qSuppose D Î DN is a structured Nonlinear (Time-varying) Uncertainty and suppose D is constant scaling matrix
such that DDD-1 Î DN . (Note that we do not require DD=DD.)
q Then a sufficient stability condition for all D Î DN with ||D||¥< 1, is (by small gain theorem)
•||D-1G(s)D||¥ £ 1
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