Multiloop Controlled Fed-batch Fermentation Process Using a Selftuning Controller

Abstract

A fed-batch fermentation process is controlled by a multiloop control structure, which contains a selftuning controller in order to meet the demands of a process with timevarying parameters and noisy conditions. It is shown that a biochemical multi-input multioutput process model can be rearranged into a simple ARMAX structured model. This model proved to be accurate enough to predict the biomass output within a few percent. The sel ftuning controller is based on the pole-assignment principle, and provided at the same time the opportunity to verify the estimated process parameters with those calculated from the biochemical modelling and from test results under ideal conditions. The set point used will increase steadily because of its dependence on the internal state of the process. This leads to the design of a multiloop control structure, where the selftuner takes care of a well-defined inner loop and a conventional controller is part of the outer loop. Some experiments carried out on a 10 litre vessel proved that the designed multiloop structure behaved rather well. The results of these experiments will be presented in the paper. This work has been performed as part of a close cooperation between the Delft University of Technology and Gist-Brocades, a fermentation company in The Netherlands.