Date of Award

Spring 1999

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Electrical & Computer Engineering

Program/Concentration

Electrical Engineering

Committee Director

W. Steven Gray

Committee Member

Stephen A. Zahorian

Committee Member

Oscar R. Gonzalez

Call Number for Print

Special Collections LD4331.E55 D637

Abstract

Most electronic and electrical equipment is not only a potential source of electromagnetic interference (EMI) but can also malfunction when exposed to certain levels of ambient EMI. This phenomena becomes more significant for digital control-computers automating the command and control performances in complex plants. Such EM disturbances can introduce transient signals on analog sensor and actuator lines, change data values on digital buses and in memory, or even produce logic changes in the CPU. The result of these so called computer upsets is the introduction of some degree of degradation in the quality of the control signal ranging from a perturbation error over a few sample periods to a permanent error mode or computer failure. Under these conditions, the primary concern of the control engineer is to insure that the closed-loop system remains stable after the disturbance subsides and/or corrective actions are taken.

The main objective of this study was to obtain stability conditions for discrete-time linear systems which are subject to abrupt changes in their structure and parameters due to electromagnetic (EM) disturbances from both natural and manmade sources. We considered particularly that class of disturbances which can be modeled by a Markov chain with a finite state space. The main results of the study are a stochastic disturbance model and a set of associated stability assessment tools for determining stability robustness of a nominal closed-loop system subject to electromagnetic disturbances. The focus was primarily on flight control applications, but much of the methodology is suitable for any application where highly reliable digital control is needed. The methodology was demonstrated on a variety of simple examples and a stabilizing controller for the longitudinal dynamics of the AFTI/F-16 aircraft.

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DOI

10.25777/3mba-mx21

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