ETFP: a new fibre positioner concept for future Multi-Object Spectrographs

Louth, Tom; Watson, Stephen; González, O.

doi:10.1117/12.2627714

Cited by 2 publications

References 1 publication

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Flexure based fibre positioners: design optimisation to follow arbitrary focal plane curvature

Louth,

Watson,

Montgomery

2024

Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation VI

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The use of flexures to achieve fibre positioner motion is being actively investigated by several institutes, for example at the UK Astronomy Technology Centre (UKATC) and Leibniz-Institute for Astrophysics Potsdam [1]. One challenge when designing with flexures is the large number of degrees of freedom available which makes it difficult or impossible to optimise their motion by hand.In this paper we demonstrate two approaches for optimising flexure geometry to follow arbitrary focal surface curvature and to orient the optical fibre with arbitrary tilt. These approaches are: analytical using MATLAB models and FEA based using Ansys. The approaches are complementary allowing the designer to efficiently explore the parameter space and then do precise optimisation of the flexure geometry. We demonstrate the applicability both to the UKATC's preferred design for WST, and to flexure-based fibre positioner designs generally. We also present a sensitivity analysis relating small changes in design parameters to changes in fibre tip motion. Finally we briefly present the UKATC's preferred geometry for the WST fibre positioner.

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Flexure based fibre positioners: design optimisation to follow arbitrary focal plane curvature

Louth,

Watson,

Montgomery

2024

Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation VI

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The Calibration of theta-phi Fiber Positioners Based on the Differential Evolution Algorithm

Zhang,

Huang,

Chen

et al. 2024

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Robotic fiber positioner (RFP) arrays are commonly adopted in multiobject spectroscopic instruments. The positioning accuracy is a common but vital issue for RFP as inaccurate fiber placement may heavily affect the observation performance. The calibration of RFP can effectively improve the positioning accuracy. Least-square is a widely used calibration method. However, it has disadvantages, such as sensitivity to the initial values and calculation complexity. To improve the positioning accuracy and reduce the iteration moves, we propose a new calibration method based on the differential evolution algorithm and verify it by calibrating the RFP of the Large Sky Area Multi-Object Fiber Spectroscopy Telescope. We first build the kinematic models of the RFP based on the Denavit–Hartenberg matrix and geometry relationship. Then, we analyze the error components and present the proposed calibration algorithms. The experiments are done with the digital universal tool microscope 19JC and the errors are calculated using the distance between the positions of achieved and target. Results show that the proposed algorithm can achieve higher accuracy than the least-square method and the average positioning accuracy is improved by 78.94% after calibration. Combined with the “pulse reduction” strategy and close-loop compensation, after two moves, the positioners can place the fiber ends within 40 μm of the intended location. The proposed calibration method is also suitable for other similar theta-phi positioners.

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ETFP: a new fibre positioner concept for future Multi-Object Spectrographs

Cited by 2 publications

References 1 publication

Flexure based fibre positioners: design optimisation to follow arbitrary focal plane curvature

Flexure based fibre positioners: design optimisation to follow arbitrary focal plane curvature

The Calibration of theta-phi Fiber Positioners Based on the Differential Evolution Algorithm

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