Disturbance decoupling problems by measurements feedback: a characterization of all solutions and fixed modes

This paper presents a new approach to disturbance decoupling problems by measurement feedback (DDPM). The novelty in this approach is that it yields a characterization of the sets of all solutions to DDPM and DDPM with internal stability and that the set of fixed modes of DDPM with respect to dynamic output feedback is easily identified. The central object used in deriving these results is a minimal polynomial basis of a rational vector space which conveniently represents the problem data.