Reaction wheel assembly experimental impact dynamics characterisation

Reaction wheel assemblies (RWAs) are mechanisms which allow in-orbit attitude corrections by torque application to the spacecraft. They consist of a flywheel, DC motor and housing. Due to imperfections and tolerances in the mechanical parts, such as flywheel bearings, micro-vibrations emanate as the RWA operates. A suspension system can be integrated in the wheel to isolate the satellite structure from these disturbances. However, for a soft suspension system, the launch environment can cause the flywheel to contact the housing, introducing a dynamic impact problem to be addressed. These impacts can damage the RWA bearings. A novel experimental procedure has been developed to characterise the impacts and induced bearing loads. Firstly, the complex vibro-impact dynamics are reduced to a practically tractable 1D equivalent. It is reproduced by a tailored experimental setup, which is tested on a shaker with loads representative of the launch environment. The approach underpins the development of a low-order mathematical model, capable of efficiently predicting peak shock loads.