Fuzzy-model based pH control

The inherent nonlinearity of the pH process often renders conventional control difficult. This nonlinearity does however suggests that pH control would be a suitable application area for a fuzzy control system, whose ability to handle nonlinearities is well known. Many fuzzy controllers are of the rule based type where the controllers output response is described by a series of control rules. However, the controller described in this paper is of a fuzzy-model based type which means that a fuzzy model of the process itself is embedded into the predictive control structure. The authors present the performance of a fuzzy-model based pH controller for a strong base-weak acid neutralisation carried out in a constant volume CSTR. A study of possible use of clustering techniques is done to define the reference sets. The performance of the fuzzy-model based controller is tested for various set points on the neutralisation curve