[Bre] dug up this excellent robot fish prototype project. The PPF-O9 has three servos. One on the forward fins to control depth, one on the middle joint, and one final one drives the tail fin. The battery box is mounted to the underside. The control scheme is interesting: the right stick controls left/right and up/down while the left stick controls the frequency and amplitude of the motion. They say the robot is fairly stable, but swimming and turning can be slow. They’ve included CAD files for almost every component to help you with your own designs.
In June, we highlighted a robofish designed for swarm communication.
This is the kind of engineering that gets us excited, and not just because we like machines modeled on living things. Science Daily reports that Associate professor [Kristi Morgansen] from The University of Washington has developed these robofish for underwater data collection. Her technology is notable for two major reasons: the small robots use fins for locomotion instead of propellers, which reduces drag and creates greater maneuverability. The second and more important reason is that the robofish can communicate with each other via sonar, largely obviating the need for the robofish to surface for more instructions. Both design concepts were inspired by the shape and behavior of real fish. Currently the robots are only programmed to swim with or away from each other, but these are still prototypes and the technology looks promising. For more tech specs on these “Fin Actuated Autonomous Underwater Vehicles” (see why Robofish is better?), you can have a look at Morgansen’s notes.