Structural vibration design of a pod structure including an optical system of a fighter aircraft

Structural vibration design of a pod structure including an optical system installed on a fighter aircraft is very significant in improving accuracy of targeting system to the target objects. To reduce and isolate the vibration generated during the flight, it is crucial to properly design the rubber mount between the pod and the aircraft. In this study, free vibration analysis of the pod is conducted through finite element analysis (FEA) and experimental modal analysis (EMA). Correlations are performed with reasonably acceptable accuracy about the natural frequencies, mode shapes, and frequency response functions obtained by FEA and EMA. Then to optimize the structural dynamics of the pod, three variables are considered, which are mass of the dummies, the number of and positions of rubber mounts, and hyperelastic property of rubber mounts. In addition, the position of the pod on the fighter is analysed by FEM to estimate the possibility of further enhancement of its structural dynamics. Finally, forced vibration experiment is undertaken with a shaker using random signals of 1Grms, 2Grms and 2.65Grms considering the test standard. It is found out that frequency responses of the pod are sensitive below 100 Hz to the values of the excitation signals. It is thus indeed to design appropriately the rubber mounts to improve structural dynamics of the pod, which results in the accuracy of targeting system.