On the Design of Optimal Decoupled Multivariable Feedback Control Systems

An important consideration in the design of many control systems is decoupling (each command input controlling only one output). The 2DOF (two-degree-of-freedom) or 3DOF (three-degree-of-freedom) structure is ideally suited to this task since it permits one to separate the problem of realizing a desirable stability margin from that of decoupling. A decoupling constraint, however, can lead to some deterioration in achievable system performance. A design procedure which minimizes this performance deterioration is established here.