Modeling, Analysis, and Optimization Issues for Large Space Structures

Topics concerning the modeling, analysis, and optimization of large space structures are discussed including structure-control interaction, structural and structural dynamics modeling, thermal analysis, testing, and design

Analog, hybrid, and digital simulation

Analog, hybrid, and digital computerized simulation technique

Asymptotic approximations to the error probability for detecting Gaussian signals.

Massachusetts Institute of Technology. Dept. of Electrical Engineering. Thesis. 1968. Sc.D.Vita.Bibliography: leaves 213-220.Sc.D

AFIT School of Engineering Contributions to Air Force Research and Technology. Calendar Year 1971

This report contains abstracts of Master of Science theses and Doctoral Dissertations completed during the 1971 calendar year at the School of Engineering, Air Force Institute of Technology

Nonlinear robust H∞ control.

A new theory is proposed for the full-information finite and infinite horizontime robust H∞ control that is equivalently effective for the regulation and/or tracking problems of the general class of time-varying nonlinear systems under the presence of exogenous disturbance inputs. The theory employs the sequence of linear-quadratic and time-varying approximations, that were recently introduced in the optimal control framework, to transform the nonlinear H∞ control problem into a sequence of linearquadratic robust H∞ control problems by using well-known results from the existing Riccati-based theory of the maturing classical linear robust control. The proposed method, as in the optimal control case, requires solving an approximating sequence of Riccati equations (ASRE), to find linear time-varying feedback controllers for such disturbed nonlinear systems while employing classical methods. Under very mild conditions of local Lipschitz continuity, these iterative sequences of solutions are known to converge to the unique viscosity solution of the Hamilton-lacobi-Bellman partial differential equation of the original nonlinear optimal control problem in the weak form (Cimen, 2003); and should hold for the robust control problems herein. The theory is analytically illustrated by directly applying it to some sophisticated nonlinear dynamical models of practical real-world applications. Under a r -iteration sense, such a theory gives the control engineer and designer more transparent control requirements to be incorporated a priori to fine-tune between robustness and optimality needs. It is believed, however, that the automatic state-regulation robust ASRE feedback control systems and techniques provided in this thesis yield very effective control actions in theory, in view of its computational simplicity and its validation by means of classical numerical techniques, and can straightforwardly be implemented in practice as the feedback controller is constrained to be linear with respect to its inputs

Energy harvesting of random wide-band vibrations with applications to an electro-magnetic rotational energy harvester

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 205-207).In general, vibration energy harvesting is the scavenging of ambient vibration by transduction of mechanical kinetic energy into electrical energy. Many mechanical or electro-mechanical systems produce mechanical vibrations. The kinetic energy associated with these mechanical vibrations represents a potential source of energy for sensors and other electronics. In fact, as the energy requirements for electronics and wireless communications systems has reduced, harvested energy from vibrations has been successfully used to power several wireless sensors. However, these sensors are implemented on systems with harmonic vibration sources. Most ambient vibrations are noisy, wide-band, and/or stochastic. As such, a resonant tuned-mass damper, with a narrow band-width, filters and discards much of the energy in the vibration spectrum, or worse, resonant harvesters will not resonate in stochastic environments. Several solutions are commonly proposed for harvesting energy from wide-band excitations; multiple resonators tuned to different frequencies (farm systems), non-linear systems, input excitation rectification, and frequency tuning are the most common. This thesis addresses some of the wide-band and/or stochastic challenges to vibration energy harvesting by investigating vibration energy harvesting as a power source for sensors and communications in a down-hole environment. This thesis shows that regardless of the transducer, a single resonant harvester tuned to the frequency with the maximum displacement times frequency cubed produces more power than a farm of resonant harvesters tuned to a range of frequencies. Additionally, this thesis shows that an electromagnetic harvester can be passively tuned to increase the power in a non-stationary system with a peak frequency that is a function of time. Finally, this thesis presents a new resonant, rotational architecture, which has the advantage of simultaneously maximizing the coupling inertia and displacement.by A. Zachary Trimble.Ph.D