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 A. Newman

Committee Member

Thomas E. Alberts

Committee Member

Chuh Mei

Call Number for Print

Special Collections; LD4331.E535 J46 2005

Abstract

Standard sequential loop closure design based on Evans root migration concepts is a well accepted, insightful and effective technique for meeting nominal performance objectives and traditional gain-phase stability margin requirements. Unfortunately, assessment of closed-loop variations resulting from parameter error is a post-process, implying an undesirable design-assess-redesign procedure is necessary if variations are found unacceptable. Further, the modem parameter uncertainty assessment framework is often inconsistent, both quantitatively and qualitatively, with the redesign task. Specifically, the parameter uncertainty assessment variables are not readily apparent in the sequential loop design framework, and these variables provide little guidance for the redesign strategy. Therefore, enhancing the root migration sequential loop design methodology to incorporate the parameter uncertainty framework is explored in this thesis. A sequential loop closure design procedure is expanded to include closed-loop transfer function polynomials as a function of parameter uncertainty in such a way that allows uncertainty root locus plots to be carried along in successive design steps. This graphical information facilitates insight into key closed-loop poles and zeros and system characteristics that influence parameter robustness properties. The engineer can evaluate and tune traditional stability and performance metrics simultaneously with newer parameter uncertainty metrics at each design step leading to the final overall multivariable control system. To demonstrate this methodology, control of single axis spacecraft motion with two flexible modes using a multivariable control law is considered.

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DOI

10.25777/tmaz-yv17

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