Three-dimensional reconstruction of specular surface for a gas tungsten arc weld pool

Observing the weld pool and measuring its geometrical parameters are key issues for developing the next generation intelligent welding machine and modeling the complex welding process. In the past few years, different techniques have been applied, but the dynamic specular weld pool surface and the strong weld arc complicate these approaches and make observation difficult. To resolve the problem, a new three-dimensional sensing system using structured light is proposed for a gas tungsten arc welding (GTAW) process. In the system, a dot-matrix laser pattern is projected on the specular weld pool surface, which can reflect light onto an imaging plane. The reflected images are captured by a high-speed camera and can successfully be processed by image processing algorithms developed. With the acquired information, a three-dimensional reconstruction scheme is proposed and discussed in this paper. A surface reconstruction method with several slope-based algorithms is first developed to rebuild the region of weld pool surface which reflects the laser pattern. Then a two-dimensional piecewise model is provided to calculate weld pool boundary by utilizing the edge condition. Finally the optimal estimate of the three-dimensional weld pool surface is synthesized. The acceptable accuracy of the results verified the effectiveness of the reconstruction scheme.