HERI II: A Robust and Flexible Robotic Hand based on Modular Finger design and Under Actuation Principles

This paper introduces the design of a novel under-actuated hand with highly integrated modular finger units, which can be easily reconfigured in terms of finger arrangement and number to account for the manipulation needs of different applications. Each finger module is powered by a single actuator through an under-actuated transmission and equipped with a sensory system for delicate and precise grasping, which includes absolute position measurements, contact pressure sensing at finger phalanxes and motor current readings. Finally, intrinsic elasticity integrated in the transmission system make the hand robust and adaptive to impacts when interacting with the objects and environment. This highly integrated hand (HERI II) was developed for the Centauro Robot to enable robust and resilient manipulation. A set of experiments demonstrating the hand's grasping performance were carried out and fully verified the design effectiveness of the proposed hand.

I. Introduction

Robotics hands typically function as the end-effector of robotics arms to undertake significant missions for grasping and manipulation. In the past few decades, many multi-fingered robotics hands have been developed for manipulative dexterity, grasping robustness and human operability [1]. They can be classified into two categories based on the Degree of Actuation (DoA): fully-actuated hands [2]–[5], and under-actuated hands [6]–[11]. Despite a set of advantages of fully-actuated hands, such as independent finger joint motion and the ability to mimic most of the sophisticated human hand motions [12], the supremacy of under-actuated hands, in terms of reduced complexity, higher grasping force capacity, simplified control requirements and low cost, have been attracting more and more attention to its development.