Model reference control in two degree of freedom control systems: Adaptivemin-max approach

The design of a control system, that provides a model reference performance specification for the command response and, at the same time, achieves som e prespecified feedback properties, is discussed. The use of a particular c onfiguration of a two degree-of freedom controller will allow the feedback and performance specifications to be tackled independently through the desi gn of a feedback controller for the nominal plant and the model reference p art by means of model matching in a min-max sense. A closed-form solution i s provided for the optimal min-max controller. This closed-form solution wi ll be very useful when using this controller in an adaptive way. The result ing adaptive controller will consist of a fixed feedback part and an adapti ve open-loop part. Only one degree-of-freedom is adapted. An example will s how that it is possible to match the model reference performance specificat ion, even near the stability limit.