S. Robla

A similarity measure for 3D rigid registration of point clouds using image-based descriptors with low overlap

This paper introduces a novel similarity measure for 3D rigid registration algorithms that use comparison between image-based descriptors in order to find correspondences between two partial 3D point clouds belonging to the same object. Unlike the similarity measures based on correlation coefficient, joint entropy, mutual information or others that have been used by the most popular 3D registration algorithms this similarity measure is based on distance between pixels and takes into account the problems of clutter and occlusion that can appear in real situations that need 3D registration or object recognition.

Accurate Estimation of Airborne Ultrasonic Time-of-Flight for Overlapping Echoes

In this work, an analysis of the transmission of ultrasonic signals generated by piezoelectric sensors for air applications is presented. Based on this analysis, an ultrasonic response model is obtained for its application to the recognition of objects and structured environments for navigation by autonomous mobile robots. This model enables the analysis of the ultrasonic response that is generated using a pair of sensors in transmitter-receiver configuration using the pulse-echo technique. This is very interesting for recognizing surfaces that simultaneously generate a multiple echo response. This model takes into account the effect of the radiation pattern, the resonant frequency of the sensor, the number of cycles of the excitation pulse, the dynamics of the sensor and the attenuation with distance in the medium. This model has been developed, programmed and verified through a battery of experimental tests. Using this model a new procedure for obtaining accurate time of flight is proposed. This new method is compared with traditional ones, such as threshold or correlation, to highlight its advantages and drawbacks. Finally the advantages of this method are demonstrated for calculating multiple times of flight when the echo is formed by several overlapping echoes.

An approach for tracking oil slicks by using active contours on satellite images

This paper describes a process for achieving oil spill detection in satellite images acquired after tanker accidents. These images have been treated with image processing techniques, such us image equalization, image binarization and morphological operations, to obtain the residue segmentation. Once the oil slick is segmented and localized in the image, an active contour is generated around it and fitted to it. The active contour provides useful information about the shape and localization of the oil spill, even providing an estimation of the deformation and the displacement that it could suffer over the time. This information could allow the evolution of residues dumped at sea to be tracked. The validity of this process is demonstrated using several ENVISAT-ASAR images acquired over several regions (Spanish, Philippine and Korean coasts), in which a tanker accident has occurred and as a consequence oil spillage has taken place.

An Approach for detecting and tracking oil slicks on satellite images

This paper describes the combination of several image processing techniques to achieve an approach to the detection and tracking of oil slick using satellite images taken after some accidents over the sea, as tanker accidents or oil rig explosions. This work attempts to be a contribution to such task. To get information about the shape and located of the oil spill, once it has been segmented and localized in the image, an active contour is generated around the oil slick and fitted to it. The use of active contours can provide an estimation of the deformation and the displacement that oil slicks experience over the time. This information could help to estimate the evolution of these residues dumped into the sea and to allow their tracking. Several ENVISAT-ASAR images obtained over several regions in which a tanker accident occurred, such as it happened over the Spanish, Philippine, Portugal, and Korean coasts, or accidents like the oil rig explosion in the Gulf of Mexico, have been used as testing images of this process.

Compensation of environmental parameters for driving-aid ultrasonic systems in foggy conditions

The use of driving-aid ultrasonic systems in low visibility conditions due to fog, makes it necessary to study the influence of environmental parameters such as temperature, humidity or air velocity on the ultrasonic propagation. The present work tries to construct simple empirical models for velocity and echo amplitude that includes temperature and relative humidity as inputs. We present the results obtained in the modelling of the ultrasonic propagation in environments with variable conditions of humidity and temperature, including foggy conditions

Visual sensor fusion for active security in robotic industrial environments

This work presents a method of information fusion involving data captured by both a standard charge-coupled device (CCD) camera and a time-of-flight (ToF) camera to be used in the detection of the proximity between a manipulator robot and a human. Both cameras are assumed to be located above the work area of an industrial robot. The fusion of colour images and time-of-flight information makes it possible to know the 3D localization of objects with respect to a world coordinate system. At the same time, this allows to know their colour information. Considering that ToF information given by the range camera contains innacuracies including distance error, border error, and pixel saturation, some corrections over the ToF information are proposed and developed to improve the results. The proposed fusion method uses the calibration parameters of both cameras to reproject 3D ToF points, expressed in a common coordinate system for both cameras and a robot arm, in 2D colour images. In addition to this, using the 3D information, the motion detection in a robot industrial environment is achieved, and the fusion of information is applied to the foreground objects previously detected. This combination of information results in a matrix that links colour and 3D information, giving the possibility of characterising the object by its colour in addition to its 3D localisation. Further development of these methods will make it possible to identify objects and their position in the real world and to use this information to prevent possible collisions between the robot and such objects.

CIRCON: An Alternative 3D Shape Representation for Surface Matching

This paper introduces an alternative 3D Shape Representation: CIRCON (cylindrical image of radial contours), that both enables the compression of the 3D data, making them more manageable, and facilitates the tasks related to surface matching, such as 3D registration and object recognition, by making use of its inherent properties. A 3D vision system has been designed in order to facilitate the generation of this kind of 3D shape representation while the objects are being sensed