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Adaptive control schemes are presented for a class of uncertain
time delay systems. These schemes have the advantage that in
addition to the standard assumption about the uncertainty of
the systems, the strength of uncertainties is assumed unknown.
Provided certain structural constraints are satisfied, the
adaptation gains automatically adjust to levels that assure
stability of the system. We drive the unknown systems toward
the performance of the chosen system reference models, as close
as desired. It is important to note that the resulting adaptive
schemes retain the stability property and robustness to
nonlinearities that is enjoyed by the fixed-gain controllers.
Furthermore, the adaptive schemes will perhaps use lower gains,
since adaptation will only be to the level that is necessary
for the required performance, instead of to the conservatively
high level that may have been determined through a fixed gain
design procedure. The main contributions for state estimation
in this thesis can be divided into two parts. First, memoryless
observers are designed. Without storing any state trajectory,
the proposed observer is convenient for implementation.
Secondly, based solely on output measurements and some a priori
knowledge of the plant structure, the proposed observer based
controllers asymptotically stabilize the uncertain time delay
systems.
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