Scurrying centipedes inspire multi-legged robots that can traverse difficult terrain

The centipede is known for its wobbly walk. With tens to hundreds of feet, they can traverse any terrain without stopping.

The centipede is known for its wobbly walk. With tens to hundreds of feet, they can traverse any terrain without stopping.

“When you see a centipede scurrying about, you are essentially looking at an animal that inhabits a world that is very different from our world of motion,” said Daniel Goldman, the Dunn Family Professor in the School of Physics. “Our movements are mostly dominated by inertia. If I swing my leg, I land on my foot and I move forward. But in the world of centipedes, if they stop wiggling their limbs and limbs, they basically stop moving instantly.”

Curious to see if multiple limbs could aid movement in this world, a team of physicists, engineers, and mathematicians at the Georgia Institute of Technology used this style of movement to their advantage. They developed a new theory of multi-legged locomotion and created a model of a multi-legged robot, discovering a robot with redundant legs could move across uneven surfaces without additional sensing or control technology as the theory had predicted.

These robots can move over complex, undulating terrain — and there’s potential for using them for agriculture, space exploration, and even search and rescue.

The researchers presented their work in the paper, “Multilegged Matter Transport: A Framework for Locomotion on Noisy Landscapes,” at Science in May and “Self-Propulsion via Slipping: Friction Swimming in a Multilegged Locomotor,” in Proceedings of the National Academy of Sciences in March.

Leg Lift

For Science In the paper, the researchers were motivated by mathematician Claude Shannon’s communication theory, which demonstrated how to reliably transmit signals over long distances, to understand why multi-legged robots are so successful at moving. Communication theory suggests that one way to ensure a message gets from point A to point B on a noisy path is not to transmit it as an analog signal, but to break it down into discrete digital units and repeat these units with the appropriate codes. .

“We were inspired by this theory, and we tried to see if redundancy could help in the transportation of matter,” said Baxi Chong, a postdoctoral researcher in physics. “So we started this project to see what would happen if we had more legs on the robot: four, six, eight legs and even 16 feet.”

A team led by Chong, including School of Mathematics postdoctoral fellows Daniel Irvine and Professor Greg Blekherman, developed a theory proposing that adding pairs of legs to a robot enhances its ability to move forcefully over challenging surfaces – a concept they call spatial redundancy. This redundancy allows the robotic leg to operate on its own without the need for sensors to interpret the environment. If one leg is wobbly, many legs keep it moving. As a result, the robot becomes a reliable system for transporting itself and even loads from A to B over difficult or “noisy” landscapes. The concept is comparable to how punctuality can be guaranteed on wheeled transportation if the track or rail is smooth enough but without having to engineer the environment to create that punctuality.

“With advanced bipedal robots, it usually takes a lot of sensors to control them in real time,” said Chong. “But in applications such as search and rescue, Mars exploration, or even microrobots, there is a need to drive robots with limited sensing. There are many reasons for such censorship-free initiatives. The sensors can be expensive and fragile, or the environment can change so rapidly that it does not allow sufficient sensor controller response time.”

To test this, Juntao He, Ph.D. student in robotics, conducted a series of experiments in which he and Daniel Soto, a master’s student at the George W. Woodruff School of Mechanical Engineering, constructed terrain to mimic the inconsistent natural environment. He then tested the robot by increasing the number of legs by two at a time, starting with six and eventually growing to 16. As the number of legs increased, the robot was able to move more nimbly across terrain, even without sensors (PGR1), because theory predicted. Finally, they tested the robot outdoors on real terrain, where it could traverse various environments.

“It was impressive to witness the adeptness of a multi-legged robot in navigating laboratory-based terrain and outdoor environments,” said Juntao. “While bipedal and quadrupedal robots rely heavily on sensors to traverse complex terrain, our multi-legged robot uses leg redundancy and can accomplish similar tasks with open-loop control.”

The next step

Researchers are already applying their discoveries to agriculture. Goldman has co-founded a company that dreams of using these robots to weed farmland where weed killers are not effective.

“They’re like Roomba but outside for complex soils,” says Goldman. “Roomba works because it has wheels that work well on flat ground. Until the development of our framework, we could not confidently predict the reliability of the locomotor on bumpy, rocky and debris-strewn terrain. We now have the beginnings of such a scheme, which can be used to ensure that our robot traverses a crop field in a given time.”

The researchers also want to perfect the robot. They know why the centipede’s robotic skeleton works, but now they determine the optimal number of legs to achieve motionless motion in a way that’s cost-effective but retains its benefits.

“In this paper, we asked, ‘How would you predict the minimum number of legs to achieve such a task?’” says Chong. “Right now we are only proving the minimum number exists, but we don’t know the exact number of legs needed. Next, we need to better understand the trade-offs between energy, speed, power and robustness in such complex systems.”


Baxi Chong et al., Multi-legged material transport: A framework for locomotion in noisy landscapes.Science 380,509-515(2023).DOI:10.1126/science.ade4985


Georgia Institute of Technology, or Georgia Tech, is one of the leading public research universities in the US, developing leaders who advance technology and improve the human condition. The Institute offers degrees in business, computing, design, engineering, liberal arts, and science. More than 45,000 undergraduate and graduate students, representing 50 states and more than 148 countries, study on the main campus in Atlanta, on campuses in France and China, and through distance and online learning. As a leading technology university, Georgia Tech is an engine of economic development for Georgia, the Southeast, and the nation, conducting more than $1 billion in research each year for government, industry, and society.

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