Conditions for preservation of stability of adaptive controllers for systems with unmodeled delay

Some recent results from the mathematical literature are used to derive conditions under which stability of an adaptive controlled system (first-order plant with output feedback) is preserved in spite of the presence of a time delay in the plant input. Bounds on the delay, for which stability is preserved, are derived for three robust versions of the gradient update law: fixed sigma modification with and without normalization and a time-varying sigma modification.<
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