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When humans run, their legs exhibit minimal contact with the ground. Six-legged insects, however, run fastest when using a three-legged, or “tripod,” gait. This means they have three legs on the ground at all times – two on one side of their body and one on the other. Engineers have long believed that mimicking this tripod gait would make six-legged robots move fastest.
However, researchers at the École Polytechnique Fédérale de Lausanne and the University of Lausanne in Switzerland have found that there is a faster way for six-legged robots to locomote on flat ground. Instead of a tripod gait, the researchers found that a “bipod” gait was more effective.
The team used an “evolutionary-like” algorithm to optimise the walking speed of a simulated insect model based on Drosophila – the most commonly studied insect in biology. It sifted through different possible gaits, eliminating the slowest and shortlisting the fastest. “To test the fast walking gait we built a six-legged robot. It proved the bipod gait was faster, corroborating the simulation algorithm’s results,” said co-lead and co-author of the study Pavan Ramdya (pictured right with co-lead author Robin Thandiackal).
The experimenters also examined real insects to see if leg adhesion might play a role in the walking coordination of flies. They put polymer drops on the flies’ legs to cover their claws and adhesive pads and found they quickly began to use the bipod-like gait like the one discovered in the simulations, proving animals can adapt to find new ways of walking under different conditions.
Dr Fumiya Iida, lecturer in mechatronics at the University of Cambridge, said that the research shows how engineering methods can give a new insight into the nature of biological systems.
“It is a very good first step towards big innovation, particularly as it reveals information about walking gaits that we didn’t know much about in nature before,” said Iida. “Legs are such a big mystery for engineers as they are everywhere in nature but appear nowhere in the engineering world. If you look at all the machines needing mobility they typically use wheels.”
Ramdya said that faster bipod gaits could mean that hexapod robots might be able to more quickly survey a disaster area or deliver packages to customers.