Robotic fish learn to go with the flow

We’ve already seen several underwater robots that mimic the swimming abilities of fish. The European FILOSE research project, however, is also interested in copying another feature of our finned friends – their lateral line. The result could be swimming robots that use differences in water pressure to navigate and save energy.

A fish’s lateral line is comprised of a row of hair cells that run length-wise down either side of the animal’s body. These cells are capable of detecting changes in water pressure, as might be caused by water flowing around underwater objects. It’s by using sensory input from their lateral line that fish are able to quickly find their way around in murky water, without crashing into rocks or other obstacles.

The FILOSE researchers have created a series of lab-based robotic fishes based on the rainbow trout, that have their own man-made lateral lines. These lines incorporate tiny cantilevered piezoelectric sensors that bend in response to flow – the stronger the current, the more they bend, and the greater the electrical signal that they produce.

Through experiments in a flow tank, the scientists have determined that robots equipped with such a feature can not only seek out areas where disruptive currents are weakest, but that they can also utilize eddies to actually help push them forward. Additionally, by using their lateral lines to determine the direction and speed of the current, they can either swim upstream or hold their position, moving their tails at such a rate that they neither drift downstream nor travel forward.

As whitewater kayakers will do, the robots are also able to temporarily escape the current by pulling in behind objects that block it – a less energy-intensive alternative to holding their place by swimming against the current.

The FILOSE team is made of scientists from the University of Bath (UK), Tallinn University of Technology (Estonia), Riga Technical University (Latvia), Verona University (Italy), and the Italian Institute of Technology. A paper on their research was recently published in the journal Proceedings of the Royal Society A. More information on the project is available in the rather kooky video below.

This isn’t the first time that scientists have created artificial lateral lines. Teams from Nanyang Technological University/MIT, the University of Illinois/Northwestern University, and Technische Universitaet Muenchen have also done so with success.

Source: FILOSE, Tallinn University of Technology