Analysis and Testing of Microvibrations Produced by Momentum Wheel Assemblies

The microvibrations produced by momentum wheel assemblies (MWA) can degrade the performance of instruments with high pointing precision and stability on spacecraft. This paper concentrates on analyzing and testing the microvibrations produced by MWA. We analyze the disturbance sources produced by mass imbalance, structural mode, bearing irregularity and nonlinear stiffness, and random noise; then, test a well-balanced MWA by a highly sensitive measurement system consisting of a Kistler table and an optical tabletop. The results show that the test system has a resolution of less than 0.003 N in the frequency range of 3–300 Hz. The dynamic imbalance of the MWA cannot excite the radial rocking mode, but there are dynamic amplifications when the poly-harmonic disturbances intersect with the structural modes. Especially at high rotational speed (>3 000 rev/min), the main disturbance sources of the MWA come from the bearing irregularity interacting with radial translation mode in the high frequency range. Thus, bearing noise deserves more attention for the well-balanced MWA, and alternative of high quality bearings are proposed to reduce the microvibrations.