On the design of optimal decoupled two-degree-of-freedom multivariable feedback control systems

An important consideration in the design of many control systems is decoupling (each command input controlling only one output). The two-degree-of-freedom structure is ideally suited to this task since it permits one to separate the problem of decoupling from the problem of realizing a desirable stability margin. A decoupling constraint, however, can lead to some deterioration in achievable system performance. A design procedure which minimizes this performance deterioration is outlined here.