A research team from the Swiss Federal Institute of Technology recently designed and built their own swimming robot modeled on oceanic eels. Despite its relatively simple design, the bot’s award-winning underwater undulations could provide key insights into its eel inspirations’ biology.
As New Scientist first highlighted on November 30, a video showcase of the collaborators’ work. The clip highlights the abilities of 1-guilla, the team’s nearly three-foot-long, waterproof robot. Featuring eight motorized segments, a malleable tail fin, as well as a head piece containing its frontal battery and computational unit, 1-guilla was named in honor of the more technical term for an eel’s body—anguilliform. The video of the machine’s aquatic journeys recently took home a Gallery of Fluid Motion award during last month’s annual American Physical Society’s Division of Fluid Dynamics.
While anguilliform evolutionary design allows flesh-and-blood eels to migrate thousands of miles without eating, biologists are not fully sure how the fish subspecies accomplishes such a feat. Enter 1-guilla, whose body movements could be tinkered with by its designers to explore various physical patterns, as well as the interplay between energy efficiency and a speed
During testing, a “standing wave” motion occurred when 1-guilla repeatedly alternated between an S-shape and its original, straight position—only to thrash about in the water. Researchers then programmed 1-guilla to undulate so an S-shape traveled down its body. During this phase, the robot created a “traveling wave” motion allowing it to move forward. Increasing the “amplitude” of its body bending alongside lengthening its S-shape “wavelength” also led to a speedier swim.
But the main influence in how quickly 1-guilla could move through water is its tailfin. Increasing the tail’s angle to its maximum 45-degree range offered the most speed—but at a steep cost. Maximum range, perhaps predictably, requires maximum energy usage, which isn’t exactly a winning strategy for traveling long distances.
[Related: NASA hopes its snake robot can search for alien life on Saturn’s moon Enceladus.]
“To calculate efficiency, the motor’s power consumption (P) is divided by its speed (U) to get the Cost of Transport (CoT),” the team explains in its demonstration video.
The more 1-guilla’s motions resembled traveling waves, the lower its cost of transport. Knowing this, the researchers hypothesize that overall efficiency, not the fastest speed possible, is the key to an actual eel’s lengthy migration while on a comparatively empty stomach.
Serpentine robots are all the rage right now. NASA, for example, is putting the final touches on its aptly named Exobiology Extant Life Surveyor (EELS) prototype. Ostensibly 1-guilla’s 16-foot-long, 200-pound bigger sibling, EELS could one day find itself traversing both the surface and underground passageways on Saturn’s icy, possibly life-hosting moon, Enceladus. Meanwhile, MIT engineers recently unveiled their own three-foot-long, modular eel-bot made from simple lattice-like structures known as “voxels.”
