On the robust Popov criterion for interval Lur´e systems

A robust version of the classical Popov criterion is given for robust absolute stability of Lur´e systems including parametric uncertainty. The parametric dependence is modeled by an interval plant description. The generalized criterion is obtained in terms of a vertex result for the Popov strict positive realness condition. For the case of interval Lur´e systems, a sufficient condition is established for absolute stability requiring the application of the Popov condition to a finite number of linear plants independent of the order of the linear system