Numerical and experimental study on the dynamic equivalent methodology of a membrane antenna structure and a grid membrane structure

Abstract

The dynamic equivalent methodology utilizing a grid membrane substitute for a planar membrane for vibration test verification on the ground has been demonstrated in small sizes with simple constraints. The method lacks accuracy and validity for a real complex membrane antenna. This paper thus focuses on the applicability of the equivalence approach to a membrane antenna and the factors affecting its dynamic equivalence to verify whether the grid membrane structure can replace the membrane antenna structure for modal identification on the ground. To this end, an experimental system is developed to conduct vibration tests on the grid membrane structure in air, using the grid membrane model with unidirectional tension as a substitute for the membrane array. The connecting strips attach the grid membrane to thin-walled lenticular booms (TWLBs) to allow for unidirectional tension. A laser displacement sensor array is employed to obtain the vibration data. A combination of the Fast Fourier Transfer (FFT) and Stochastic Subspace Identification (SSI) methods is applied to identify the structural frequencies and mode shapes. Vibration tests on the grid membranes with different added masses and tensile forces are conducted. Meanwhile, the numerical results for the rectangular membrane are chosen as a reference for comparison with the experimental results for the grid membrane. In conclusion, the numerical results for the membrane antenna structure and the experimental results for the grid membrane structure show good agreement in terms of frequency and mode shape. Additionally, both the added masses in the intersection areas of the grid membrane and the tensile force have a significant effect on the dynamic equivalence.