Shape memory alloy-based mechanism for aeronautical application: Theory, optimization and experiment

Efforts to create efficient and lighter aeronautical structures are defining morphing systems especially those associated with smart materials. In this regard, three simple mechanisms using shape memory alloy (SMA) wires are investigated to generate torque that could be used for flap actuation. The devices consist of an SMA wire biased by a linear spring in the following configurations: concurrent, collinear, and in parallel attached to a pulley. The design of such mechanisms are modeled, optimized, and experimentally verified. The model for the flap consists of two rigid bodies, one fixed and the other rotating, with a single actuator connected to each body. Aerodynamic loading and heat transfer analysis are also considered. The model utilizes the thermomechanical properties for an SMA wire experimentally characterized via improved inverse problem techniques. A multiobjective genetic optimization is implemented to find designs for the three configurations that minimize power consumption and maximize flap deflection magnitude. Overall, as design complexity (i.e., number of degrees of freedom) increases, the power to achieve a certain flap deflection decreases. The maximum deflection for all three mechanisms is sufficient for typical aircraft operations. Finally, numerical results were verified via an experimental apparatus, where similar performance to the model was achieved.