Hidden modes of two degrees of freedom systems in control design

A complete treatment of the hidden modes of two-degrees-of-freedom control systems is presented. The uncontrollable and/or unobservable hidden models are characterized in terms of transfer matrices of the interconnected system and in terms of design parameters. This characterization leads directly to design conditions, which can be used to adequately control the hidden modes, thus avoiding unnecessarily high order controllers and undesirable behavior. Internal stability is guaranteed by a stability theorem which adds insight to the problem.<
>