Accession Number : ADA329676

Title :   Reorientations of Flexible Spacecraft Using Momentum Exchange Devices

Descriptive Note : Doctoral thesis

Corporate Author : AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING

Personal Author(s) : Ford, Kevin A.

PDF Url : ADA329676

Report Date : SEP 1997

Pagination or Media Count : 148

Abstract : We study rest-to-rest reorientations of flexible spacecraft using momentum exchange devices. A new and concise form of the equations of motion for a rigid body containing a cluster of gimbaled momentum wheels is developed using the Euler-Newton approach. Special restrictions of the gimbaled momentum wheel equations yield equations of motion for the momentum wheel cluster and the control moment gyroscope cluster. A mathematical model of a free spacecraft with Euler-Bernoulli appendages is developed. Using the assumed modes method, a complete set of equations is developed which describes the dynamics of a spacecraft with flexible appendages and gimbaled momentum wheels. Special attention is paid to singularity problems in control moment gyro clusters. A control law based on the singular value decomposition is developed which avoids torque output commands in the nearly singular direction. The stationary platform maneuver, a maneuver along the set of equilibrium solutions of a zero angular velocity spacecraft, is extended to the control moment gyro cluster. The set of equilibria for a control moment gyro cluster is a unique surface in gimbal angle space. A control law which reorients the spacecraft while remaining close to this surface is developed using a Lyapunov method.

Descriptors :   *SPACECRAFT, *ATTITUDE CONTROL SYSTEMS, *EQUATIONS OF MOTION, THESES, MANEUVERS, CONTROL THEORY, GYROSCOPES, FLEXIBLE STRUCTURES, ANGULAR MOMENTUM, GIMBALS, MOMENTUM TRANSFER, LYAPUNOV FUNCTIONS.

Subject Categories : Theoretical Mathematics
      Spacecraft Trajectories and Reentry

Distribution Statement : APPROVED FOR PUBLIC RELEASE