Fuzzy control of a neutralization process

This paper studies the control of a pH neutralization process by using a fuzzy controller. As the process to be controlled is highly nonlinear the PI-type fuzzy controller used generally is not able to control the system adequately. For this, based on prior knowledge, the pH neutralization process is divided into fuzzy regions such as high-gain, medium-gain and low-gain, and an auxiliary variable is used to detect the process operation region. Then the fuzzy logic controller designed using this auxiliary variable as input, can give satisfactory performance in all regions. This controller was tested in real-time on a bench plant. Online results show that the designed control system allows the plant to operate in a range of pH values, despite perturbations and variations of the plant parameters, obtaining good performance at the desired workings points.