Tired of the complexities involved in creating a robotic version of the human hand, a group of American scientists decided to think outside of the box.
The Universal Jamming Grabber is simple in its construction, comparatively cheap to produce and is able to accomplish tasks that far more complicated designs have failed to perform. In a sense, the Universal Jamming Grabber is a sackful of coffee attached to a tiny vacuum. When pressed against an object that needs to be picked up, a small pipe sucks the air out of the sack, and the sack contracts around the object.
It is not without its limitations, it reportedly has trouble with “flat objects such as plastic disks and porous objects such as cotton balls” and it cannot pick up anything bigger than half its size. John Amend, of Cornell University, explained that the strength of the Universal Jamming Gripper is its versatility – as long as it can fold around approximately one-fourth of an object’s surface, it will be able to pick it up.
For amputees, this translates into more effective prostheses that are likely to cost significantly less than models with articulated joints.
Abstract from the Proceedings of the National Academy of Sciences [PNAS]. Authors: Eric Brown, Nicholas Rodenberg, John Amend, Annan Mozeika, Erik Steltz, Mitchell R. Zakin, Hod Lipson, and Heinrich M. Jaeger.
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 multifingered 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 advance opens up new possibilities for the design of simple, yet highly adaptive systems that excel at fast gripping of complex objects.
Sources
Science Mag: Robot ‘Hands’ Write Without Fingers.
PNAS: Universal robotic gripper based on the jamming of granular material.
