Joint design method based on factorized representation of plant and controller of 2-DOF control system

Most previous joint model identification and control design methods are not applicable to unstable plants because the identified plant model is usually used as the design parameter. We (1997) have previously analyzed the internal structure of 2-DOF control system using a coprime factorization on RH, and shown that two free parameters, K and Q /spl epsiv/ RH/sub /spl infin//, specify the tracking performance and the feedback performance, respectively. Tay et al. have proposed a parametrization of the plant dynamics by switching the role of the controlled plant and the controller, and introduced a free parameter R /spl epsiv/ 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 (including unstable plants) the conventional joint design method. Finally, the usefulness of the proposed method is verified by some simulations.