A remote-controlled fish 2 X-ray image of the Aqua_ray Aqua_ray without skin acting pairs of muscles. Their force of contraction is transferred by artificial tendons of high-strength Dyneema® cord via spools and sheathstothewings and the tail,whichinturntransformthetendon travelof 55mm intoaverticalwingamplitude of morethan550mm. Through the use of new elastic materials for all moving components and for the 3D-deformable skin,and by matching the elasticity and self-adaptive characteristics of the internal wing and tail structurestothehydrodynamicforces, it has been possible to reproduce the kinematics of nature’s marine model. Water is essential to Aqua_ray’s function,since entirely authenticmovement can only beattainedin combinationwith this medium and itsspecial characteristics. The change in direction of force effected by the tendons makes it possible to relocate the dorsal and thoracic muscles to the side, thus providing more room for energy storage and transformation components along with the control and sensory units. The requirements regarding technology and performance efficiency, e.g. pay-load, could thus be reconciled with the biological advantages of aquatic movement. Analysis of various types of movement through water has established that rays are perfectionists in submarine“flight”and gliding. The up-and-down motion of their flanks in water closely resembles the flapping of a bird’s wings in the air. This wavelike movement perfectlycombinesmaximumpropulsionwithminimumenergy consumption. The streamlined form lends graceful movement to the manta ray,inparticular,andmakesitaveritable submarine acrobat. Aqua_ray is a remote-controlled fish with a water-hydraulic drive unit; its form and kinematics are modelled on the movement patterns of the manta ray. Bionic fluidic muscles from Festo serve as actuators. These largely consist of hollow elastomer tubes with integrated woven aramide fibres. When the fluidic muscle is filled with air or water, its diameterincreasesanditcontractslongitudinally,givingriseto smoothly flowing elastic movement. The fluidic muscle from Festo, in combination with the Fin Ray Effect®,constitutesAqua_ray’scentralpropulsion and control unit. The Fin Ray Effect® is a construction that is derived from the functional anatomy of a fish’s fin and imitates almost perfectly the modeofpropulsionexecutedby the naturalmodel.It is entirely due to the mechanics of the fin ray’s-bony rods that constitute the fin’s supporting structure – that the wing can be arched to ensure even distribution of forces; this makes for a highly efficient drive mechanism. Likeaheart,Aqua_ray’s water-driven central vane cell pump generates the propulsion energy, which is conveyed in the form of pressure via specially developed valves to three antagonistically
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