Modeling of the SOFIA secondary mirror controller

Andreas Reinacher; Hans-Peter Roeser

doi:10.1117/12.915590

10 November 2011 Modeling of the SOFIA secondary mirror controller

Andreas Reinacher, Hans-Peter Roeser

Proceedings Volume 8336, Integrated Modeling of Complex Optomechanical Systems; 83360S (2011) https://doi.org/10.1117/12.915590
Event: Integrated Modeling of Complex Optomechanical Systems, 2011, Kiruna, Sweden

Abstract

The Stratospheric Observatory for Infrared Astronomy (SOFIA) is a 2.5m infrared telescope built into a Boeing 747SP. During observations the telescope will not only be subject to aircraft vibrations and maneuver loads - by opening a large door to give the observatory an unhindered view of the sky, there will also be aerodynamic and aeroacoustic disturbances. A critical factor in the overall telescope performance is the SOFIA Secondary Mirror Assembly (SMA). The 35cm silicon carbide mirror is mounted on the Secondary Mirror Mechanism (SMM), which has five degrees-offreedom and consists of two parts: The slow moving base for focusing and centering, and on top of that the Tilt Chop Mechanism (TCM) for chopping with a frequency of up to 20Hz and a chop throw of up to 10arcmin. The development of the controller that is used to meet the stringent performance requirements relys heavily on a state space model of the system. A pole-placement controller is compared to an optimal LQG control approach which makes use of the model to calculate all required system states in real-time. The paper explains the modeling of the TCM with linear differential equations and the optimization via a grey-box model approach with system identification data. Simulated data is then compared to measurements taken on ground and in flight.

Citation Download Citation

Andreas Reinacher and Hans-Peter Roeser "Modeling of the SOFIA secondary mirror controller", Proc. SPIE 8336, Integrated Modeling of Complex Optomechanical Systems, 83360S (10 November 2011); https://doi.org/10.1117/12.915590

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