The marine flatworm, the cuttlefish and the African knifefish have one thing in common: in order to propel themselves, they use their longitudinal fins to create a continuous wave which advances along their entire length. The BionicFinWave also uses this undulating fin movement to manoeuvre through a pipe system made of acrylic glass. At the same time, the autonomous underwater robot is able to communicate with the outside world wirelessly and transmit data – such as the recorded sensor values for temperature and pressure – to a tablet.
The longitudinal fins of the natural role models run from head to tail and are located either on the back, the belly or on both sides of the body. The fish use the wave-shaped movement of the fins to push the water behind them, thereby creating a forward thrust. Conversely, the creatures can also swim backwards in this way and, depending on the wave pattern, create uplift, downforce or even lateral thrust.
The BionicFinWave uses its two side fins to move along. They are completely cast from silicone and do not require any struts or other support elements. This makes them extremely pliable and thus able to faithfully replicate the fluid wave movements of their biological role models.
For this purpose, the two fins on the left and right are each fastened to nine small lever arms. These, in turn, are driven by two servo motors located in the body of the underwater robot. Two attached crankshafts transfer the force to the levers in such a way that the two fins can move individually. They can thus generate different wave patterns which are particularly suitable for a slow and precise movement and whirl up water less than a conventional screw propulsion system does, for example.