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Evaluation of control laws and actuator locations for control systems applicable to deformable astronomical telescope mirrorsSome of the major difficulties associated with large orbiting astronomical telescopes are the cost of manufacturing the primary mirror to precise tolerances and the maintaining of diffraction-limited tolerances while in orbit. One successfully demonstrated approach for minimizing these problem areas is the technique of actively deforming the primary mirror by applying discrete forces to the rear of the mirror. A modal control technique, as applied to active optics, has previously been developed and analyzed. The modal control technique represents the plant to be controlled in terms of its eigenvalues and eigenfunctions which are estimated via numerical approximation techniques. The report includes an extension of previous work using the modal control technique and also describes an optimal feedback controller. The equations for both control laws are developed in state-space differential form and include such considerations as stability, controllability, and observability. These equations are general and allow the incorporation of various mode-analyzer designs; two design approaches are presented. The report also includes a technique for placing actuator and sensor locations at points on the mirror based upon the flexibility matrix of the uncontrolled or unobserved modes of the structure. The locations selected by this technique are used in the computer runs which are described. The results are based upon three different initial error distributions, two mode-analyzer designs, and both the modal and optimal control laws.
Document ID
19730024415
Acquisition Source
Legacy CDMS
Document Type
Other - NASA Technical Note (TN)
Authors
Ostroff, A. J. (NASA Langley Research Center Hampton, VA, United States)
Date Acquired
September 2, 2013
Publication Date
October 1, 1973
Subject Category
Electronics
Report/Patent Number
L-8862
NASA-TN-D-7276
Accession Number
73N33148
Funding Number(s)
PROJECT: RTOP 188-78-57-07
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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