Control system modeling for the Thirty Meter Telescope primary mirror

Abstract

The Thirty Meter Telescope primary mirror is composed of 492 segments that are controlled to high precision in the presence of wind and vibration disturbances, despite the interaction with structural dynamics. The higher bandwidth and larger number of segments compared with the Keck telescopes requires greater attention to modeling to ensure success. We focus here on the development and validation of a suite of quasi-static and dynamic modeling tools required to support the design process, including robustness verification, performance estimation, and requirements flowdown. Models are used to predict the dynamic response due to wind and vibration disturbances, estimate achievable bandwidth in the presence of control-structure-interaction (CSI) and uncertainty in the interaction matrix, and simulate and analyze control algorithms and strategies, e.g. for control of focus-mode, and sensor calibration. Representative results illustrate TMT performance scaling with parameters, but the emphasis is on the modeling framework itself.

Integrated modeling and systems engineering for the Thirty Meter Telescope

“…The essential models generating the performance matrices are (i) MACOS with Matlab pre-and post-processors for the optical system [10], (ii) DOCS, implemented in Matlab for dynamic control simulations [11], [12], (iii) structural and thermal finite element models (FEA) for the optics and its support [13], and (iv) computational fluid dynamic (CFD) models for the aero-thermal characterization of the inside and outside environment of the observatory [14].…”

Unsteady wind loads for TMT: replacing parametric models with CFD

“…3,4 Previous models of wind loading on the telescope structure for TMT have been based on a parametric model [4][5][6] informed by a combination of Gemini data, 7,8 wind tunnel testing 9 and CFD. Advances in CFD now allow the unsteady forces on the structure and optics to be computed directly, as a function of external wind speed, orientation of the telescope with respect to the wind, and with enclosure vents either open or closed.…”