Control and Feedback Organization -- Review and Terminology

The issue of organization of the feedback loops and control algorithms to achieve the objective of required performance is reviewed. For SISO system there are the one, two and (n) degrees of freedom architectures. These are based on heuristic, experience, intuition and experimentation. The control systems literature lacks concise and comprehensive definitions required for the clear and unique description of the control-feedback organization issue. As an introduction a terminology is defined at the system theoretic level. Using these definitions the problem of feedback organization is defined over the set theory within the well-established functional analysis and optimal control theories.