Camera-based monitoring of the rigid-body displacement of a mandrel in superconducting cable production

We describe a machine vision measurement head that is used to monitor the mandrel position in production of superconducting cables. Two cameras are orthogonally aligned, viewing different sections of the cylindrical part of the mandrel. The use of telecentric lenses obviates the need for re-calibration after the replacement of mandrel. All parameters of rigid-body motion are obtained in linear theory by using a multivariate least-squares fitting procedure on dynamically corresponded sets of target points that vary due to partial blocking by rotating wires. A rigorous analysis of measurement uncertainty is given.