Underwater aquatic research seems to be taking up a new motto: do as the fish do! There is an undeniable trend in the field to explore the development of new research tools that not only blend into the aquatic environment more easily but also mimic deep sea residents. For example, MIT created a robotic fish called SoFi, and even more recently a student at TU Delft utilized 3D printing to create a robotic fish that swims through water like a tuna.
The student in question, Sander van den Berg, is pursuing his master’s degree in Industrial Design Engineering and decided to create the fish-inspired drone for his graduate project. The drone, which draws inspiration from some of the ocean’s fastest fish, is able to swim up to 0.85 meters per second—a record-breaking speed for robotic fish.
The robotic fish drone—still in its prototype stage—is made up of low-cost 3D printed plastic body, flexible sheet plastic and a soft silicone skin for the moving tail segment. The fish-drone’s design is based on a fairly simple principle: to increase speed by making one part of the robot (the head) passive, and the other (the tail) active.
The active portion of the drone was developed by van den Berg using computer modeling and mimics the motions of thunniform swimming. Seen in tunas and many lamnid sharks, thunniform swimming is defined by a large, often crescent-shaped tail doing the bulk of the sideways movement. This approach allows for rapid speed increases and for long distance swimming.
As it turns out, by trying to mimic the motion of some of the fastest fish, van den Berg was able to create a relatively fast robotic fish. (A yellowfin tuna is reportedly capable of reaching speeds of up to 75 km/h, so it’s safe to say the robotic tuna wouldn’t be a match there!)
Still, the robotic 3D printed fish is an achievement, as industrial design student found a way to stabilize the drone—which had previously been a difficult feat with this type of movement. The problem was overcome by installing a motor into the fish’s head, which pulls the tail’s active segment from side to side. The forward motion is also encouraged by the adjoining passive segment of the tail, which continues to bend and flap with the water resistance.
There are several advantages to designing underwater drones that utilize fish-inspired movements rather than propellers. For one, tail-like movements are more efficient than propellers and can achieve faster speeds. Second, they are safer than propellers, which have a high risk of harm for sea life and even humans. For research purposes, having a robotic drone that moves like a fish is also less disruptive than a propeller-powered drone, which whirrs and disrupts water. Finally, the undulating motion is also more viable at deeper depths, where rotating parts become less efficient.
In practice, underwater drones—especially less invasive fish-inspired ones—would have applications in underwater research, diver assistance, boat inspection and more.[Source: Dezeen]