A team of researchers from the Harvard John A Paulson School of Engineering and Applied Sciences (SEAS) has designed a revolutionary new type of soft, robotic gripper that uses a collection of thin tentacles to entangle and ensnare objects, in much the same was as a jellyfish collects its stunned prey.
Currently, most robotic grippers are relatively clumsy, relying on embedded sensors, complex feedback loops, or advanced machine learning algorithms, combined with the skill of the operator, to grasp fragile or irregularly shaped objects. The new gripper, on the other hand, relies on simple inflation to wrap around objects and doesn’t require sensing, planning or feedback control. While the individual tentacles, or filaments, are relatively weak, acting together, they can grasp and securely hold heavy and oddly shaped objects.
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‘With this research, we wanted to reimagine how we interact with objects,’ said Kaitlyn Becker, a former graduate student and postdoctoral fellow at SEAS. ‘By taking advantage of the natural compliance of soft robotics and enhancing it with a compliant structure, we designed a gripper that is greater than the sum of its parts and a grasping strategy that can adapt to a range of complex objects with minimal planning and perception.’
The gripper’s strength and adaptability come from its ability to entangle itself with the object it’s attempting to grasp. The 30-centimetre-long filaments are hollow, rubber tubes. One side of the tube has thicker rubber than the other, so when the tube is pressurised, it curls like a pig’s tail or like straightened hair on a rainy day.
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The curls knot and entangle with each other and the object, with each entanglement increasing the strength of the hold. While the collective hold is strong, each contact is individually weak and won’t damage even the most fragile object. To release the object, the filaments are simply depressurised.
The researchers used simulations and experiments to test the efficacy of the gripper, picking up a range of objects, including a range of houseplants and toys. The gripper could be used in real-world applications to grasp soft fruits and vegetables for agricultural production and distribution, and fragile, irregularly shaped objects, such as glassware, in warehouses.
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‘Entanglement enables each highly compliant filament to conform locally with a target object, leading to a secure but gentle topological grasp that is relatively independent of the details of the nature of the contact,’ said Professor L. Mahadevan, the Lola England de Valpine professor of applied mathematics at SEAS.
‘This new approach to robotic grasping complements existing solutions by replacing simple, traditional grippers that require complex control strategies with extremely compliant and morphologically complex filaments that can operate with very simple control,’ said Professor Robert Wood, the Harry Lewis and Marlyn McGrath professor of engineering and applied sciences at SEAS. ‘This approach expands the range of what’s possible to pick up with robotic grippers.’
The research has been published in the Proceedings of the National Academy of Sciences.