Design of a Passive Finger-Tip Changer for Modular Robotic Manipulation

Abstract

This paper presents a compact and lightweight fingertip changer (FTC) mechanism developed for multi-fingered robotic hands, facilitating autonomous, repeatable, and secure exchange without additional actuators. Unlike existing methods that require external power or pneumatic systems, the proposed passive mechanism is small enough to be mounted on a fingertip, adding only 33 g per finger, while ensuring high mechanical reliability. A key feature of the design is that attachment and detachment occur through a unified linear motion along the <inline-formula><tex-math notation="LaTeX">$z$</tex-math></inline-formula>-axis, simplifying motion planning and enhancing compatibility with confined spaces. Mechanical analysis and experimental evaluations demonstrate that the mechanism sustains a structural gripping force of up to 90 N, providing a significant safety margin for the hand’s 2.5 kg pinching payload. The detachment threshold was strategically set at 25 N to enable autonomous exchange using the robot’s inherent maneuvering force. Validation with diverse tool sets showed success rates of 100% for rigid modules and 94% for soft modules under an optimized spring constant of <inline-formula><tex-math notation="LaTeX">$k = 2.0$</tex-math></inline-formula> N/mm. Furthermore, the system proved robust against positional misalignments of up to <inline-formula><tex-math notation="LaTeX">$\pm 2$</tex-math></inline-formula> mm, indicating that the proposed design provides a practical, lightweight, and scalable solution for modular robot manipulation.