As much as we enjoyed all of the robots performing the ETH Zurich Autonomous Systems Lab’s video, one robot in particular stood out because it didn’t look familiar. You may have spotted it too, at about 1:30: a robot with four orthogonal fins called Sepios. We did some hardcore journalistic research (consisting primarily of a Google search) and found a website on it, along with a very cool video of the robot swimming in the ocean.
The official Sepios swimout was in May of this (not much longer this, but still this) year. It’s a student project from ETH Zurich inspired by the noble cuttlefish, which is a friendly sort of cephalopod that propels itself with a pair of undulating fins. Cuttlefish are highly maneuverable little critters, but Sepios is an upgrade, with four independently controllable fins that allow it to rotate on any axis and translate in any direction. It’s sort of like combining a cuttlefish with two knifefish, one of which is upside-down. If you’re not familiar, with a knifefish, here’s a robot from Northwestern University that was inspired by one:
Rather than running Sepios’ fins on shafts that cause them to undulate at a fixed frequency and amplitude, each ray of each fin is controlled with its own servo and can move over a range of 270 degrees. That’s 36 servos total, and the completed robot only takes about 4,600 more parts to put together. When it’s in one piece and behaving, Sepios has a top speed of 1.8 km/hr, a maximum depth of 10 meters, and a battery life of an hour and a half, which is easily enough time for an ocean expedition:
Sepios has no trouble moving through dense patches of seagrass, even in surge, which would be a tangled nightmare for any underwater vehicle relying on propulsion systems that produce thrust by spinning. It also generates a minimal amount of turbulence, and the ETH team says that these kinds of qualities might make it ideal for observing marine life. The website suggests that future work might include outfitting Sepios with sensors to allow it to traverse an obstacle course, but to be really useful, we're hoping that Sepios acquires a tentacle (or eight).
[ Sepios ]
Evan Ackerman is a senior editor at IEEE Spectrum. Since 2007, he has written over 6,000 articles on robotics and technology. He has a degree in Martian geology and is excellent at playing bagpipes.