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21 July 2010 LINC-NIRVANA piston control elements
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We review the status of hardware developments related to the Linc-Nirvana optical path difference (OPD) control. The status of our telescope vibration measurements is given. We present the design concept of a feed-forward loop to damp the impact of telescope mirror vibrations on the OPD seen by Linc-Nirvana. At the focus of the article is a description of the actuator of the OPD control loop. The weight and vibration optimized construction of this actuator (aka piston mirror) and its mount has a complex dynamical behavior, which prevents classical PI feedback control from delivering fast and precise motion of the mirror surface. Therefore, an H-; optimized control strategy will be applied, custom designed for the piston mirror. The effort of realizing a custom controller on a DSP to drive the piezo is balanced by the outlook of achieving more than 5x faster servo bandwidths. The laboratory set-up to identify the system, and verify the closed loop control performance is presented. Our goal is to achieve 30 Hz closed-loop control bandwidth at a precision of 30 nm.
© (2010) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Mario Brix, Jörg-Uwe Pott, Thomas Bertram, Steffen Rost, Jose Luis Borelli, Thomas M. Herbst, Martin Kuerster, and Ralf-Rainer Rohloff "LINC-NIRVANA piston control elements", Proc. SPIE 7734, Optical and Infrared Interferometry II, 77341U (21 July 2010); doi: 10.1117/12.857403;


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