COMPUTATION-ORIENTED EXPRESSION OF A NONCONSERVATIVE CONDITION FOR ROBUST STABILITY OF SAMPLED-DATA SYSTEMS

A new expression of a non-conservative robust stability condition is d erived for sampled-data systems taking into consideration its convenie nce in numerical computation. Our expression is described using a glob al maximum of a certain differentiable function, while the conventiona l expression includes a global maximum of a structured singular value, which is expensive to compute. When the sampling period is long, the advantages of our expression become clear. A possible problem is that the maximized function may be multimodal. However, the conventional ex pression has the same problem and even a local maximum is shown to giv e useful information. Our expression is applicable to a fairly large c lass of systems including the multi-input multi-output additive and mu ltiplicative perturbation models. Using an example, we show how our ex pression is computed and make a comparison with the conventional expre ssion.