Vision-based automatic verification of machining setup : application to machine tools safety

Le terme "usinage à porte fermée", fréquemment employé par les PME de l’aéronautique et de l’automobile, désigne l’automatisation sécurisée du processus d’usinage des pièces mécaniques. Dans le cadre de notre travail, nous nous focalisons sur la vérification du montage d’usinage, avant de lancer la phase d’usinage proprement dite. Nous proposons une solution sans contact, basée sur la vision monoculaire (une caméra), permettant de reconnaitre automatiquement les éléments du montage (brut à usiner, pions de positionnement, tiges de fixation,etc.), de vérifier que leur implantation réelle (réalisée par l’opérateur) est conforme au modèle 3D numérique de montage souhaité (modèle CAO), afin de prévenir tout risque de collision avec l’outil d’usinage.In High Speed Machining it is of key importance to avoid any collision between the machining tool and the machining setup. If the machining setup has not been assembled correctly by the operator and is not conform to the 3D CAD model sent to the machining unit, such collisions can occur. We have developed a vision system, that utilizes a single camera, to automatically check the conformity of the actual machining setup within the desired 3D CAD model, before launching the machining operation. First, we propose a configuration of the camera within the machining setup to ensure a best acquisition of the scene. In the aim to segmente the image in regions of interest, e.g. regions of the clamping elements and piece, based-on 3D CAD model, we realise a matching between graphes, theorical and real graphe computed from theorical image of 3D-CAD model and real image given by real camera. The graphs are constructed from a simple feature, such as circles and lines, that are manely present in the machining setup. In the aim to define the regions of interest (ROI) in real image within ROI given by 3D CAD model, we project a 3D CAD model in the real image, e.g. augmented reality. To automatically check the accordance between every region defined, we propose to compute three parametres, such as skeleton to represente the form, edges to represent a geometry and Area to represent dimension. We compute a score of accordance between three parameters that will be analyzed in fuzzy system to get a decision of conformity of the clamping element within it definition given in the CAD model. Some cases of machining setup configurations require 3D information to test the trajectory of the machine tool. To get out this situation, we have proposed a new depth from defocus based-method to compute a depth map of the scene. Finally, we present the result of our solution and we show the feasibility and robustness of the proposed solution in differents case of machining setup