On the Design of Mechanically Programmable Underactuated Anthropomorphic Robotic and Prosthetic Grippers

Abstract

This paper presents several innovative features that aim at improving the mechanical design of underactuated anthropomorphic grippers. Based on prototypes previously developed, the characteristics of a tendon-driven underactuated finger and a reconfigurable thumb are first presented. Their geometry, coverings and attachment principles are detailed. Then, a novel approach to mechanically couple the thumb with the four fingers is presented. Using a lever, this approach provides the ability to mechanically prescribe a desired distribution of the forces/velocities during the actuation. A static model is developed to visualize the possibilities offered by this principle. Also, a compact mechanism that allows underactuation between the four fingers is described. This mechanism significantly improves the synchronization of the outputs. Additionally, a mechanical selector is introduced that makes the gripper mechanically programmable by allowing to selectively block one or many outputs. The use of this mechanical selector, combined with the reconfigurable thumb and the underactuation between the fingers, allows a gripper to produce several grasping modes without the need of additional actuation. Finally, a prototype including all these features is briefly described.