Multirate LQG AO control

• Type: Article in International Conference Proceedings Book
• Date: 2008

Authors

Raynaud, HF (Author) Other; Kulcsar, C (Author) Other; Da Silva, CC (Author) Other; Conan, JM (Author) Other

Conference proceedings International

Title: ADAPTIVE OPTICS SYSTEMS, PTS 1-3

Adaptive Optics Systems

Marseille, 23 June 2008 through 26 June 2008

Indexing

Scopus - 7 Citations

Other information

Authenticus ID: P-009-EA5

DOI: 10.1117/12.789231

Abstract (EN): All thing being equal, increasing the sampling rate of a computer-controlled feedback loop extends its effective bandwidth, and thus the achievable performance in terms of disturbance ejection. This applies to AO systems, where deformable mirror's (DM) control voltages are omputed from wavefront sensor's (WFS) measurements. However, faster sampling, i.e. shorter xposure time for the WFS's CCD, results (especially for low-flux astronomical applications) n higher measurement noise, thereby degrading overall performance. A way to circumvent this imitation is to increase only the DM's control rate. However, standard integral AO control s inherently ill-suited for such multirate mode, because integrators require an uninterrupted easurement stream to maintain closed-loop stability. On the other hand, Linear Quadratic aussian (LQG) AO control, where DM controls are computed from explicit predictions of future alues of the turbulent phase provided by a Kalman filter, can be easily adapted to multirate onfigurations where the WFS sampling period is a multiple of the DM's one, provided that a tochastic model of the turbulent phase at the fast (DM) rate is available. The Kalman filter, between two successive measurements, operates in (observer) open-loop mode, with predictions pdated by extrapolating current trends in the turbulent phase's trajectory. Thus, while imple vector-valued AR(1) turbulence models are sufficient for single-rate LQG AO loops, more omplex stochastic models are likely to be needed to achieve good performance in multirate onfigurations.

Language: English

Type (Professor's evaluation): Scientific