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A soft robot is presented which replicates the ability of cephalopods to travel in the aquatic environment by means of pulsed jet propulsion. In this mode of propulsion, a discontinuous stream of fluid is ejected through a nozzle and rolls into a vortex ring. The occurrence of the vortex ring at the nozzle-exit plane has been proven to provide an additional thrust to the one generated by a continuous jet. A number of authors have experimented with vortex thrusting devices in the form of piston-cylinder chambers and oscillating diaphragms. Here, the focus is placed on designing a faithful biomimesis of the structural and functional characteristics of the Octopus vulgaris. To do so, the overall shape of this swimming robot is achieved by moulding a silicone cast of an actual octopus, hence offering a credible replica of both the exterior and interior of an octopus mantle chamber. The activation cycle relies on the cable-driven contraction/release of the elastic chamber, which drives the fluid through a siphon-like nozzle and eventually provides the suitable thrust for propelling the robot. The prototype presented herein demonstrates the fitness of vortex enhanced propulsion in designing soft unmanned underwater vehicles.
Date of Publication: April 2013