Use of Multiple SMA Wires for Morphing of Inflatable Wings

The concept of inflatable wings has design heritage and they have recently seen renewed interest, largely due to the increased demand in unmanned aerial vehicles (UAVs). They offer design advantages over conventional wings, particularly with regard to stowage and portability, since they can be tightly packed when undeployed. Unfortunately current methods of flight control involve the use of additional control surfaces attached to the trailing edge of the wing, adversely affecting the stowage capabilities. One way of overcoming this restriction is to use the wing itself as a control surface, by morphing the very shape of the wing to achieve the desired results. This article outlines the research performed at the University of Southampton into differing configurations of Shape Memory Alloy (SMA) wires as a controllable actuator for the wing morphing. Specifically the use of multiple wires to further enhance this control was the focus of this work. A simple test rig was constructed in order to evaluate the pulling force achievable by combinations of SMA wires in a number of configurations. The most promising of these configurations was then attached to an inflatable wing model for further testing. Both static testing and wind tunnel testing was undertaken, evaluating the authority of flight control such a system could achieve. The test results are presented in this paper, giving an initial performance assessment of the proposed control method.