Five-fingered Hand with Wide Range of Thumb Using Combination of Machined Springs and Variable Stiffness Joints

TL;DR

The paper tackles the dual challenge of achieving both dexterity and high gripping power in robotic hands. It introduces a five-finger hand built around machined-spring joints, featuring a wide-range thumb CM joint and a variable-rigidity MP mechanism driven by forearm-mounted actuators. The approach enables diverse grasp types, substantial load-bearing capacity (up to ~400 N before failure) and practical manipulation tasks such as lever switching and door-knob turning, validated through a series of experiments. This work advances humanoid manipulation capabilities by combining structural biomimicry with robust actuation, while outlining avenues for enhanced sensing and hardware refinement.

Abstract

Human hands can not only grasp objects of various shape and size and manipulate them in hands but also exert such a large gripping force that they can support the body in the situations such as dangling a bar and climbing a ladder. On the other hand, it is difficult for most robot hands to manage both. Therefore in this paper we developed the hand which can grasp various objects and exert large gripping force. To develop such hand, we focused on the thumb CM joint with wide range of motion and the MP joints of four fingers with the DOF of abduction and adduction. Based on the hand with large gripping force and flexibility using machined spring, we applied above mentioned joint mechanism to the hand. The thumb CM joint has wide range of motion because of the combination of three machined springs and MP joints of four fingers have variable rigidity mechanism instead of driving each joint independently in order to move joint in limited space and by limited actuators. Using the developed hand, we achieved the grasping of various objects, supporting a large load and several motions with an arm.

Figures (16)

• Figure 1: Developed hand in this study.
• Figure 2: Structure of human hand.
• Figure 3: The size of newly developed hand.
• Figure 4: Detail of fingers.
• Figure 5: Fabrication of finger.