Wing warping

Abstract: any military and commercial applications for Unmanned Aerial Vehicles (UAVs) have been identified and numerous vehicles are under development. Many of these vehicles have a need to stow their wings and control surfaces into very small volumes to permit gun launch or packaging into aircraft mounted aerial drop assemblies. One technology that has shown promise in achieving this goal is the inflatable wing. Coincidentally, aircraft developers and researchers have identified a need for aircraft components that can morph to provide performance enhancements over traditional wing and tail assemblies, through the elimination of mechanical actuation system complexity and improved aerodynamics. The combination of the inflatable and morphing system technologies has lead to a unique approach for small UAV platforms with deployable, controllable wings that may also facilitate transition through multiple flight regimes. Inflatable wings have been in existence for decades and have found application in manned aircraft, UAVs, munitions control surfaces, and Lighter Than Air (LTA) vehicles. Recent system design challenges have ushered advances in the areas of materials, manufacturing, and configuration that have advanced this technology into a practical form for near term application. Inflatable wings can be packed into volumes tens of times smaller than their deployed volume without damaging the structural integrity of the wing. Deployment can occur on the ground or in flight in less than one second depending on the size of the wing and the type of inflation system used. The focus of this paper is to discuss efforts in reshaping, or morphing, the inflatable wing to provide roll control through wing warping, i.e. actuation of the aft end of the wing to achieve changes in section camber. Several approaches have been developed that lend themselves to camber control via locally altering the geometry of the wing. Apart from use as a stand-alone aerodynamic surface on a small UAV, the inflatable assemblies can also be used as an aspect ratio increasing device on a larger aircraft to enable a more radical change in wing configuration. This approach serves to improve system efficiencies across changing flight regimes, allowing transitions from highspeed target approach to low speed loitering. Several actuation methods that are applicable to flexible structures have been studied and traded-off. Actuators with strong force generation capability (i.e. high blocked stress) can be added to inflatable structures to alter the length of the load bearing textile components of inflatable wings, thus altering overall shape. Performance requirements for such actuators were derived from a consideration of useful roll rate in a representative aircraft. Other requirements were also compiled and include such items as high frequency response, ability to be folded and packed, low mass, low power consumption, and high cycle life. Some of the actuator types considered include piezoelectric actuators, electro-active polymers, shape memory alloys, pneumatic chambers, nastic cells, and distributed motor-actuator assemblies. * Manager, Research & Technology, AIAA Associate Fellow. Cadogan@ilcdover.com. † Principal Investigator, AIAA member. ‡ Project Engineer. § Design Engineer, AIAA member. AIAA 2004-1807 SDM Adaptive Structures Forum M