Computer-Aided Development and Simulation Tools for Shape-Memory Actuators

This article discusses the dynamic properties of shape-memory alloy (SMA) actuators, which are characterized by their rate of heating and cooling procedures and can be described only insufficiently for different boundary conditions. Based on an analysis of energy fluxes into and out of the actuator, a numerical model implemented in MATLAB/SIMULINK (MathWorks, Natick, MA) is presented. Besides the fluxes, the time-variable parameters like the latent heat of transformation or the influence of stress on the transformation temperatures are also included in the model. These parameters, depending on actuator geometry and temperature, the fraction of martensite, and the environmental conditions, are considered in the simulation in real time. In addition, this publication sums up the needed empirical data (e.g., fatigue behavior) to create a general-purpose engineering tool. The SMA wire-based actuation system can be configured by drag-and-drop tools and finally simulated and graphically displayed for different actuator systems. The development and verification of such a tool (called CASMADA) from theoretical equations to the verification on real elements is the main topic of this publication.