This squirrel-like robot has some serious hops

Salto the robot is acting a bit squirrelly.

It can take a flying leap and land on a narrow pipe, just like a squirrel soaring from branch to branch. It’s the first time scientists have been able to get a robot to land — balanced — on such a tiny target.

“We’ve been inspired by squirrels,” says Justin Yim. He’s an engineer who worked on the project at the University of California, Berkeley. (Now he works at the University of Illinois Urbana-Champaign.) The Salto team reported its new results March 19 in Science Robotics.

Squirrels are one of nature’s acrobats. They can scamper over telephone wires and vault between trees. They can even navigate Ninja Warrior-style obstacle courses.

A secret to squirrels’ parkour prowess is exceptional balance. Even if a jump carries them a bit beyond or short of their target, squirrels can maneuver their bodies so that they stay upright. One way is by adjusting how hard their legs push against a branch as they land.

Salto can now make similar adjustments. Yim was part of the team that described how April 4 in the Journal of Experimental Biology.

Think of playing hopscotch, he says. If you land on a square and feel like you’re going to fall forward, you might try to stand up tall. To prevent yourself from toppling over, you’d push your feet hard against the ground. And if you land too far back, you might crouch down, so you don’t tip backward.

Yim’s team tried to help Salto mimic those tactics.

This spindly little hopping bot was developed in 2016. It was named for saltatorial — a term for things that leap or are adapted to leaping. In 2020, Salto’s developers figured out how to make Salto stick a landing on flat surfaces. For the new work, they made two big changes. They added a clawlike gripper to Salto’s foot. Now it can catch a pipe during landings. They also gave Salto the ability to stand or crouch. This can help improve its balance.

In test jumps in the lab, Salto leapt from one plastic pipe to another. It successfully did this 25 times out of 30. It caught the tube, swinging over or under it most of the time. But in two trials, Salto leapt, landed and perched just perfectly. It stuck a balanced upright hold on the pipe.

“There’s lots of room for improvement,” Yim says. Salto may not be ready to join that circus group Cirque du Soleil yet. Still, Yim has ideas about how to improve the robot’s balance. They could improve Salto’s gripper, for a better grasp when trying to land on a pipe. That would work like a squirrel squeezing a branch with its toes.

Yim envisions future robots that are even more agile than Salto. To help with construction, for instance, they might one day hop onto pipes or beams while carrying cameras for inspection. Or maybe Salto could leap throughout a forest as an environmental monitor.

But Salto will need many more tweaks to catch up to its bushy-tailed brothers, Yim says. “The robot is definitely not able to do what a squirrel can do just yet.”