Designing high performance two-degree of freedom controllers

A new generic optimal controller structure and a related regulator design method is introduced. The optimality is expressed by two simple serial compensators. It is shown how these filters-depending on the reference signal, the output disturbance and the invariant process factors-should be selected by the solutions of Diophantine equations if optimality is important. The optimal sensitivity properties of the new scheme is also analyzed and if is shown that this controller has the minimum variance to unknown process variations.