Simultaneous stabilization with almost disturbance decoupling Part I: Uniform rank systems

In this paper we study the problem of stabilization with almost disturbance decoupling for a family of linear time-invariant finite dimensional uniform-rank plants with a fixed controller. It is shown that, for a family of minimum-phase plants which have the same order of infinite zeros and have high frequency gain matrices satisfying a certain condition, such a fixed controller exists. This restriction on the high frequency gain matrices is equivalent to requiring that the sign of high frequency gain for SISO plants be known.