ESA GNC Conference Papers Repository

The characterization and mitigation of micro-vibration perturbations generated by on-board mechanical devices are investigated. These jitter type of perturbations when not isolated are amplied by the satellite structure and propagate towards the optical instruments leading to image distortions and blurring. Mastering the root cause of micro-vibrations is a key issue for scientic and observatory space missions which require ultimate pointing accuracy over a wide spectral range. By using formal and experimental methods, the impact of these perturbations can be efficiently predicted and attenuated. Experimental design results of a mixed active-passive control strategy for the multi-harmonics micro-vibrations mitigation of flexible space structures are presented. An elastomer-based passive isolation stage is considered in order to reject broadband high frequency disturbances. For the low frequency range an active micro-vibration attenuation scheme has been adopted and illustrated using two control strategies. The first strategy uses a demodulated measurement signal for exact plant disturbance cancellation. The second approach employs an experimentally determined model dynamics including measured uncertainty bounds re reflecting all potential plant variations. This model is used as basis for a -synthesis control design that allows for systematic handling of the performance and robustness objectives. The plant model dynamics, derived using an ARMAX-system identification procedure are based on data collected from a reaction wheel test bench that includes all actuator and sensor dynamics. Both control solutions have been efficiently implemented on a hardware in the loop test setup. Experimental performance assessment results demonstrate in perfectly well known conditions the efectiveness of both active/passive isolation strategies. However in o-nominal conditions, the robust control solution evidences shows no signs of performance degradation in the face of plant variations and variable disturbance frequencies. This suggests that for future high stability missions a more practical candidate active isolation solution would go along the robust control approach.