Vibration suppression for the Gemini Planet Imager

Maly, Joseph R.; Erickson, Darren; Pargett, Timothy J.

doi:10.1117/12.857699

Cited by 14 publications

(6 citation statements)

References 4 publications

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“…Therefore, the telescope control system is a crucial part of the long-distance laser communication system or quantum communication system. One of the main challenges of the telescope control system is to suppress the structural vibrations, because they destroy the optical path from the main mirror to the focus plane and make it hard to reach its resolution limit [7,8]. The frame structure of the telescope is so huge that its enormous inertia limits the driving bandwidth, which means it cannot effectively reject the vibrations.…”

Section: Introductionmentioning

confidence: 99%

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The Frequency-Domain Fusion Virtual Multi-Loop Feedback Control System with Measured Disturbance Feedforward Method in Telescopes

et al. 2019

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In the optical telescope, the stable precision of the optical path is affected by the structural vibrations. The image sensor with time delay and the micro electro-mechanical system (MEMS) accelerometer with massive drift limit the disturbance suppression performance of the closed loops. The current control methods cannot reject sufficiently vibrations due to the deficiency of the sensors, causality, and stability restrictions. In this study, the frequency-domain fusion virtual multi-loop feedback control system with measured disturbance feedforward method is proposed to suppress more structural vibrations. In spite of the deficiency of the sensors, we propose the frequency-domain fusion virtual gyroscopes (VGYR) to measure extra velocity of the system. The VGYR is estimated from the MEMS accelerometer with drift and corrected by the image sensor, and it replaces the fiber-optical gyroscopes (FOG) on the fast-stable platform because the weight of FOG is not negligible. To suppress more vibrations, the VGYR and the replaced FOG are utilized to build the virtual multi-loop feedback control system with measured disturbance feedforward, because it is not limited by the causality and stability restrictions. Therefore, the proposed method with causal ideal compensator can effectively improve stable precision and suppress much more structural vibrations in the wider frequency range. Detailed comparative experimental results adequately illustrate the advantages and effectiveness of this method.

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Section: Introductionmentioning

confidence: 99%

“…The limited sampling rate and time delay of the CCD limit obtaining a higher tracking bandwidth [9]. Thus, the conventional feedback control loop cannot effectively counteract the structural vibrations [7,10]. Therefore, some new methods have been proposed.…”

Section: Introductionmentioning

confidence: 99%

The Frequency-Domain Fusion Virtual Multi-Loop Feedback Control System with Measured Disturbance Feedforward Method in Telescopes

et al. 2019

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“…As AO systems become better at correcting the atmospheric turbulence, other factors such as vibrations in the instruments and the telescope itself become increasingly important to gain the next step in performance. This is especially true for exoplanet AO systems where the residual wavefront error is very low, but it might also impact significantly the performance of other AO systems [1][2][3][4][5].…”

Section: Introductionmentioning

confidence: 99%

Comparison of vibration mitigation controllers for adaptive optics systems

et al. 2012

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Vibrations are detrimental to the performance of modern adaptive optics (AO) systems. In this paper, we describe new methods tested to mitigate the vibrations encountered in some of the instruments of the Gemini South telescope. By implementing a spectral analysis of the slope measurements from several wavefront sensors and an imager, we can determine the frequencies and magnitude of these vibrations. We found a persistent vibration at 55 Hz with others occurring occasionally at 14 and 100 Hz. Two types of AO controllers were designed and implemented, Kalman and H∞, in the multiconjugate AO tip-tilt loop. The first results show a similar performance for these advanced controllers and a clear improvement in vibration rejection and overall performance over the classical integrator scheme. It is shown that the reduction in the standard deviation of the residual slopes (as measured by wavefront sensors) is highly dependent on turbulence, wind speed, and vibration conditions, ranging--in terms of slopes RMS value--from an almost negligible reduction for high speed wind to a factor of 5 for a combination of low wind and strong vibrations.

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“…As AO systems become better at correcting the atmospheric turbulence, other factors such as vibrations in the instruments and the telescope itself become increasingly important to gain the next step in performance. This is especially true for exo-planet AO systems where the residual wavefront error is very low, but it might also impact significantly the performance of other AO systems [1][2][3][4][5] .…”

Section: Introductionmentioning

confidence: 99%

Design of frequency-based controllers for vibration mitigation at the Gemini-South telescope

et al. 2012

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Reduction of tip and tilt vibrations at the Gemini South MCAO System (GeMS) is addressed in this paper. A frequency framework for the synthesis of controllers is described, with particular emphasis on the search for better closed-loop performances by minimizing a H 2 norm of the tilt residuals. Previous results have shown that modeling the turbulence via identification tools using standard AR or Laplace representations can lead to non-optimal solutions, resulting in excessive rejection of certain frequencies or an unbalanced residual spectrum due to poor modeling of vibrations. In this novel approach we reconstruct the open loop slopes (pseudo-open-loop) from on-sky data and then perform a fine tuning of the controller by finding the parameters that minimize the variance of residuals during a sequence of closed-loop runs with increasing controller complexity. Although the method is not optimal, it effectively rejects the main vibrations in the loop and it also improves the overall performance of the system. The method is compared to two standard integrators: one with fixed gain and the other with optimized integral gain. Results show substantial improvements of this new method when compared to the classical integrator.

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Vibration suppression for the Gemini Planet Imager

Cited by 14 publications

References 4 publications

The Frequency-Domain Fusion Virtual Multi-Loop Feedback Control System with Measured Disturbance Feedforward Method in Telescopes

The Frequency-Domain Fusion Virtual Multi-Loop Feedback Control System with Measured Disturbance Feedforward Method in Telescopes

Comparison of vibration mitigation controllers for adaptive optics systems

Design of frequency-based controllers for vibration mitigation at the Gemini-South telescope

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