Optical EngineeringRobust control of the Multiple Mirror Telescope adaptive secondary mirror
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For force-actuated, thin facesheet mirrors, structural flexibility within the control bandwidth calls for a new approach to adaptive optics. Dynamic influence functions are used to characterize the influence of each actuator on the entire surface of a deformable mirror. A linearized model of atmospheric distortion is combined with these dynamic influence functions to produce a dynamic reconstructor for providing actuator inputs in response to wavefront sensor measurements. This dynamic reconstructor is recognized as an optimal-control problem. A hierarchic control scheme that seeks to emulate the quasistatic control approach that is generally used in adaptive optics is compared with the dynamic reconstruction technique. Although dynamic reconstruction requires somewhat more computational power to implement, it achieves better performance with less power usage, and is less sensitive to errors than the hierarchic technique because it incorporates a dynamic model of the deformable mirror.