Redefinición de indicadores y planificación del proceso de recogida de datos de la Biblioteca Virtual de la Universitat Oberta de Catalunya

Pre-print.

A Camera-Projector System for Robot Positioning by Visual Servoing

Positioning a robot with respect to objects by using data provided by a camera is a well known technique called visual servoing. In order to perform a task, the object must exhibit visual features which can be extracted from different points of view. Then, visual servoing is object-dependent as it depends on the object appearance. Therefore, performing the positioning task is not possible in presence of nontextured objets or objets for which extracting visual features is too complex or too costly. This paper proposes a solution to tackle this limitation inherent to the current visual servoing techniques. Our proposal is based on the coded structured light approach as a reliable and fast way to solve the correspondence problem. In this case, a coded light pattern is projected providing robust visual features independently of the object appearance

An approach to visual servoing based on coded light

Positioning a robot with respect to objects by using data provided by a camera is a well known technique called visual servoing. In order to perform a task, the object must exhibit visual features which can be extracted from different points of view. Then, visual servoing is object-dependent as it depends on the object appearance. Therefore, performing the positioning task is not possible in presence of non-textured objects or objects for which extracting visual features is too complex or too costly. This paper proposes a solution to tackle this limitation inherent to the current visual servoing techniques. Our proposal is based on the coded structured light approach as a reliable and fast way to solve the correspondence problem. In this case, a coded light pattern is projected providing robust visual features independently of the object appearance

Robust decoupled visual servoing based on structured light

This paper focuses on the problem of realizing a plane-to-plane virtual link between a camera attached to the end-effector of a robot and a planar object. In order to do the system independent to the object surface appearance, a structured light emitter is linked to the camera so that 4 laser pointers are projected onto the object. In a previous paper we showed that such a system has good performance and nice characteristics like partial decoupling near the desired state and robustness against misalignment of the emitter and the camera (J. Pages et al., 2004). However, no analytical results concerning the global asymptotic stability of the system were obtained due to the high complexity of the visual features utilized. In this work we present a better set of visual features which improves the properties of the features in (J. Pages et al., 2004) and for which it is possible to prove the global asymptotic stability

Plane-to-plane positioning from image-based visual servoing and structured light

In this paper we face the problem of positioning a camera attached to the end-effector of a robotic manipulator so that it gets parallel to a planar object. Such problem has been treated for a long time in visual servoing. Our approach is based on linking to the camera several laser pointers so that its configuration is aimed to produce a suitable set of visual features. The aim of using structured light is not only for easing the image processing and to allow low-textured objects to be treated, but also for producing a control scheme with nice properties like decoupling, stability, well conditioning and good camera trajectory

A new optimised De Bruijn coding strategy for structured light patterns

Coded structured light is an optical technique based on active stereovision that obtains the shape of objects. One shot techniques are based on projecting a unique light pattern with an LCD projector so that grabbing an image with a camera, a large number of correspondences can be obtained. Then, a 3D reconstruction of the illuminated object can be recovered by means of triangulation. The most used strategy to encode one-shot patterns is based on De Bruijn sequences. In This work a new way to design patterns using this type of sequences is presented. The new coding strategy minimises the number of required colours and maximises both the resolution and the accuracy

Overview of coded light projection techniques for automatic 3D profiling

Obtaining automatic 3D profile of objects is one of the most important issues in computer vision. With this information, a large number of applications become feasible: from visual inspection of industrial parts to 3D reconstruction of the environment for mobile robots. In order to achieve 3D data, range finders can be used. Coded structured light approach is one of the most widely used techniques to retrieve 3D information of an unknown surface. An overview of the existing techniques as well as a new classification of patterns for structured light sensors is presented. This kind of systems belong to the group of active triangulation method, which are based on projecting a light pattern and imaging the illuminated scene from one or more points of view. Since the patterns are coded, correspondences between points of the image(s) and points of the projected pattern can be easily found. Once correspondences are found, a classical triangulation strategy between camera(s) and projector device leads to the reconstruction of the surface. Advantages and constraints of the different patterns are discussed

Implementation of a robust coded structured light technique for dynamic 3D measurements

This paper presents the implementation details of a coded structured light system for rapid shape acquisition of unknown surfaces. Such techniques are based on the projection of patterns onto a measuring surface and grabbing images of every projection with a camera. Analyzing the pattern deformations that appear in the images, 3D information of the surface can be calculated. The implemented technique projects a unique pattern so that it can be used to measure moving surfaces. The structure of the pattern is a grid where the color of the slits are selected using a De Bruijn sequence. Moreover, since both axis of the pattern are coded, the cross points of the grid have two codewords (which permits to reconstruct them very precisely), while pixels belonging to horizontal and vertical slits have also a codeword. Different sets of colors are used for horizontal and vertical slits, so the resulting pattern is invariant to rotation. Therefore, the alignment constraint between camera and projector considered by a lot of authors is not necessary

A survey addressing the fundamental matrix estimation problem

Epipolar geometry is a key point in computer vision and the fundamental matrix estimation is the only way to compute it. This article surveys several methods of fundamental matrix estimation which have been classified into linear methods, iterative methods and robust methods. All of these methods have been programmed and their accuracy analysed using real images. A summary, accompanied with experimental results, is given

Martin Heidegger

Nota biogràfica sobre el filòsof Martin Heidegger on es fa, per una banda, un breu repàs dels principals fets de la seva vida com a filòsof i, per una altra banda, un breu repàs de la seva obra

Monitorització d'un centre de processament de dades d'una administració pública, mitjançant Nagios i Centreon

Es mostra la implantació d'un sistema de monitorització d'un CPD en una administració pública amb Nagios i Centreon, i es compara breument amb algunes alternatives.

El solatge clàssic en la poesia angladiana

Anàlisi sobre la influència que exerciren els clàssics grcollatins sobre l'obra poètica de M. Àngels Anglada

Estratègies de teràpia gènica per a neuropatia diabètica

L'objectiu del projecte consisteix en desenvolupar estratègies de teràpia gènica per al tractament de la neuropatia diabètica. Per a la teràpia gènica és necessària la utilització de vectors per tal d'introduir el material genètic exogen en les cèl•lules diana. En aquest projecte s'utilitzen vectors derivats de virus adenoassociats i es fan estudis de tropisme de diferents serotips de vectors administrant-los per diferents vies. D’aquesta manera es pot escollir quin és el millor vector i la millor via d'administració per a cada cas, i en el cas d'aquest projecte, per a tractar les cèl•lules afectades en la neuropatia diabètica. La neuropatia diabètica és una complicació de la diabetis per a la qual no hi ha cap tractament. Afecta les cèl•lules del sistema nerviós perifèric (neurones sensorials, neurones motores i cèl•lules de Schwann) i és la causa la major part de les amputacions d'extremitats inferiors. En aquest projecte es pretén estudiar quines són les possibles causes del desenvolupament de la neuropatia diabètica analitzant canvis a nivell de l'expressió gènica en models de ratolins diabètics i també en els models in vitro dissenyats per al projecte. Posteriorment es vol proposar un tractament de teràpia gènica mitjançant els resultats dels estudis de tropisme dels vectors virals i dels estudis d'expressió gènica dels models de diabetis.

Luck and the control theory of knowledge

The dissertation accomplishes two aims: 1) to diagnose what prevents true beliefs from being knowledge; 2) to give an positive account of knowledge. Concerning the first aim, it offers an account of the notion of luck. It defends the view that luck is a form of risk and distinguishes two types of luck. Then, it applies the account to the problem of epistemic luck and distinguishes, accordingly, two types of epistemic luck. It is argued that these two types of epistemic luck explain the whole range of cases of not-known true belief. Concerning the second aim, the dissertation advances an account of knowledge in terms of the notion of cognitive control that deals with the two forms of epistemic luck distinguished.

Epidemiologia de la fractura a l’atenció primària de catalunya

Utilitzant una base de dades amb informació clínica extreta de l’historial d’Atenció Primària (AP) a Catalunya, hem portat a terme un estudi de cohorts retrospectiu l’any 2009, incloent individus  50 anys. Hem identificat les fractures osteoporòtiques majors utilitzant codis CIE-10. 2.011.430 individus van ser inclosos. La incidència total va ser de 10’91/1.000 persones-any. La fractura més freqüent entre les dones va ser la d’avantbraç i entre els homes la vertebral simptomàtica. Totes les fractures van augmentar amb l’edat però es van observar diferents patrons segons localització. Aquesta informació és rellevant per la planificació dels serveis d’AP al nostre país.