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Active Control of Large Telescopes: Active Optics

  • André Preumont
Chapter
Part of the Solid Mechanics and Its Applications book series (SMIA, volume 246)

Abstract

This chapter deals with the control of the primary mirror of large telescopes in order to compensate the deformation due to manufacturing errors, the thermal gradients, and the changing gravity loads. The case of a monolithic mirror is considered first, followed by that of segmented mirrors (all telescopes with a primary mirror larger than 8 m will be segmented). The control strategy is based on a quasi-static model between the actuator inputs and the sensor outputs (Jacobian); the feedback loop uses a singular value decomposition (SVD) controller shaped in the frequency domain. Next, the dynamic response of the telescope is considered and its possible interaction with the SVD controller is analyzed. A stability robustness test is used to evaluate the stability margin and derive guidelines on the control bandwidth, natural frequency, and structural damping of the telescope structure to avoid spillover instability. The final section discusses some important scaling rules for telescopes of increasing size. The chapter concludes with a reference list.

Keywords

Active optics E-ELT Segmented mirror Edge sensor Co-phasing SVD controller Loop shaping Spillover Control-structure interaction 

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Copyright information

© Springer International Publishing AG 2018

Authors and Affiliations

  1. 1.Active Structures LaboratoryUniversité Libre de BruxellesBrusselsBelgium

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