26 June 2017 Removing damped sinusoidal vibrations in adaptive optics systems using a DFT-based estimation method
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Abstract
The problem of a vibrations rejection in adaptive optics systems is still present in publications. These undesirable signals emerge because of shaking the system structure, the tracking process, etc., and they usually are damped sinusoidal signals. There are some mechanical solutions to reduce the signals but they are not very effective. One of software solutions are very popular adaptive methods. An AVC (Adaptive Vibration Cancellation) method has been presented and developed in recent years. The method is based on the estimation of three vibrations parameters and values of frequency, amplitude and phase are essential to produce and adjust a proper signal to reduce or eliminate vibrations signals. This paper presents a fast (below 10 ms) and accurate estimation method of frequency, amplitude and phase of a multifrequency signal that can be used in the AVC method to increase the AO system performance. The method accuracy depends on several parameters: CiR – number of signal periods in a measurement window, N – number of samples in the FFT procedure, H – time window order, SNR, THD, b – number of A/D converter bits in a real time system, γ – the damping ratio of the tested signal, φ – the phase of the tested signal. Systematic errors increase when N, CiR, H decrease and when γ increases. The value of systematic error for γ = 0.1%, CiR = 1.1 and N = 32 is approximately 10^-4 Hz/Hz. This paper focuses on systematic errors of and effect of the signal phase and values of γ on the results.
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Dariusz Kania, "Removing damped sinusoidal vibrations in adaptive optics systems using a DFT-based estimation method", Proc. SPIE 10330, Modeling Aspects in Optical Metrology VI, 1033020 (26 June 2017); doi: 10.1117/12.2275598; https://doi.org/10.1117/12.2275598
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