Augmented state Kalman filtering for AUV navigation

Addresses the problem of estimating the motion of an autonomous underwater vehicle (AUV), while it constructs a visual map ("mosaic" image) of the ocean floor. The vehicle is equipped with a down-looking camera which is used to compute its motion with respect to the seafloor. As the mosaic increases in size, a systematic bias is introduced in the alignment of the images which form the mosaic. Therefore, this accumulative error produces a drift in the estimation of the position of the vehicle. When the arbitrary trajectory of the AUV crosses over itself, it is possible to reduce this propagation of image alignment errors within the mosaic. A Kalman filter with augmented state is proposed to optimally estimate both the visual map and the vehicle position

Lumbar-sacral pedicle screw insertion with preoperative CT-based navigation

Objectif: Nous avons effectué une étude chez 135 patients ayant subis une chirurgie lombo-sacrée avec vissage pédiculaire sous navigation par tomographie axiale. Nous avons évalué la précision des vis pédiculaires et les résultats cliniques. Méthodes: Cette étude comporte 44 hommes et 91 femmes (âge moyen=61, intervalle 24-90 ans). Les diamètres, longueurs et trajectoires des 836 vis ont été planifiés en préopératoire avec un système de navigation (SNN, Surgical Navigation Network, Mississauga). Les patients ont subi une fusion lombaire (55), lombo-sacrée (73) et thoraco-lombo-sacrée (7). La perforation pédiculaire, la longueur des vis et les spondylolisthesis sont évalués par tomographies axiales postopératoires. Le niveau de douleur est mesuré par autoévaluations, échelles visuelles analogues et questionnaires (Oswestry et SF-36). La fusion osseuse a été évaluée par l’examen des radiographies postopératoires. Résultats: Une perforation des pédicules est présente pour 49/836 (5.9%) des vis (2.4% latéral, 1.7% inférieur, 1.1% supérieur, 0.7% médial). Les erreurs ont été mineures (0.1-2mm, 46/49) ou intermédiaires (2.1 - 4mm, 3/49 en latéral). Il y a aucune erreur majeure (≥ 4.1mm). Certaines vis ont été jugées trop longues (66/836, 8%). Le temps moyen pour insérer une vis en navigation a été de 19.1 minutes de l΄application au retrait du cadre de référence. Un an postopératoire on note une amélioration de la douleur des jambes et lombaire de 72% et 48% en moyenne respectivement. L’amélioration reste stable après 2 ans. La dégénérescence radiologique au dessus et sous la fusion a été retrouvée chez 44 patients (33%) and 3 patients respectivement (2%). Elle est survenue en moyenne 22.2 ± 2.6 mois après la chirurgie. Les fusions se terminant à L2 ont été associées à plus de dégénération (14/25, 56%). Conclusion: La navigation spinale basée sur des images tomographiques préopératoires est une technique sécuritaire et précise. Elle donne de bons résultats à court terme justifiant l’investissement de temps chirurgical. La dégénérescence segmentaire peut avoir un impact négatif sur les résultats radiologique et cliniques.

Un oeil sur la langue : aspects neuro-cognitifs du processus de la navigation chez l'aveugle-né

La vision est un élément très important pour la navigation en général. Grâce à des mécanismes compensatoires les aveugles de naissance ne sont pas handicapés dans leurs compétences spatio-cognitives, ni dans la formation de nouvelles cartes spatiales. Malgré l’essor des études sur la plasticité du cerveau et la navigation chez les aveugles, les substrats neuronaux compensatoires pour la préservation de cette fonction demeurent incompris. Nous avons démontré récemment (article 1) en utilisant une technique d’analyse volumétrique (Voxel-Based Morphometry) que les aveugles de naissance (AN) montrent une diminution de la partie postérieure de l’hippocampe droit, structure cérébrale importante dans la formation de cartes spatiales. Comment les AN forment-ils des cartes cognitives de leur environnement avec un hippocampe postérieur droit qui est significativement réduit ? Pour répondre à cette question nous avons choisi d’exploiter un appareil de substitution sensorielle qui pourrait potentiellement servir à la navigation chez les AN. Cet appareil d’affichage lingual (Tongue display unit -TDU-) retransmet l’information graphique issue d’une caméra sur la langue. Avant de demander à nos sujets de naviguer à l’aide du TDU, il était nécessaire de nous assurer qu’ils pouvaient « voir » des objets dans l’environnement grâce au TDU. Nous avons donc tout d’abord évalué l’acuité « visuo »-tactile (article 2) des sujets AN pour les comparer aux performances des voyants ayant les yeux bandées et munis du TDU. Ensuite les sujets ont appris à négocier un chemin à travers un parcours parsemé d’obstacles i (article 3). Leur tâche consistait à pointer vers (détection), et contourner (négociation) un passage autour des obstacles. Nous avons démontré que les sujets aveugles de naissance non seulement arrivaient à accomplir cette tâche, mais encore avaient une performance meilleure que celle des voyants aux yeux bandés, et ce, malgré l’atrophie structurelle de l’hippocampe postérieur droit, et un système visuel atrophié (Ptito et al., 2008). Pour déterminer quels sont les corrélats neuronaux de la navigation, nous avons créé des routes virtuelles envoyées sur la langue par le biais du TDU que les sujets devaient reconnaitre alors qu’ils étaient dans un scanneur IRMf (article 4). Nous démontrons grâce à ces techniques que les aveugles utilisent un autre réseau cortical impliqué dans la mémoire topographique que les voyants quand ils suivent des routes virtuelles sur la langue. Nous avons mis l’emphase sur des réseaux neuronaux connectant les cortex pariétaux et frontaux au lobe occipital puisque ces réseaux sont renforcés chez les aveugles de naissance. Ces résultats démontrent aussi que la langue peut être utilisée comme une porte d’entrée vers le cerveau en y acheminant des informations sur l’environnement visuel du sujet, lui permettant ainsi d’élaborer des stratégies d’évitement d’obstacles et de se mouvoir adéquatement.

Interface issues in the ESCHER visual database editor

Presentation at the 1997 Dagstuhl Seminar "Evaluation of Multimedia Information Retrieval", Norbert Fuhr, Keith van Rijsbergen, Alan F. Smeaton (eds.), Dagstuhl Seminar Report 175, 14.04. - 18.04.97 (9716). - Abstract: This presentation will introduce ESCHER, a database editor which supports visualization in non-standard applications in engineering, science, tourism and the entertainment industry. It was originally based on the extended nested relational data model and is currently extended to include object-relational properties like inheritance, object types, integrity constraints and methods. It serves as a research platform into areas such as multimedia and visual information systems, QBE-like queries, computer-supported concurrent work (CSCW) and novel storage techniques. In its role as a Visual Information System, a database editor must support browsing and navigation. ESCHER provides this access to data by means of so called fingers. They generalize the cursor paradigm in graphical and text editors. On the graphical display, a finger is reflected by a colored area which corresponds to the object a finger is currently pointing at. In a table more than one finger may point to objects, one of which is the active finger and is used for navigating through the table. The talk will mostly concentrate on giving examples for this type of navigation and will discuss some of the architectural needs for fast object traversal and display. ESCHER is available as public domain software from our ftp site in Kassel. The portable C source can be easily compiled for any machine running UNIX and OSF/Motif, in particular our working environments IBM RS/6000 and Intel-based LINUX systems. A porting to Tcl/Tk is under way.

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

Towards a real-time vision-based navigation system for a small-class UUV

This paper deals with the problem of navigation for an unmanned underwater vehicle (UUV) through image mosaicking. It represents a first step towards a real-time vision-based navigation system for a small-class low-cost UUV. We propose a navigation system composed by: (i) an image mosaicking module which provides velocity estimates; and (ii) an extended Kalman filter based on the hydrodynamic equation of motion, previously identified for this particular UUV. The obtained system is able to estimate the position and velocity of the robot. Moreover, it is able to deal with visual occlusions that usually appear when the sea bottom does not have enough visual features to solve the correspondence problem in a certain area of the trajectory

Augmented state Kalman filtering for AUV navigation

Addresses the problem of estimating the motion of an autonomous underwater vehicle (AUV), while it constructs a visual map ("mosaic" image) of the ocean floor. The vehicle is equipped with a down-looking camera which is used to compute its motion with respect to the seafloor. As the mosaic increases in size, a systematic bias is introduced in the alignment of the images which form the mosaic. Therefore, this accumulative error produces a drift in the estimation of the position of the vehicle. When the arbitrary trajectory of the AUV crosses over itself, it is possible to reduce this propagation of image alignment errors within the mosaic. A Kalman filter with augmented state is proposed to optimally estimate both the visual map and the vehicle position

WMR navigation using local potential field corridors and narrow local occupancy grid perception

Path planning and control strategies applied to autonomous mobile robots should fulfil safety rules as well as achieve final goals. Trajectory planning applications should be fast and flexible to allow real time implementations as well as environment interactions. The methodology presented uses the on robot information as the meaningful data necessary to plan a narrow passage by using a corridor based on attraction potential fields that approaches the mobile robot to the final desired configuration. It employs local and dense occupancy grid perception to avoid collisions. The key goals of this research project are computational simplicity as well as the possibility of integrating this method with other methods reported by the research community. Another important aspect of this work consist in testing the proposed method by using a mobile robot with a perception system composed of a monocular camera and odometers placed on the two wheels of the differential driven motion system. Hence, visual data are used as a local horizon of perception in which trajectories without collisions are computed by satisfying final goal approaches and safety criteria

Visual efficiency detection index : a new composite measure of visual search

Visual search is an important component of our interaction with our surroundings, allowing us to successfully identify external cues that impact our spatial navigation. Previous research has established fixation duration, fixation count, saccade velocity, and saccade amplitude as important indices of visual search. We examined the Visual Efficiency Detection Index (VEDI) comprising multiple aspects of visual search performance into a single measure of global visual performance. Forty participants, 10 adults ages 22-48, and children ages 6, 8, and 10, completed tests of working memory and visual search in response to stimuli relevant to pedestrian decision making. Results indicated VEDI statistically relates to established indices of visual search in relation to their interpretability for human performance. The VEDI was also sensitive to developmental differences in visual search performance, suggesting insight to its utility in the developmental psychological literature.

Learning associations between places and visual cues without learning to navigate: neither fornix nor entorhinal cortex is required

Rats with fornix transection, or with cytotoxic retrohippocampal lesions that removed entorhinal cortex plus ventral subiculum, performed a task that permits incidental learning about either allocentric (Allo) or egocentric (Ego) spatial cues without the need to navigate by them. Rats learned eight visual discriminations among computer-displayed scenes in a Y-maze, using the constant-negative paradigm. Every discrimination problem included two familiar scenes (constants) and many less familiar scenes (variables). On each trial, the rats chose between a constant and a variable scene, with the choice of the variable rewarded. In six problems, the two constant scenes had correlated spatial properties, either Alto (each constant appeared always in the same maze arm) or Ego (each constant always appeared in a fixed direction from the start arm) or both (Allo + Ego). In two No-Cue (NC) problems, the two constants appeared in randomly determined arms and directions. Intact rats learn problems with an added Allo or Ego cue faster than NC problems; this facilitation provides indirect evidence that they learn the associations between scenes and spatial cues, even though that is not required for problem solution. Fornix and retrohippocampal-lesioned groups learned NC problems at a similar rate to sham-operated controls and showed as much facilitation of learning by added spatial cues as did the controls; therefore, both lesion groups must have encoded the spatial cues and have incidentally learned their associations with particular constant scenes. Similar facilitation was seen in subgroups that had short or long prior experience with the apparatus and task. Therefore, neither major hippocampal input-output system is crucial for learning about allocentric or egocentric cues in this paradigm, which does not require rats to control their choices or navigation directly by spatial cues.

Visual surveillance using deformable models of vehicles

This paper presents recent developments to a vision-based traffic surveillance system which relies extensively on the use of geometrical and scene context. Firstly, a highly parametrised 3-D model is reported, able to adopt the shape of a wide variety of different classes of vehicle (e.g. cars, vans, buses etc.), and its subsequent specialisation to a generic car class which accounts for commonly encountered types of car (including saloon, batchback and estate cars). Sample data collected from video images, by means of an interactive tool, have been subjected to principal component analysis (PCA) to define a deformable model having 6 degrees of freedom. Secondly, a new pose refinement technique using “active” models is described, able to recover both the pose of a rigid object, and the structure of a deformable model; an assessment of its performance is examined in comparison with previously reported “passive” model-based techniques in the context of traffic surveillance. The new method is more stable, and requires fewer iterations, especially when the number of free parameters increases, but shows somewhat poorer convergence. Typical applications for this work include robot surveillance and navigation tasks.

Issues and benefits of using 3D Interfaces: visual and verbal tasks

Spatial memory is important for locating objects in hierarchical data structures, such as desktop folders. There are, however, some contradictions in literature concerning the effectiveness of 3D user interfaces when compared to their 2D counterparts. This paper uses a task-based approach in order to investigate the effectiveness of adding a third dimension to specific user tasks, i.e. the impact of depth on navigation in a 3D file manager. Results highlight issues and benefits of using 3D interfaces for visual and verbal tasks, and introduces the possible existence of a correlation between aptitude scores achieved on the Guilford- Zimmerman Orientation Survey and Electroencephalography- measured brainwave activity as participants search for targets of variable perceptual salience in 2D and 3D environments.

Navegação cooperativa de um robô humanóide e um robô com rodas usando informação visual

This work presents a cooperative navigation systemof a humanoid robot and a wheeled robot using visual information, aiming to navigate the non-instrumented humanoid robot using information obtained from the instrumented wheeled robot. Despite the humanoid not having sensors to its navigation, it can be remotely controlled by infra-red signals. Thus, the wheeled robot can control the humanoid positioning itself behind him and, through visual information, find it and navigate it. The location of the wheeled robot is obtained merging information from odometers and from landmarks detection, using the Extended Kalman Filter. The marks are visually detected, and their features are extracted by image processing. Parameters obtained by image processing are directly used in the Extended Kalman Filter. Thus, while the wheeled robot locates and navigates the humanoid, it also simultaneously calculates its own location and maps the environment (SLAM). The navigation is done through heuristic algorithms based on errors between the actual and desired pose for each robot. The main contribution of this work was the implementation of a cooperative navigation system for two robots based on visual information, which can be extended to other robotic applications, as the ability to control robots without interfering on its hardware, or attaching communication devices

Evaluation of the Cartographic Communication Performance of a Route Guidance and Navigation System

This study evaluates the influence of different cartographic representations of in-car navigation systems on visual demand, subjective preference, and navigational error. It takes into account the type and complexity of the representation, maneuvering complexity, road layout, and driver gender. A group of 28 drivers (14 male and 14 female) participated in this experiment which was performed in a low-cost driving simulator. The tests were performed on a limited number of instances for each type of representation, and their purpose was to carry out a preliminary assessment and provide future avenues for further studies. Data collected for the visual demand study were analyzed using non-parametric statistical analyses. Results confirmed previous research that showed that different levels of design complexity significantly influence visual demand. Non-grid-like road networks, for example, influence significantly visual demand and navigational error. An analysis of simple maneuvers on a grid-like road network showed that static and blinking arrows did not present significant differences. From the set of representations analyzed to assess visual demand, both arrows were equally efficient. From a gender perspective, women seem to took at the display more than men, but this factor was not significant. With respect to subjective preferences, drivers prefer representations with mimetic landmarks when they perform straight-ahead tasks. For maneuvering tasks, landmarks in a perspective model created higher visual demands.

Orientação espacial em adultos com deficiência visual: efeitos de um treinamento de navegação

O objetivo deste estudo foi demonstrar se um programa de navegação pode ajudar indivíduos com deficiência visual a melhorar a acurácia na orientação dinâmica. Nove participantes com deficiência visual retornaram a um ponto de partida após percorrer rotas em linha reta e triangular. Pré e pós-avaliações foram feitas entre um período de 4 meses, durante o qual o treinamento com navegação foi realizado. Entre pré e pós-teste, erros relativos de desvios angulares (ERDA) foram diferentes apenas na tarefa em linha reta. O valor de ERDA foi maior na tarefa em linha reta possivelmente por causa da magnitude do giro inicial antes de retornar ao ponto de partida (i.e., 180º) em contraste com a tarefa triângulo (i.e., 45º). Conclui-se que, em tarefas de orientação, os erros no desvio angular dependem da amplitude do giro inicial ao retornar para o ponto de partida. Ainda, a acurácia na manutenção da direção é influenciada por um treinamento específico com navegação.