Segmented primary mirror telescopes require dedicated piston-tip-tilt actuators for optimal optical performance. TNO has developed various prototypes of such actuators, in particular for the E-ELT. In this paper the control results of a specific two-stage prototype will be presented. First, the dynamics of the actuator in interconnection with the to-be-positioned mass has been analyzed, both using frequency response measurements and first principles modeling, resulting in a detailed understanding of the dynamic behavior of the system. Next, feedback controllers for both the fine and the coarse stage have been designed and implemented. Finally, the feedback controlled actuator has been subjected to a realistic tracking experiment; the results have demonstrated that the TNO actuator is able to suppress wind force disturbances and ground vibrations with more than a factor 10₃, down to 1.4 nm RMS, which is compliant with the requirements.

Date Published: 22 July 2014
PDF: 14 pages
Proc. SPIE 9145, Ground-based and Airborne Telescopes V, 91451S (22 July 2014); doi: 10.1117/12.2056901

Published in SPIE Proceedings Vol. 9145:
Ground-based and Airborne Telescopes V
Larry M. Stepp; Roberto Gilmozzi; Helen J. Hall, Editor(s)