In this article, we treat robust stability design of decoupling controllers for the plant with multiplicative-type uncertainty. We show that the robust stability condition in terms of matrix H ∞-norm leads to interpolation problems on scalar functions and we derive the relative degree conditions on the interpolating scalar functions to guarantee the properness of resulting controllers. Nevanlinna–Pick algorithm with relative degree constraints is presented to solve the interpolation problems with the relative degree constraints.
['Taedong Park', 'Kiheon Park']
Robust stability design of decoupling controllers using Nevanlinna–Pick algorithm with relative degree constraints