Application of robust and multimodel control methods to an ill-conditioned distillation column

A set of linear models of an ill-conditioned two-product distillation column is used for controller design. A number of controller design methods are studied, each with the aim of achieving sufficient robustness and performance by using the description of plant variations and uncertainties provided by the model set. The investigated methods comprise multimodel H-2 optimal control, mixed H-2/H-infinity control with nominal H-2 performance, mixed H-2/H-infinity control with robust H-2 performance. mixed-sensitivity loop shaping using structured-singular-value synthesis, robust loop shaping according to Glover and McFarlane, multivariable IMC and optimally tuned decentralized PI control. The controllers obtained by the various design methods are tested by a series of setpoint change experiments on the pilot-scale distillation column. The experimental results are reported and the different control methods are evaluated and compared with respect to obtained performance. Design issues are briefly discussed. (C) 2001 Elsevier Science Ltd. All rights reserved.