Independent parametrization of two-degree-of-freedom compensators in general robust tracking systems

In this paper, we consider a general robust tracking problem with two-degree-of-freedom compensator, where the controlled object is a linear multivariable system whose measured variables are not necessary coincident with the output variables to be controlled. A necessary and sufficient condition for the two-degree-of-freedom compensator to achieve the robust tracking system with internal stability is given. After deriving an existence condition of such a compensator, the class of all such compensators is parametrized, where two specifications with respect to responses for reference commands and feedback properties can be satisfied independently by derived two free parameters.