Shape Memory Actuators for Tab-Assisted Control Surfaces

Actuation equations for a tab control system have been derived based on one-dimensional shape memory behavior. This actuation model accounts for the active tendon having to pull against the relaxing tendon in a two-tendon actuator. That is, the passive tendon will provide a negative moment, subtracting from the total moment available for moving the tab. In addition, studies on the heat convection of SMA in water and moving water have been performed in an attempt to determine the available control moment in moving water and to predict the amount of energy needed. These results identify the research issues that must be overcome in making a recommendation regarding the feasibility of using SMA in a submarine for actuation. The result is that use of SMA is feasible, but the exact performance results are not predictable with the current state-of-the-art in SMA modeling. Furthermore, predictive design models specific to applications in moving water are needed to understand the issues of 1 exact moment prediction, 2 exact heat signature, and 3 control predictions for maneuvering.