Distance-based and Orientation-based Visual Servoing from Three Points

International audienceThis paper is concerned with the use of a spherical-projection model for visual servoing from three points. We propose a new set of six features to control a 6-degree-of-freedom (DOF) robotic system with good decoupling properties. The first part of the set consists of three invariants to camera rotations. These invariants are built using the Cartesian distances between the spherical projections of the three points. The second part of the set corresponds to the angle-axis representation of a rotation matrix measured from the image of two points. Regarding the theoretical comparison with the classical perspective coordinates of points, the new set does not present more singularities. In addition, using the new set inside its nonsingular domain, a classical control law is proven to be optimal for pure rotational motions. The theoretical results and the robustness to points range errors of the new control scheme are validated through simulations and experiments on a 6-DOF robot arm

Vision-based Control of 2D Plane Poiseuille Flow

International audienceThis paper introduces a new approach for active fluid flows control: the vision-based approach. By using vision, dense flow velocity maps can be estimated and used in an observer-free closed-loop scheme to control a flow. This new approach is validated on a 2D plane Poiseuille flow and is proven to outperform the existing Poiseuille flow control appraches which use a limited number of available shear stress measurements

Commande basée vision d'écoulements fluides

[Departement_IRSTEA]Ecotechnologies [TR1_IRSTEA]SPEE [Departement_IRSTEA]Ecotechnologies [TR1_IRSTEA]SPEEColloque avec actes et comité de lecture. Internationale.National audienceCet article propose une nouvelle approche de commande en boucle fermée d'un écoulement fluide. Cette approche permet de s'affranchir de la synthèse d'un observateur. Pour ce faire, un dispositif de visualisation est utilisé, il permet de remonter au champ de vitesses des particules via des techniques de flot optique. Nous montrons très nettement les bénéfices d'utilisation d'une telle approche en présence du bruit de mesures par rapport aux approches classiques utilisant le frottement pariétal. Ces dernières approches sont également surpassées dans le cas d'une mauvaise initialisation de leur observateur nécessaire à la loi de commande

Fluid Flows Control using Visual Servoing

International audienceThis paper introduces for the first time the control of a fluid flow using visual servoing. The control consists to regulate a flow around a desired velocities profile. The originality here is the possibility to use optical flow measurements, computed from the observed flow, in a visual servo control scheme. Compared to existing approaches that uses a limited set of measurements to control a fluid flow, our approach is shown to be a major improvement in terms of the flow state estimation and control

Visual servoing from spheres using a spherical projection model

International audienceIn this paper, we investigate the use of a spherical projection model to search for optimal visual features for visual servoing. A new minimal set of three visual features is proposed for visual servoing from spheres using any central catadioptric system. Using this set of features, a classical control method is proved to be globally stable even in the presence of modeling error and locally stable to calibration errors on perspective cameras. Using this type of cameras, experimental results are presented and validate the proposed theoretical results

Commande des écoulements fluides par asservissement visuel

[Departement_IRSTEA]Ecotechnologies [TR1_IRSTEA]SPEEInternational audienceThis paper introduces for the first time the control of a fluid flow using visual servoing. The control consists to regulate a flow around a desired velocities profile. The originality here is the possibility to use optical flow measurements, computed from the observed flow, in a visual servo control scheme. Compared to existing approaches that uses a limited set of measurements to control a fluid flow, our approach is shown to be a major improvement in terms of the flow state estimation and control

Visual servoing from spheres with paracatadioptric cameras

A paracatadioptric camera consists of the coupling of a parabolic mirror with a telecentric lens which realizes an orthographic projection to the image sensor. This type of camera provides large field of view images and has therefore potential applications for mobile and aerial robots. This paper is concerned with visual servoing using paracatadioptric cameras. A new optimal combination of visual features is proposed for visual servoing from spheres. Using this combination, a classical control law is proved to be globally stable even in the presence of modeling error. Experimental and simulation results validate the proposed theoretical results

Distance-based and Orientation-based Visual Servoing from Three Points

International audienceThis paper is concerned with the use of a spherical-projection model for visual servoing from three points. We propose a new set of six features to control a 6-degree-of-freedom (DOF) robotic system with good decoupling properties. The first part of the set consists of three invariants to camera rotations. These invariants are built using the Cartesian distances between the spherical projections of the three points. The second part of the set corresponds to the angle-axis representation of a rotation matrix measured from the image of two points. Regarding the theoretical comparison with the classical perspective coordinates of points, the new set does not present more singularities. In addition, using the new set inside its nonsingular domain, a classical control law is proven to be optimal for pure rotational motions. The theoretical results and the robustness to points range errors of the new control scheme are validated through simulations and experiments on a 6-DOF robot arm

Une nouvelle approche pour la commande des écoulements fluides

International audienceFluid flow control is of great economical interests in many fields of applications. Controlling a flow consists in changing its state or to maintain it in its current state. In this presentation, we show that existing flow control methods suffer from limited observations, from measurements noise, and from the initialization process involved in the observer required to reconstruct the flow state. To deal with these issues, we present a very promising approach: the vision-based approach