Cornell scientists have helped develop a robot-controlled gripping device that could expand the capabilities of robots beyond the routine tasks used in factories.        

Unlike many previous robotic end effectors — implements attached to the end of robotic arms — which have had fingers modeled after the human hand, the “gripper” looks like an amorphous blob.

The design is quite simple: a balloon made of tough latex and filled with ground coffee. The physics, however, is not.

Mechanical engineering student John Amend Jr. grad explained that the grains “are like [thousands of] gears rolling against one another.” 

Prof. Heinrich Jaeger, physics, University of Chicago, who was also involved in the project, said the grains could be compared to heavy traffic on a freeway. He said a small decrease in available space, such as a lane closure, or a vacuum taking a little air out of the balloon, and “suddenly things get jammed –– the particles are unable to move past each other.”

The critical density is called the “jamming transition,” and crossing it causes a remarkable change in the balloon, as dramatic as from liquid to solid or from beanbag chair to rock. When a robotic arm pushes the gripper onto the edge of an object — such as the lip of a mug — and sucks the right amount air out, the rigidity essentially locks the gripper in place and securely holds it until the vacuum is broken.

The gripper’s versatility is its main asset, Amend and Jaeger said.

Typical robotic “hands” with parts such as fingers and joints are complicated to use; they can have ten or more motors, and to achieve the best grasp each part must be moved and controlled individually, like a real hand. These type of robotic hands allow for tasks to be repeated over and over again.

“In a factory, of course you could optimize something better than ours,” Jaeger said.

Because of the Gripper’s structureless design with no distinct parts, there is no need for direct human control or multiple motors, as the balloon squishes around the desired object before locking on. Thus, this gripper is “more suited for situations where you have to grip things you’ve never seen before,” Amend said.

Jaeger said that because it “doesn’t put pressure on what it holds,” the gripper can move fragile objects with little risk of crushing or dropping them.

“We’re continuing to work on the ability to manipulate objects; [it is an] ongoing challenge,” said Chris Jones, a spokesman for iRobot, another partner in the research.

Advances in object manipulation could lead to progress in one difficult area: human prosthetics. A major struggle for previous generations of robotic hands has been adapting to the wide variety of tasks humans do with their hands, a job this gripper does with comparative ease. Right now, Amend said, “a lot of the best technology for humans is just a hook.”

There are many applications in home-service robotics as well. Jones declined to detail specific projects, but said the past success of his company’s Roomba self-controlling vacuum cleaner.

Though the gripper does not incorporate any particular new technology, Jaeger and Amend are both excited about its prospects.

“This is one of the first times we have gone all the way from the basic physical principles to a finished product,” Jaeger said. However, he later characterized the latest version of the gripper as more of a “first prototype.”

Both Jaeger and Amend stressed that they have not focused much effort into optimizing the balloon or the coffee grains inside. Balloons, even those made of tough latex, are not known for their durability; and though ground coffee performed the best out of the materials they tried, Amend noted that “there are definitely better materials out there.”

The ultimate achievement, it seems, would be to create and precisely control a complicated hand, as the human body does.

“Working in an environment with humans, a human hand would be ideal,” Amend said. “[This is] somewhere between a claw and a hand.”

Still, the gripper is inexpensive, simple, and functional.

“We can do this eventually,” Chris Jones, the spokesperson, said. “This is feasible.”