On the target feedback loop parameterization for H∞/LTR control

A new approach on the target feedback loop (TFL) parameterization for the H∞/LTR control is presented in this paper. Based on a similarity transformation, the proposed approach provides a systematic tool to shape the sensitivity function of the TFL to achieve a similar first-order system behavior. Therefore, the process plant should not be necessarily expanded by a pole at the origin as proposed in the Athans´ hint, but by any stable real-finite pole. Eliminating the steady-state error is undesirable or even prohibitive in some applications, and thus the proposed procedure is advantageous, since it is not limited to expanding the process plant to a pole at the origin.