Omnidirectional Vision-Based Control from Homography

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Visual servoing of mobile robots using non-central catadioptric cameras

This paper presents novel contributions on image-based control of a mobile robot using a general catadioptric camera model. A catadioptric camera is usually made up by a combination of a conventional camera and a curved mirror resulting in an omnidirectional sensor capable of providing 360° panoramic views of a scene. Modeling such cameras has been the subject of significant research interest in the computer vision community leading to a deeper understanding of the image properties and also to different models for different types of configurations. Visual servoing applications using catadioptric cameras have essentially been using central cameras and the corresponding unified projection model. So far only in a few cases more general models have been used. In this paper we address the problem of visual servoing using the so-called radial model. The radial model can be applied to many camera configurations and in particular to non-central catadioptric systems with mirrors that are symmetric around an axis coinciding with the optical axis. In this case, we show that the radial model can be used with a non-central catadioptric camera to allow effective image-based visual servoing (IBVS) of a mobile robot. Using this model, which is valid for a large set of catadioptric cameras (central or non-central), new visual features are proposed to control the degrees of freedom of a mobile robot moving on a plane. In addition to several simulation results, a set of experiments was carried out on Robot Operating System (ROS)-based platform which validates the applicability, effectiveness and robustness of the proposed method for image-based control of a non-holonomic robot

Visual Servoing from straight lines

In this paper we consider the problem of controlling a robotic system by using the projection of 3D straight lines in the image plane of central catadioptric systems. Most of the effort in visual servoing are devoted to points, only few works have investigated the use of lines in visual servoing with traditional cameras and none has explored the case of omnidirectional cameras. First a generic central catadioptric interaction matrix for the projection of 3D straight lines is derived from the projection model of an entire class of camera. Then an image-based control law is designed and validated through simulation results and real experiments with a mobile robot.Dans cet article, nous présentons une stratégie de commande de systèmes robotiques en utilisant comme entrées d'une boucle d'asservissement visuel des primitives relatives à la projection de droites dans le plan image d'une caméra panoramique à point central unique. Afin de réaliser la commande d'un système robotique par asservissement visuel, il est nécessaire d'estimer la matrice d'interaction liant les mouvements de la caméra aux mouvements des primitives visuelles dans l'image. Dans cet article, nous dérivons la forme analytique de la matrice d'interaction générique relative à la projection de droites à partir d'un modèle de projection englobant la classe entière des caméras à point central unique. Elle est ensuite utilisée dans un schéma d'asservissement visuel. Des simulations ainsi que des résultats expérimentaux sur un robot mobile valident l'approche proposée

Relating vanishing points to catadioptric camera calibration

This paper presents the analysis and derivation of the geometric relation between vanishing points and camera parameters of central catadioptric camera systems. These vanishing points correspond to the three mutually orthogonal directions of 3D real world coordinate system (i.e. X, Y and Z axes). Compared to vanishing points (VPs) in the perspective projection, the advantages of VPs under central catadioptric projection are that there are normally two vanishing points for each set of parallel lines, since lines are projected to conics in the catadioptric image plane. Also, their vanishing points are usually located inside the image frame. We show that knowledge of the VPs corresponding to XYZ axes from a single image can lead to simple derivation of both intrinsic and extrinsic parameters of the central catadioptric system. This derived novel theory is demonstrated and tested on both synthetic and real data with respect to noise sensitivity

Photometric visual servoing for omnidirectional cameras

International audience2D visual servoing consists in using data provided by a vision sensor for controlling the motions of a dynamic system. Most of visual servoing approaches has relied on the geometric features that have to be tracked and matched in the image acquired by the camera. Recent works have highlighted the interest of taking into account the photometric information of the entire image. This approach was tackled with images of perspective cameras. We propose, in this paper, to extend this technique to central cameras. This generalization allows to apply this kind of method to catadioptric cameras and wide field of view cameras. Several experiments have been successfully done with a fisheye camera in order to control a 6 degrees of freedom (dof) robot and with a catadioptric camera for a mobile robot navigation task

Proyecciones cónicas de rectas en sistemas catadióptricos para percepción visual en entornos construidos por el hombre

Los sistemas de visión omnidireccional son dispositivos que permiten la adquisición de imágenes con un campo de vista de 360º en un eje y superior 180º en el otro. La necesidad de integrar estas cámaras en sistemas de visión por computador ha impulsado la investigación en este campo profundizando en los modelos matemáticos y la base teórica necesaria que permite la implementación de aplicaciones. Existen diversas tecnologías para obtener imágenes omnidireccionales. Los sistemas catadióptricos son aquellos que consiguen aumentar el campo de vista utilizando espejos. Entre estos, encontramos los sistemas hiper-catadióptricos que son aquellos que utilizan una cámara perspectiva y un espejo hiperbólico. La geometría hiperbólica del espejo garantiza que el sistema sea central. En estos sistemas adquieren una especial relevancia las rectas del espacio, en la medida en que, rectas largas son completamente visibles en única imagen. La recta es una forma geométrica abundante en entornos construidos por el hombre que además acostumbra a ordenarse según direcciones dominantes. Salvo construcciones singulares, la fuerza de la gravedad fija una dirección vertical que puede utilizarse como referencia en el cálculo de la orientación del sistema. Sin embargo el uso de rectas en sistemas catadióptricos implica la dificultad añadida de trabajar con un modelo proyectivo no lineal en el que las rectas 3d son proyectadas en cónicas. Este TFM recoge el trabajo que se presenta en el artículo "Significant Conics on Catadioptric Images for 3D Orientation and Image Rectification" que pretendemos enviar a "Robotics and Autonomous Systems". En él se presenta un método para calcular la orientación de un sistema hiper-catadióptrico utilizando las cónicas que son proyecciones de rectas 3D. El método calcula la orientación respecto del sistema de referencia absoluto definido por el conjunto de puntos de fuga en un entorno en que existan direcciones dominantes