ON THE SCHMIDT PAIRS OF MULTIVARIABLE HANKEL-OPERATORS AND ROBUST-CONTROL

We study here a particular application of the theory of Hankel operators to robust control. The techniques of superoptimal Nehari extension developed by Young are employed to derive some properties of a particular controller of a rational function G, called the superoptimally robust stabilizing controller. Using this controller, we generalize to the multivariable case some results due to Fuhrmann and Ober. We also give a characterization of all plants G which are stabilized by the same superoptimally robust stabilizing controller.