Gecko-Inspired Gripper May Soon Snag Space Junk
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I'm not sure when your last spacewalk was, but you probably remember it being a bit difficult to manipulate objects, what with the gloves and the microgravity and all. As such, your tools were tethered, though that doesn't necessarily mean your tool bag can't float away. Now imagine a robot arm trying to manage the same.
Even here on Earth, robots struggle with even the most mundane manipulations. Something as simple as picking up a bottle of water is tough for a robot, especially if it isn’t expecting the bottle to crumple under the force. Up in space, gripping objects takes on a whole new absurdity. Suction cups are right out, given they don’t work in a vacuum. And extreme temperature fluctuations rule out any sort of sticky adhesive.
But who needs glue when you’ve got geckos? Well, not actual geckos, but a grabber inspired by their remarkable, gravity-snubbing feet. A clever new kind of robotic gripper for space does just that, Stanford University and NASA JPL researchers report today in Science Robotics. It could not only help robots get a good grip on things like space debris, but supercharge robots right here on Earth.
Geckos can walk on walls because their feet are covered in tiny hairs, which themselves split into even smaller hairs known as spatulae. Each of these is so small that it makes extremely close contact with the surface, forming a minute attraction on a molecular level. Minute on its own, sure, but we're talking millions upon millions of spatulae. So those attractions, known as van der Waals forces, really add up, to the point where a gecko can stick to a wall.
This new gripper works on the same principle. It consists of pads covered with not hairs, but microscale wedges made of silicone rubber—the same stuff that those fancy spatulas are made of. So silicone rubber can withstand the heat of a stove, the chill of a freezer, and the wild temperature extremes of space.
Squares of gecko-inspired adhesive glow as they grip a piece of lit glass.
Kurt Hickman
The handheld gripper consists of pairs of adhesive pads, whose microscale wedges point in opposite directions. The pairs are connected by cables—that's the robotic bit. “We pull them together and it creates an internal force," says Stanford University mechanical engineer Mark Cutkosky, co-author of the paper. "And that's what produces the adhesion." The wedges lie flat, making super close contact with the object, and boom, adhesion.
The question then becomes: How to scale this up to grip large objects? The trick is to make sure the load is the same on each pad. Otherwise, you risk one taking on too much and losing its grip. "If you don't do something to prevent it, it will just cascade across the whole area like an avalanche and the thing will come off," says Cutkosky. But because the pads are working together instead of independently, they evenly distribute the load.
Now, if you want to clean up space junk, your problems are two-fold. For one, you’d be working with flat or curved surfaces—think the shape of a rocket—without a good point to grasp with a traditional robotic hand. And two, this would be an extremely delicate operation. If you were to try to harpoon a piece of space junk or launch a net at it, you’d be throwing around some unwieldy forces.
This gripper could solve both problems. Because it lies flat, it could stick to a wayward solar panel like a suction cup, only without the suction. And it can tackle curved objects thanks to adhesive arms that fold out and embrace the surface. In their tests in zero gravity flights, the researchers would grab objects like cylinders and release their gripper’s grip and then … nothing. “Nothing,” Cutkosky says. “Absolutely nothing. It doesn't impart any bit of bobble or disturbance or extra momentum to it, and that's the effect you want in space.”
And like a lot of other tech developed for or by NASA, the gripper could well make its way into terrestrial robotics. Think of gripping not just space debris, but objects on an assembly line. After all, if it’s good enough for geckos and it’s good enough NASA, it’s good enough for the rest of us.
Singularity
via https://www.wired.com
June 28, 2017 at 01:09PM
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