Leaping robots take physics lessons from grasshoppers

Insects like grasshoppers could help build the next generation of jumping robots.
Meadow grasshopper sitting on blade of grass
Leaping robots could soon traverse malleable environments like grass and sand. Deposit Photos

To give grasshoppers some credit—leaping across yards and between branches takes a lot more expertise than it might appear. There are incredibly tiny factors to consider, such as the resistance in launchpad material (Are the blades of grass bouncy? Is the plant twig brittle?), as well as desired distance, speed, and landing.

Most jumping robots can’t compete with the insect, as their leaps are limited to starting atop extremely rigid surfaces. But a new bouncing bot developed by researchers in Carnegie Mellon’s College of Engineering is soaring over those hurdles, and showing immense promise for how autonomous devices could operate in the future.

[Related: Watch these tiny bugs catapult urine with their butts.]

A team of scientists led by professor of mechanical engineering Sarah Bergbreiter recently optimized a robot’s latch mechanisms used to propel it upward. Previously, these latches were primarily thought of as simple “on/off” switches that enabled the release of stored energy. However, Bergbreiter and her team employed mathematical modeling to illustrate that these latches both were capable of steering energy output, as well as controlling the transfer of energy between the jumper and the launch surface.

Credit: Carnegie Mellon University

To test their work, the team positioned a small leaping robot atop a tree branch and recorded the precise energy transfers in its jumps’ first moments. Watching the branch recoil before the robot jumped, they could tell the device recovered at least a bit of the energy first transferred to the branch right before liftoff.

“We found that the latch can not only mediate energy output but can also mediate energy transfer between the jumper and the environment that it is jumping from,” said Bergbreiter.

Researchers also noticed an “unconventional” energy recovery in other instances which employed a different latch variety. In those situations, the branch actually provided a little push for the bot after it leaped off its surface, thus returning some of its momentum to boost it higher.

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Now that researchers better understand the interactions at play in the opening moments of leaping, they can now begin working on ways to integrate this into future robotic designs. Likewise, biologists can gain a better insight into how insects maneuver through variable terrains, such as grass or sand.

“It has been nearly impossible to design controlled insect-sized robots because they are launched in just milliseconds,” explained Bergbreiter. “Now, we have more control over whether our robots are jumping up one foot or three… It’s really fascinating that the latch— something that we already need in our robots—can be used to control outputs that we couldn’t have controlled before.”