Research On Intelligent Control Technology For Forming The Large Diameter Longitudinal-Seam Submerged Arc Welded Pipes With JCO Process

Since the first longitudinal-seam submerged arc welded (LSAW) pipes production line with JCO forming process was established in Julong Steel Pipe Co., Ltd, the unfinished pipe forming process and the correlated technology have been investigated by the researchers. Due to the key technology and the forming press from abroad, the systematical basic research on the forming process has not been conducted yet. And the pipe quality and processing parameters adjustment are conducted according to accumulated experience with the characteristics of large error, high personnel working strength and unstable production quality. As one of the effective method to improve the pipe quality, the intelligent control technology is introduced to real-time monitor the pipe quality and to adjust the processing parameters automatically.Based on the research achievements of the intelligent control technology for the sheet metal bending, the key technologies of intelligent bending for unfinished pipe forming with JCO process are analyzed, and the relevant issues to the theoretical analysis, the process monitoring, the identified model of material properties and the predicted model of optimal processing parameters have been studied in this paper.In this investigation, based on the elementary theory of plastic bending, the mechanical model which can describe the bending process and springback behavior adequately has been established. The equations for the rotation angle and radius of each point in neutral surface for any bending process are derived. And the calculated model of springback after removing the punch load is derived according to the uploading theory. The finite element method and experiment were introduced to verify the validation of the mechanical model established before and analyze the dominant factors influenced on the bending and springback process. And the investigation is carried out to provide the theoretic basis for the intelligent control for unfinished pipe forming with JCO process.Based on machine vision and sensor technology, the system for real-time monitoring the sheet metal bending process is developed, which can measure the bending force, punch displacement and the unbend angle with high precision. The processing algorithms of image pre-processing and line detection, which are simple, efficient and suitable for the pipe ending surface image, are studied in detail. According to the comparison of the image processing results, a series of algorithms suitable for the images are identified. Focused on the live condition, a new camera calibration method has been put forward to transform the angle in image into the actual angle. The experimental data indicates that the calibration method proposed has advantages of simple operation, fast completion and the high precision, which is very suitable for live system calibration.The identification model of material properties and the prediction model of optimal processing parameters have been constructed employing the neural network technology. In the identification model, the bending force, the punch displacement and the unbend angle are denoted as the input variables, and the material properties are the output variables. The Levenberg-Marquarat is chosen as the optimal algorithm of neural network whose topology structure is feedforward network, and Matlab language is to program.Employing the research results above, an intelligent control code for unfinished pipe forming with JCO process is developed with Visual C++ language, including the development of calculated code theoretic analysis for sheet metal air bending process, the development of building code of the neural network training sample data, the development of gathering code of bending force and the bending displacement, the development of calibration code, the development of unbend angle identifying code, and the development of the interface code between the signal control and the identification model. At last, employing the portable DAQ card and camera CCD and other hardware, the intelligent control system for the unfinished pipe forming with JCO process is established.The physical simulated experiments have been conducted with the intelligent control system, which showed that the system operated stably, the punch displacement predicted is reliable, and can obtain high quality pipes. As the final achievement of research work, the intelligent control system has been transplanted to the LSAW pipe production line with JCO process successfully, improving the production efficiency and the product quality and realizing the intelligent control for the unfinished pipe bending process.