Numerical Model for Shape Memory Alloy Actuators

In order to realize a control system for Shape Memory Alloy (SMA) actuators, that ensure high displacement precisions, a numerical model that simulates SMA wire behavior subjected to thermo-mechanical actions, up to high number of cycles, has been set up. In particular, the constitutive model of Brinson, 1993,[1] coupled by a suitable kinetic low has been used. Beginning from such model, some corrections have been performed to take into account the deviations, in term of characteristic temperatures and mechanical responds, due to a numerous thermo-mechanical cycles. Furthermore, in order to complete and check the numerical model, experimental tests have been performed; initially the employed SMA wires have been characterized by several particular metallographic tests and DSC analysis in order to determine the phase transformations kind. Such results allowed to obtain a more correct expression of the numerical model. Starting from the experimental results, a code of numerical simulation in MATLAB© environment has been realized. The solution algorithm that has been used, in order to work out the complex non linear equations system that describe the SMA system, has been chosen taking into account both the speed of convergence and the computational complexity.