(An) application of model reference adaptive computer control to a continuous distillation column

Abstract

A model reference adaptive control (MRAC) scheme, developed recently for a single-input single-output plant by Narendra and Valavani, and Ichikawa, is utilized in conjunction with the adaptation rules proposed for a multi-input multioutput plant. This MRAC scheme is evaluated using digital computer simulation and experimental application to a small size distillation column interfaced with online digital computer. The application of the MRAC scheme to control of chemical processes with time delays is also investigated. Simulation study is performed to investigate the effects of adaptation parameters on the control performance and to determine the sensitivy of the system to step change in the reference input. The effects of filter dynamics used in the MRAC scheme for a single-input single-output system are investigated on the responses of the MRAC system. In simulation study with time delay free model of the plant, the MRAC system shows good performance for various sets of the adaptation parameters. Particularly, equally good results are obtained for repeated disturbances in the reference input. Faster dynamics of filters results in faster responses as expected. However, limitations on choosing the faster filters for the MRAC system are from the stability condition of strictly positive real of the reference model and sampling time. Simulation studies with model of the plant containing time delay show that the reference model with a simple first-order approximate term of time delay gives good responses in comparison with those obtained by use of the other complicate approximate terms. The MRAC system is shown to be intensitive to the types of the reference model. To confirm the results of the simulation and to examine the practicality of MRAC scheme for industrial application, experimental study is carried out on a pilot plant, packed distillation column, separation a methanol/water mixture at atmospheric pressure. An on-line microcomputer is used for the MRAC sch...