https://works.bepress.com/jing-wu/29/download/

Research evolution on intelligentized technologies for arc welding process

Control of 3D weld pool surface

Robust measurement of the specular weld pool surface can help better understand the complex welding processes and provide feedback for robotic welding. The strong arc light and the specular surface of the weld pool make it difficult for the direct sensing measurement. In this paper, a novel imaging and measurement system is proposed, and it makes use of the strong penetrability of the laser to avoid the interference of arc light and obtain the surface information of the weld pool. By intercepting the reflection of a projected laser pattern twice, the proposed system gives a closed-form solution for each reflected ray and a closed-form solution for the corresponding point on the weld pool surface. The weld pool surface can be thus reconstructed by one-shot structured light projection. To increase the robustness of the measurement system, the least deformation principle is proposed to rectify the coefficient errors of the computed plane equation. Finally, a sequence of 3-D weld pools is reconstructed and compared with state-of-art literature. The comparison verifies that our method is significantly better than all the other methods in measuring the 3-D weld pool shapes.

An Imaging and Measurement System for Robust Reconstruction of Weld Pool During Arc Welding

Application of sensing techniques and artificial intelligence-based methods to laser welding real-time monitoring: A critical review of recent literature

Automatic multi-pass route planning is one of key technologies for thick plate in robotic metal active gas (MAG) arc welding. In this research, a scheme for the extracting feature points of the weld seam profile to implement automatic multi-pass route planning, and guidance of the initial welding position in each layer during MAG arc welding, is presented. It consists of two steps: first a vision sensor based on structured light is employed to capture laser stripes and molten pools simultaneously within the same frame, and the laser stripe, forming the weld seam profile is detected by a visual attention model based on saliency. Then a methodology of polynomial fitting plus derivatives for feature point extraction of the weld seam profile is suggested. With respect to the effectiveness of highlighting the laser stripe, the proposed model is much better than the classic ones in this field, whereas the feature point extraction methodology in this paper outperforms typical template matching. Finally, the performance of the proposed scheme is demonstrated on different weld seam images captured in different layers and different welding experiments. New vision sensor captures laser stripes and molten pools simultaneously.A visual attention model for detecting weld seam profiles is proposed.Three kinds of feature points of weld seam profiles can be extracted.Different images captured in different layers validate the proposed methods.The extracted feature points can be used for multi-pass route planning.

Weld seam profile detection and feature point extraction for multi-pass route planning based on visual attention model

In this paper, visual sensing and penetration control in aluminum (Al) alloy pulse gas tungsten arc welding were researched. Firstly, a three-optical-route visual sensor was designed. The sensor can capture the weld pool from three directions at the same time. After analyzing the influences of different factors on weld pool image, serials of clear and stable weld pool images were obtained. Then, image processing technologies were developed to compute back topside weld pool geometry parameters. Wavelet transform and Canny operator were synthesized to get all edges in the weld pool image. After noise removal and calibration, the breaking edges of weld pool were obtained, and then piecewise curve fitting based on polynomial function were used to recover the whole weld pool edge. Lastly, proportional-integral-differential and a multiplex controller were designed to control penetration in welding process. Experiments proved that visual-based penetration control can insure welding quality well from weld pool width and reinforcement.

Chongjian Fan

Papers

Visual sensing and penetration control in aluminum alloy pulsed GTA welding .