Reaction wheel microvibration finite element analysis

Microvibrations onboard satellites are a common phenomenon that excite the satellite structure with low-level accelerations, microg (µg). These vibrations need to be controlled to avoid degradation of the highly sensitive payload performances. Rotating devices such as reaction and momentum wheels (RMW) are considered the most consistent source of microvibration disturbances. Misalignments and unbalances on the high-speed rotating flywheel are the primary cause of disturbance forces and moments that are discharged on the satellite structure at the wheel assembly mounting points. Second-order defects like geometric imperfections inside the bearings rolling elements increase undesirable broadband frequency disturbances which can then excite resonances that amplify the disturbances. This work focuses on developing an analytical model, combined with a high-fidelity RMW ball bearing finite element analysis (FEA). One of the main aims consists of studying the microvibration disturbances origin focusing on the effects produced by imperfections in the elements of a reaction wheel assembly (RWA). The approach adopted in the analytical and in the FEM consists of introducing a geometric deformation on the several rotating and rolling bearings elements to characterize the frequency and especially the amplitude of the microvibrations produced onboard the satellite. Until now, any model has been developed to predict the magnitude of the disturbances generated onboard by a non-perfect bearing rotating inside this high speed RW devices. This research provides a better understanding of the amplitude of the RW microvibration generated onboard the spacecraft and contributes to the improvements required to reduce these disturbances by adopting specific structural solutions.