Cooperative Towing by Multi-Robot System That Maintains Welding Cable in Optimized Shape

Abstract

As considerable amounts of welding are required during ship construction, robotic automation is being promoted. However, current welding robots do not automate work in high or narrow places. One reason is that welding cannot be performed with sufficient accuracy because a welding robot with a torch cannot tow a heavy cable and thus may go off path.This paper proposes a multi-robot system for automating the execution of long welds in high and narrow places to address this problem. In the proposed method, towing vehicles are placed along the supply cable to reduce the load on the lead welding vehicle. In confined-space welding, the cable must not be excessively loaded, and obstacles such as walls must be avoided. Under the proposed method, autonomous movement of the towing vehicles is achieved by solving an optimization problem that considers these aims and minimizes the amount of change from the estimated current cable shape. The method was evaluated through simulation and real-world tests, in which it was applied successfully to tow the cable with a welding torch in a working area of 2.6 × 10 m 2 (simulation) and of 3.4 × 5.5 m 2 (real-world environment) without disturbing the lead vehicle's movement.

Joint Calibration Method for Robot Measurement Systems

“…Several patterns can be observed in Figure 5. (1) The fitted diameter of all measurement points is larger than the theoretical diameter. (2) The fitted diameter decreases obviously as the z-axis coordinate increases.…”

“…In addition, the error model should consider the following characteristics based on the measurement principle and existing studies [21,22,29,30]. (1) The error increases as the measurement point moves away from point S, which is the intersection point of the two cameras' lines of sight. This indicates the presence of a distortion field around S, as illustrated in Figure 3.…”

“…Industrial robots are preferred for their high flexibility, low cost, and wide working range, and they have started to gradually replace manual labor in many scenarios, such as welding, shot peening, and palletizing [1][2][3]. A 3D camera utilizes the parallax principle to measure 3D coordinates, providing benefits such as high stability and measurement accuracy [4].…”