3 Bionic transfer: the Fin Ray® structure in the AquaJelly tentacles … … and in the fingers of the adaptive gripper DHDG Natural role model: The peristaltic thrust propulsion of the AquaJelly has a strong resemblance to the natural movements of the jellyfish. Highly integrated lightweight construction objects The AquaJellies consist of a translucent hemisphere, a central pressurised body and eight tentacles for propulsion. The hemisphere is equipped with a ring-shaped control board with integrated infrared, pressure and radio sensors. A processor permanently monitors the position of the drive system. The watertight pressurised body in the centre of the jellyfish contains the central electrical drive unit, the two lithium ion polymer batteries and the servomotors for a swashplate. The electric drive unit moves two drive plates on the top and bottom of the pressurised body, which uses rhombus-shaped joints to set the jellyfish's eight tentacles in motion. Tentacles with Fin Ray® structure Each tentacle is designed with a Fin Ray® structure, a construction derived from the functional anatomy of a fish's fin. The structure itself consists of an alternating traction and pressure flank connected by ribs. If a flank is put under pressure, the geometrical structure automatically bends against the direction of the applied force. From the bionic floating object to the customer application In the meantime Festo has put this effect into industrial practice. With the adaptive gripper DHDG, the structure locks its fingers around the object being gripped, thus enabling fragile and irregularly shaped objects to be handled safely without breaking them. The AquaJellies' delayed activation of the individual tentacles and their bending action leads to all eight arms making a simultaneous wave motion. This produces a peristaltic forward motion similar to that of their biological role model. Their motion in three-dimensional space is controlled by weight displacement. For this purpose, two servomotors integrated in the body control a swash plate. The plate operates a four-armed pendulum that can be deflected in four spatial directions. When the pendulum tilts in a particular direction, the jellyfish's centre of gravity is displaced accordingly and it then swims in this direction. Combined with the peristaltic propulsion, the AquaJellies can therefore swim in any spatial direction.
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