SDSS-V Algorithms: Fast, Collision-free Trajectory Planning for Heavily Overlapping Robotic Fiber Positioners (original) (raw)
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Astronomy & Astrophysics, 2014
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.
Collision avoidance in next-generation fiber positioner robotic system for large survey spectrograph
Astronomy & Astrophysics, 2014
Some of the next generation massive spectroscopic survey projects, such as DESI and PFS, plan to use thousands of fiber positioner robots packed at a focal plane to quickly move in parallel the fiber-ends from the previous to the next target points. The most direct trajectories are prone to collision that could damage the robots and impact 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 for the proof of convergence and collision avoidance. Decentralization results in linear complexity for the motion planning as well as dependency of motion duration with respect to the number of positioners. Therefore the coordination method is scalable for large-scale spectrograph robots. The short in-motion duration of positioner robots (∼2.5 seconds using typical actuator constraints), will thus allow the time dedicated for observation to be maximized.
Collision-free motion planning for fiber positioner robots: discretization of velocity profiles
Software and Cyberinfrastructure for Astronomy III, 2014
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.
March of the Starbugs: Configuring Fibre-bearing Robots on the UK-Schmidt Optical Plane
The TAIPAN instrument, currently being developed for the Australian Astronomical Observatory's UK Schmidt telescope at Siding Spring Observatory, makes use of the AAO's Starbug technology to deploy 150 science fibres to target positions on the optical plane. This paper describes the software system for controlling and deploying the fibre-bearing Starbug robots. The TAIPAN software is responsible for allocating each Starbug to its next target position based on its current position and the distribution of targets, finding a collision-free path for each Starbug, and then simultaneously controlling the Starbug hardware in a closed loop, with a metrology camera used to determine the position of each Starbug in the field during reconfiguration. The software is written in C++ and Java and employs a DRAMA middleware layer (Farrell et al. 1995).
Roadmap search based motion planning for MIRADAS probe arms
Journal of Astronomical Telescopes, Instruments, and Systems, 2018
MIRADAS is a near-infrared multiobject echelle spectrograph operating at spectral resolution R ¼ 20;000 over the 1 to 2.5 μm bandpass for Gran Telescopio Canarias. It possesses a multiplexing system with 12 cryogenic robotic probe arms, each capable of independently selecting a user-defined target in the instrument field of view. The arms are distributed around a circular bench, becoming a very packed workspace when all of them are in simultaneous operation. Therefore, their motions have to be carefully coordinated. We propose here a motion planning method for the MIRADAS probe arms. Our offline algorithm relies on roadmaps comprising alternative paths, which are discretized in a state-time space. The determination of collision-free trajectories in such space is achieved by means of a graph-search technique. The approach considers the constraints imposed by the particular architecture of the probe arms as well as the limitations of the commercial off-the-shelf motor controllers used in the mechanical design. We test our solution with real science targets and a typical MIRADAS scenario presenting some instances of the two identified collision conflicts that can arise between any pair of probe arms. Experiments show the method is versatile enough to compute trajectories fulfilling the requirements.
Journal of Intelligent & Robotic Systems, 2018
The use of multiple Autonomous Industrial Robots (AIRs) as opposed to a single AIR to perform fiber placement brings about many challenges which have not been addressed by researchers. These challenges include optimal division and allocation of the work and performing path planning in a coordinated manner while considering the requirements and constraints that are unique to the fiber placement task. To solve these challenges, a two-stage approach is proposed in this paper. The first stage considers multiple objectives to optimally allocate each AIR with surface areas, while the second stage aims to generate coordinated paths for the AIRs. Within each stage, mathematical models are developed with several unique objectives and constraints that are specific to the multi-AIR collaborative fiber placement. Several case studies are presented to validate the approach and the proposed mathematical models. Comparison studies using a different number of AIRs and variations of the developed mathematical models are also presented.
An 8-mm diameter fibre robot positioner for massive spectroscopy surveys
Monthly Notices of the Royal Astronomical Society, 2015
Massive spectroscopic survey are becoming trendy in astrophysics and cosmology, as they can address new fundamental knowledge such as understanding the formation of the Milky Way and probing the nature of the mysterious dark energy. To enable massive spectroscopic surveys, new technology has been developed to place thousands of optical fibres at a given position on a focal plane. This technology needs to be: (1) accurate, with micrometer positional accuracy; (2) fast to minimize overhead; (3) robust to minimize failure; and (4) low cost. In this paper, we present the development, properties, and performance of a new single 8-mm in diameter fibre positioner robot, using two 4-mm DC-brushless gearmotors, that allows us to achieve accuracies up to 0.07 arcsec (5 µm). This device has been developed in the context of the Dark Energy Spectroscopic Instrument. 1