COMPARISON OF INTERNAL MODEL CONTROL AND LINEAR QUADRATIC OPTIMAL-CONTROL FOR SISO SYSTEMS

In this paper internal model control (IMC) is formulated for general inputs and compared with linear quadratic (H-2) optimal control (LQOC) with a general (dynamic) input penalty weight. Analogies and differences between the two methods for robustness study are clearly pointed out. Both controllers can be expressed in terms of the same nominal controller and a robustness filter. The difference is that the LQOC filter depends also on process and disturbance parameters. As a consequence, performance may be different in general, even if in many cases quite similar results are obtained. The design for robustness is much more straightforward in IMC.