Criterion for loop stability in mimo feedback systems having an uncertain plant

In the Horowitz design technique for MIMO systems, the objective is to design the compensators and prefilters such that given closed loop specifications are achieved Over a given range of plant uncertainty. In this paper, an algebraic condition is presented which ensures that no extra right half-plane poles are inserted into the equivalent SISO plant of each design step due to the previously designed compensators. For some problems the loop bandwidth may then be lowered and conditional stability avoided. In the case of non-minimum phase plants, plants with pure time delay and non-linear plants solved by the global linear time invariant procedure, it may be essential to use this condition in order to successfully to apply the Horowitz technique.A two-input two-output example is presented.