Automated unfastening method of hexagonal headed screws based on force feedback

To address the challenge of automated screw removal from retired power batteries, a novel approach and strategy leveraging collaborative robotics for screw removal have been introduced. Firstly, the force dynamics between the wrench and screw under varying contact conditions were scrutinized, establishing a correlation model linking their relative positions to the contact forces. Secondly, a directional search methodology incorporating force sensing and compliance control was devised to address positioning challenges. This approach entails the wrench approaching the screw, utilizing force feedback from several tentative contacts to ascertain the driving hole's orientation, subsequently facilitating smooth insertion and engagement. Furthermore, an analysis delved into the relationship between the screw's unscrewing state and the contact forces exchanged between the wrench and screw. Based on this understanding, a force-sensing-based strategy was devised to assess the completion of unscrewing, effectively eliminating unnecessary or incomplete unscrewing attempts. Finally, to substantiate the viability of this automated screw removal method and strategy, experiments were conducted on the surface of box structures, successfully demonstrating its feasibility.