The Mid-infrared ELT Imager and Spectrograph (METIS) enables high-resolution spectroscopic and coronagraphic imaging in the wavelength range 3 . . . 13 μm. To obtain diffraction-limited measurements, METIS uses a single conjugate adaptive optics (SCAO) system comprising the deformable mirror M4, the tip-tilt mirror M5, and an infrared pyramid wavefront sensor. Due the non-negligible spatio-temporal dynamics and the redundant tip-tilt corrections of M4 and M5, the development of suitable SCAO controllers for METIS is nontrivial. Therefore, we present an advanced model-based SCAO controller. This controller is based on the mechanical modes of the correcting mirrors and considers stroke constraints of the mirrors to prevent windup phenomena. Moreover, the presented controller is fully compatible with the latest Instrument-ELT-Interface and offers several advantages, such as: it can be easily reconfigured to compensate faulty mirror actuators; its controller design can be fully customized to the dynamics of the correcting mirrors. Furthermore, the proposed control concept promises an advanced wavefront correction despite the challenging characteristics of the METIS-SCAO system. Finally, we investigate the presented controller by end-to-end simulations.
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