Dynamic analysis of the activley controlled segmented mirror of the W. M. Keck ten-meter telescope

Aubrun, Jean-Noel; Lorell, Kenneth R.; Mast, Terry S.; Nelson, Jerry

doi:10.1109/mcs.1987.1105386

Cited by 34 publications

(11 citation statements)

References 5 publications

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“…The inset shows the principal loop gain, no larger than 0.25 near structural resonances. Illustration of wind modeling process, and typical M1 response to 1 m/s wind, in nm, from [2]. Representative pressure screen (left), mirror response without control (center), and with 1 Hz M1CS control bandwidth (right); focus-mode bandwidth here is 0.1 Hz.…”

Section: Dynamic Performance 41 Windmentioning

confidence: 99%

Control system modeling for the Thirty Meter Telescope primary mirror

MacMynowski

Thompson

Shelton

et al. 2011

Integrated Modeling of Complex Optomechanical Systems

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The Thirty Meter Telescope primary mirror is composed of 492 segments that are controlled to high precision in the presence of wind and vibration disturbances, despite the interaction with structural dynamics. The higher bandwidth and larger number of segments compared with the Keck telescopes requires greater attention to modeling to ensure success. We focus here on the development and validation of a suite of quasi-static and dynamic modeling tools required to support the design process, including robustness verification, performance estimation, and requirements flowdown. Models are used to predict the dynamic response due to wind and vibration disturbances, estimate achievable bandwidth in the presence of control-structure-interaction (CSI) and uncertainty in the interaction matrix, and simulate and analyze control algorithms and strategies, e.g. for control of focus-mode, and sensor calibration. Representative results illustrate TMT performance scaling with parameters, but the emphasis is on the modeling framework itself.

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Section: Dynamic Performance 41 Windmentioning

confidence: 99%

Control system modeling for the Thirty Meter Telescope primary mirror

MacMynowski

Thompson

Shelton

et al. 2011

Integrated Modeling of Complex Optomechanical Systems

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“…The OWL, composed of about 1000 segments, is going to be an astounding 100 meters in diameter, ten times larger and one hundred times more sensitive than the Keck [3] !…”

Section: Telescope Historymentioning

confidence: 99%

A novel calibration character study for micro-displacement actuators with segmented mirrors

et al. 2008

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Not only could the segmented mirrors synthetic aperture optical system improve the sensitivity and resolution of telescope system, but also meet the demands of NGST (next generation space telescope).In order to ensure segmented mirrors keep the same optical performance of mono-mirror, that is, the phase error less thanλ/20，each segmented mirror should have its own nano-grade high precision correcting device. In this paper, the synthetic aperture is composed of three segmented mirrors, one fixed and the other two adjustable, each of which achieved 6-DOF adjustment by three micro-displacement actuators and the characters of the actuators are researched. For the purpose of nano-grade positioning, PZT is used as the micro-displacement actuator. In our research, the jointing process is rough-tuned by mechanical structure before fine-tuned by PZT, so there's no need for the PZT to work in the full range. In order to provide basic support for nano-grade phase error correction, it is very necessary to calibrate the relationship between the elongation distribution of each PZT and the regulating voltage for each actuator, in its own scope of work with small step, because of the hysteresis of PZT.

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“…The wind-induced primary mirror response for Keck was predicted to be 44 nm rms 11 . While the Keck worst-case wind vibration did not exceed the error budget allocated to it, the worst-case wind vibration of the primary mirror for CELT may require attention.…”

Section: Naturalmentioning

confidence: 99%

“…The resonance of a segment on its support for Keck is roughly 30 Hz, and this of course varies slightly between segments, and varies with orientation of the telescope. The overall structural model for Keck, including both segment dynamics and the mirror cell, has resonances as low as 10 Hz, and the interaction with these mirror cell modes limited the achievable bandwidth at Keck to about 0.5 Hz or less to avoid instability 11 . Because of the difficulty of adding passive damping at the low vibration levels encountered, many of the modes on Keck have an estimated quality factor Q ≈ 100.…”

Section: Bandwidthmentioning

confidence: 99%

Active control issues for the California Extremely Large Telescope

MacMartin

Mast

Cruz

et al. 2001

AIAA Guidance, Navigation, and Control Conference and Exhibit

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A team of researchers from the University of California and Caltech are investigating the feasibility of building a 30 meter diameter segmented mirror telescope, following the design approach pioneered by the 36-segment Keck telescopes. The current design concept for the California Extremely Large Telescope (CELT) has 1080 segments forming the primary mirror, with the piston, tip, and tilt of each segment controlled by three actuators. The control approach must correct for gravity-and temperature-induced deformations of the mirror support structure, and potentially wind and seismic disturbances, with a cost effective design. We discuss some of the active control issues, including requirements (optical and cost), estimates of the disturbances, actuator options, and control analysis. Several candidate actuator technologies appear capable of meeting the technical and cost requirements, and preliminary error propagation analyses indicate that the optical error budget can likely be met. Additional issues being addressed are identified.

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Dynamic analysis of the activley controlled segmented mirror of the W. M. Keck ten-meter telescope

Cited by 34 publications

References 5 publications

Control system modeling for the Thirty Meter Telescope primary mirror

Control system modeling for the Thirty Meter Telescope primary mirror

A novel calibration character study for micro-displacement actuators with segmented mirrors

Active control issues for the California Extremely Large Telescope

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