Characterization of matched systems

A new principle of control system design called matching was recently intro duced by Zakian. The principle requires the designer to choose a controller which makes a system match its environment. Characterization of matched co ntrollers by means of Youla parameterization is discussed in this paper. Su fficient conditions for matching are given in the form of inequality constr aints on the norm of the free parameters in the parametrizations based on n ominal matched controllers.