The control problem examined is to stablize a large, spaceborne Cassegrain telescope. Modal gain factors and known characteristics of disturbances are used to determine which structural modes affect line-of-sight (LOS) the most and are candidates for active control. The approach is then to: (0 actively control/maintain alignment of optical components; (ii) place structural control actuators for optimum impact on the selected modes for active vibration control; (iii) feed back the best available estimate of LOS error for direct LOS control. Local analog loops are used for high BW control; multi-variable digital control for lower BW control. The control law is synthesized in the frequency domain using the charac-teristic gain approach. Robustness is measured by employing conicity, which is an outgrowth of the positivity approach to robust feedback system design.
R. P. Iwens,
R. J. Benhabib,
C. S. Major,
"An Approach To Optical Structures Control", Proc. SPIE 0748, Structural Mechanics of Optical Systems II, (3 June 1987); doi: 10.1117/12.939824; https://doi.org/10.1117/12.939824