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Shape Analysis for Quality Assurance of Steel Coils

Johannes Atzelsberger


Sheet metal for cars has to achieve very strict quality standards.

The sheet is delivered in coils (see Figure).
An image processing system should be developed, which recognizes geometric errors of these coils and which is able to decide, whether the coil achieves minimal geometric constraints.

Figure 1: Steel-Coil

This project can only be seen as a preliminary survey, so firstly already known methods for estimating the ellipse parameters are investigated in order to split the coil images into cylinder base and cylinder barrel segments (Errors on the cylinder base are different to the errors on the cylinder barrel). Secondly the developed algorithms are tested on real images acquired of ILL (Industrie-Logistik-Linz).

Above all, the base area of the steel coil in its real size is calculated out of the ellipse (diagonal view of the base area) and the geometric relation of the coil with respect to the camera (vantage point), in order to decide if the base area of the inspected coil achieves strict tolerances. Finally, the parameter estimation of the ellipse and the evaluation of the base area in its real size is implemented in a Matlab® graphical user interface (GUI).

June 27, 2007