Development of a Twisting Wing Powered by a Shape Memory Alloy Actuator

A variably twisting wing has many beneficial qualities that can improve aircraft performance for a variety of flight conditions. Beneficial variable wing twist features include a means to reduce induced drag in cruise conditions, to increase lift performance, and to increase roll control. However, the actuation hardware usually required to twist large scale wings, especially given their structural stiffness, presents a substantial limitation. Through the use of shape memory alloy (SMA) torque tubes and other associated active spars, such structural deformations can be enabled. In this work, we consider the development of a benchtop and wind tunnel testing platform for potentially assessing the response of a variety of SMA-based wing twisting concepts. Using additive manufacturing (3D printing), we have designed, built, and tested a small scale prototype. The SMA actuated twisting wing developed herein consists of a rapid prototype shell that was specifically designed using a finite element approach to maintain stiffness in bending while reducing torsional rigidity. Using LabView and a simple PID controller, we have shown that an SMA torque tube was able to drive and steadily maintain the spanwise linear twist in the wing under both benchtop and wind tunnel conditions. This prototype will allow future assessment of new control schemes, new SMA actuator materials, and new structural configurations toward the development of flight-capable self-twisting wings.

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