This research was funded by the National Science Foundation under grant
number DDM-9115417 from April 1992 to September 1995. The Principal
Investigators were Dr. Murray Black
and Dr. Guy Beale of the Electrical and Computer Engineering Department. Significant contributions to
the research were provided by Research Associate Professor Dr. Yong Lai
Tian; Graduate Research Assistants Francisco Arteaga-Bravo and Mengli
Li; and by our industrial
collaborators, Dr. Richard Silberglitt and Dr. Iftikhar Ahmad.
The purpose of this research was to develop an automatic control system
to prevent thermal runaway from occurring when low-loss ceramics, such as
alumina or mullite, are heated by microwave energy. The result was a
computer-based control system which uses measurements of temperature and
reflected microwave power to control the value of the applied microwave
power, the position of a mechanical plunger, and the size of an inductive
iris. The iris and plunger were adjusted to minimize the amount of
reflected power, and the applied power level was controlled to regulate
the temperature of the specimen at the correct value.
The design of the temperature control system was based on an analytic
model of the heating process. The movements of the plunger and iris are
controlled by a search process based on expert knowledge. Actual heating
experiments with silicon carbide rods and with mullite tubes have
verified the ability of the control system to prevent thermal runaway and
the robustness of the control system to wide variation in material
properties.
Figures with brief descriptions of specific
results of this research.
Publications related to this research.
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