Microvibrations Induced by a Cantilevered Wheel Assembly with a Soft-Suspension System

Abstract

Microvibration management onboard spacecraft with high stability requirements has drawn increasing interest from engineers and scientists, and this paper discusses a reaction wheel design that allows a significant reduction of mid-to high-frequency microvibrations and that has been practically implemented in industry. Disturbances typically induced by mechanical systems onboard a spacecraft (especially rotating devices such as reaction wheel assemblies and momentum wheel assemblies) can severely degrade the performance of sensitive instruments. Traditionally, wheel-induced high-frequency (over 100-200 Hz) vibrations, generated by a combination of phenomena from bearing noise to dynamic amplifications due to internal resonances, are especially difficult to control. In this paper, the dynamic behavior of a newly designed wheel assembly, with a cantilevered flywheel configuration supported by a soft-suspension system, is investigated. The wheel assembly's mathematical model is developed and later verified with vibration tests. Wheel-assembly-induced lateral and axial microvibrations are accurately measured using a seismic-mass microvibration measurement system, which represents an alternative to typical microvibration measurement setups. Finally, the performance of this wheel assembly in terms of microvibration emissions is compared with a traditional design (with a rigid suspension) through comparison of frequency spectra, and it is shown that this design produces significantly lower vibrations at high frequency. = at wheel-assembly/seismic-mass interface, in x and y directions md = dynamic imbalance condition ms = static imbalance condition r = torsional (spring and dashpot) s = wheel and seismic system s xx , s yy , s zz = orthogonal directions of wheel-assembly and seismic-mass system sx, sy, sz = orthogonal directions of wheel-assembly and seismic-mass system t = linear (spring and dashpot) w = flywheel x, y, z = orthogonal directions

Dynamic Mass of a Reaction Wheel Including Gyroscopic Effects: An Experimental Approach

“…The RWA disturbance model was developed in [17] and subsequently re-elaborated in [35]. An energy approach is here implemented to derive the generalized Equation of Motion (EoM) through Lagrange's equation [36].…”

“…[7,1419]. Moreover, their mitigation and control using passive or active damping systems have been thoroughly investigated, for example [16,17,2022], with the nal objective to estimate and minimise payload pointing errors [23,24].…”

“…hard-mounted boundary condition) the RWA on a dynamometric table (e.g. Kistler table) and measure the forces and moments whilst the RWA is in operation [14,15,17,2527]. The data are subsequently used as input to the satellite Finite Element (FE) model to predict the induced eects on the payload.…”

A stochastic methodology for predictions of the environment created by multiple microvibration sources

“…the effective masses corresponding to the modal participation factors have to sum up to the total mass of the spacecraft after each randomisation), but gives the advantage of obtaining more reliable predictions, as it will be shown in section 2.3. In addition the paper illustrates a semi-empirical method to couple multiple sources of microvibrations (which are notoriously difficult to model appropriately [36,37]) with the spacecraft structure with the overall purpose to obtain predictions that envelope the actual response. The method also applies to non-microvibration implementations, but it is of particular interest in this field because of the mid-frequency being an issue when microvibration sources are acting.…”

Modelling the effect of electrical harness on microvibration response of structures

“…The research has focused on many aspects related to microvibrations, starting with the sources [7,8], and throughout the years various methodologies have been proposed for their modelling and control [9][10][11][12], e.g., simulating the interface between sources and spacecraft structures and predicting payload pointing errors [13,14]. Among the difficulties related to microvibrations, one of the main ones is their analysis, having to deal with extremely low amplitudes (µg) and a bandwidth that goes up to several hundred Hz.…”