Method and apparatus for checking tyres for vehicle wheels

Abstract

Method and apparatus for checking tires for vehicle wheels. A tire to be checked is fed to a checking station. A sidewall of the tire lies on a supporting portion of a rotating table. The supporting portion lies on a plane while the rotating table has a rotation axis perpendicular to the plane. A centring operation is carried out to align, in the plane, the rotation axis of the tire with the rotation axis of the rotating table. The centring operation includes identification, in the plane, of the rotation axis of the tire by: a) acquisition of an image of the tire laid on the supporting portion of the rotating table; b) definition, in the acquired image, of a number of analysis directions intersecting at one selected central point; c) for each analysis direction: c1) definition, in the acquired image, of a number of potential axes of symmetry, perpendicular to the analysis direction; c2) calculation of a level of symmetry of the image with respect to each potential axis of symmetry, where the level of symmetry is indicative of the probability that the center of the tire is on the respective potential axis of symmetry; c3) determination of a probability distribution indicative of a variation of the level of symmetry along the analysis direction; d) determination of a center of the tire on the basis of a cumulative probability distribution obtained through a combination of the probability distributions calculated for the analysis directions; e) identification of the rotation axis of the tire in an axis that passes through the determined center and perpendicular to the plane.