On partial disturbance rejection by measurement feedback with internal stability

In this paper a natural framework for partial disturbance rejection problems is introduced. This framework basically consists of the subrings of proper and stable rational functions and their quotient rings. Using this framework, the set of all solutions of the problem and the solvability conditions are easily determined. The parametrization of the set of all solutions provides an opportunity to use partial disturbance rejection together with, for instance H_∞ design methods. This aspect of the problem is explained and illustrated by an example