A DISCRETE-TIME INTERNAL MODEL-BASED H-INFINITY CONTROLLER AND ITS APPLICATION TO A BINARY DISTILLATION COLUMN

Explicit state-space formulae for an H-infinity two degrees-of-freedom (2-DOF) Internal Model Control (IMC)based controller are derived. The IMC controller solves a special H-infinity control problem directly i n discrete-time, providing robust stability against coprime factor unc ertainty, and a degree of robust performance in the sense of making th e closed-loop system match a pre-specified reference model. The IMC co ntroller structure is shown to comprise a plant state observer, an on- line step response model, and a generalised state-feedback law associa ted with the plant and model states. A design for a binary (methanol/w ater) distillation column is presented as an illustrative example. (C) 1997 Elsevier Science Ltd.