Stability analysis of reduced-stiffness photovoltaic arrays on MB-6 and MB-15 configurations of space station Freedom

Reduced-stiffness photovoltaic (PV) arrays on two configurations of the space station Freedom (SSF) were analyzed to determine stability trends. Flexible modes of the SSF in which array motion is considered dominant were chosen for analysis, and root locus plots were generated. Two symmetric configurations were studied. One had four arrays and a stiff truss, the other had eight arrays and large mass. For both models, three different beta joint control frequencies were found to be stable for nominal array stiffness through root locus analysis at a time-slice. Beta joint roots moved further into the left-half plane with increasing control frequency and/or array stiffness, while other control roots remained stationary. No modes became unstable with decreasing array stiffness