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International audience; Previous works on the visual servoing of parallel robots using the observation of their leg directions validated the feasibility of the approach but they have enlighten two main surprising results for which no answer was given: (i) the observed robot which is composed of n legs could be controlled in most cases using the observation of only m leg directions (m < n), and that (ii) in some cases, the robot did not converge to the desired end-effector pose, even if the observed leg directions did (i.e. there was not a global diffeomorphism between the observation space and the robot space). Recently, it was shown that the visual servoing of the leg directions of the Gough-Stewart platform and the Adept Quattro with 3 translational degrees of freedom was equivalent to controlling other virtual robots that have assembly modes and singular configurations different from those of the real ones. These hidden robot models are tangible visualizations of the mapping between the observation space and the real robots Cartesian space. Thanks to this concept, all the aforementioned points were answered for the mentioned robots. In this paper, the concept of hidden robot model is generalized for any type of parallel robots controlled using visual servos based on the observation of the leg directions. It is shown that the concept of hidden robot model is a powerful tool that gives useful insights about the visual servoing of robots using leg direction observation. With the concept of hidden robot model, the singularity problem of the controller can be addressed and the convergence issues of the controller can be explained, understood and solved. All these results are validated in simulations and through experiments on a Quattro robot.

International audience; In the last decades, robotics has exerted an important role in the research on diverse knowledge domains, such as, artificial intelligence, biology, neuroscience and psychology. In particular, the study of knowledge representation and thinking, has led to the proposal of cognitive architectures; capturing essential structures and processes of cognition and behavior. Robotists have also attempted to design automatic systems using these proposals. Though, certain difficulties have been reported for obtaining efficient low-level processing while sensing or controlling the robot. The main challenges involve the treatment of the differences between the computational paradigms employed by the cognitive and the robotic architectures. The objective of this work, is to propose a methodology for designing robotic systems capable of decision making and learning when executing manipulative tasks. The development of a system called the Cognitive Reaching Robot (CRR) will be reported. CRR combines the advantages of using a psychologically-oriented cognitive architecture, with efficient low-level behavior implementations through the visual servoing control technique.

International audience; This paper presents the use of 3D visual features in the so-called "Visual Servo-ing Approach". After having brie y recalled how the task function approach is used in visual servoing, we present the notion of 3D logical vision sensors which permit us to extract visual information. In particular, we a r e i n terested in those composed of the estimation of both a 3D point and a 3D attitude. We g i v e t h e c o n trol law expression with regard to the two kinds of visual features performed at video rate with our robotic platform. We present some of the experimental results and show the good convergence of the control laws.

National audience; Dans cet article, nous présentons un schéma d'asservisse-ment visuel en utilisant une nouvelle représentation de la projection des droites dans l'image fournie par une caméra omnidirectionnelle. En effet, la projection d'une droite de l'espace dans l'image d'une caméra catadioptrique, est une conique représentée par cinq coefficients alors que celle-ci ne possède que deux degrés de liberté. Afin d'obte-nir une représentation minimale nous proposons d'utiliser les droites polaires relatives à la projection des droites 3D dans l'image omnidirectionnelle. Nous définissons ainsi une caméra perspective virtuelle observant des droites. Nous donnons la forme analytique de la matrice d'interaction, liant les déplacements de la caméra catadioptrique aux variations des observations visuelles, dans les espaces nor-malisé et pixelique. Nous exploitons ensuite ce résultat pour construire une loi de commande adéquate. Des résultats de simulation et expérimentaux confirment la validité de notre approche.

International audience; This paper focuses on the benefits of using computer vision to control a Gough-Stewart parallel robot. Namely, it is recalled that observing the legs of such a mechanism with a calibrated camera, thus following the redundant metrology paradigm, simplifies the control law. Then, we prove in this paper that such a control law depends on a reduced set of kinematic parameters (only those attached to the geometry of the robot base) and that these parameters can be obtained by solving a linear system. Moreover, we show that the camera can be calibrated without much experimental effort, simply using images of the robot itself. All this means that setting up the control system consists only in placing the camera in front of the robot.

International audience; In this paper we present a new approach to control the 6 degrees of freedom of a manipulator using the projection of 3D lines extracted from the image plane of an omnidi-rectional camera. The main motivation of this work is to overcome the problem of visibility when using classical vision sensor. Indeed one of the principal deficiency of classical visual servoing strategy is that some parts of the visual features may get out of the field of view during servoing leading to its failure. Panoramic cameras overcome this problem because of their wider field of view. The present paper is concerned with the use of lines in paracataioptric visual servoing. Indeed when dealing with real environments (in-door or outdoor) or industrial workpiece, the extraction and the tracking of lines is natural. We derive the panoramic image jacobian for lines in the case of image based visual servoing. The corresponding control law is then designed and validated.

International audience; In this paper we present a new approach to control the 6 degrees of freedom of a manipulator using the projection of 3D lines extracted from the image plane of an omni-directional camera. The main motivation of this work is to overcome the problem of visibility when using classical vision sensor. Indeed one of the principal deficiency of classical visual servoing strategy is that some parts of the visual features may get out of the field of view during servoing leading to its failure. Panoramic cameras overcome this problem because of their wider field of view. The present paper is concerned with the use of lines in omnidirectional visual servoing. Indeed when dealing with real environments (indoor or outdoor) or industrial workpiece, the extraction and the tracking of lines is natural. We derive the panoramic image jacobian for lines in the cases of image based and position based visual servoing. The corresponding control laws are then designed and validated.; Dans cet article nous présentons une stratégie de com-mande de robots manipulateurs à six degrés de liberté 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 (image catadioptrique). La motivation principal de ce travail est de répondre aux problèmes de visibilité lorsque des in-formations issues d'une caméra classique sont intégrées à une boucle de commande. En effet, une des princi-pales sources d'échec des schémas d'asservissement est relative aux sorties de champs des primitives visuelles. L'utilisation de caméras omnidirectionnelles permet de résoudre cette difficulté puisque leurs champs de vision est bien supérieur à celui des caméras classiques. Cet article concerne en particulier l'utilisation de la projection de droites dans l'image d'une caméra omnidirec-tionnelle comme entrée de la boucle de commande. Afin de réaliser la commande d'un système robotique par as-servissement visuel, il est nécessaire d'estimer la ma-trice jacobienne (matrice d'interaction) liant les mou-vements de la caméra aux mouvements des primitives visuelles dans l'image catadioptrique. Dans cet article, nous donnons la forme analytique de la matrice d'in-teraction pour la projection de droites dans l'image ca-tadioptrique permettant de construire une loi de com-mande adéquate.

International audience; We have been interested in Automatic Guided Vehicles (AGV) for several years. In this paper, we synthesize controllers for AGV applications using monocular vision. In particular, we are interested in road following and direction change tasks, and in analyzing the influence of extrinsic camera parameter perturbations on vehicle behavior. We use the bicycle as the kinematic vehicle model, and we choose the position of the white band on the road as the sensor signal. We define an interaction between the camera, which is mounted inside the vehicle, and the white band detected in the image space. Using this kind of interaction, we present how to use a pole assignment technique to solve the servoing task. We show the simulation and experimental results (1/10 scale demonstrator) with and without perturbations. We then investigate the use of a robust controller to slow down the effect of perturbations on the behavior of the vehicle.

International audience; We have been interested in Automatic Guided Vehicles (AGV) for several years. In this paper, we synthesize controllers for AGV applications. Particularly, we are interested in road following and direction change tasks, and in analyzing the in uence of roll and pitch perturbations on vehicle behaviour. We use the bicycle as the kinematic vehicle model, and we c hoose the white band position of the road as the sensor signal. We de ne an interaction between the camera, which i s mounted inside the vehicle, and the white band detected in the image space. Using this kind of interaction, we present how to use a pole assignment technique to solve the servoing task. We show the simulation and experimental results (1/10 scale demonstrator) with and without perturbations.

International audience; This work is a synthesis of our experience over parallel kinematic machine control, which aims at changing the standard conceptual approach to this problem. Indeed, since the task space, the state space and the measurement space can coincide in this class of mechanism, we came to redefine the complete modeling, identification and control methodology. Thus, it is shown in this paper that, generically and with the help of sensor-based control, this methodology does not require any joint measurement, thus opening a path to simplified mechanical design and reducing the number of kinematic parameters to identify. This novel approach was validated on the reference parallel kinematic mechanism (the Gough-Stewart platform) with vision as the exteroceptive sensor.

International audience; In this paper, it is shown that computer vision, used as a redundant metrology mean, allows the control of a Gough-Stewart parallel robot without using any joint sensor. This result is highly relevant for the control of parallel mechanisms hard to instrument (for instance , hydraulically actuated ones) or with large displacements (for instance, large telescopes positioning systems). It is also very interesting since it turns computer vision, usually considered as an exteroceptive sensor, into a proprioceptive one, yet preserving its exteroceptive nature and non contact measurement.