Robust Automated Unscrewing with Cost-Effective Robot Control System

Abstract Research in the field of automated disassembly, in relation to end-of-life electric car batteries, has focused on the removal of screws over the last ten years. The most common detection system is based on visual recognition, which is unable to recognize the pitch or length of the screw. The unscrewing process therefore relies on knowledge from databases, human cooperation, or force sensors to regulate the movement of the robot in the direction of the screw axis during unscrewing. This movement is crucial during the screwing process to maintain the screwdriver’s engagement with the screw drive and ensure the successful removal of the screw. In this paper, a new cost-efficient solution is presented in which a spring system and a foil potentiometer are embedded in a conventional industrial fixed screwdriver to measure the spring travel caused by contact between tool tip and screw head. Tests were carried out to determine the accuracy and precision of the spring travel measurement. The control of the robot’s movements via flexible G-code programming is explained and mathematically proven to be safe, depending on the robot’s feed rate and its processing time. Finally, practical experiments were performed to verify the correct execution of the process. The presented technology is intended to be easily reproduced and integrated into any CNC-controlled robot equipped with a conventional screwdriver to make the disassembly technology more accessible.