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Proceedings Paper

Design and development of a long-travel positioning actuator and tandem constant force actuator safety system for the Hobby Eberly Telescope wide-field upgrade
Author(s): Nicholas T. Mollison; Jason R. Mock; Ian M. Soukup; Timothy A. Beets; John M. Good; Joseph H. Beno; Herman J. Kriel; Sarah E. Hinze; Douglas R. Wardell; James T. Heisler
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Paper Abstract

The Wide Field Upgrade presents a five-fold increase in mass for the Hobby-Eberly Telescope's* tracker system. The design of the Hobby-Eberly Telescope places the Prime Focus Instrument Package (PFIP) at a thirty-five degree angle from horizontal. The PFIP and its associated hardware have historically been positioned along this uphill axis (referred to as the telescope's Y-axis) by a single screw-type actuator. Several factors, including increased payload mass and design for minimal light obscuration, have led to the design of a new and novel configuration for the Y-axis screw-drive as part of the tracker system upgrade. Typical screw-drive designs in this load and travel class (approximately 50 kilonewtons traveling a distance of 4 meters) utilize a stationary screw with the payload translating with the moving nut component. The new configuration employs a stationary nut and translating roller screw affixed to the moving payload, resulting in a unique drive system design. Additionally, a second cable-actuated servo drive (adapted from a system currently in use on the Southern African Large Telescope) will operate in tandem with the screw-drive in order to significantly improve telescope safety through the presence of redundant load-bearing systems. Details of the mechanical design, analysis, and topology of each servo drive system are presented in this paper, along with discussion of the issues such a configuration presents in the areas of controls, operational and failure modes, and positioning accuracy. Findings and results from investigations of alternative telescope safety systems, including deformable crash barriers, are also included.

Paper Details

Date Published: 6 August 2010
PDF: 12 pages
Proc. SPIE 7733, Ground-based and Airborne Telescopes III, 773344 (6 August 2010); doi: 10.1117/12.857249
Show Author Affiliations
Nicholas T. Mollison, The Univ. of Texas at Austin (United States)
Jason R. Mock, The Univ. of Texas at Austin (United States)
Ian M. Soukup, The Univ. of Texas at Austin (United States)
Timothy A. Beets, The Univ. of Texas at Austin (United States)
John M. Good, McDonald Observatory, The Univ. of Texas at Austin (United States)
Joseph H. Beno, The Univ. of Texas at Austin (United States)
Herman J. Kriel, McDonald Observatory, The Univ. of Texas at Austin (United States)
Sarah E. Hinze, The Univ. of Texas at Austin (United States)
Douglas R. Wardell, The Univ. of Texas at Austin (United States)
James T. Heisler, The Univ. of Texas at Austin (United States)

Published in SPIE Proceedings Vol. 7733:
Ground-based and Airborne Telescopes III
Larry M. Stepp; Roberto Gilmozzi; Helen J. Hall, Editor(s)

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