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REAL-TIME vision BASED AUV NAVIGATION SYSTEM USING A COMPLEMENTARY SENSOR SUITE

IFAC Proceedings Volumes 2007年第17期40卷 373-378页

作者： Jonathan Horgan Daniel Toal Pere Ridao Rafael Garcia Mobile and Marine Robotics Research Centre Department of Electronic and Computer Engineering University of Limerick Ireland Computer Vision and Robotics Group Institute of Informatics and Applications University of Girona Spain

This paper proposes a real-time navigation system for an AUV that takes advantage of the complementary performance of a sensor suite including a DVL, a compass, a depth sensor and altimeter sensors with a feature based motion estimator using vision. To allow for real-time performance of the vision based motion estimator a simple but fast correlation algorithm is used for feature matching. The compass and the depth sensors are used to bound the drift of the heading and depth estimations respectively. The altimeter is required in order to translate the feature displacements measured from the images into the metric displacements of the robot. While the robot must rely on DVL navigation above a certain altitude where vision is useless, DVL measurements can be complemented with higher frequency accurate motion estimates from the vision system when navigating close to the seafloor.

关键词： marine robotics robot vision Kalman filtering robot navigation

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An Approach to the Urban Scene Understanding Problem Useful for Autonomous Navigation

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IFAC Proceedings Volumes 1998年第3期31卷 393-398页

作者： Jordi Freixenet Joan Martí Joan Batlle Computer Vision and Robotics Group Institute of Informatics and Applications University of Girona. Avda. Lluis Santaló s/n. 17003 - GIRONA (Spain)

This paper presents an approach to the urban scene understanding problem, providing a robust expert system able to take out natural elements such as trees or plants. The system is based on a wide range of natural features associated to seasons, weather, chromatic components, sunshine levels, etc. A particularity of the system is that it is only dealing with pixels, so video-rate processing can be achieved in an easy way, whereas others which deal with regions. Then, the proposed expert system works as a pre-processor and needs, indeed, knowledgement about the environment. Although, pixels candidates could be associated to regions in order to be useful for a further high level processing. In this sense, the system would be applied to a mobile robot in order to use the trees as landmarks for navigation.

关键词： vision computer expert systems scene understanding pixel classification natural scenes mobile robot navigation

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On the way to solve lighting problems in underwater imaging

On the way to solve lighting problems in underwater imaging

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OCEANS

作者： R. Garcia T. Nicosevici X. Cufi Computer Vision and Robotics Group Institute of Informatics and Applications E.P.S. University of Girona Girona Spain

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.

关键词： Lighting Absorption Layout Oceans Light scattering Underwater vehicles Light sources Application software computer vision Image analysis

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

Detection of matchings in a sequence of underwater images th...

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IEEE International Conference on Image Processing

作者： R. Garcia C. Xevi J. Battle Computer Vision and Robotics Group Institute of Informatics and Applications University of Girona Girona Spain Computer Vision and Robotics Group E.P.S. Girona Spain Universitat de Girona Girona Catalunya ES

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.

关键词： Underwater tracking Image analysis Image sequence analysis Image texture analysis Robot vision systems Cameras Motion detection Vehicle detection Underwater vehicles Testing

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

An approach to vision-based station keeping for an unmanned ...

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IEEE International Workshop on Intelligent Robots and Systems (IROS)

作者： X. Cufi R. Garcia P. Ridao Computer Vision and Robotics Group Institute oflnformatics and Applications University of Girona Girona Spain

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.

关键词： Underwater vehicles Cameras Remotely operated vehicles Motion estimation computer vision Motion detection Robot vision systems Testing Vehicle detection Sea floor

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Classification of textures seen from different distances and under varying illumination direction

Classification of textures seen from different distances and...

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IEEE International Conference on Image Processing

作者： X. Llado J. Marti M. Petrou Computer Vision and Robotics Group University of Girona Girona Spain Informatics and Telematic Institute EKETA Thessaloniki Greece

Changes in the angle of illumination incident upon a 3D surface texture can significantly alter its appearance, implying variations in the image texture. These texture variations produce displacements of class members in the feature space, increasing the failure rates of texture classifiers. To avoid this problem, a model-based texture recognition system which classifies textures seen from different distances and under different illumination directions is presented in this paper. The system works on the basis of a surface model obtained by means of 4-source colour photometric stereo, used to generate 2D image textures under different illumination directions. The recognition system combines coocurrence matrices for feature extraction with a Nearest Neighbour classifier. Moreover, the recognition allows one to guess the approximate direction of the illumination used to capture the test image.

关键词： Lighting Surface texture Image texture Photometry Cameras informatics computer vision Robot vision systems Application software Stereo vision

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Sensorial and Navigation Systems for a Mobile Robot (Roger)

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IFAC Proceedings Volumes 1998年第3期31卷 279-284页

作者： Pere Ridao Josep Forest Lluís Pacheco Rafael García Xavier Cufí Computer Vision and Robotics Group Institute of Informatics and Applications University of Girona Avda. Lluis Santaló s/n 17003 - GIRONA (Spain). Tel: +34 - 72 - 418474 Fax:+34 - 72 - 418098

This paper presents basically the sensorial system, the navigation systems and the data communication of the ROGER autonomous mobile robot. This robot is capable to operate in structured indoor environments and in certain outdoor environments. The robot can place itself independently in its workspace, and can perform some basic manipulation operations. These features make possible the use this mobile robot in a wide range of applications (industrial, social, etc.)

关键词： mobile robots computer vision colour teleoperation autonomous navigation

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Calibration of A Structured Light-Based Stereo Catadioptric Sensor

Calibration of A Structured Light-Based Stereo Catadioptric ...

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Conference on computer vision and Pattern Recognition Workshop, CVPRW 2003

作者： Orghidan, Radu Salvi, Joaquim Mouaddib, El Mustapha Computer Vision and Robotics Group Institute of Informatics and Applications Universitat de Girona Avda. Lluis Santalo s/n GironaCatalonia17071 Spain Centre de Robotique Electrotechnique et d'Automatique Université de Picardie Jules Verne Rue du Moulin Neuf Amiens80000 France

ISBN: (纸本)0769519008

Catadioptric sensors are combinations of mirrors and lenses made in order to obtain a wide field of view. In this paper we propose a new sensor that has omnidirectional viewing ability and it also provides depth information about the nearby surrounding. The sensor is based on a conventional camera coupled with a laser emitter and two hyperbolic mirrors. Mathematical formulation and precise specifications of the intrinsic and extrinsic parameters of the sensor are discussed. Our approach overcomes limitations of the existing omni-directional sensors and eventually leads to reduced costs of production. © 2003 IEEE.

关键词： Stereo vision

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Elastic modulus imaging using optical flow and image registration

Elastic modulus imaging using optical flow and image registr...

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IEEE International Conference on Image Processing

作者： Robert Martí Alison Noble Computer Vision and Robotics Group Institute of Informatics and Applications University of Girona Spain Biomedical Image Analysis Laboratory Institute of Biomedical Engineering University of Oxford UK

Elastography, the imaging technique for estimating the elastic tissue properties, or more specifically elastic modulus imaging, are becoming important diagnosis tools in computer aided diagnosis system, specially focusing on ultrasound and MRI images. This technique still presents unsolved challenges in the analysis of deformations in sequences of images. The aim of this paper is twofold: to evaluate the applicability of the deformation field obtained by state of the art optical flow and image registration algorithms for elastic modulus imaging and to quantitatively evaluate two different methods for estimation of the elastic modulus distribution. Results show that optical-flow methods provide a slightly better reconstruction and that the reconstruction has been shown to be more accurate using the method proposed by Sumi et al.

关键词： Image reconstruction Optical imaging Strain Young's modulus Image registration Lesions

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Feature based slam using side-scan salient objects

Feature based slam using side-scan salient objects

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OCEANS

作者： Josep Aulinas Xavier Lladó Joaquim Salvi Yvan R. Petillot Computer Vision and Robotics Group Institute of Informatics and Applications University of Girona Girona Spain Oceans Systems Laboratory School of Engineering and Physical Sciences Heriot-Watt University Edinburgh UK

Different underwater vehicles have been developed in order to explore underwater regions, specially those of difficult access for humans. Autonomous Underwater Vehicles (AUVs) are equipped with on-board sensors, which provide valuable information about the vehicle state and the environment. This information is used to build an approximate map of the area and estimate the position of the vehicle within this map. This is the so called Simultaneous Localization and Mapping (SLAM) problem. In this paper we propose a feature based submapping SLAM approach which uses side-scan salient objects as landmarks for the map building process. The detection of salient features in this environment is a complex task, since sonar images are noisy. We present in this paper an algorithm based on a set of image preprocessing steps and the use of a boosted cascade of Haar-like features to perform the automatic detection in side-scan images. Our experimental results show that the method produces consistent maps, while the vehicle is precisely localized.

关键词： Simultaneous localization and mapping Vehicles Feature extraction Sonar detection Object detection Sonar navigation

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