A Necessary and Sufficient Condition for High-Frequency Robustness of Non-Strictly-Proper Feedback Systems
نویسنده
چکیده
We consider stability and robustness of feedback systems, where plant and compensator need not be strictly proper. In an earlier paper [1] we described a functional R∞ which, when negative, guarantees closed-loop instability as a result of parasitic interactions in the feedback loop. In our main result, Theorem 5, we prove that, when R∞ > 0, there exist perturbations of plant and compensator from a narrow class which result in closed-loop stability and convergence. Hence, we may view R∞ > 0 as a necessary and sufficient condition for closed-loop robustness in non-strictly-proper feedback loops.
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