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22 July 2014 Accelerometer-based position reconstruction for the feedforward compensation of fast telescope vibrations in the E-ELT/MICADO
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The amount of image motion caused by vibrations of the telescope structure increases with the size of the telescope. Compensating the effects of structural vibrations in the optical path will be a major design question for adaptive optics (AO) systems in future extremely large telescopes like the E-ELT. A promising control system architecture is the recently developed Dual-Loop-Approach, with a feedforward loop based on accelerometer measurements, compensating for the vibrations in addition to the classical AO feedback loop compensating for atmospheric turbulences. We present our efforts to develop sophisticated estimation and control algorithms for this feedforward loop. The major task from a control engineering point of view is reconstructing the position of the vibrating elements from accelerometer measurements highly deteriorated by low-frequency drift and highfrequency noise. The algorithms are evaluated and compared using a realistic Tip-Tilt-Vibration laboratory test setup. Position reconstruction for a realistic 8 Hz structural resonance with an error of only 4% is achieved. Our ultimate goal is to achieve longer and more sensitive wavefront sensor (WFS) integrations by permitting a smaller bandwidth of the AO feedback loop in the E-ELT/MICADO.
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Alexander Keck, Jörg-Uwe Pott, and Oliver Sawodny "Accelerometer-based position reconstruction for the feedforward compensation of fast telescope vibrations in the E-ELT/MICADO", Proc. SPIE 9145, Ground-based and Airborne Telescopes V, 91454H (22 July 2014); doi: 10.1117/12.2053769;

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