Control configurationfor robustness enhancement

This paper proposes a design framework for robust control system design. The approach is based on improving the robustness of a previously existing controller instead of the design of a Robust Controller: therefore the consideration of the Controller Robustification problem. The method is based on the generation of a complement to the control signal of the initial controller by means of a Robustification Block. This robustification part, which is based on the Observer-Controller configuration, will add an additional free parameter to the initial controller and will provide an IMC-like control scheme. Consequently, two important facts follows: the robustness properties of the initial controller are improved and it is not necessary to modify the initial controller. The approach is presented as a two-step design and we will concentrate on the second stage by designing for Robust Stability. To illustrate the proposed design, the temperature of an open-loop unstable bach chemical reactor is controlled.