1. Field
Embodiments of the disclosure relate generally to the field of control surface actuation systems and more particularly to embodiments for a shape memory alloy actuator with dual collinear shape memory alloy tubes having antagonistic reaction about a control temperature point.
2. Background
Wind tunnel models typically require movable control surfaces to allow simulation of various control aspects of the vehicle being modeled. Unmotorized surfaces are often used due to their simplicity. However, such surfaces must be positioned by hand requiring interruption of testing to position the surfaces at desired control angles. Models are typically of reduced scale and therefore full size actuators which would be employed in actual vehicles are not readily adaptable for use. Various actuation systems have been employed in wind tunnel models including electromechanical actuators and shape memory alloy (SMA) actuators using wires for hinge moment actuation using differential pull from SMA wires. However, electromechanical actuation is relatively bulky because of low power densities and the need for complex electric motor/gear assemblies. As such, the amount of space required in the supporting structure (for example in a vertical tail) may limit the amount of instrumentation such as pressure sensors that can be installed in the model and may reduce the structural strength which tends to limit their use to lower pressure tunnels having lower loads. Lower pressure tunnels do not match the aerodynamic characteristics of a full scale airplane as well which limits their fidelity as design tools for testing aircraft configurations. SMA wire actuation has limited power and strength, and therefore is similarly suitable for low pressure wind tunnel testing only.
It is therefore desirable to provide actuators for use in models, or other space constrained applications, to improve wind tunnel test efficiency by reducing the number of times the wind tunnel has to be opened to complete model changes while providing an actuator with sufficient force capability for higher pressure wind tunnels. It is also desirable to provide an actuator having power density much greater than traditional solutions for actuated control surfaces allowing its implementation into applications requiring higher forces and into more restrictive spaces. It is further desirable to provide an actuator with the ability to place the actuating elements on the hinge line of a control surface.