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Proceedings Paper

Collision-free motion planning for fiber positioner robots: discretization of velocity profiles
Author(s): Laleh Makarem; Jean-Paul Kneib; Denis Gillet; Hannes Bleuler; Mohamed Bouri; Philippe Hörler; Laurent Jenni; Francisco Prada; Justo Sánchez
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Paper Abstract

The next generation of large-scale spectroscopic survey experiments such as DESI, will use thousands of fiber positioner robots packed on a focal plate. In order to maximize the observing time with this robotic system we need to move in parallel the fiber-ends of all positioners from the previous to the next target coordinates. Direct trajectories are not feasible due to collision risks that could undeniably damage the robots and impact the survey operation and performance. We have previously developed a motion planning method based on a novel decentralized navigation function for collision-free coordination of fiber positioners. The navigation function takes into account the configuration of positioners as well as their envelope constraints. The motion planning scheme has linear complexity and short motion duration (2.5 seconds with the maximum speed of 30 rpm for the positioner), which is independent of the number of positioners. These two key advantages of the decentralization designate the method as a promising solution for the collision-free motion-planning problem in the next-generation of fiber-fed spectrographs. In a framework where a centralized computer communicates with the positioner robots, communication overhead can be reduced significantly by using velocity profiles consisting of a few bits only. We present here the discretization of velocity profiles to ensure the feasibility of a real-time coordination for a large number of positioners. The modified motion planning method that generates piecewise linearized position profiles guarantees collision-free trajectories for all the robots. The velocity profiles fit few bits at the expense of higher computational costs.

Paper Details

Date Published: 18 July 2014
PDF: 10 pages
Proc. SPIE 9152, Software and Cyberinfrastructure for Astronomy III, 91520Q (18 July 2014); doi: 10.1117/12.2055185
Show Author Affiliations
Laleh Makarem, Ecole Polytechnique Fédérale de Lausanne (Switzerland)
Jean-Paul Kneib, Ecole Polytechnique Fédérale de Lausanne (Switzerland)
Lab. d'Astrophysique de Marseille, CNRS, Aix-Marseille Univ. (France)
Denis Gillet, Ecole Polytechnique Fédérale de Lausanne (Switzerland)
Hannes Bleuler, Ecole Polytechnique Fédérale de Lausanne (Switzerland)
Mohamed Bouri, Ecole Polytechnique Fédérale de Lausanne (Switzerland)
Philippe Hörler, Ecole Polytechnique Fédérale de Lausanne (Switzerland)
Laurent Jenni, Ecole Polytechnique Fédérale de Lausanne (Switzerland)
Francisco Prada, Instituto de Astrofísica de Andalucía (Spain)
Univ. Autónoma de Madrid (Spain)
Justo Sánchez, Univ. Autónoma de Madrid (Spain)

Published in SPIE Proceedings Vol. 9152:
Software and Cyberinfrastructure for Astronomy III
Gianluca Chiozzi; Nicole M. Radziwill, Editor(s)

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