Robojelly bell kinematics and resistance feedback control

Abstract

A comparative kinematics analysis was conducted between natural Aurelia aurita medusa and biomimetic robotic jellyfish (Robojelly). A resistance feedback controller was implemented to tailor the deformation profile of BISMAC actuators embedded in Robojelly. Robojelly's performance was quantified in terms of thrust production and power consumption during vertical swimming experiments. A maximum average instantaneous thrust production of 0.006 N was achieved at a driving current (I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">hi</sub> ) of 1.5 A with 35% duty cycle. Rapid heating of SMA wires was found to reduce power consumption and increase thrust. The bell kinematic analysis revealed resemblance and differences in bell deformation trajectories of the biomimetic and natural jellyfish. The inflexion point of the A. aurita was found to convert an inner bell trajectory into an outer one during contraction which assists the thrust production.