On the system identification for an optical quality membrane mirrors

In 2001, the Directed Energy Directorate demonstrated the feasibility of an optical quality polymer membrane mirror. This technology has created new set challenges in the area of structures, controls, wavefront correctors, and wavefront sensors. When comparing a membrane mirror to a conventional glass, the optical figure and dynamic stability of a conventional optic is maintained using a structurally stiff mirror, where the aspect ratio of the diameter to thickness is on the order of 10:1. The aspect ratio of a membrane mirror might be on the order of 10⁶:1. The benefit of the membrane is less weight at the cost of significantly more optical aberrations, both static and dynamic. New advanced wavefront control technologies will provide the capability to correct for a significant static aberration but membrane dynamics will prove to be a substantial challenge for the advanced wavefront controller. Thus controlling membrane dynamics is a critical enabling technology. A system identification of the membrane mirror will provide a plant model for the development of the system control architecture. This research will show how one motion sensor can do a reasonably good job of tracking the free response of a planar membrane.