Real-time Detection And Control Of The Back Weld Width In Aluminum Alloys GTAW

In the process of Aluminum alloys GTAW, uniform of back weld is a critical problem. It is difficult to achieve the quality requirements using a constant welding standard, If the possibilities of real-time detecting and the feedback loop control, then it will greatly improve the efficiency and quality of welding. In this paper, based on the back of the CCD camera allowed placed, intelligent control of the back penetration in the process of Aluminum alloys GTAW was studied from aspects of sensing of arc process, digital image processing technique, the dynamic characteristic analysis, the controller design.Firstly, the hardware devices of experiment were designed and completed, including EWS - 844 integration workstation, digital acquisition card, image acquisition card, CCD camera and Miller Dynasty 700 welder. And then, the back penetration control system in the process of Aluminum alloys GTAW was developed under Microsoft Visual C++ 6.0 programming environment and a complete system platform was established.In order to get back weld width, through analysis of back weld pool images, the different image processing algorithms of the back weld pool were developed according to the different characteristics of the images. It contains piecewise linear increase, median filtering, edge sharpness, feature extraction, etc. Through practical applications, it showed that the algorithms had a good real-time performance, high precision and had laid a good foundation for the welding process control.Control method was investigated, in which controlled variable was the welding current and controlling variable were the error of back weld width and the changes of error. The experiments on control of Aluminum alloys GTAW with the work pieces of 3mm thickness and the experiments on control of Aluminum alloys Tungsten helium arc welding with the work pieces of 6mm thickness were completed and the fuzzy controller was optimized through the analysis of the results of actual welding. Results show that the designed controller could effectively keep pace with the back weld pool width very well.