@inproceedings{5e0e2add055e44e7a2f334a88ebea4ca,
title = "A Starbug's life: a material trade study using fatigue life criteria for high-altitude robotic fibre positioning instruments",
abstract = "Starbugs are self-motile fibre optic positioning robots developed by AAO-MQ. The MANIFEST (MANy Instrument FibrE SysTem) is a facility class Instrument which will operate up to 900 Starbugs on the Giant Magellan Telescope (GMT). The FOBOS (Fibre-Optic Broadband Optical Spectrograph) Fibre Positioner is a facility class Instrument which will operate up to 1800 Starbugs on the Keck Telescope. The Starbugs deliver an optical payload to the location of an astronomical object on the telescope focal plane. The Starbugs are made from a pair of concentric Piezoceramic Tubes (PZT), and a high-voltage waveform is applied to the PZT to create an actuation. Staging of the waveform creates successive microsteps, on the order of 3-20 μm each, at a driven frequency of 100Hz. The Starbugs are adhered to the Glass Field Plate (GFP) using an ancillary vacuum system. The Starbugs have an airtight vacuum sealing component between the PZT and the GFP, called Slippers, which serve as a traction surface against the polished GFP. The Slippers set the science fibre focus offset, which has functional requirements that trace to Observatory level requirements. The Slipper components are subject to non-zero centred fully reversed fatigue loading due to the combined load case of the vacuum induced compression and the shear load of the PZT actuation as the Starbug completes the step. The contact interface between the Slipper and the GFP is subject to surface fatigue and functions as a sacrificial wear surface to ensure the longevity of both the PZT and the optical payload. The fatigue life behaviour of the Slipper, with particular interest on this interface, was defined using industry standard methods and informed the trade study to select the appropriate material for the Slippers to survive a nominal period on-sky (fatigue life). The trade study terms were vacuum sealing ability as a function of mechanical hardness versus fatigue life (108 cycles). Several suitable materials were identified and will be physically prototyped, with results reported in this manuscript.",
keywords = "Fibre positioning system, Goodman Criteria, MTTF, RUL, fatigue life cycle, fibre robots, surface fatigue",
author = "O'Brien, {Ellie G.} and Jon Lawrence and Lacombe, {Celestina S.} and Michael Thomakos and Michael Goodwin and James Gilbert and Slavko Mali and Rolf Muller and Nirmala Kunwar and Jahanzeb Zahoor and Lew Waller and Tony Farrell",
note = "Publisher Copyright: {\textcopyright} 2022 SPIE.; Ground-Based and Airborne Telescopes IX 2022 ; Conference date: 17-07-2022 Through 22-07-2022",
year = "2022",
doi = "10.1117/12.2629152",
language = "English",
series = "Proceedings of SPIE - The International Society for Optical Engineering",
publisher = "SPIE",
editor = "Marshall, {Heather K.} and Jason Spyromilio and Tomonori Usuda",
booktitle = "Ground-Based and Airborne Telescopes IX",
address = "United States",
}