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 Dr. Christopher Hall Committee Chair Dr. Craig Woolsey Committee Member Dr. Mary Kasarda 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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