# Orbital-Based Automatic Multi-Layer Multi-Pass Welding Equipment for Small Assembly Plates
## 4 Equipment Operation Testing and Visual Scanning Simulation
### Equipment Scanning Strategy  
#### 4.4.1 Scanning Trajectory and Spatial Poses  
In terms of weld groove scanning strategies, some studies have proposed the multi-step method [27] and the smooth spline curve planning method [28] to extract weld features. Although these methods ensure operational precision, they can introduce a series of unpredictability for rail operations. This paper formulates a rail-based scanning strategy for the web and panel in small assembly working conditions, including the equipment's \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Serial Number** & **Symbols** & **Numerical Values (Panel)** & **Numerical Values (Vertical Plate)** \\ \hline \(1\) & L1 & 6 mm & 5 mm \\ \(2\) & L2 & 8 mm & 10 mm \\ \(3\) & L3 & 8 mm & 10 mm \\ \(4\) & L4 & 5 mm & 4 mm \\ \(5\) & \(\alpha\) & 45\({}^{\circ}\) & 45\({}^{\circ}\) \\ \(6\) & \(T\) & 11 mm & 13 mm \\ \hline \hline \end{tabular}
\end{table} 
Table 11: Plate butt level parameters. Figure 34: Equipment operation test chart. scanning path, motion posture, weld groove information extraction, and point cloud processing. The technical parameters in the scanning strategy are detailed in Appendix A. After completing the overall mechanical and communication connections of the equipment, the robotic arm is debugged to connect with the external axis, and automatic operation is initiated. The equipment first reaches the initial scanning position and posture at point 0 specified for the workpiece, then changes posture to reach point 1, which is located 390 mm in the Y-direction and 495 mm in the Z-direction from the Cartesian coordinate origin at the center of the robotic arm base. After the automatic welding equipment moves to the fixed position at point 2 via the external axis, the robotic arm adjusts its posture and position to points 3 through 6. This adjustment aligns the laser beam perpendicular to the Z-axis of the reference coordinate system, directing it onto the bottom plate of the workpiece and initiating the laser swing scanning mode. At this point, the external axis is temporarily fixed. This position and posture ensure that the robotic arm's TCP (tool center point) is not lower than the height of the base center point. Subsequently, the robotic arm moves along the Z-axis via the external axis to the sub-assembly panel while adjusting its posture to point 7. When the laser projects onto the panel, the operation stops, and the external axis is temporarily fixed. Meanwhile, the robotic arm adjusts its posture through points 8 to 10 to acquire the panel groove information and the plate height and dimension data. After acquiring the information, the robotic arm moves back to the initial scanning position at point 7, then moves along the Z-direction via the external axis to locate point 11. Carrying the laser sensor, the robotic arm moves to the position with the most accurate viewing distance to obtain the bottom plate information of the workpiece and analyzes to calculate the distance between the panel and the robotic arm base. The robotic arm adjusts its posture and position to reach point 12, directing the laser sensor toward the side web of the workpiece, and analyzes to calculate the distance information between the robotic arm base and the sub-assembly side web. It then adjusts position and posture to make the laser beam parallel to the Z-axis of the reference coordinate system while moving to point 13, where it is completely parallel and coincides with the junction of the sub-assembly web and the bottom plate base surface within the workpiece. Scanning in the positive X-direction under the reference coordinate system, it extracts the entire sub-assembly groove web information and plate width data. At this point, the scanning ends and returns to point 0. For this workpiece, Figure 35 shows the TCP motion trajectory projection diagram of the laser sensor scanning process.