🤖 AI Summary
This study addresses the optimization of degree-of-freedom (DoF) allocation between the palm and fingers to enhance thumb opposition capability in robotic hands under a fixed total DoF budget. The authors propose a quantitative evaluation framework that does not rely on object or contact models, instead employing voxelized modeling of fingertip reachable workspaces and using their overlapping volume as a metric for opposition performance. Results show that while incorporating palm DoFs does not substantially expand the overall reachable workspace, it effectively improves opposition capability in the regions associated with the ring and little fingers by repositioning finger bases. Under a constant total DoF constraint, reallocating DoFs to the palm enlarges the overlapping workspace, albeit at the cost of increased kinematic redundancy, thereby revealing a complementary relationship between palm and finger DoFs in opposition kinematics.
📝 Abstract
This study investigates the kinematic role of palm degrees of freedom (DoF) in enhancing thumb opposability in a five-finger robotic hand. A hand model consisting of a five DoF thumb and four fingers with three to four DoF is analyzed, where palm motion is introduced between adjacent fingers. To quantitatively evaluate thumb-finger interaction, the overlap workspace volume is defined based on voxelized fingertip reachable regions. Seven cases are considered, including configurations with increased total DoF and configurations in which the total DoF is maintained by redistributing DoF from the fingers to the palm. The results show that palm DoF significantly improves opposability, particularly for the ring and little fingers, by repositioning their base locations rather than simply extending their reachable range. However, when the total DoF is constrained, redistributing DoF to the palm leads to trade-offs between overlap workspace expansion and kinematic redundancy. These findings indicate that palm DoF and finger DoF play distinct roles in hand kinematics and should be considered jointly in design. This study provides a quantitative framework for evaluating palm-induced opposability without relying on object or contact models and offers practical design guidelines for incorporating palm motion in robotic hands.