Design of a Theta/Phi fiber positioner robot for the Sloan Digital Sky Survey V

Araújo, Ricardo; Bouri, Mohamed; Brandon, Christopher; Caseiro, Stefane; Gillet, Denis; Grossen, Loïc; Kronig, Luzius; Macktoobian, Matin; O’Brien, T. P.; Pogge, Richard W.; Tuttle, Sarah; Kneib, Jean-Paul

doi:10.1117/12.2563234

Cited by 6 publications

(6 citation statements)

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“…However, it should be noted that some brushless DC motors do possess cogging torque. Araujo et al (2020) have observed this phenomenon and noted that when powering off the motor coils, the axis might slightly move during their tests. The solution to this issue is to apply a small current into the motor coil to keep the position, causing additional thermal dissipation.…”

Section: Introductionmentioning

confidence: 94%

The Application of Permanent Magnet Synchronous Motor with Small Electrical Time Constant in Fiber Positioner

Guo,

Yang,

Yin

et al. 2024

Res. Astron. Astrophys.

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With the development of cutting-edge multi-object spectrographs, fiber positioners located in focal plane are being scaled down in size, and miniature hollow-cup Permanent Magnet motors are now being considered as a suitable replacement for Faulhaber Precistep stepper motors. However, the small electrical time constant of such coreless motors poses a challenge, as the problem of severe commutation torque ripple in a fiber positioner running a position loop has been tricky. To overcome this challenge, it is advised to increase the Pulse Width Modulation frequency as much as possible to mitigate the effects of the current fluctuation. This must be done while ensuring adequate resolution of the PWM generator. By employing a voltage Open-loop Field-oriented control based on a modulation frequency of 1MHz, the drive current only costs 25mA under a 3.3V power supply. The sine degree of phase current is immaculate, and the repeat positioning accuracy can reach 2um. Moreover, it is possible to further shrink the bill of devices and the layout area of the Printed Circuit Board, especially in size-sensitive applications. This device has been developed under the new generation of The Large Sky Area Multi-Object Fiber Spectroscopic Telescope.

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Section: Introductionmentioning

confidence: 94%

The Application of Permanent Magnet Synchronous Motor with Small Electrical Time Constant in Fiber Positioner

Guo,

Yang,

Yin

et al. 2024

Res. Astron. Astrophys.

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“…The second stage of LAMOST will involve adopting newly designed smaller RFPs and increasing the number of RFPs to 5000 (Duan et al 2022;Guo et al 2022). This conceptual design has also been adopted by projects such as the Multi-Object Optical and Near-infrared Spectrograph (MOONS; Horler et al 2018), Prime Focus Spectrograph (Sugai et al 2015), Dark Energy Spectroscopic Instrument (DESI; Fahim et al 2015;Martini et al 2018;Silber et al 2023) and the fifth generation of the Sloan Digital Sky Survey (SDSS-V; Araujo et al 2020).…”

Section: Introductionmentioning

confidence: 99%

Motion Planning for the Robotic Fiber Positioners of the Large Sky Area Multiobject Fiber Spectrocopy Telescope

Zhang,

Chen,

Wang

et al. 2024

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The Large Sky Area Multi-Object Fiber Spectroscopy Telescope (LAMOST) is one of the most effective multiobject spectroscopic instruments. Its survey efficiency is guaranteed by simultaneously positioning multiple fibers via 4000 robotic fiber positioners (RFPs). With the further updates to LAMOST, the new-generation RFPs will be smaller, and the number of RFPs will increase to 5000. The RFPs are densely packed with shared working space. Thus, they may collide with each other, leading to them damaged and reducing the survey speed. In this study, we propose a new motion planning algorithm that prevents the collision of RFPs. To simplify the collision avoidance problem, we transform the motion planning process from a dynamic one into a static one by selecting one of the RFPs in each collision pair as the waiting robot. Accordingly, we design a method for choosing the waiting robot, and use a rapidly exploring random tree to plan a collision-free path for the waiting robot. However, there may be blocks between the waiting robots and their neighbors. Therefore, we also design methods to resolve these blocks. Simulations suggest that the proposed algorithm can prevent 98.4% of the collisions. About 99.9% of the positioners can reach their targets without collisions. Although developed for LAMOST, we believe that our algorithm can also be used for other instruments with equal-arm theta-phi positioners, such as the Dark Energy Spectroscopic Instrument.

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“…The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) provides a combination of a large aperture and a large field of view. 4 The parallel controllable fiber positioning system was first realized in LAMOST. 4000 optical fiber positioners are closely distributed on the 1.75m diameter focal plate.…”

Section: Introductionmentioning

confidence: 99%

Precision control and performance of new-generation integrated fiber positioners for LAMOST

Zhang

Chen²,

Zhu³

et al. 2023

Advanced Optical Manufacturing Technologies and Applications 2022; And 2nd International Forum of Young Scientists on Advanced

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An improvement project of LAMOST will be implemented soon. To improve the observation accuracy and spectral acquisition rate, a new integrated fiber positioner was designed for the new robotic Focal Plane System. This paper designs the drive system for the integrated fiber positioner, and introduces the mechanical, electronic and software design in detail. We also built a vision measurement platform with a telecentric lenses to test the position performance. The fiber positioner positions the fiber to target by first blind positioning and multiple position corrections. After the positioner completes the first blind move, the camera takes the fiber image and calculates the offset between the actual position of the fiber from its target position. Then, the drive system controls the fiber positioner move according the offset value to correct the fiber position. We achieve the final accuracy through iterative position corrections. Experimental results show that both the drive system and the fiber positioner have reliable performance and high efficiency. With a first blind move inside of its workspace, the positioner can position the fibers with a planar precision better than 100um, the position error is less than 10um after the second correction and the RMS error is less than 3um.

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Design of a Theta/Phi fiber positioner robot for the Sloan Digital Sky Survey V

Cited by 6 publications

References 0 publications

The Application of Permanent Magnet Synchronous Motor with Small Electrical Time Constant in Fiber Positioner

The Application of Permanent Magnet Synchronous Motor with Small Electrical Time Constant in Fiber Positioner

Motion Planning for the Robotic Fiber Positioners of the Large Sky Area Multiobject Fiber Spectrocopy Telescope

Precision control and performance of new-generation integrated fiber positioners for LAMOST

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