Title page for ETD etd-12092003-165833


Type of Document Master's Thesis
Author Pressl, Marcus Carl
Author's Email Address mpressl@vt.edu
URN etd-12092003-165833
Title Internal Torques and Forces in Gyrostats with Magnetically Suspended Rotors
Degree Master of Science
Department Aerospace and Ocean Engineering
Advisory Committee
Advisor Name Title
Hall, Christopher D. Committee Chair
Kasarda, Mary E. F. Committee Member
Woolsey, Craig A. Committee Member
Keywords
  • Spacecraft Simulator
  • Gyrostat
  • Active Magnetic Bearings
  • Internal Torques
Date of Defense 2003-11-14
Availability unrestricted
Abstract
Active magnetic bearings have several potential applications in spacecraft design. Based on the gyrostat model, we develop equations that describe the internal torques and forces that occur between the body and one of the attached wheels. We evaluate the transverse torques for the torque--free gyrostat and a gyrostat undergoing attitude maneuvers using momentum wheels and external torques. We then apply these internal forces to a model of an active magnetic bearing system and discuss their effects on the force limit, the actuator slew rate and the equivalent stiffness and damping parameters. As a basis for this study we use the Distributed Spacecraft Attitude Control System Simulator (DSACSS) with a Revolve MBRotor active magnetic bearing system. The results of several numerical simulations show that the magnitude and frequency of the internal torques remain small over the estimated range of motion of the DSACSS--MBRotor gyrostat. As such, the transverse torques caused by the rotational motion remain less than the discussed performance limits. We show that the magnitude of the internal torques can also be minimized by reducing the axial moment of inertia of the wheel. Furthermore, we discuss the equivalent Jeffcott model. By applying a standard Proportional--Integral--Derivative controller to the active magnetic bearing both the equivalent stiffness and damping parameters remain constant.
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