Ill conditioned plants: a case study

The authors present a case study of a two-input-two-output ill-conditioned plant using the quantitative feedback theory (QFT) approach. No iterative steps were needed to find the controller, and a good compatibility with time domain performance was achieved. The pre-filter, on the other hand, required five iterations because the performance was given in the time domain. The Horowitz design philosophy which emphasize tolerances at each frequency and design to the exact uncertain plant, i.e. no norm-bounded uncertainty, justified itself as a design tool for ill-conditioned plants to achieve an economical bandwidth solution.<>