Maximizing Results with 3D Printing – DfAM Part 3


If you’ve ever played the claw game in an arcade, you know how difficult it is to grab and hold objects using robotic grippers. Imagine how much more nerve-wracking this game would be if, instead of stuffed animals, you were trying to grab a fragile piece of endangered coral or a priceless artifact from a sunken ship.

Most of today’s robotic grippers rely on built-in sensors, complex feedback loops, or advanced machine learning algorithms, combined with operator skill, to grip fragile or odd-shaped objects. But researchers from Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) demonstrated an easier way.

Taking inspiration from nature, they designed a new kind of soft robotic claw that uses a collection of slender tentacles to entangle and trap objects, much like jellyfish collect stunned prey. Only the individual tentacles, or filaments, are weak. But together, the collection of filaments can securely grip and hold heavy and oddly shaped objects. The gripper relies on simple inflation to wrap around objects and does not require sensing, planning or feedback control.

The research was published in the Proceedings of the National Academy of Sciences (PNAS).

“With this research, we wanted to reimagine the way we interact with objects,” said Kaitlyn Becker, former graduate student and postdoctoral fellow at SEAS and first author of the paper. “By taking advantage of the natural conformance of soft robotics and enhancing it with a conformal structure, we have designed a gripper that is greater than the sum of its parts and a gripping strategy that can adapt to a range of ‘complex objects with minimal planning and perception.

Becker is currently an assistant professor of mechanical engineering at MIT.

© Harvard Microrobotics Lab/Harvard SEAS

Close up of pincer filaments wrapping around an object.

The strength and adaptability of the gripper comes from its ability to become entangled with the object it is trying to grasp. The foot-long filaments are hollow rubber tubes. One side of the tube has thicker rubber than the other, so when the tube is under pressure, it curls up like a pigtail or like slicked back hair on a rainy day.

The loops knot and tangle with each other and with the object, each tangle increasing the strength of the grip. While the collective grip is strong, each contact is individually weak and won’t damage even the most fragile object. To release the object, the filaments are simply depressurized.

The researchers used simulations and experiments to test the claw’s effectiveness, picking up a range of objects including various houseplants and toys. The gripper could be used in real-world applications to grab soft fruits and vegetables for agricultural production and distribution, delicate fabrics in medical environments, even oddly shaped objects in warehouses, such as glassware.

This new approach to typing combines the research of Professor L. Mahadevan on the topological mechanics of entangled filaments with Professor Robert Wood research on flexible robotic grippers.

“Tangle-up allows each highly conforming filament to conform locally to a target object, leading to safe but gentle topological capture that is relatively independent of the details of the nature of the contact,” says Valpine Professor Lola England Mahadevan. of applied mathematics at SEAS, and of organismal and evolutionary biology, and physics in FAS and corresponding co-author of the article.

“This new approach to robotic gripping complements existing solutions by replacing simple, traditional grippers that require complex control strategies with highly conformable and morphologically complex filaments that can operate with very simple control,” says Wood, professor of engineering Harry Lewis and Marlyn McGrath. and applied sciences and corresponding co-author of the article. “This approach expands the range of what is possible to grab with robotic grippers.”

The research was co-authored by Clark Teeple, Nicholas Charles, Yeonsu Jung, Daniel Baum, and James C. Weaver. It was supported in part by the Office of Naval Research, under grant N00014-17-1-206 and the National Science Foundation under grants EFRI-1830901, DMR-1922321, DMR-2011754, DBI-1556164, and EFMA-1830901 and the Simons Foundation and the Henri Seydoux Fund.


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