Industrieller Einsatz von Methoden der digitalen Bildverarbeitung und Nahbereichsphotogrammetrie zur Qualitätssicherung von Stahlcoils

These days metal processing companies like car manufacturers are demanding a high level of quality for the provided base materials. The base material, usually steel is supplied by producers in the form of coils. Coils consist of thin steel sheets which are wound into a roll. Due to imperfections in the winding process or due to problems during the transport, sheet metal layers can move axially to each other. When the resulting winding displacement reaches a certain level, the likelihood of damaging the sheet thru the handling of the coil will increase. To ensure a complete quality assurance, a measurement system was developed in this diploma thesis, which is able to measure winding displacements with a resolution of less than 1 mm. For a complete description of the laser line projection on the object surface a mathematical model was developed, which can further be used to compensate the errors relating to the laser alignment. The extraction of the laser line from the images was realized with an adaptive algorithm that detects only laser segments, which can clearly be assigned to the coil. This adaptive algorithm allows to exclude laser line segments placed on edge protection material or background objects from further processing. Finally, the critical sectors for the transport of the coil are detected by using the previously determined coil profile. As an example for the functionality of the implemented measurement system, an image of a coil and the result of the detection algorithm are shown in Figure 3.