GREAT GAIT!
Researchers at EPFL (École
polytechnique
fédérale de Lausanne )
and UNIL (Université
de Lausanne) have
discovered a faster
way for six-legged
robots to move on
flat ground, provided
they don’t have the
adhesive pads used by
insects to climb walls
and ceilings.
This suggests designers of insect-inspired robots should ditch the tripod-gait paradigm and instead consider other possibilities including a new
locomotion strategy called the “bipod gait.”
“We wanted to determine why insects use a tripod gait and identify
whether it is, indeed, the fastest way for six-legged animals and robots to
walk,” says Pavan Ramdya, co-lead and corresponding author of the study.
To test the various combinations, the researchers used an evolutionary-like algorithm to optimize the walking speed of a simulated insect model based
on Drosophila melanogaster — a commonly studied insect in biology. Step-by-step, this algorithm sifted through many different possible gaits, eliminating the
slowest and shortlisting the fastest.
The researchers found that the common insect tripod gait did emerge
when they optimized their insect model to climb vertical surfaces with
adhesion on the tips of its legs. By contrast, simulations of ground walking
without the adhesiveness of insect’s legs revealed that bipod gaits — where
only two legs are on the ground at any given time — are faster and more
efficient. Although, in nature, no insects actually walk this way.
The researchers then built a six-legged robot capable of employing either
the tripod or bipod gait. The bipod gait again demonstrated to be faster,
corroborating the simulation algorithm’s results.
The experimenters also examined real insects. To see if leg adhesion might
also play a role in the walking coordination of real flies, they put polymer
drops on the flies’ legs to cover their claws and adhesive pads — kind of like
the flies were wearing boots — and watched what happened. The flies quickly
began to use bipod-like leg coordination similar to the one discovered in the
simulation.
“This result shows that, unlike most robots, animals can adapt to find new
ways of walking under new circumstances,” says Robin Thandiackal, a co-lead
author of the study. “There is a natural dialogue between robotics and biology:
Many robot designers are inspired by nature and biologists can use robots to
better understand the behavior of animal species. We believe that our work
represents an important contribution to the study of animal and robotic
locomotion.”
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