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

Abstract

In the recent years, driven by the increasingly stringent stability requirements imposed by some satellites' payloads (e.g. the new generation of optical instruments), the issue of accurate on-board spacecraft microvibration modelling has attracted signicant interest from engineers and scientists. This paper investigates the microvibrationinduced phenomenon on a cantilever congured reaction wheel assembly including sub and higher harmonic amplications due to modal resonances and broadband noise. A mathematical model of the reaction wheel assembly is developed and validated against experimental test results. The model is capable to represent each conguration in which the reaction wheel assembly will operate whether it is hard-mounted on a dynamometric platform or suspended free-free. The outcomes of this analysis are used to establish a novel methodology to retrieve the dynamic mass of the reaction wheel assembly in its operative range of speeds. An alternative measurement procedure has been developed for this purpose, showing to produce good estimates over a wide range of frequency using a less complex test campaign compared to typical dynamic mass setups. Furthermore, the gyroscopic eect inuence in the reaction wheel assembly response is thoroughly examined both analytically and experimentally. Finally, to what extent the noise aects the convergence of the novel approach is investigated.

Effect of Reaction Wheel Imbalances on Attitude and Stabilization Accuracy

“…The model is rather detailed but the influence of RW imbalances on satellite attitude dynamics is not investigated. Similar results supplemented by experiments are obtained in [16][17][18][19][20]. In the study of [21], the numerical study of the imbalance effect is presented.…”

“…As one can see, both dynamic and static imbalances lead to the additional terms in the right parts of Equations ( 15) and (20), which do not depend on satellite state vector components for the first order approximation, so the total stabilization accuracy is the sum of Equations ( 17) and (21). )…”

The effect of assembly and static unbalance on reaction wheel assembly bearing harmonics

“…Low-level mechanical disturbances also known as microvibrations have become an increasingly important aspect in the design of scientific satellites. Microvibrations usually have an amplitude in the range of μg's and typically occur up to 1 kHz [1,2]. These disturbances are especially concerning for the design of satellites used in earth observation and space astronomy as they can cause poor pointing stability and imaging, leading to adverse effects on the satellites' instrumentation [3][4][5].…”

A semiempirical methodology to characterise a family of microvibration sources

“…In this framework, the safety factor associated to disturbances produced by RWs plays an important role; literature shows that vibrations produced by these devices are among the most significant on board the spacecraft, [23,24]. This justifies the great amount of research on RWs, in terms of mathematical models, [25,26], experimental validation and characterisation, [27,28].…”