Quantitative feedback control for multivariable model matching and disturbance rejection

This article extends two recent contributions in the field of quantitative feedback theory to the multivariable case. They concern the model matching and the measured disturbance rejection problems. The model matching problem is a tracking control problem with specifications given as acceptable deviations from an ideal response. The measured disturbance rejection problem balances feedback and feedforward actions to reject disturbances. Both perspectives present advantages over classical quantitative feedback theory techniques in certain situations. This paper develops the necessary tools to solve both control problems in the case of multi‐input multi‐output plants. In particular, it shows how to derive nonconservative controller bounds for each of the single‐input single‐output control problems in which the overall multivariable problem is divided. The result is a systematic controller design methodology for multi‐input multi‐output plants with structured uncertainty. The application of the technique to the well‐known quadruple‐tank process illustrates the benefits of the method. Copyright © 2016 John Wiley & Sons, Ltd.