MacMynowski, Douglas G. and Colavita, M. Mark and Skidmore, Warren and Vogiatzis, Konstantinos (2010) Primary mirror dynamic disturbance models for TMT: vibration and wind. In: Modeling, Systems Engineering, and Project Management for Astronomy IV. Proceedings of SPIE (7738). Society of Photo-optical Instrumentation Engineers (SPIE) , Bellingham, WA, Art. No. 77380E. ISBN 978-0-81948-228-0 http://resolver.caltech.edu/CaltechAUTHORS:20110324-124026578
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The principal dynamic disturbances acting on a telescope segmented primary mirror are unsteady wind pressure (turbulence) and narrowband vibration from rotating equipment. Understanding these disturbances is essential for the design of the segment support assembly (SSA), segment actuators, and primary mirror control system (M1CS). The wind disturbance is relatively low frequency, and is partially compensated by M1CS; the response depends on the control bandwidth and the quasi-static stiffness of the actuator and SSA. Equipment vibration is at frequencies higher than the M1CS bandwidth; the response depends on segment damping, and the proximity of segment support resonances to dominant vibration tones. We present here both disturbance models and parametric response. Wind modeling is informed by CFD and based on propagation of a von Karman pressure screen. The vibration model is informed by analysis of accelerometer and adaptive optics data from Keck. This information is extrapolated to TMT and applied to the telescope structural model to understand the response dependence on actuator design parameters in particular. Whether the vibration response or the wind response is larger depends on these design choices; "soft" (e.g. voice-coil) actuators provide better vibration reduction but require high servo bandwidth for wind rejection, while "hard" (e.g. piezo-electric) actuators provide good wind rejection but require damping to avoid excessive vibration transmission to the primary mirror segments. The results for both nominal and worst-case disturbances and design parameters are incorporated into the TMT actuator performance assessment.
|Item Type:||Book Section|
|Additional Information:||© 2010 SPIE. The finite element models used herein for the telescope structure and the primary segment assembly were developed by DSL and by HYTEC Inc., respectively. Actuator parameters used here are based on prototypes from Marjan Research and the Jet Propulsion Laboratory. The contributions of these organizations are gratefully acknowledged. The TMT Project gratefully acknowledges the support of the TMT partner institutions. They are the Association of Canadian Universities for Research in Astronomy (ACURA), the California Institute of Technology and the University of California. This work was supported as well by the Gordon and Betty Moore Foundation, the Canada Foundation for Innovation, the Ontario Ministry of Research and Innovation, the National Research Council of Canada, the Natural Sciences and Engineering Research Council of Canada, the British Columbia Knowledge Development Fund, the Association of Universities for Research in Astronomy (AURA) and the U.S. National Science Foundation. A portion of the research in this paper was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.|
|Official Citation:||Douglas G. MacMynowski, M. Mark Colavita, Warren Skidmore and Konstantinos Vogiatzis, "Primary mirror dynamic disturbance models for TMT: vibration and wind", Proc. SPIE 7738, 77380E (2010); doi:10.1117/12.857395|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||18 Apr 2011 16:43|
|Last Modified:||18 Apr 2011 16:43|
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