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Water Vortex Suction Feet Help This Hexapod Sploosh Up Walls

A spinning ring of water allows this robot to stick to rough surfaces

3 min read
Water Vortex Suction Feet Help This Hexapod Sploosh Up Walls
Photo: Zhejiang University

Suction is a useful tool in many robotic applications, as long as those applications are grasping objects that are suction-friendly—that is, objects that are impermeable and generally smooth-ish and flat-ish. If you can’t form a seal on a surface, your suction gripper is going to have a bad time, which is why you don’t often see suction systems working outside of an environment that’s at least semi-constrained. Warehouses? Yes. Kitchens? Maybe. The outdoors? Almost certainly not.

In general, getting robotic grippers (and robots themselves) to adhere to smooth surfaces and rough surfaces requires completely different technology. But researchers from Zhejiang University in China have come up with a new kind of suction gripper that can very efficiently handle surfaces like widely-spaced tile and even rough concrete, by augmenting the sealing system with a spinning vortex of water.

Suction climbing robotTo climb, the robot uses a micro-vacuum pump coupled to a rapidly rotating fan and a water source. Centripetal force causes the spinning water to form a ring around the outside of the vacuum chamber. Because water can get into all those surface irregularities that doom traditional vacuum grippers, the seal is much stronger.Image: Zhejiang University

The paper is a little bit dense, but from what I can make out, what’s going on is that you’ve got a traditional suction gripper with a vacuum pump, modified with a water injection system and a fan. The fan has nothing to do with creating or maintaining a vacuum—its job is to get the water spinning at up to 90 rotations per second. Centripetal force causes the spinning water to form a ring around the outside of the vacuum chamber, which keeps the water from being sucked out through the vacuum pump while also maintaining a liquid seal between the vacuum chamber and the surface. Because water can get into all of those annoying little nooks and crannies that can mean doom for traditional vacuum grippers, the seal is much better, resulting in far higher performance, especially on surfaces with high roughness.

Climbing robot with water vortex vacuum gripperOne of the potential applications for the water-vortex suction robot is as a “Spider-Man” wall-climbing device.Photo: Zhejiang University

For example, a single suction unit weighing 0.8 kg was able to generate a suction force of over 245 N on a rough surface using less than 400 W, while a traditional suction unit of the same footprint would need several thousand watts (and weigh dozens of kilograms) to generate a comparable amount of suction, since the rough surface would cause a significant amount of leakage (although not a loss of suction). At very high power, the efficiency does decrease a bit— the “Spider-Man” system weighs 3 kg per unit, with a suction force of 2000 N using 650 W.

And as for the downsides? Er, well, it does kind of leak all over the place, especially when disengaging. The “Spider-Man” version leaks over 2 liters per minute. It’s only water, but still. And since it leaks, it needs to be provided with a constant water supply, which limits its versatility. The researchers are working on ways of significantly reducing water consumption to make the system more independent, but personally, I feel like the splooshyness is part of the appeal.

Vacuum suction unit based on the zero pressure difference method,” by Kaige Shi and Xin Li from Zhejiang University in China, is published in Physics of Fluids.

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How the U.S. Army Is Turning Robots Into Team Players

Engineers battle the limits of deep learning for battlefield bots

11 min read
Robot with threads near a fallen branch

RoMan, the Army Research Laboratory's robotic manipulator, considers the best way to grasp and move a tree branch at the Adelphi Laboratory Center, in Maryland.

Evan Ackerman

“I should probably not be standing this close," I think to myself, as the robot slowly approaches a large tree branch on the floor in front of me. It's not the size of the branch that makes me nervous—it's that the robot is operating autonomously, and that while I know what it's supposed to do, I'm not entirely sure what it will do. If everything works the way the roboticists at the U.S. Army Research Laboratory (ARL) in Adelphi, Md., expect, the robot will identify the branch, grasp it, and drag it out of the way. These folks know what they're doing, but I've spent enough time around robots that I take a small step backwards anyway.

This article is part of our special report on AI, “The Great AI Reckoning.”

The robot, named RoMan, for Robotic Manipulator, is about the size of a large lawn mower, with a tracked base that helps it handle most kinds of terrain. At the front, it has a squat torso equipped with cameras and depth sensors, as well as a pair of arms that were harvested from a prototype disaster-response robot originally developed at NASA's Jet Propulsion Laboratory for a DARPA robotics competition. RoMan's job today is roadway clearing, a multistep task that ARL wants the robot to complete as autonomously as possible. Instead of instructing the robot to grasp specific objects in specific ways and move them to specific places, the operators tell RoMan to "go clear a path." It's then up to the robot to make all the decisions necessary to achieve that objective.

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