Jellyfish inspired soft robot prototype which uses circumferential contraction for jet propulsion

Abstract

Several robotic jellyfish have been designed over the years, yet none have properly mimicked the very efficient method of propulsion that jellyfish use. Using circumferential contraction, water is pushed out the bottom of the bell creating upwards thrust. Jellyfish use this basic movement along with more complex features to move around the seas. In this paper, we attempt to mimic this circumferential contraction using hydraulically actuated silicone bellows that expand and contract a bell made of flexible silicone skin. 3D printed polylactic acid (PLA) was used to make the structure of the robot, and hinges and jubilee clips were used to fasten it together in order to maintain exchangeability of parts. The jellyfish expands and contracts using a pump with a simple on-off control which switches dependent on the internal pressure of the hydraulic system. This very simple control mechanism is similar to real jellyfish, and much like jellyfish, our design attempts to use both passive and active movements to maximize thrust.