Robust controller design using H∞ loop-shaping and the method of inequalities

A new approach to robust controller design is proposed. By using plant weighting functions as the design parameters, the approach combines the method of inequalities with robust stabilization of normalized coprime factor descriptions of the weighted plant to design explicitly for closed-loop performance and stability robustness. A procedure for the design of robust, two degree-of-freedom controllers is presented, and is illustrated on a high-purity distillation column example