Robust controller design for uncertain systems with variable time delay

A Smith predictor controller (SPC) is designed for an uncertain pasteurisat ion process exhibiting variable time delay. As the SPC may be very sensitiv e to model-plant mismatch, especial attention must be paid to ensure robust ness of the design when the model of the plant is not precisely known. This paper introduces two criteria for such cases. The first criterion is based on bandwidth considerations and the second one introduces some guidelines to improve the design by using the quantitative feedback theory technique. An experimental verification of the proposed methodology on the pasteurisat ion plant is also presented. (C) 2001 Elsevier Science Ltd. All rights rese rved.