Title :
Control of the secondary mirror unit for the SOFIA telescope
Author :
Moerschell, Joseph ; Onillon, Emmanuel
Author_Institution :
HEVS, Sion, Switzerland
Abstract :
SOFIA is a 2.5-m telescope to be carried on a special Boeing 747 for astronomic observations at altitudes of about 15,000 m. The paper describes the main features of the secondary mirror unit. The SOFIA secondary mirror needs active control for alignment along five degrees of freedom as well as for very fast chopping with a frequency up to 20 Hz. The SOFIA secondary mirror chopping mechanism and control system are described. A state space model derived from the mechanical and electrical equations of the system is then introduced. This model can be used for the design of a state space controller based on a pole placement algorithm, making the system to behave as a fourth order Bessel filter. To avoid overshoots due to current and voltage limitations, a variable speed limitation which is function of the position error is added to the controller
Keywords :
astronomical telescopes; flexible structures; mirrors; observers; pole assignment; position control; state-space methods; 15000 m; 2.5 m; Bessel filter; SOFIA telescope; active control; alignment; astronomic observations; chopping mechanism; flexible structure; observer; pole placement; secondary mirror; state space model; Algorithm design and analysis; Control systems; Electric variables control; Equations; Frequency; Mechanical variables control; Mirrors; State feedback; State-space methods; Telescopes;
Conference_Titel :
Advanced Intelligent Mechatronics, 2001. Proceedings. 2001 IEEE/ASME International Conference on
Conference_Location :
Como
Print_ISBN :
0-7803-6736-7
DOI :
10.1109/AIM.2001.936775
