Development of a calculation and experimental method for modal analysis of large transformable space structures

The developed calculation and experimental method for modal analysis of large transformable space structures consists in dividing the structure into component parts, modal testing of these parts, correction of mathematical models of component parts based on test results, synthesis of mathematical models of components for constructing a global model of the entire structure, determination of the dynamic characteristics of the entire structure by the global mathematical model. The method for determining the parameters of the structures component parts eigentones in modal tests is described, which has a low sensitivity to measurement errors and the mutual influence of tones with close eigenfrequencies. The effectiveness of this method is illustrated by the results of testing of aircrafts and the spacecraft unit. To correct the mathematical models of the components, the stiffness and inertia matrices undergo a reduction procedure. The structure global mathematical model is the result of the synthesis of the corrected reduced inertia and stiffness matrices of the component parts. It is reasonable to solve the problem of determining the modal characteristics of the transformable space structures by the results of the components testing, owing to their large dimensions and complexity in the assembled form. In addition, large space structures have, as a rule, low eigenfrequencies – up to a tenth of a hertz. Experimental modal analysis of such structures comes with serious difficulties. As an implementation example of the method being developed, the results of the modal analysis of the spacecraft umbrella antenna model are presented.