Thursday, December 08, 2016

Robot Parkour: Powerful Jumping Robot Inspired by Search-and-Rescue Needs

Meet Salto, a cute robot with unprecedented jumping skills. Don’t be fooled, though—Salto is more than a fun experiment and something most kids (ok, and adults) would like to own. He’s an incarnation of new research that could help address critical search-and-rescue needs in urban areas. Built in a lab at the University of California at Berkeley, Salto was inspired by galagos (also called “bush babies”), which are small, nocturnal primates that can reach great heights with numerous powerful jumps in quick succession.

Salto (SAltatorial Locomotion on Terrain Obstacles)
Image Credit: Stephen McNally.

What does this have to do with urban search-and-rescue? In earthquake ravaged areas, burnt-down buildings, and war torn streets, searching the rubble for signs of life is grueling and dangerous work. Robots could alleviate some of the risk, but navigating uneven terrain and unsteady wreckage is difficult for people, and harder still for robots. Search-and-rescue robots need to be lightweight and agile, and right now there aren’t any that fit the bill.

Inspired by a visit to the FEMA Urban Search and Rescue Training Site in Menlo Park, CA, the Berkeley team began exploring how to design robots for this kind of application. Their idea is kind of like robot parkour—imagine a lightweight robot that can navigate debris by swiftly jumping from one surface to another, up barriers and off walls. Imagine you could survey a landscape, use a computer program to pinpoint the best route for such a robot to take to your target, and then let him go.

The first step to this kind of system is a lightweight, agile robot that can climb quickly. In this study, the team compared the “vertical jumping agility” of animals and existing robots. Vertical jumping agility describes the vertical height a robot (or animal) can reach over time. The time starts when a robot (or animal) crouches down, and ends when the robot reaches its maximum height. To put this in context, a robot that can jump 2 meters high but needs to wind up for 60 seconds first will have a lower vertical jumping agility than a robot that can jump 1 meter but only needs 10 seconds to wind up. The team’s work shows that the robot with the best vertical jumping agility before now was Minitaur, with a vertical jumping agility of 1.1 m/s.

Most jumping robots are inspired by animals, but no animal or robot is better at successive vertical jumps than galagos. They have a vertical jumping agility of 2.2 m/s, which is twice as high as Minitaur’s. Galagos can start from rest and bound upward with as much as 15 times more power than can be attributed to their muscles alone.

This power boost comes from energy that is transferred from the muscles to the tendons in the legs as the animal crouches and begins the jump. The energy is stored in the tendons and released rapidly later in the jump with increased power. This phenomenon of storing energy to increase power is called power modulation.

After examining current designs for jumping robots and the structure of a galago leg, the researchers came up with a modified design. The resulting robot, Salto, is the size of a galago. Like a galago, Salto uses power modulation to produce more powerful jumps. The key is in the design of his leg, which includes a special feature that enhances the power modulation.

As you can see in the video below, Salto starts from a significantly crouched position. At the beginning of the jump, energy is stored in a spring attached to his motor that is later released at a higher power. With this design, Salto reached a vertical jumping agility much closer to that of a galago than any other untethered and non-exploding robot, 1.7 m/s.

Not only can he jump high in succession, he can jump off a wall and reach even greater heights. This looks cool, is potentially very useful when traveling through piles of rubble, and it is a great visual of the fact that he doesn’t need any time to recharge—if he did, he’d just fall right off the wall.

“The interesting thing,” according to Duncan Haldane, lead author on the paper, “is that the height Salto can reach off the wall is higher than its best jump from the floor, so this robot that can't climb or perch, can dynamically use its environment to get places it wouldn't otherwise be able to reach, which is only possible because it's such an accomplished jumper.”

Check out Salto’s parkour stunts in this video.

Salto achieved 78 percent of the vertical jumping agility of a galago, the animal kingdom's most vertically agile creature.
Film Credit: Roxanne Makasdjian and Stephen McNally.

Duncan Haldane is a PhD student at Berkeley, not to be confused with F. Duncan Haldane, who shared the Nobel Prize in physics this year for work in a completely different area of physics. I guess 2016 was a good year for the Duncan Haldanes of the world! His co-authors include Mark Plecnik, Justin Yim, and Ronald Fearing. Salto was introduced to the world this week in Science Robotics, a brand-new journal published by the American Association for the Advancement of Science.

Kendra Redmond

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