No description available.

This study presents methods for understanding, modeling and control of tele-operated pneumatic actuators for rehabilitation in Magnetic Resonance Imaging (MRI). Pneumatic actuators have excellent MRI-compatibility as opposed to conventional electro-mechanical systems; however, the actuator and the system drivers cannot be co-located due to the MRI-compatibility requirements. The actuators are driven via long transmission lines, which affect the system dynamics significantly. Methods provided in this work produced accurate pressure estimation and control by accounting for the pressure dynamics in the lines, which has been neglected by previous work in this area. The effectiveness of the presented modeling and control methods were demonstrated on tele-operation test setups. This research also includes the design of necessary system components for the developed algorithms. An MRI-compatible optical sensor was developed for force feedback and its design was analyzed for high precision. Directions and opportunities for future research are discussed.

No description available.

published_or_final_version / Electrical Engineering / Doctoral / Doctor of Philosophy

A more accurate and flexible grid analysis is achieved through an adaptive and dynamic calculation of line parameters. This is needed for future smart grid implementation. The primary objective of this thesis is to analyze the calculation of transmission line parameters. The impact certain assumptions have on the accuracy of line parameters and fault location algorithms are evaluated. In particular, the impact of the grounded shield wire assumption on the accuracy of fault location algorithms is analyzed. This implies that the impedance of towers be taken into consideration, rather than the simplification of a direct connection of the earth wire to ground. Secondly, the phenomenon of skin-effect is analyzed and evaluated in regards to a more accurate representation of line parameters and a minimization of parameter inaccuracy. / text

No description available.

The general expressions for finding the network functions, e.g., the immittance and the scattering parameters, of a general, uniformly coupled n-line structure in an inhomogeneous medium are derived in terms of the normal mode parameters of the system. These are used to compute or to derive the explicit expressions for the elements of the immittance matrix in terms of normal mode parameters. The scattering parameters of a general non-symmetrical directional coupler with arbitrary terminations are derived in terms of the known scattering parameters with a specified set of terminations such as characteristic non-mode converting terminations. The formulation is quite general and can be applied to various coupled guided wave systems, including coupled microstrip lines, slot lines, comb lines, dielectric waveguides and various other uniformly coupled transmission systems. The results obtained are used to present the procedure to determine the optimum terminations for directional couplers and sensitivity of various multiports, including couplers, to changes in terminations. It is shown that the coupler performance can be optimized in terms of the terminating impedances. The analysis and design procedure for both symmetrical and nonsymmetrical four-port coupled structures consisting of the symmetrical three lines in an inhomogeneous medium such as microstrips are presented. Tables and charts for the design of three-line structure are based on the closed form expressions for the immittance parameters. The analysis and design procedure for open-circuited interdigital multiple coupled microstrip line structures for applications as wideband DC blocks and filters are also presented. As in the case of the other microstrip structures, the initial design is based on the TEM assumption and the final geometry is then determined by the exact computation of the frequency response of the two ports. For larger numbers of lines, the design is based on the equivalent even- and odd-mode parameters of the n-line system. For this case, the TEM design equations, derived in terms of even- and odd-mode impedances of a pair of lines, can be translated into a physical configuration by using published results on coupled lines. / Graduation date: 1983

Coplanar microstrip structures placed on dielectric substrates are used as high frequency electro-optic modulators. The method of lines, a mathematical technique for solving partial differential equations, has been applied to solve for the propagation characteristics of such a configuration. It has been determined that simple transmission line models are adequate to describe this system. The propagation characteristics are expressed in terms of the equivalent impedance and the phase velocity of the signal on the microstrip. In order to maximize the effective bandwidth of the modulator, the impedance is matched to that of the surrounding dielectric substrate, and the difference in the phase velocities of the two signals is minimized. The numerical technique developed here allows for the analysis of inhomogeneous dielectric substrates, so that trench structures for tuning the propagation characteristics to their desired values can be modelled. The numerical results for typical structures are presented, and suggest that the method of lines is a viable one for analyzing these modulator structures. / Graduation date: 1991

In this thesis a numerical technique to model general microstrip asymmetric and multiple step discontinuities is presented. The method is based on a magnetic wall waveguide model that is assumed to be valid for describing the electromagnetic fields associated with the microstrip line and in the vicinity of microstrip discontinuities. The fields are expanded in the uniform regions and the mode-matching method is applied at the discontinuities to analyze for the frequency dependent transmission properties of the multi ports. The generalized scattering matrix technique is used to model cascaded interacting discontinuities and is used to compute the properties of double-step and multi port structures. The generalized scattering matrix formulation takes into account the scattering phenomena of the dominant and all of the higher-order modes including evanescent ones. The validity of this model has been discussed extensively, and it is shown that the model can be used to describe the microstrip discontinuities with acceptable accuracy. The technique is applied (1) to study the transmission characteristics of asymmetric step discontinuities; (2) to design a filter for a desired frequency range using interacting asymmetric double step micros trip line; and (3) to design a new nominal 3db power devider of large bandwidth consisting of a three port rectangular patch. The techniques and models presented can be used in computer-aided analysis and design of such circuits. / Graduation date: 1993

Thesis (M.S. in Systems Engineering (Electronic Warfare))--Naval Postgraduate School, September 1990. / Thesis Advisor(s): Atwater, Harry A. Second Reader: Janaswamy, Rama. "September 1990." Description based on title screen as viewed on December 29, 2009. DTIC Identifier(s): Suspended striplines, microstrip lines, equivalent circuits, program listings, theses. Author(s) subject terms: Suspended-microstrip line, step discontinuity, equivalent circuit model, step-change. Includes bibliographical references (p. 60). Also available in print.