Speedy, springy robot ‘Salto’ catches some serious air

Meet the robot that can do crazy acrobatics.

Salto is a lightweight bot that stands on one skinny leg like a flamingo. But unlike a flamingo, it can leap from floor to wall, then off again. Its antics are like those of parkour athletes — people who bounce between buildings, vault and flip over railings and scramble up walls. Researchers at the University of California, Berkeley, described their agile robot December 6 in Science Robotics.

The palm-sized machine weighs just 100 grams (3.5 ounces) — or about as much as two large eggs. It’s not the highest jumping robot, but it’s got something others lack: speed. The new bot can spring a meter (39 inches) off the ground in just 0.58 seconds. That’s about what a bullfrog can do, noted coauthor Duncan Haldane in a December 5 news conference.

The robot’s mix of air and speed might one day aid search-and-rescue teams, he said. Ideally, a rescue robot would be able to move quickly and nimbly over rubble. To do that, Haldane explains, “It has to be able to jump.”

Salto isn’t able to help out in situations like that yet, though. For now, it is just “great eye candy,” says roboticist Jeff Duperret. He works at the University of Pennsylvania in Philadelphia and wasn’t involved with the study. Its authors, he says, “came up with a new idea and showed it really clearly.”

Haldane’s bot was inspired by a tiny, saucer-eyed primate called the lesser galago. (It’s also known as a bush baby.) “Animals can outclass any robot when it comes to jumping,” Haldane said. Galagos, in particular, stand out. They’ve got the highest known vertical jumping agility. That’s the ratio of maximum jumping height to the time it takes to complete a jump. 

Before jumping, galagos hunker down in a kind of “supercrouch.” This stance lets them access more energy before they spring into a jump, Haldane said. That allows them “to jump high and do it quickly.”

His team built this capability into Salto’s single leg. That leg is a spindly series of eight bars. Made with carbon fibers, they’re super-strong but lightweight. Aluminum pins connect the bars. The team also attached a kind of spring that’s like a twisted rubber band. In sits in the robot’s body between the leg and the motor that powers the bot. When the team turns its motor on, the bot’s spring twists, storing energy.

As the device settles into a deeper and deeper crouch, Haldane explains, the motor has more time to twist the spring. And that gives Salto extra oomph when it finally jumps and the spring untwists.

It’s like the robot is getting a mega boost, Duperret says. The robot crouches again as it lands and can then immediately jump off again.

That’s an added bonus, said study coauthor Justin Yim. “The spring can store some of the energy of landing for use in the next jump.” It’s like a bouncing ball, he said.

Salto joins a growing list of robots that hop off walls, spring off water or even launch themselves into the air with an explosion.