Analyzing the effect of parametric variations on the performance of antagonistic SMA spring actuator

Abstract

This paper presents a mathematical model of a shape memory alloy (SMA) spring actuator in an antagonistic configuration to determine the work generation potential. As SMAs are observed as configuration-dependent, traveled path history becomes an important parameter to be considered in the mathematical model. Moreover, in most real-world applications, loads are found to be unpredictable and fluctuating in nature, which results in an incomplete transformation of the material. Based on the above observations, for the first time in the published literature, the current work considers these two parameters - loading history and arbitrary loading in the mathematical model for SMA antagonistic springs. The model comprising of heat dynamics, constitutive model, and phase kinetics with loading history is implemented under normal as well as arbitrary loading conditions. Performance of antagonistic SMA spring actuator is investigated for its force generation capability and displacement, considering its material properties, geometrical parameters, and applied input voltage. At least three investigations are carried out for each parametric variation. Simulation results are found to be qualitatively in agreement with the published literature. Higher force generation capability of antagonistic SMA spring pair is reported under arbitrary thermo-mechanical loading conditions. It is concluded that the geometrical parameters of SMA spring such as the number of turns, diameter of spring wire, and spring index significantly affect the performance of the antagonistic spring pair than the material parameters.