Joint design method of 2DOF control system based on its factorized representation

In many cases, control system synthesis is formulated as minimization of prescribed closed loop performance reflecting control requirements. Since the closed loop performance is a function of a controlled plant and a controller, a model identification and a controller design must interact with each other. This motivates us to consider the model identification and the controller design simultaneously. However, most of the previous joint design methods are not applicable to unstable plants. On the other hand, we have analyzed the internal structure of 2D0F control system using a coprime factorization on RH/sub /spl infin// and shown that two free parameters, K and Q /spl epsi/ RH/sub /spl infin//, specify the tracking performance and the feedback performance, respectively. Also Tay et. al. have proposed a parameterization of the plant dynamics by switching the role of the controlled plant and the controller, and introduced a free parameter R /spl epsi/ RH/sub /spl infin//. In this paper, we propose a new joint design strategy based on the identification of R and the design of Q. Since the identified plant parameter R is always stable, the proposed joint design strategy can be applied to a wider class than the conventional joint design methods. Finally, the usefulness of the proposed method is verified by some experiments.