Frequency sweeping tests for asymptotic stability: a model transformation for multiple delays

Focuses on stability properties of linear delay-differential systems involving multiple discrete delays. Sufficient conditions for characterizing bounded and unbounded stability regions in the delays-parameter space are derived. The proposed results are expressed in terms of structured singular values and consist of some frequency sweeping tests, which improve (or recover) previous delay-dependent (delay-independent or mixed) criteria from the literature. Comments on the conservatism of the method are also considered.