Decomposition of error based control system optimization

Decomposition possibilities of closed-loop control error is investigated to find the limits of optimality in generic two-degree of freedom control systems. New relationships are introduced for the different degradation components in a general and in a Youla-parametrized control system. It is investigated, how the major components in the decomposed problem can be optimized for open-loop stable plants. The new decomposition approach introduced helps the construction of new algorithms for simultaneous robust identification and control.