Date of Award

Fall 2005

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical & Aerospace Engineering

Program/Concentration

Aerospace Engineering

Committee Director

Brett Newman

Committee Member

Thomas Alberts

Committee Member

Martin Waszak

Call Number for Print

Special Collections; LD4331.E535 P569 2005

Abstract

Due to the conservative nature of the standard singular value robustness tests there is ambiguity in the results that they provide. The tests only establish a sufficient condition and therefore provide little insight to the stability robustness of a system that fails the test. However, for a single parameter uncertain system that is modeled using structured uncertainty, an Evans root locus can be derived that shows how system closed-loop poles change with the magnitude of the single parameter uncertainty. This technique provides clear stability robustness insight. Further, another Evans root locus can be derived that shows how system closed-loop zeros change with the magnitude of the single parameter uncertainty, thereby providing performance robustness insight. These techniques are implemented and proven through analysis and design of a control system for spacecraft rotation about a single axis. Additionally, the uncertainty root locus is used as a tool to design a robust compensator for the spacecraft system. This compensator is implemented using a dynamic output feedback controller designed via eigen structure assignment. However, the compensator fails to produce the desired uncertainty root locus and desired step response. This failure occurs due to the inability of the eigen structure assignment method to fully realize the desired eigen structure in the under actuated and under sensed system. Regardless, the robustness compensator does provide an increase in robustness margin, albeit a minimal increase.

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DOI

10.25777/wfwr-3c12

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