Absolute stabilization based on circle criterion: H/sub /spl infin// and LMI approach

In this paper, a new dynamic output feedback approach for absolute stabilization of Lur´e system with time-varying feedback nonlinearity is presented. Based on circle criterion, the absolute stabilization problem is recast into the framework of H/sub /spl infin// sub-optimal control by using loop transformation and a sufficient condition is obtained for absolute stabilizability in terms of a set of LMIs. Besides the unperturbed system, the system with norm-bounded unstructured uncertainty in the linear plant is also considered and another LMI sufficient condition for absolute stabilizability of such system is devised. With the feasible solution of these LMIs, the desired output feedback stabilizer can be constructed consequently. Illustrative example is given to demonstrate the feasibility of the proposed approaches.