CAD-based calibration for on-machine measurement using vision
Résumé
On-machine inspection is often performed using a vision based-system. Vision-based systems are used for the verification of machine set-ups [6], the survey of tool trajectories, part inspection of socket production, and so on [3]. These systems present various advantages: low cost, rapidity, flexibility and simplicity of implementation in the context of production. A minor drawback is the system calibration. Calibration is necessary to transform a 2D point (or a point belonging to the picture) into a 3D point expressed in the reference frame. Within the context of on-machine inspection, the positioning of the camera frame relatively to the reference frame must be performed for each measurement operation. More generally, the reference frame of calibration can be anything. To enhance the interoperability between machining and inspection, it could be interesting that the reference frame or CAM frame, associated to machining operations, should coincide with the reference frame used for calibration. This removes an additional step of frame registration which is penalizing in terms of computational time and quality. This paper deals with a CAD-based calibration method for on-machine inspection. Its originality is that the CAM frame is not only used to define the machining operations, but it is also the calibration reference frame and thus the measurement frame. For this purpose, the reference frame must be built from features of the machine tool scene. In the approach developed in this paper, features represented in the CAD frame are used to map the vision calibration frame to the machining frame in which both measurements and machining operations will be performed.
Domaines
Génie mécanique [physics.class-ph]
Origine : Fichiers produits par l'(les) auteur(s)
Loading...