A Novel Self-Aligning Socket Tool with Torque Feedback for Robotic Maintenance: Design, Calibration, and Experimental Validation

Robotic maintenance tasks frequently require reliable engagement with fasteners such as caps, bolts, and locks. However, small angular misalignments between the robot and the fastener often led to unreliable engagement, creating potential safety risks, while also causing increased wear on components and excessive contact forces during operation. This paper presents the design and experimental validation of a flexible self-aligning socket tool capable of compensating for rotational misalignments through a passive mechanical mechanism while providing real time torque feedback. The tool incorporates a slope-based self-alignment interface, a mechanically compliant socket assembly, and a current-sensor-based torque estimation model calibrated using a custom test rig. The complete system is integrated with both collaborative and industrial robot platforms. Experimental evaluations demonstrate reliable cap engagement, accurate torque estimation, and a significant reduction in normal forces compared with conventional engagement methods. The findings indicate that the proposed tool enhances robustness, safety, and adaptability in robotic maintenance applications.