A Stiffness-Changeable Soft Finger Based on Chain Mail Jamming

This paper presents a stiffness-changeable soft finger using chain mail jamming. This finger can achieve adaptive grasping and in-hand manipulation by reshaping and exerting changeable gripping force. The jamming phenomenon happens when particles in a chamber get interlocked where confining pressure is exerted at their boundaries, which is widely used to construct mechanisms with changeable stiffness. Compared with the traditional granular media, chain mail has a lower packing fraction and provides a stronger tensile force. In this paper, we proposed to apply chain mail jamming to the field of robotic finger design. Especially, we propose the design of the finger, the fabrication process, the method of predicting gripping force, and the grasping strategies. The experiments quantitatively verify the model of gripping force prediction. The demonstrations validate the advantages of adaptive grasp by picking a variety of items including foods, goods, and industrial components, and show the application of in-hand manipulation.

I. Introduction

SOFT grippers exhibit effective adaptation and safety in manipulating objects with various properties, stiffness, shapes, and consistencies. The functions of soft grippers mainly consist of three categories [1]: changeable stiffness [2] [3], changeable adhesion [4] [5], actuation [6] [7]. They show their advantages on different fields. One may choose and combine the preferred technologies to construct a soft gripper according to task constraints.