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Now, a bionic cuttlefish takes to the water

18 June, 2018

Just two months after it unveiled bionic spiders and fruit bats at the Hannover Fair, Festo has come up with another one of its mechatronic creatures – this time, a 370mm-long cuttlefish that was swimming through a transparent pipe filled with water at the Achema process industry show in Germany.

Like its living counterpart, the bionic cuttlefish – called the BionicFinWave – propels itself using undulating movements of “fins” on either side of its body.

The longitudinal fins a cuttlefish (and similar creatures, such as the Nile perch) extend from the head to the tail – along their backs, their undersides or both sides of their torsos. To move through the water, they use these fins to generate a continuous wave that progresses along the length of their bodies. This undulation forces the water backwards, producing a forward thrust. The BionicFinWave uses this principle to manoeuvre itself forwards or backwards.

The creature’s two lateral fins are moulded from silicone, without using any reinforcement struts or other supporting elements. They are therefore extremely flexible and can emulate the gently flowing movements of their biological copunterparts realistically. Each of the two fins is attached to nine small lever arms with a deflection angle of 45 degrees, which are driven by two Savöx servomotors housed in the body. Two flat crankshafts transmit the forces to the arms, so that the two fins can move independently of each other and can generate different wave patterns simultaneously. To swim in a curve, for example, the outer fin moves faster than the inner one – like the treads of an bulldozer.

To move up or down, the BionicFinWave uses a third servomotor to bend its body in the desired direction. To give the single-piece crankshafts extra flexibility, universal joints are located between the lever segments. The plastic crankshafts, as well as the joints and piston rod, are 3D-printed to create integral components.

Festo's BionicFinWave mimics the movements of a cuttlefish to propel itself through water

The remaining body elements of the 430-gramme BionicFinWave are also 3D-printed, allowing complex geometries to be produced. They contain waterproof cavities that give buoyancy, as well as a housing for the control and regulation technology. A pressure sensor and ultrasound sensors monitor the BionicFinWave’s distance from the tube walls and its depth in the water, thus preventing collisions with the sides of the plastic tube. This autonomous navigation required the development of compact, efficient and waterproof or water-resistant components that could be coordinated and regulated by software.

The fin drive is particularly suitable for slow, precise movements and causes less turbulence in the water than a conventional screw propulsion drive, for example. As it moves through its plastic tube, the underwater robot can communicate with the outside world via radio, and transmit data, such as temperature and pressure sensor readings, to a smart device such as a tablet.

Festo says that the BionicFinWave could lead to new drive technologies for use in fluid media, as well as advances in autonomous robots. The concept could be developed further for tasks such as inspection, making measurements or data acquisition in, for example, for in the process or water industries. The knowledge gained could also be used in the manufacturing of soft robotics components.

Part of the internal mechanism that the BionicFinWave uses to create wavelike movements of its fins

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