Relationship between internal model control and LQG controller structures

This paper describes how the conventional LQG controller structure can be rearranged into that of the Internal Model Control (IMC) structure. The IMC structure provides a useful framework for the analysis of control system performance, especially its robustness properties. Analysis of an LQG control scheme within the IMC structure, is useful in determining the effect of the various optimal return-difference transfer-functions. A design example is given to illustrate the IMC technique. The effectiveness of dynamic control weightings and coloured measurement noise, in shaping system robustness properties, is discussed. © 1989.