Accession Number : ADA453617


Title :   LQG/LTR Optimal Attitude Control of Small Flexible Spacecraft Using Free-Free Boundary Conditions


Descriptive Note : Doctoral thesis


Corporate Author : COLORADO UNIV AT BOULDER DEPT OF AEROSPACE ENGINEERING SCIENCES


Personal Author(s) : Fulton, Joseph M


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a453617.pdf


Report Date : 03 Aug 2006


Pagination or Media Count : 220


Abstract : Due to the volume and power limitations of a small satellite, careful consideration must be taken while designing an attitude control system for 3-axis stabilization. Placing redundancy in the system proves difficult and utilizing power hungry, high accuracy, active actuators is not a viable option. Thus, it is customary to find dependable, passive actuators used in conjunction with small scale active control components. This document describes the application of Elastic Memory Composite materials in the construction of a flexible spacecraft appendage, such as a gravity gradient boom. Assumed modes methods are used with Finite Element Modeling information to obtain the equations of motion for the system while assuming free-free boundary conditions. A discussion is provided to illustrate how cantilever mode shapes are not always the best assumption when modeling small flexible spacecraft. A key point of interest is first resonant modes may be needed in the system design plant in spite of these modes being greater than one order of magnitude in frequency when compared to the crossover frequency of the controller. LQG/LTR optimal control techniques are implemented to compute attitude control gains while controller robustness considerations determine appropriate reduced order controllers and which flexible modes to include in the design model. Key satellite designer concerns in the areas of computer processor sizing, material uncertainty impacts on the system model, and system performance variations resulting from appendage length modifications are addressed.


Descriptors :   *ATTITUDE CONTROL SYSTEMS , *ARTIFICIAL SATELLITES , *FLEXIBLE STRUCTURES , STABILIZATION , EQUATIONS OF MOTION , APPENDAGES , ACTUATORS , FINITE ELEMENT ANALYSIS , KALMAN FILTERING , THESES


Subject Categories : Unmanned Spacecraft
      Spacecraft Trajectories and Reentry
      Numerical Mathematics
      Theoretical Mathematics


Distribution Statement : APPROVED FOR PUBLIC RELEASE