The surface machining of cracks is a key issue to ensure the quality of steel rods and billets. The aim is to grind these defects out of the material. This paper presents a real-time optical servo-system, consisting of three image processing systems and an industrial robot, which fully automate this process. A high resolution color progressive scan camera, placed at a suitable position above the roller conveyor, observes the material and detects color markings indicating the presence of a crack. This camera system controls the roller conveyor transporting the material until a marked crack is detected. Diffuse light sources provide homogeneous lighting to ensure reliable detection of the markings. A demosaicing algorithm, RGB to HSL color modeling and thresholding with statistical morphology are used to identify the marked areas. On detecting a crack the material is automatically positioned within the working area of an industrial robot. A collineation is used to generate metric two-dimensional coordinates corresponding to the bounding rectangle of the detected error. At this point two plane-of-light scanners are used to acquire a cross section of the material to the left and the right of the robot's working area. From this, a three-dimensional model for the rod or billet surface is calculated and the two-dimensional coordinates of the color marking are projected onto this surface to generate a patch. The coordinates of this patch are sent to the 6R industrial robot, which then grinds out the defect. A new concept has been implemented which enables the calibration of the three image processing systems and the industrial robot so as to have one common coordinate system. Operational results have shown the full functionality of the system concept in the harsh environment of a steel production facility.
The recent introduction of high dynamic range CMOS-cameras with logarithmic response to light intensity, justify a serious evaluation of the technology as an alternative technology for laser profiling. This paper presents a series of comparative tests of a high quality CCD-camera and a high-dynamic range CMOS-camera. Standard gray scale charts are used to verify the intensity response and the signal to noise ratio at different f-stops. It is shown that the high dynamic range of the CMOS-sensor makes the camera suitable for differential image laser profiling. Furthermore, the cross-section of steel rods and wires are observed to verify the industrial applicability
of the different standards. Both, material at room temperature and red-hot glowing steel bars were measured. The advantages and disadvantages for each technology are shown on the basis of these tests. Finally, a laser profiler was manufactured with the CMOS-camera and successfully implemented in a steel-mill.