Analytical Determination of UAV Wing Stiffness Requirements for a Structurally Integrated Conformal Antenna Array

Abstract

The OSU chapter of Engineers Without Borders (EWB)has examined the possibility of installing a water piping network in rural Guatemala. This requires an elevation survey of the area to be undertaken. The hilly terrain and forest canopy pose significant challenges to both traditional and airborne survey methods. A low frequency cruciform antenna mounted conformally to the lower surface of a small UAV is identified as a potential solution. The antenna is mounted to the underside of the wings and will deflect with them in flight according to the aerodynamic loads. This deflection of the antenna elements will cause changes to antenna gain and beamwidth. Under steady flight conditions this deflection can be countered by adjusting the phasing to match the nominal flight conditions. Small changes to wing loading from gusts or maneuver loads may not be corrected for with phasing. The effect of these small deflections on the antenna performance is chosen for further study. A study is developed using CAD to model several representative wings for a ground mapping airplane. These wings are tested under loading conditions to determine deflections. These deflections are then used in a MATLAB program based on antenna array theory to determine the gain and beamwidth for antennas mounted to the wings. The results show that antenna performance at low frequencies is largely immune to the effects of small changes in loading. A stiffer wing does mitigate the effects to a degree, but the effects are only significant at higher frequencies. Overall, such a system shows a high degree of promise for a ground mapping mission.