STUDY OF FRACTIONAL WIENER/HAMMERSTEIN SYSTEMS IN CLOSED-LOOP

The stability criterion proposed by Popov is commonly used to prove the stability of systems with interconnected memoryless nonlinearity and rational linear system. Fractional linear systems are tackled in this paper. Then it is shown how this criterion can be used to take into account nonlinearity lying in a sector with a corresponding complex gain. Then, for the design of a fractional order robust controller, this gain is interpreted as an unstructured uncertainty added to the structured uncertainty of the linear part of a plant model.