Design and Implementation of a Shape Memory Alloy Actuated Reconfigurable Airfoil

Abstract

The unique thermal and mechanical properties exhibited by shape memory alloys (SMAs) present exciting design possibilities in the field of aerospace engineering. When properly trained, SMA wires act as linear actuators by contracting when heated and returning to their original shape when cooled. These SMA wire actuators can be attached to points on the inside of an airfoil, and can be activated to alter the shape of the airfoil. This shape-change can effectively increase the efficiency of a wing in flight at several different flow regimes. To determine the necessary placement of the SMA wire actuators within the wing, a global optimization method that incorporates a coupled structural, thermal, and aerodynamic analysis has been utilized. A genetic algorithm has been chosen as the optimization tool to efficiently converge to a design solution. The genetic algorithm used in this case is a hybrid version with global search and optimization capabilities augmented by the simplex method with selective line search as a local search technique. A cost function based on the aerodynamic properties of the airfoil has been used to optimize this design problem to maximize the lift-to-drag ratio for a reconfigured airfoil shape at subsonic flow conditions. A wind tunnel model reconfigurable wing was fabricated based on the design optimization to verify the predicted structural and aerodynamic response. Wind tunnel tests indicated an increase in lift for a given flow velocity and angle of attack by activating the SMA wire actuators. The pressure data taken during the wind tunnel tests followed the trends expected from the numerical pressure results.

Passive control of the flutter instability on a two-degrees-of-freedom system with pseudoelastic shape-memory alloy springs.

“…In this contribution, we focus on a passive control device for mitigating the flutter instability by using springs composed of shape memory alloys (SMA). In their pseudoelastic regime, SMA are known for showing the ability of dissipating an important amount of energy thanks to the hysteresis loop appearing in their stress-strain relationship, and has thus already been used in numerous applications ranging from civil engineering, aeronautics to medical industry [2,3]. Recent contributions have considered the dynamical responses of SMA springs from the theoretical viewpoint [4][5][6] in order to properly quantify the most proeminent features of the vibrations of simple single dof systems.…”

Pseudoelastic Shape Memory Alloys to Mitigate the Flutter Instability: A Numerical Study

“…In this contribution, we focus on a passive control device for mitigating the flutter instability by using springs composed of shape memory alloys (SMA). In their pseudo-elastic regime, SMA are known for showing the ability of 1 dissipating an important amount of energy thanks to the hysteresis loop appearing in their stress-strain relationship [11], and has thus already been used in numerous applications ranging from civil engineering, aeronautics to medical industry [13,14]. The goal of this study is, in a first step, not to describe the system as accurately as possible but to exhibit the interest of using an hysteretic phenomenon in the view of controlling an aeroelastic instability and studying the influence of different SMA parameters for the flutter control.…”

Inertial attitude control of a bat-like morphing-wing air vehicle

“…The possibility of having actuated wings has allowed the design of new mechanisms that improve over classical fixed/rotary-wings MAV flight performance. As a result, different morphing-wing concepts and materials have emerged together with control methodologies that allow for accurate wing-actuation [4], [5], [6], [7], [8], [9].…”