Research On Plate Flatness Measurement Technology Based On Machine Vision

The flatness is a key quality index of plates. It always influences the application of products and operation of milling line. In recent years, with the development of modern manufacturing, there is a higher quality demand for flatness. For example, the height precision of extensibility fiber should be millimeter-scaled. And the flatness measurement system provides feedback data to flatness control system, which has a direct impact to the flatness of plates. The level of flatness measuring technology reflects a nation’s precision rolling development status and the overall strength. Conduct research about flatness measurement technology has a great and far-reaching significance in promoting our national high technology industries such as ultra-precision machining and measurement, national military industry and advanced manufacturing.Based on the review of domestic and international research and application of flatness measurement, this thesis put emphasis on the fundamental of laser triangulation, the calibration methods, the analysis and disposal of noise signal, the design and realization of system’s software and the construction of flatness measuring system.In the first chapter, firstly, the background and significance of this thesis, the definition of flatness and typical flatness defects was introduced. Then the research status of characteristics of contact and non-contact flatness measuring technology was stated. Finally, main research contents and the structure of the thesis was presented.In the second chapter, based on the fundamental of laser triangulation, the theoretical models were built and the measuring range and resolution of them were compared with each other. Then calibration by curve-fitting was proposed which was based on space geometric transformation and camera imaging. Finally, the overall scheme of flatness measurement system was designed.In the third chapter, the sources of noise in flatness detecting procedure were given. And some image process algorithms were researched, which used to handle those noise. Then the processing methods of typical noise image, such as dust, scratches and drop were discussed.In the fourth chapter, the software’s structure was designed. Communication protocol of the whole system was given, which was realized by clusters of Labview. And the MySQL database was set up according to the characteristic of flatness measurement system.In the fifth chapter, the flatness measurement system based on machine vision was constructed. In order to verify the effectiveness of this design, the calibrating experiment, calibration verifying experiment, plate flatness measuring experiment and noise experiment were carried out.In the sixth chapter, the research work was summarized.