Optimization of floor cleaning coverage performance of a random path-planning mobile robot

Floor cleaning is a typical robot application. There are several mobile robots aviable in the market for domestic applications most of them with random path-planning algorithms. In this paper we study the cleaning coverage performances of a random path-planning mobile robot and propose an optimized control algorithm, some methods to estimate the are of the room, the evolution of the cleaning and the time needed for complete coverage.

An approach to vision-based station keeping for an unmanned underwater vehicle

This paper presents an automatic vision-based system for UUV station keeping. The vehicle is equipped with a down-looking camera, which provides images of the sea-floor. The station keeping system is based on a feature-based motion detection algorithm, which exploits standard correlation and explicit textural analysis to solve the correspondence problem. A visual map of the area surveyed by the vehicle is constructed to increase the flexibility of the system, allowing the vehicle to position itself when it has lost the reference image. The testing platform is the URIS underwater vehicle. Experimental results demonstrating the behavior of the system on a real environment are presented

Perspectives of auto-correcting lens distortions in mosaic-based underwater navigation

When unmanned underwater vehicles (UUVs) perform missions near the ocean floor, optical sensors can be used to improve local navigation. Video mosaics allow to efficiently process the images acquired by the vehicle, and also to obtain position estimates. We discuss in this paper the role of lens distortions in this context, proving that degenerate mosaics have their origin not only in the selected motion model or in registration errors, but also in the cumulative effect of radial distortion residuals. Additionally, we present results on the accuracy of different feature-based approaches for self-correction of lens distortions that may guide the choice of appropriate techniques for correcting distortions

Large-Area Photo-Mosaics Using Global Alignment and Navigation Data

Seafloor imagery is a rich source of data for the study of biological and geological processes. Among several applications, still images of the ocean floor can be used to build image composites referred to as photo-mosaics. Photo-mosaics provide a wide-area visual representation of the benthos, and enable applications as diverse as geological surveys, mapping and detection of temporal changes in the morphology of biodiversity. We present an approach for creating globally aligned photo-mosaics using 3D position estimates provided by navigation sensors available in deep water surveys. Without image registration, such navigation data does not provide enough accuracy to produce useful composite images. Results from a challenging data set of the Lucky Strike vent field at the Mid Atlantic Ridge are reported

A system to evaluate the accuracy of a visual mosaicking methodology

When underwater vehicles navigate close to the ocean floor, computer vision techniques can be applied to obtain motion estimates. A complete system to create visual mosaics of the seabed is described in this paper. Unfortunately, the accuracy of the constructed mosaic is difficult to evaluate. The use of a laboratory setup to obtain an accurate error measurement is proposed. The system consists on a robot arm carrying a downward looking camera. A pattern formed by a white background and a matrix of black dots uniformly distributed along the surveyed scene is used to find the exact image registration parameters. When the robot executes a trajectory (simulating the motion of a submersible), an image sequence is acquired by the camera. The estimated motion computed from the encoders of the robot is refined by detecting, to subpixel accuracy, the black dots of the image sequence, and computing the 2D projective transform which relates two consecutive images. The pattern is then substituted by a poster of the sea floor and the trajectory is executed again, acquiring the image sequence used to test the accuracy of the mosaicking system

Estimating the motion of an underwater robot from a monocular image sequence

When underwater vehicles perform navigation close to the ocean floor, computer vision techniques can be applied to obtain quite accurate motion estimates. The most crucial step in the vision-based estimation of the vehicle motion consists on detecting matchings between image pairs. Here we propose the extensive use of texture analysis as a tool to ameliorate the correspondence problem in underwater images. Once a robust set of correspondences has been found, the three-dimensional motion of the vehicle can be computed with respect to the bed of the sea. Finally, motion estimates allow the construction of a map that could aid to the navigation of the robot

Correction of shading effects in vision-based UUV localization

This paper describes the improvements achieved in our mosaicking system to assist unmanned underwater vehicle navigation. A major advance has been attained in the processing of images of the ocean floor when light absorption effects are evident. Due to the absorption of natural light, underwater vehicles often require artificial light sources attached to them to provide the adequate illumination for processing underwater images. Unfortunately, these flashlights tend to illuminate the scene in a nonuniform fashion. In this paper a technique to correct non-uniform lighting is proposed. The acquired frames are compensated through a point-by-point division of the image by an estimation of the illumination field. Then, the gray-levels of the obtained image remapped to enhance image contrast. Experiments with real images are presented

On the way to solve lighting problems in underwater imaging

A major obstacle to processing images of the ocean floor comes from the absorption and scattering effects of the light in the aquatic environment. Due to the absorption of the natural light, underwater vehicles often require artificial light sources attached to them to provide the adequate illumination. Unfortunately, these flashlights tend to illuminate the scene in a nonuniform fashion, and, as the vehicle moves, induce shadows in the scene. For this reason, the first step towards application of standard computer vision techniques to underwater imaging requires dealing first with these lighting problems. This paper analyses and compares existing methodologies to deal with low-contrast, nonuniform illumination in underwater image sequences. The reviewed techniques include: (i) study of the illumination-reflectance model, (ii) local histogram equalization, (iii) homomorphic filtering, and, (iv) subtraction of the illumination field. Several experiments on real data have been conducted to compare the different approaches

Detection of matchings in a sequence of underwater images through texture analysis

This paper presents an approach to ameliorate the reliability of the correspondence points relating two consecutive images of a sequence. The images are especially difficult to handle, since they have been acquired by a camera looking at the sea floor while carried by an underwater robot. Underwater images are usually difficult to process due to light absorption, changing image radiance and lack of well-defined features. A new approach based on gray-level region matching and selective texture analysis significantly improves the matching reliability

Efecte de la recurrència dels incendis sobre la vegetació i el sòl a les zones de matollar del Macizo Central Ourensano

El matollar sec europeu format per Erica australis, Erica arborea, Pterosparum tridentatum, Halimium lasianthum i Calluna vulgaris com a espècies predominants és cremat en les serralades del Massís Central de forma repetida durant el pas dels anys. Això ha sigut, tradicionalment, a causa de la necessitat de mantenir-lo transitable per al bestiar, encara que altres circumstàncies s’han afegit actualment a aquesta necessitat, que incrementen el risc d’incendi d’aquesta comunitat, disparant-se el número d’incendis en els últims 30 anys. Sabent això, vam decidir realitzar un estudi a les zones de matollar que trobem al Massís Central situat a la zona del Concello de Villariño de Conso, a Ourense, per conèixer com es comporten les espècies característiques d’aquest tipus d’ecosistema després dels incendis, mitjançant la realització de mostrejos i perfils del sòl. D’aquesta manera hem volgut veure com es desenvolupen les espècies vegetals de matollar al llarg del temps, després de ser cremats. Gràcies a l’estudi hem pogut veure com el matollar observat te unes característiques que li permet sobreviure als incendis i tindre una capacitat de regeneració elevada després de patir aquesta pertorbació. Això es degut a la capacitat per rebrotar d’aquestes espècies arbustives i a la seva competitivitat. També hem vist com a necessari, donar un valor econòmic a la bona conservació de l’hàbitat, per tal de que la població local abandoni pràctiques de gestió forestal nocives, com el foc.

Determinants of Decentralization within the Firm: Some Empirical Evidence from Spanish Small and Medium- Sized Enterprise

This paper examines empirically the determinants of decentralization of decision- making in the firm for small and medium-sized enterprises (SMEs) that tend to be highly centralized. By decentralization of decisions we mean the delegation of decision rights from the owner or manager to the plant supervisor or even to floor workers. Our findings show that the allocation of authority to basic workers or a team of workers depends on firm characteristics such as firm size, the use of internal networks or the number of workplaces, and workers characteristics, in particular, the composition of the laborforce in terms of education and seniority and whether or not workers receive pay incentives. External factors such as the intensity of competition and the firm s export intensity are also important determinants of the allocation of authority.

Sistema d'AGV (vehicles-robot de guiatge automàtic) per a magatzems i plantes de manufactura

Una de les solucions per a minimitzar els costos de producció o d'emmagatzematge és automatitzarne la logística interna. Per dissenyar les aplicacions corresponents és convenient poder validar-les amb un prototipatge. Això ha motivat la realització d'aquest projecte, on s'ha obtingut un prototip d'AGV (automated guided vehicle) que rep les ordres per Bluetooth i, mitjançant uns infrarojos per poder seguir unes línies al terra, és capaç d'anar des del punt inicial fins on se li ha encarregat i tornar al punt inicial. Aquest vehicle pot servir de base per a la implementació d'AGV orientats a aplicacions reals i, per tant, per a la construcció de sistemes més grans i que poden ser utilitzats en plantes de producció, laboratoris, magatzems, ports i d'altres aplicacions diverses.

How important are tobacco prices in the propensity to start and quit smoking? An analysis of smoking histories from the Spanish National Health Survey

This paper analyses the effect of tobacco prices on the propensity tostart and quit smoking using a pool of the 1993, 1995 and 1997 editionsof the Spanish National Health Surveys. The estimates for severalparametric models of the hazard rate for starting and quitting suggestthat i) The public health measures applied as of 1992 have had asignificative effect on both reducing the hazard of starting andincreasing the hazard of quitting, ii) Prices have a very weak effect onthe hazard of starting in the male population and no significant effectin the female population, iii) The price floor of cigarrettes, proxiedby the average price of a pack of black cigarrettes, has a significanteffect on the quitting hazard which is robust across specifications andapplies to both men and women. The implied price elasticity of the timeup to quitting is situated around -1.4.

Morfogénesis del valle de Sant Miquel de Campmajor

A series of circumstances which converge in a little valley in the province of Girona, result in a peculiar type of morphogenetic evolution and a quite singular mechanical instability of its buttons. Very recent tectonic movements as well as dissolution phenomena of its subsoil due to pressurized underground water have played an important role in the morphogenesis. Such conditions have resulted in a fast morphological evolution which a progressive lowering of the valley floor as well as peculiar morphological features which favour the existence of numerous pits caused by sudden collapses distributed in altitude and time

Estudio comparado de la génesis de espeleotemas silíceos en granitoides de climas semiáridos y templados húmedos

Silica speleothems take differenr forms such as cylindrical stems growing from either the floor or the ceiling in granitic caves. Mineralogically they are opal-A and accumulate in successive layers with a whiskery druse tip formed by gypsum crystals. Initially they are porous but progressively become infilled by opal precipitation. This results in formation of solid speleothems. their size is only a few millimetres long. Bacterial activity accelerate quartz dissolution