检索结果-内蒙古大学图书馆

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

来源：评论

学校读者我要写书评

暂无评论

A system to evaluate the accuracy of a visual mosaicking methodology

A system to evaluate the accuracy of a visual mosaicking met...

引用

OCEANS

作者： R. Garcia J. Batlle X. Cufi Institute of Informatics and Applications Computer Vision and Robotics Group University of Girona Girona Spain

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.

关键词： Image sequences Underwater vehicles Motion estimation Robot vision systems Cameras Navigation Oceans computer vision Laboratories computer errors

来源：评论

学校读者我要写书评

暂无评论

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

Estimating the motion of an underwater robot from a monocula...

引用

IEEE International Workshop on Intelligent Robots and Systems (IROS)

作者： R. Garcia X. Cufi M. Carreras Computer Vision and Robotics Group Institute of Informatics and Applications University of Girona Girona Spain

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.

关键词： Motion estimation Robots Navigation Underwater vehicles Oceans Floors computer vision Motion detection Vehicle detection Image analysis

来源：评论

学校读者我要写书评

暂无评论

Implementation of a Real-Time Target Tracking Behaviour Using Video Sensors

引用

IFAC Proceedings Volumes 2001年第7期34卷 517-521页

作者： V. lla P. Ridao J.De La Cruz J. Batlle Computer Vision and Robotics Group Institute of Informatics and Applications. University of Girona Edifici Politecnica ll Campus Montilivi 17071 Girona Spain

Using software OS, real-time operation is constrained by acquisition and preprocessing tasks of input signals. In this way, this paper presents an implementation of a real time target tracking behaviour, from snapped images of the environment, as an example of how to take advantage of real-time hardware devices as a helpful systems for control architectures. A specific board based on FPGA/DSP processors has been used in order to reach this goal. The system has been thought for a marine and underwater environment and it has been tested using GARBI autonomous underwater vehicle. The implemented behaviours allow the robot to navigate autonomously and follow a diver.

关键词： behaviour binary image autonomous vehicle computer control

来源：评论

学校读者我要写书评

暂无评论

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

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

引用

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

来源：评论

学校读者我要写书评

暂无评论

O 2 CA 2 : A New Hybrid Control Architecture for a Low Cost AUV

引用

IFAC Proceedings Volumes 2001年第7期34卷 311-316页

作者： P. Ridao M. Carreras J. Batlle J. Amat Computer Vision and Robotics Group Institute of Informatics and Applications University of Girona Edifici Politècnica II Campus Montilivi 17071 Girona Spain Department of Automatic Control and Computer Engineering Politechnical University of Catalunya. Pau Gargallo n°5 08028 Barcelona (Spain).

The Object Oriented Control Architecture for Autonomy (O 2 CA 2 ) is a control architecture being developed at the University of Girona for the GARBI underwater vehicle. Conceived as a hybrid, it is organised in three layers (Deliberative, Control Execution and Reactive) merging the deliberation mechanisms of planning with reactive behaviours in charge of controlling the robot. The aim of this paper is to provide an overall description of the whole architecture and an in depth description of the Reactive-layer. The concepts of the architecture have been tested with the simulation of a simple mission consisting of navigating through a sequence of way-points while avoiding contact with obstacles.

关键词： Autonomous Vehicles Control architectures behaviour fuzzy systems guidance navigation marine systems

来源：评论

学校读者我要写书评

暂无评论

A new approach to segmentation based on fusing circumscribed contours, region growing and clustering

A new approach to segmentation based on fusing circumscribed...

引用

IEEE International Conference on Image Processing

作者： X. Munoz X. Cufi J. Freixenet J. Marti Computer Vision and Robotics Group Institute of Informatics and Applications University of Girona Catalonia Spain

ISBN: (纸本)0780362977

One of the major problems in machine vision is the segmentation of images of natural scenes. This paper presents a new proposal for the image segmentation problem which has been based on the integration of edge and region information. The main contours of the scene are detected and used to guide the posterior region growing process. The algorithm places a number of seeds at both sides of a contour allowing stating a set of concurrent growing processes. A previous analysis of the seeds permits to adjust the homogeneity criterion to the regions's characteristics. A new homogeneity criterion based on clustering analysis and convex hull construction is proposed.

关键词： Image segmentation Image edge detection Layout Clustering algorithms computer vision Robot vision systems informatics Application software Machine vision Proposals

来源：评论

学校读者我要写书评

暂无评论

Use of decision trees in colour feature selection. Application to object recognition in outdoor scenes

Use of decision trees in colour feature selection. Applicati...

引用

IEEE International Conference on Image Processing

作者： J. Freixenet X. Llado J. Marti X. Cufi Computer Vision and Robotics Group Institute of Informatics and Applications University of Girona Catalonia Spain

A new method for the automated selection of colour features is described. The algorithm consists of two stages of processing. In the first, a complete set of colour features is calculated for every object of interest in an image. In the second stage, each object is mapped into several n-dimensional feature spaces in order to select the feature set with the smallest variables able to discriminate the remaining objects. The evaluation of the discrimination power for each concrete subset of features is performed by means of decision trees composed of linear discrimination functions. This method can provide valuable help in outdoor scene analysis where no colour space has been demonstrated as being the most suitable. Experiment results recognizing objects in outdoor scenes are reported.

关键词： Decision trees Object recognition Layout Application software Geometry computer vision Robot vision systems robotics and automation informatics Concrete

来源：评论

学校读者我要写书评

暂无评论

Image Mosaicking for Estimating the Motion of an Underwater Vehicle

引用

IFAC Proceedings Volumes 2000年第21期33卷 147-152页

作者： Rafael García Xevi Cufí Lluís Pacheco Computer Vision and Robotics Group Institute of Informatics and Applications University of Girona Edifici Politècnica II Escola Politecnica Superior 17071 Girona Spain

A composite image constructed by combining a set of smaller images is known as mosaic. Mosaics of the ocean floor are very useful in undersea exploration, creation of visual maps, navigation, etc. A feature-based mosaicking method is proposed, based on textural parameters of certain parts of the image. Textures significantly help in the identification of given features of the image. The tracking of these features over time solves the matching problem in consecutive frames. The correspondence is established with the aid of a cross-correlation algorithm, applied to the colour components of the image in the HSI space. Once the correspondence has been found a displacement vector is obtained relating the features of two images of the sequence. The motion parameters between consecutive frames are estimated through an error minimisation technique. Once the best transformation between two frames has been found, images are warped together composing the mosaic, and information about the vehicle motion is recovered. The experimental results on real images show the effectiveness of the proposed method.

关键词： computer vision Motion estimation Autonomous vehicles Image registration Robot navigation Marine Systems

来源：评论

学校读者我要写书评

暂无评论

Steering and Depth Control of an Underwater Robot Using Fuzzy-Like PD Controller

引用

IFAC Proceedings Volumes 2000年第21期33卷 239-244页

作者： I.S. Akkizidis G.N. Roberts P. Ridao J. Batlle Mechatronics Research Centre University of Wales College Newport Allt-yr-yn Campus PO Box 180 Newport South Wales NP9 5XR UK Computer Vision and Robotics Group Institute of Informatics and Applications Edifici Politècnica II Campus Montilivi 7071-Girona SPAIN

The design of a steering and depth control of an underwater vehicle is of interest from the point of view of motion stabilisation as well as manoeuvring performance. The paper describes how a Fuzzy-like Proportional Derivative Controller (Fuzzy-like PD Control) is used to control the course-changing and course-keeping tracking mission and motion of an underwater vehicle. The idea for this type of control architecture is to identify the optimum values, in terms of control performance and robustness, of the parameters of the F-like PD Controller. These parameters may be the scaling factors that are applied in the input/output of the PD part of the controller as well as the fuzzy sets of the fuzzy part of the controller. The values of the scaling factors for the error, the change-of-error and the control output are optimised based on experiments. In this work a method has been developed to control the yaw and depth of an underwater robot in terms of course-changing and course-keeping. The controller is synthesised in two parts. Firstly it is applied in horizontal xy and secondly in vertical xz surface. Experiments in a real environment were planned using the Taguchi Design of Experiments and performed to investigate the capabilities of the controller. The results are presented and analysed extensively.

关键词： Fuzzy like-PD Controller Yaw and Depth Control Taguchi Design of Experiments

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：