Speedy, springy robot 'Salto' catches some serious air

One day, lightweight robots like Salto could help search rubble at disaster sites
Jan 4, 2017 — 7:00 am EST
Salto robot

This lightweight robot, nicknamed Salto, uses a twisted spring to quickly jump a meter (more than 3 feet) from floor to wall. Someday, researchers say, robots like it could help search through rubble at disaster sites.

Stephen McNally and Roxanne Makasdjian/UC Berkeley

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.”

Bush baby
Salto was inspired by a primate called the lesser galago, or bush baby. Before jumping, galagos hunker down in a “supercrouch” that lets them access more energy for jumping.

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.

Salto, a lightweight, palm-sized robot, crouches low and then springs from floor to wall and down again — all in barely half a second.
Stephen McNally and Roxanne Makasdjian/UC Berkeley

Power Words

(for more about Power Words, click here)

aluminum     A metallic element, the third most abundant in Earth’s crust. It is light and soft, and used in many items from bicycles to spacecraft.

carbon     The chemical element having the atomic number 6. It is the physical basis of all life on Earth. Carbon exists freely as graphite and diamond. It is an important part of coal, limestone and petroleum, and is capable of self-bonding, chemically, to form an enormous number of chemically, biologically and commercially important molecules.

coauthor     One of a group (two or more people) who together had prepared a written work, such as a book, report or research paper. Not all coauthors may have contributed equally.

fiber     Something whose shape resembles a thread or filament of some kind. (in nutrition) Components of many fibrous plant-based foods. These so-called non-digestible fiber tends to come from cellulose, lignin, and pectin — all plant constituents that resist breakdown by the body’s digestive enzymes.

galagos     Also known as bush babies, these are small, large-eyed, nocturnal, tree-dwelling African primates. They get their name for their baby-like cries. Known as vertical clingers and leapers, they can spring off the trunk of one tree and turn around in mid-air to face the next tree it will latch onto.

mega     A prefix for units of measurement meaning million in the international metric system.

motor     A device that converts electricity into mechanical motion.

parkour     A term, from the French, for a type of gymnastics-like activity where people soar through an environment by jumping, leaping and scrambling up, around and between walls and other obstacles. Movements tend to be very rapid and fluid. Some may involve vaulting or flipping over railings, stairs or other structures. People may even climb up walls or leap from one wall or fence to some other structure.

primate     The order of mammals that includes humans, apes, monkeys and related animals (such as tarsiers, the Daubentonia and other lemurs).

ratio     The relationship between two numbers or amounts. When written out, the numbers usually are separated by a colon, such as a 50:50. That would mean that for every 50 units of one thing (on the left) there would also be 50 units of another thing (represented by the number on the right).

robot     A machine that can sense its environment, process information and respond with specific actions. Some robots can act without any human input, while others are guided by a human.

vertical     A term for the direction of a line or plane that runs up and down, as the vertical post for a streetlight does. It’s the opposite of horizontal, which would run parallel to the ground.


Journal: D. W. Haldane et al. Robotic vertical jumping agility via series-elastic power modulationScience Robotics. Vol. 1, December 6, 2016. doi:10.1126/scirobotics/aag2048.