When two is better than three: Robot study improves on nature
In designing robots, engineers often turn to nature for inspiration and can sometimes improve on the skills evolution has bestowed upon our fellow creatures. That was the case last year with a high-jumping cockroach-inspired robot from UC Berkeley. Now, researchers at the Ecole Polytechnique Fédérale de Lausanne (EPFL) have figured out a better way to move a six-legged robot, making it faster than its counterpart in the wild.
When insects run, they use what's known as a tripod gait where three of their legs are in contact with the ground at any one time – two on one side and one on the other. So it might make logical sense that a robot that's designed like an insect would do well do move the same way. But the EPFL researchers found something different.
By modeling dozens of computer simulations, they determined that a bipod gait, where only two legs at a time touch the ground, actually speeds up locomotion. This tracks well with what we know about vertebrates, who gain speed by having as little contact with the ground as possible when running.
To test out the validity of the simulations, the researchers programmed a six-legged robot to try out each of the gaits. Sure enough, when employing the bipod gait, the robot was able to motor along faster than when using the tripod gait.
The researchers wondered if the reason why insects would employ a strategy that would slow them down was because of the adhesive properties found at the tips of their legs. So they put polymer drops on the insects to cover their pads and claws, effectively encasing them in a kind of chemical boot. Then they set them loose and found that the flies began to adopt the more efficient two-legged gait over their usual three-legged one.
"Our findings support the idea that insects use a tripod gait to most effectively walk on surfaces in three dimensions, and because their legs have adhesive properties," said Pavan Ramdya, co-lead and corresponding author of the study. "This confirms a long-standing biological hypothesis. Ground robots should therefore break free from only using the tripod gait."
The work of the researchers, which appears in the journal Nature Communications not only provides insight into the locomotion of insects for biologists, but could further inform the work of roboticists.
"There is a natural dialogue between robotics and biology" said Robin Thandiackal, a co-lead author of the study. "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."
The following video offers more insight into the research.