Evaluation of the characteristics of a shape memory alloy spring actuator

A shape memory alloy (SMA) spring actuator for an active catheter was fabricated by the heat treatment of wound SMA wire on a mandrel. In order to evaluate the characteristics of the fabricated SMA spring actuator, four types of tests were performed, as follows: isothermal loading and unloading, measurement of shape recovery force, temperature follow-up, and load follow-up tests. In this work, it was first developed that the prediction method of the shape recovery force was based on the neural network theory. The prediction results were better than the results from the conventional constitutive equation of SMA. From the experimental results, it was also proved that the following characteristic for loads was better than that for temperature and the following characteristics could be enhanced according to cooling and control methods.