Wing strike reduction for small fixed wing uncrewed aerial vehicles

Abstract

This work presents the development of a leading edge strike resilient system for small, fixed wing unmanned aerial vehicles. This method uses passive, mechanically-linked wing sweep motion with a spring and buckling strip in parallel. Additive manufacturing is leveraged to prototype a geared substructure where rotation is resisted by a buckling strip and wing position is restored after impact by a linear spring. Experimental validation of the mechanism is conducted via drop-tower testing. For a rigid configuration the yaw impulse associated with impact grows with impact speed, while yaw impulse is thresholded by the yaw alleviation system. For the tested cases, impact moment is reduced by approximately 50% compared to the rigid case. A wind tunnel model was created to study the impact loading and changes in aerodynamic loads as the wings sweep backward and return forward after impact. Flight experimentation was conducted for symmetric and asymmetric impacts with manual flight recovery after impact while flying at 31 m/s at 2.4 m altitude. In the laboratory and in flight, mechanical impact loading on the vehicle is significantly reduced at a variety of airspeed and impact speeds with aerodynamic loading shown to damp the detrimental moments associated with leading edge strike.