Universal Robotic Gripper based on the Jamming of Granular Material

TL;DR

This paper introduces a universal robotic gripper that uses granular material jamming to conform to and securely hold objects of various shapes without complex control systems.

Contribution

It presents a novel granular jamming-based gripper that simplifies design and enhances adaptability compared to traditional multi-fingered robotic hands.

Findings

Gripper can reliably hold objects with less than 0.5% volume change.

Gripping forces exceed many times the object's weight.

The mechanism relies on friction, suction, and interlocking in the jammed state.

Abstract

Gripping and holding of objects are key tasks for robotic manipulators. The development of universal grippers able to pick up unfamiliar objects of widely varying shape and surface properties remains, however, challenging. Most current designs are based on the multi-fingered hand, but this approach introduces hardware and software complexities. These include large numbers of controllable joints, the need for force sensing if objects are to be handled securely without crushing them, and the computational overhead to decide how much stress each finger should apply and where. Here we demonstrate a completely different approach to a universal gripper. Individual fingers are replaced by a single mass of granular material that, when pressed onto a target object, flows around it and conforms to its shape. Upon application of a vacuum the granular material contracts and hardens quickly to pinch and hold the object without requiring sensory feedback. We find that volume changes of less than 0.5% suffice to grip objects reliably and hold them with forces exceeding many times their weight. We show that the operating principle is the ability of granular materials to transition between an unjammed, deformable state and a jammed state with solid-like rigidity. We delineate three separate mechanisms, friction, suction and interlocking, that contribute to the gripping force. Using a simple model we relate each of them to the mechanical strength of the jammed state. This opens up new possibilities for the design of simple, yet highly adaptive systems that excel at fast gripping of complex objects.