Abstract
In the recent years, micro-vibrations have been an issue of growing importance, due to the high-stability requirements imposed by some modern payloads. These low level mechanical disturbances, occurring at frequencies from sub hertz up to 1000 Hz, are created by different sources in the spacecraft (e.g. reaction wheels) and how to model the micro-vibration environment is currently under investigation. In this paper, a methodology is presented, involving analyses techniques such as FEA (reliable at low frequencies), Monte Carlo Simulation (precise but still computationally demanding and time consuming) and Modal Hybridization (a Stochastic Finite Element Method which involves perturbation of modes and natural frequencies and will be used to refine the general methodology). The various modelling techniques also require a particular attention when dealing with micro-vibrations. For instance, mechanical equipment typically on board a spacecraft (such as harness, thermal straps etc.) affects the response caused by low level disturbances and a FEM which models them with simple non-structural mass appears to be not accurate enough. Another important aspect of the modelling is the coupling between the sources and the tested structure. All the methods described above will be applied to a bench-work model represented by the satellite platform SSTL 300 (the relative testing campaign will be also described in this paper) and comparisons between the experimental and the computational results will be performed.