On-line Vibrations Characterization of a Moving Flexible Web with a Fast Structured Lighting Stereovision System

Web vibrations phenomena which occur in winding/unwinding systems have a knock-on economical effect for the numerous firms which utilize these equipments. Among many sources of disturbances, out-of-plane vibrations of a moving web are well-known to be the most limiting factors for the velocity in the transport industry of flexible web. To tackle this problem, we address in this paper a method for the detection of out-of-plane web vibrations by means of two fast cameras(ges 2 times 100 i/s) and a laser stripe lines pattern device. The new technique we proposed for the estimation of out-of-plane web vibration properties, without contact with the web and during the winding process is the main contribution of this work. As far as we know, this is the first time a technique is proposed to capture on-line the vibration characteristics of a moving web with a fast visual inspection system. Thanks to a 3-D lines reconstruction algorithm, vibration frequencies and magnitudes are estimated from the analysis of the relative depth variations of any web cross-section with respect to the common camera frame. Experiments have been conducted on a winding plant for elastic fabric. The most significant frequencies have been estimated for a sequence of images and compared to those computed with a simple elastic string model in motion.