A Vision-Based Technique for Edge Displacement and Vibration Estimations of a Moving Flexible Web

Web vibration phenomena that occur in winding/unwinding systems have a knock-on economical effect for the numerous firms that utilize this equipment. Among many sources of disturbances, out-of-plane and lateral displacements of a moving web are well known to be two main limiting factors of web transport velocity in the industry. To tackle this problem, we address, in this paper, a new approach for the detection and monitoring of the most significant web displacements encountered, which are the simultaneous edge web lateral displacements and out-of-plane web vibrations. This technique involves a fast vision system composed of two digital cameras ( ges 2 times100 i/s) and a laser stripe lines pattern device. It is a contactless technique that allows catching out-of-plane web vibration properties during the winding process. Due to a well-known edge-tracking algorithm and fast but simple image segmentation algorithms in the field of binary machine vision, both edge web and out-of-plane vibration frequencies and magnitudes are estimated in real time. The latter are extracted from the analysis of the relative depth variations of the web surface with respect to the common camera frame. Experiments have been conducted on a winding plant for elastic fabric. Together with the 3-D displacements of the web edges, the two most significant frequencies of web vibrations have been estimated for a sequence of images and compared with those computed with a simple elastic string model in motion.