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March 14, 2019      
Rachel Gordon, MIT CSAIL

About 50 years ago, a one-armed robot assembled a simple breakfast of toast, coffee and champagne. Even today, being able to put together a meal more complicated than that would be hard for machines with rigid hands – they tend to work only in structured environments and with particular postures like the straight-on side angle.

In recent years, roboticists have made fingers out of soft, flexible materials like rubber, but such robots have traditionally been not been able to pick up large or heavy items.

To give these robots a bit of a hand, researchers from MIT and Harvard have developed a new gripper that’s both soft and strong: a cone-shaped origami structure that collapses in on objects, much like a Venus flytrap, to pick up objects that are as much as 100 times its weight. This motion lets the gripper grasp a wide range of items, including soup cans, hammers, wine glasses, drones, and even a single broccoli floret.

Origami robot hand gripper

Source: Jason Dorfman, MIT CSAIL

“One of my moonshots is to create a robot that can automatically pack groceries for you,” said MIT professor Daniela Rus, director of MIT’s Computer Science and Artificial Intelligence Laboratory (CSAIL), and one of the senior authors of a new paper about the project.

“Previous approaches to the packing problem could only handle very limited classes of objects — objects that are very light or objects that conform to shapes such as boxes and cylinders, but with the Magic Ball gripper system we’ve shown that we can do pick-and-place tasks for a large variety of items ranging from wine bottles to broccoli, grapes and eggs,” said Rus. “In other words, objects that are heavy and objects that are light. Objects that are delicate, or sturdy, or that have regular or free form shapes.”

New thinking on robot gripping

The project is one of several in recent years that has researchers thinking outside-the-box with robot design. Ball-shaped grippers, for example, can handle a wider range of objects than fingers, but still have the issue of limited angles. Softer robotic fingers typically use compressed air, but aren’t strong enough to pick up heavier objects.

The structure of this new gripper, meanwhile, takes an entirely different form. Cone-shaped, hollow, and vacuum-powered, the device was inspired by the “origami magic ball” and can envelope an entire object and successfully pick it up.

The gripper has three parts: the origami-based skeleton structure, the airtight skin to encase the structure, and the connector. The team created it using a mechanical rubber mold and a special heat-shrinking plastic that self-folds at high temperatures.

The magic ball’s skeleton is covered by either a rubber balloon or a thin fabric sheet, not unlike the team’s previous research on fluid-driven origami-inspired artificial muscles (FOAM), which consisted of an airtight skin surrounding a foldable skeleton and fluid.

The team used the gripper with a standard robot to test its strength on different objects. The gripper could grasp and lift objects 70 percent of its diameter, which allowed it to pick up and hold a variety of soft foods without causing damage. It could also pick up bottles weighing over four pounds.

“Companies like Amazon and JD want to be able to pick up a wider array of delicate or irregular-shaped objects, but can’t with finger-based and suction-cup grippers,” said Shuguang Li, a joint postdoc at MIT CSAIL and Harvard’s John A. Paulson School of Engineering and Applied Sciences (SEAS). “Suction-cups can’t pick up anything with holes – and they’d need something much stronger than a soft-finger-based gripper.”

Shape challenges, future development

The robot currently works best with cylindrical objects like bottles or cans, which could someday make it an asset for production lines in factories. Not surprisingly, the shape of the gripper makes it more difficult for it to grasp something flat, like a sandwich or book.

“One of the key features of this approach to manipulator construction is its simplicity,” said Robert Wood, co-author and Professor at Harvard’s School of Engineering and Wyss Institute for Biologically Inspired Engineering. “The materials and fabrication strategies used allow us to rapidly prototype new grippers, customized to object or environment as needed.”

In the future, the team hopes to try to solve the problem of angle and orientation by adding computer vision that would let the gripper “see”, and make it possible to grasp specific parts of objects.

“This is a very clever device that uses the power of 3-D printing, a vacuum, and soft robotics to approach the problem of grasping in a whole new way,” said Michael Wehner, an assistant professor of robotics at UC-Santa Cruz who was not involved in the project. “In the coming years, I could imagine seeing soft robots gentle and dexterous enough to pick a rose, yet strong enough to safely lift a hospital patient.”

Other co-authors of the paper include MIT undergraduates John Stampfli, Helen Xu, Elian Malkin, and Harvard REU student Evelin Villegas Diaz from St. Mary’s University. The team will present their paper at the International Conference on Robotics and Automation (ICRA) in May in Montreal, Canada.

This project was supported in part by the Defense Advanced Research Projects Agency, the National Science Foundation, and the Wyss Institute for Biologically Inspired Engineering at Harvard.