A bio-inspired shape memory alloy composite (BISMAC) actuator

Abstract

A beam-shape composite actuator using shape memory alloy (SMA) wires as the activecomponent, termed a Bio-Inspired Shape Memory Alloy Composite (BISMAC), wasdesigned to provide a large deformation profile. The BISMAC design was inspired bycontraction of a jellyfish bell, utilizing the rowing mechanism for locomotion.Characterization of maximum deformation in underwater conditions was performed fordifferent actuator configurations to analyze the effect of different design parameters,including silicone thickness, flexible steel thickness and distance between the SMA andflexible steel. A constant cross-section (CC)-BISMAC of length 16 cm was found to achievedeformation with a radius of curvature of 3.5 cm. Under equilibrium conditions, theCC-BISMAC was found to achieve 80% of maximum deformation, consuming 7.9 J/cycle drivenat 16.2 V/0.98 A and a frequency of 0.25 Hz. A detailed analytical model was developed using the transfermatrix method and a 1D finite beam element (FE) model to simulate the behavior of theBISMAC incorporating gravity, buoyancy and SMA parameters. The FE and transfermatrix models had a maximum deformation error norm of 1.505 and 1.917 cm incomparison with experimentally observed beam deformation in the CC-BISMAC. Themean curvatures predicted by the FE and transfer matrix methods were 0.292 cm−1 and0.295 cm−1 compared to a mean experimental curvature of 0.294 cm−1, a percentageerror of −5.4% and 2.77%, respectively. Using the developed analytical model, an actuator design wasfabricated mimicking the maximum deformation profile of jellyfish of the species Aureliaaurita (AA). The designed AA-BISMAC achieved a maximum curvature of 0.428 cm−1 as comparedto 0.438 cm−1 for A. aurita with an average square root error of 0.043 cm−1, 10.2% of maximum A. aurita curvature.