Browsing by Author "Lee, Li"

Now showing 1 - 5 of 5
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    Linear Fractional Transformations for the Approximation of Various Uncertainty Sets
    (1991) Lee, Li; Tits, A.L.; ISR
    Recently, it was shown that the structured singular value framework can be extended to the case when information on the phase of the uncertainty is available, and a computable upper bound on the corresponding "phase sensitive structured singular value" was obtained. Here we show that the same bound can be obtained via an entirely different approach, using a family of linear fractional transformations. Extension to various uncertainty "shapes" follows.
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    On Continuity/Discontinuity in Robustness Indicators
    (1991) Lee, Li; Tits, A.L.; ISR
    Continuity/discontinuity of robustness indicators is reviewed. For the case of real or mixed uncertainty, a regularization of the frequency dependent robustness margin is proposed and its properties are discussed. Implication of this regularization in the case of polynomial families with affine dependency on the uncertainty is pointed out.
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    On Phase Information in Multivariable Systems
    (1991) Lee, Li; Tits, A.L.; ISR
    The "median phase" and "phase spread" of a matrix are defined and properties are derived. The question of robust stability under uncertainty with phase information is addressed and a corresponding necessary and sufficient condition is given. This condition involves a "phase sensitive singular value". A computable upper bound to this quantity is obtained. The case when the uncertainty is block-structured is also considered.
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    Robustness under Bounded Uncertainty with Phase Information
    (1996) Tits, A.L.; Balakrishnan, V.; Lee, Li; ISR
    We consider uncertain linear systems where the uncertainties, in addition to being bounded, also satisfy constraints on their phase. In this context, we define the ﲰhase-sensitive structured singular value (PS-SSV) of a matrix, and show that sufficient (and sometime necessary) conditions for stability of such uncertain linear systems can be rewritten as conditions involving PS-SSV. We then derive upper bounds for PS-SSV, computable via convex optimization. We extend these results to the case where the uncertainties are structured (diagonal or block-diagonal, for instance).
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    Robustness under Uncertainly with Phase Information.
    (1989) Lee, Li; Tits, A.L.; Fan, Michael K-H.; ISR
    The framework of Doyle's structured angular value is extended to take advantage of possibly available phase information on the dynamic uncertainty. A computable upper bound is obtained for this phase-sensitive structured singular value.