The Effect of Wing Spar Cross-Sectional Profile Variation on the Unmanned Aerial Vehicle (UAV) Natural Frequency

Abstract

Natural frequency is a critical dynamic parameter in designing the unmanned aerial vehicle (UAV) wing structure. The low-value natural frequency causes the aircraft wing to deflect easily while flying. Furthermore, the low-value natural frequency can causes resonance when this natural frequency is closest to the wind frequency. An increase in the UAV natural frequency can be conducted by increasing the wing structural stiffness. However, increased stiffness by enlarging dimensions is often followed by an increase in mass that is avoided in the design of aircraft structures. One technique that can be used to increase UAV natural frequency is by increasing the cross-sectional moment of inertia of the wing spar. In this study, an analysis of the effect of the wing spar cross-sectional inertia variations on the UAV natural frequency is conducted. Several wings spar cross-sectional profiles with different cross-sectional inertia are evaluated, such as U profile, circular, T profile, square, L profile, I profile, and Z profile. The results of the investigation showed that the wing spar using T profile is better than other profiles in increasing the wing structure natural frequency. This profile could increase the 1st elastic natural frequency by 22.9%, with only a 3.4 % increase in mass.