Ground test identification o f p liable s pace s tructures by decoupling techniques

Pliable space structures, such as solar panels or array antennas for space applications, can be attached to the body of the satellite using different types of joints. To predict the dynamic behaviour of such structures under different boundary conditions, it is convenient to start from their dynamic behaviour in free-free conditions. In this situation, they would exhibit rigid body modes at zero frequency. To experimentally simulate freefree boundary conditions, flexible supports such as soft springs are typically used: with such arrangement, rigid body modes occur at low non-zero frequencies. Since pliable space structures exhibit the first flexible modes at very low frequencies, the two sets of modes become coupled and the low frequency dynamics of the free-free structure cannot be estimated directly from measurements. To overcome this problem, substructure decoupling can be used, that allows to reconstruct the dynamics of the free free structure after measuring the FRFs on the supported structure and, if necessary, on the supports. The procedure is tested on a reduced scale model of a space solar panel using different support conditions.