Design of Controllers with Disturbance Rejection Capabilities: A Loop Shaping Methodology

Typically, a process is designed to work at some specific operating point. This is usually given as solution of an economic optimisation problem. Almost certainly, it will be not possible to operative the plant right at this operating point, as processes disturbances will cause constraints violations. Thus, we want a control system that can keep the controller variables at or near their optimal values in the face of load disturbances. In this paper, we present a method to design controllers with disturbance rejection specifications. This methodology is based on a special strategy to shape the singular values of a weighted sensitivity function.