Dynamic analysis of the Green Bank Telescope structure and servo system

Trupti M. Ranka; Mario Garcia-Sanz; Arthur H. Symmes; John M. Ford; Timothy L. Weadon

doi:10.1117/1.JATIS.2.1.014001

7 January 2016 Dynamic analysis of the Green Bank Telescope structure and servo system

Trupti M. Ranka, Mario Garcia-Sanz, Arthur H. Symmes, John M. Ford, Timothy L. Weadon

Journal of Astronomical Telescopes, Instruments, and Systems, Vol. 2, Issue 1, 014001 (January 2016). https://doi.org/10.1117/1.JATIS.2.1.014001

Abstract

The Green Bank Telescope is a 100-m aperture single-dish radio telescope. For high-frequency observations (above 100 GHz), it needs a tracking error below 1.5 arc sec rms. The present system has a tracking error of 1 arc sec rms for very low wind speeds of ≤ 1 m/s, which increases well above 1.5 arc sec for wind speeds above 4 m/s. Hence, improvements in the servo control system are needed to achieve pointing accuracy goals for high-frequency observations. As a first step toward this goal, it is necessary to evaluate the dynamic response of the present servo system and the telescope, which forms a large flexible structure. We derive the model of the telescope dynamics using finite element analysis data. This model is further tuned and validated using system identification experiments performed on the telescope. A reduced model is developed for controller design by using modes with the highest Hankel singular value for frequencies up to 2 Hz. We quantify the uncertainty in azimuth axis dynamics with a change in elevation angle by varying the zeros of the model. We discuss the effects of transient response, wind disturbances, and azimuth track joint disturbances on telescope tracking performance.

Citation Download Citation

Trupti M. Ranka, Mario Garcia-Sanz, Arthur H. Symmes, John M. Ford, and Timothy L. Weadon "Dynamic analysis of the Green Bank Telescope structure and servo system," Journal of Astronomical Telescopes, Instruments, and Systems 2(1), 014001 (7 January 2016). https://doi.org/10.1117/1.JATIS.2.1.014001

Published: 7 January 2016

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