a better performance and behaviour than the classical integer-order controller in both situations, that is, with integer-order plant and fractional-order plant models. 2013-03-07T13:21:12Z http://hdl.handle.net/2117/18128 Title: Current–Mode One-Cycle control applied to linear–assisted DC/DC converters Authors: Martínez García, Herminio; Grau Saldes, Antoni; Bolea Monte, Yolanda; Gámiz Caro, Juan Abstract: This article shows the proposal of an current-mode one-cycle control for linear-assisted DC/DC converters. Linear-assisted DC/DC converters are structures that allow to take advantages of the two classic alternatives in the design of power supply systems: voltage linear regulators (classic NPN topology or LDO –low dropout–) and switching DC/DC converters. The current-mode one-cycle control technique is proposed in order to obtain the duty cycle of the linear-assisted converter switch. The proposed structure can provide an output with suitable load and line regulations. The paper shows the design and simulation results of the proposed current-mode one-cycle linearassisted converter. 2013-03-07T12:40:02Z http://hdl.handle.net/2117/18125 Title: Parallel Linear–Assisted DC-DC Switching Converter Authors: Martínez García, Herminio; Grau Saldes, Antoni; Bolea Monte, Yolanda; Gámiz Caro, Juan Abstract: Linear-assisted DC-DC converters or linear-switching hybrid DC–DC converters are power supply structures in which some important advantages from linear regulators and DC-DC switching converters converge. Normally, in linear assisted converters a series linear regulator is used in order to provide a constant ripple-free output voltage. However, this article shows the proposal of a linear–assisted DCDC converter or linear–&–switching hybrid converter including a parallel linear regulator. 2013-03-07T12:11:52Z