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The Effect of Inaccuracies in Structural Models on the Control of Large Space Structures.
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING
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Modern optimal control methods are proposed as a method for controlling the vibration of large space structures. These methods are very dependent on the structural finite element model as a basis for calculating the optimal control. This research investigates the effect of inaccuracies of these structural models on the performance of this type of controller. Any finite element model is a discretization of the actual structure. As such, it is impossible to exactly model the structure because the model is finite and discrete while the structure is continuous. These errors plus those due to inaccurate assumptions or measurements create discrepancies between what the structure is and what the controller is actually designed for. The structural model is used to calculate a number equal to the number of degrees of freedom of natural vibration frequencies with their associated mode shapes. These vibration modes can be grouped into four sets controlled, suppressed, residual and unmodeled. The structural model used for this research is the Charles Stark Draper Laboratory Model 1 CSDL1. It is a tetrahedral truss with four lumped masses yielding twelve degrees of freedom, and hence, twelve vibratory modes. Originator-Supplied Keywords Included Flexible Space Structures, Model Suppression, Computer programs, Fortran, and Linear Regulator Control Algorithm.
APPROVED FOR PUBLIC RELEASE