Inspired by manta rays, researchers at North Carolina State University have developed an energy-efficient softwarerobot, which can swim more than four times faster than previous swimming soft Robots. The robots are dubbed “butterfly robots” because their swimming motion resembles the way a human’s arms move when performing a butterfly stroke.
“So far, swimming soft robots have not been able to swim faster than one body length per second, but marine animals such as devils Fish can, and even swim faster, and more efficiently. We wanted to borrow from the biomechanics of these animals to see if we could develop faster, more energy-efficient soft robots. The prototype we developed performed particularly well.”
The researchers developed two types of butterfly robots. One was purpose-built for speed, capable of reaching an average speed of 3.74 body lengths per second. The second is designed to be highly maneuverable, capable of sharp turns to the right or left, and this prototype can reach speeds of 1.7 body lengths per second.
“Researchers who study aerodynamics and biomechanics use something called the Strouhal number to assess the energy efficiency of flying and swimming animals,” said Yinding Chi, a recent NC State doctoral graduate and first author on the paper. When animals swim or fly, the Strouhal number is between 0.2 and 0.4, and propulsion efficiency peaks. Both of our butterfly robots have Strouhal numbers in this range.”
The butterfly robots’ swimming power comes from their wings, which are “bistable,” meaning that the wings have two stable states. The wing resembles a button-style hairpin, which is initially stable unless a certain amount of energy is applied (by bending it). When the energy reaches a critical point, the hairpin buckles into a different shape, which is also stable.
In the butterfly robot, hairpin-inspired bistable wings are attached to a soft silicone body. Switching the wings between two stable states is controlled by injecting air into chambers inside the soft body. As these chambers inflate and deflate, the fuselage flexes up and down, forcing the wings to swing back and forth with it.
The butterfly robot has only one “drive unit” soft body to control its two wings, which makes it very fast but difficult to turn left or right. The steerable butterfly robot has two drive units, which are connected side by side. This design allows the user to manipulate the wings on either side, or “flap” just one wing, which is what enables it to make sharp turns.
“This work is an exciting proof of concept, but it has limitations, most notably that the current prototype robot is tethered by the long, thin tube that we use to pump the air into the air,” said Jie Yin. into a central agency. We are currently working on an untethered, automatic version.”
Relevant results have been published in the recent “Science Advances” magazine.
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