New, improved latch control helps build robots that leap like grasshoppers

The latch can be used to control jump performance across a wide range of terrains.

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Animals demonstrate impressive jumping abilities on various surfaces, yet robotic studies have focused mainly on rigid substrates. Nevertheless, researchers at Carnegie Mellon University have successfully enabled robots to mimic these natural leaps, paving the way for exciting new possibilities.

“I am interested in how we can build these very functional, very small robots that can move around diverse environments,” said Bergbreiter, a professor of mechanical engineering. “Traditionally, jumping robots are studied on rigid surfaces, so designing a jumper that can function efficiently on soft substrates is a big step for robotics.”

Bergreiter’s team used a mathematical model to demonstrate the involvement of the latch mechanism in the system’s ability to adjust its jump performance, which was previously considered as a simple switch for releasing stored energy. They then applied their findings to a robot designed for jumping, showing that the latch can effectively control jump performance on various terrains.

“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,” Bergbreiter explained. “When using a round latch, we can delay the jump and allow the robot to take advantage of the substrate’s recoil.”

After testing the jumper on a tree branch, the team observed the branch recoiling before the jumper took off, demonstrating that the jumper was able to regain some of the energy lost to the tree branch.

Insect-sized jumping robot demonstrates capabilities in nature.
Insect-sized jumping robot demonstrates capabilities in nature. Credit: Carnegie Mellon University

To their surprise, Bergbreiter’s team discovered that a sharp (zero radius) latch occasionally outperformed their rounded latch despite model predictions. In these cases, the tree branch collided with the robot after take-off, resulting in an unconventional form of energy recovery from the substrate bump. This bump provided the jumper with additional energy, allowing it to surpass the performance of the well-controlled rounded latch jumper.

“Now that we understand the natural design space, we can build something that takes advantage of the compliance of these soft substrates,” Berbreiter said.

Biologists are equally interested in studying this field to figure out how living organisms, such as grasshoppers, manage to regulate their energy expenditure while leaping through grass.

“It has been nearly impossible to design controlled insect-sized robots because they are launched in just milliseconds. Now, we have more control over whether our robots are jumping up one foot or three. Or we can simply make it jump consistently despite wide variation in substrate. 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.”

This research was published in the Royal Society in collaboration with researchers at Dickinson College and the University of California, Irvine.

Journal reference:

  1. Sathvik Divi, Crystal Reynaga, Emanuel Azizi and Sarah Bergbreiter. Adapting small jumping robots to compliant environments. Royal Society, 2024; DOI: 10.1098/rsif.2022.0778

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