Comparison of Different Methods of Modal Test on a Spacecraft Representative Structure

Abstract

FLECS designed and manufactured by ESTEC represents a typical modular spacecraft in terms of mass properties and modal density. The structures is well suited as a test item for the validation of dynamic identification methods and was therefore selected for the comparison of the following test methods, the phase resonance method with appropriated excitation (for every eigenmode an exciter force distribution is found which compensates the damping forces of the structure), the mode separation method with excitation at various locations on the structure with complex exponential and a driven-base method with undirectional base excitation. Since the structural damping level of FLECS is low compared to actual fully equipped satellite structures the modal identification methods were also applied to a configuration of FLECS with supplemental non-proportional viscous damping. For this purpose dampers were manufactured and integrated into the FLECS structure. This paper describes briefly the experience in applying the methods and compares the results.