RotM Students at Carnegie Mellon University have made a mobile goldfish bowl that the lucky fish can drive around by itself – and they've filmed it for posterity.
The video shows a reasonably large fishtank on wheels being “driven” around by an unusually active goldfish.
The Reddit thread – yup, it’s one of those – reveals that “the direction and speed of the robot is determined by the position of the fish relative to the middle.”
The video also gives a great demonstration of the free surface effect, which is where a liquid in a part-filled tank on a moving vehicle sloshes around, destabilising the vehicle. The fishtank is about three-quarters full.
If left unchecked, particularly in ships at sea with a compartment flooding through damage, the free surface effect can create a positive feedback loop, fatally destabilising the vehicle. Happily, that does not happen to the robot fishtank, which instead lurches around at the unwitting commands of an increasingly worried-looking goldfish.
The battery-powered robot was powered by a Raspberry Pi 1, and the source code for the whole project can be found on Github. ®