Collision avoidance in next-generation fiber positioner robotic systems for large survey spectrographs

¹ Coordination and Interaction Systems Group (REACT), École Polytechnique Fédérale de Lausanne (EPFL), Switzerland
e-mail: laleh.makarem@epfl.ch
² Laboratory of Astrophysics (LASTRO), École Polytechnique Fédérale de Lausanne (EPFL), Observatoire de Sauverny, 1290 Versoix, Switzerland
³ Aix-Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, 13388 Marseille, France
⁴ Laboratory of Robotic Systems (LSRO), École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
⁵ Instituto de Astrofísica de Andalucía (CSIC), 18008 Granada, Spain
⁶ Instituto de Física Teórica, (UAM/CSIC), Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain

Received: 5 December 2013
Accepted: 14 February 2014

Abstract

Some of the next-generation massive spectroscopic survey projects plan to use thousands of fiber positioner robots packed at a focal plane to quickly move the fiber ends in parallel from the previous to the next target points. The most direct trajectories are prone to collision that could damage the robots and have an impact on the survey operation. We thus present here 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 the actuator constraints. We provide details of the proof of convergence and collision avoidance. Decentralization results in linear complexity for the motion planning as well as no dependence of motion duration on the number of positioners. Therefore, the coordination method is scalable for large-scale spectrograph robots. The short in-motion duration of positioner robots will thus allow the time dedicated for observation to be maximized.