The authors introduce a novel design procedure for two-degree-of-freedom controllers. The technique will be used to design a control system for the distillation column design case study described by D. J. N. Limebeer (1991). The feedback controller and the prefilter are designed in a single step in an H∞ optimization framework. The feedback controller is used to meet the robust stability and disturbance rejection specifications, while the prefilter is used to shape the time responses of the c...