Investigation of Screw Fastening by Human-Robot Cooperation

In this study, we propose a method to realize screw fastening by human-robot cooperation. Currently, the application of robots is expected to address issues such as labor shortages and productivity improvement. However, the functions of robots are far more limited than those of workers, and theirs use is limited to applications where robots can utilize their strengths. Therefore, we focus on bolt and nut fastening performed by two workers, and aim to realize cooperative screw fastening work by replacing one of the two workers with a robot. One of the issues in this work is to prevent the nut from biting or falling off when engaging the nut and bolt. The range of relative angles of the screw thread for stable engagement was determined, and by turning the bolt in the opposite direction to the fastening direction, the worker aligned the screw thread to the successful range and achieved stable engagement. Another issue is that the robot fastens the nut while the worker holds the bolt down. However, by turning the nut while the robot applies force in the backward direction, the robot was able to generate tightening torque without being holding the bolt down by the worker.