Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

Not available / text

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 144-148). Also available via the Internet.

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 259-271). Also available via the Internet.

Thesis (M.S.)--Ohio University, March, 1990. / Title from PDF t.p.

Thesis (M.S.)--Ohio University, November, 1991. / Title from PDF t.p.

No description available.

Thesis (Ph.D.)--University of Wyoming, 2008. / Title from PDF title page (viewed on Apr. 2, 2010). Includes bibliographical references (p. 135-139).

This thesis examines several techniques for the design of decentralized control strategies for the active control of vibrational damping in large space structures. A brief description of the finite element method is presented to explain the derivation of mathematical models of flexible structures represented by systems of linear second-order ordinary differential equations. The fundamental ideas of modal analysis are introduced to explain the concepts of vibrational modes and mode shapes, and derive the modal coordinate state space representation of flexible structures. The decentralized fixed modes of a system are defined, and several important characterizations of decentralized fixed modes are presented. Alternate characterizations of fixed modes yield additional insight into the nature: of fixed modes and often provide new methods for calculating the fixed modes of a system. The use of collocated rate feedback for robust vibrational damping control is described. It is shown that the robustness of collocated rate feedback is due to the positivity of large space structures, an extension of the mathematical concept of positive real functions to dynamic systems. Another strategy for the control of vibrational damping in large space structures, known as uniform damping control, is also described. It is shown that compared to collocated rate feedback, uniform damping control achieves increased performance at the price of decreased robustness at low frequencies. The application of decomposition techniques to the design of decentralized control laws is described, and a special type of decomposition known as an overlapping decomposition is introduced. It is shown how overlapping decompositions can be used to design control laws for systems for which the more familiar disjoint decomposition techniques often fail to yield satisfactory results. Finally, these decentralized control techniques are illustrated using a model of a proposed large space structure, the NASA CO FS mast. / Master of Science

This dissertation concentrates on the three principal problems facing experimentalists during their attempts to identify and control lightly damped, large space structures (LSS). The problems are low damping, high modal density, and low natural frequencies of oscillation. They present a blend of difficulties which lead the experimentalist to turn to multiple-input multiple-output (MIMO) identification techniques and high performance compensators. Presented here are two MIMO modal identification techniques: Polyreference, and the Eigensystem Realization Algorithm, as well as two types of compensator-based controllers: Linear Quadratic Gaussian, and Independent Modal Space Control. The various techniques are described in the context of controlling lightly damped LSS. Because the research in this dissertation is primarily applications oriented, problems which experimentalists encounter in the laboratory are addressed as well as the performance of the different identification and control techniques on the test articles. Polyreference and ERA are both shown to perform very well in identifying modal frequencies while overestimating model damping ratios. Simulations show that high modal density combined with noisy data results in standard deviations that increase linearly with respect to mode separation. Pseudo- Inverse IMSC is shown to be robust with respect to system uncertainties. Block Independent Control is shown to possess minor coupling between blocks and provides a powerful control approach to overcome actuator bandwidth limitations. / Ph. D.