Fuzzy multivariable control of a class of a biotechnology process

This paper addresses one fuzzy multivariable control strategy, based on a two-dimensional fuzzy rule base, to control a biotechnology process. This process makes use of a continuous stirred tank reactor (CSTR), to convert ferrous iron (Fe/sup 2+/) into ferric iron (Fe/sup 3+/) by means of Thiobacillus Ferrooxidans bacteria. This bacteria acts as an oxidant in a biooxidation process to produce the leaching agent. The model used in this simulation was not based in a microscopic model but in a macroscopic one. The controller is a PID-type fuzzy controller based on a two-dimensional fuzzy rule base that uses only the control error and change in control error. This biotechnology process falls into the class of multivariable systems, due to the number of variables of interest involved in the process. In this case the control variables are two feed streams, a sterile water stream and a stream containing the concentrated amounts of the substrate and other nutrients. The application of this fuzzy control strategy is a novel one in the field of biotechnology.