A stereo vision method for tracking particle flow on the weld pool surface

Abstract

The oscillation of a weld pool surface makes the fluid flow motion quite complex. Two-dimensional results cannot reflect enough information to quantitatively describe the fluid flow in the weld pool; however, there are few direct three-dimensional results available. In this paper, we describe a three-dimensional reconstruction method to measure weld pool surface features based on a single high-speed camera. A stereo adapter was added in front of the high-speed camera lens to obtain two images in the same frame from different view points at the same time. According to machine vision theory, three-dimensional parameters can be reconstructed based on two such images. In this work, three-dimensional velocity fields have been obtained using this method. Based on the calibration technique employed, the associated error is estimated to be less than 11.4%. Quantitative experimental results are useful for understanding the flow pattern, and possibly for controlling the flow of liquid in the weld pool.

Virtualized welding based teleoperation with pipe gas tungsten arc welding applications

“…The weld pool geometry is believed to provide valuable insights into the state of the welding process. Several 3D weld pool measurement methods have been proposed, including model-based reconstruction [13], stereovision measurement [14,15], shape from shading [16,17], and structured light based sensing [18,19]. Depending on the sensing method used, the welding process control systems can also be categorized into pool oscillation-based control [20], radiography-based control [21], thermal-based control [22,23], and vision-based control [24][25][26][27][28][29][30][31], etc.…”

Three-dimensional reconstruction of welding pool surface by binocular vision

“…The three-dimensional(3D) reconstruction method for welding pool can be categorized into 3D structured light method, shape from shading method and binocular stereo vision method [10][11][12][13][14]. To avoid the arc interference during measurement process, Zhang and his coworkers [15] proposed a novel structured laser vision system for reconstructing 3D welding pool surface.…”

“…The results showed that the binocular vision system needed to be improved as the extra bright area on welding pool surface could not be reconstructed. Richardson [13] used particle image velocimeter (PIV) to track the movement of oxide particles to determine the velocity field on the welding pool, and then transferred the above data into 3D fluid velocity by stereo vision method. Calibration process was the main factor that influenced the measurement precision during 3D reconstruction, the average distance error between the tested corner points was 0.14 mm.…”

Study on oscillation modes of weld pool in stationary GTA welding using structure laser method

“…For the sensor measurement of GTA welding pool surface, domestic and foreign scholars have studied it by many methods. In the actual welding process, optical measurement technology is mainly used, such as structured light three-dimensional visual measurement method [2] , SFS (shape from shading) [3] and binocular stereo vision method [4] .In numerical simulation, the finite element analysis method and other numerical simulation software [5][6][7] are mainly used.…”