A Novel Fuzzy PI Control Approach for Nonlinear Processes

Abstract

Classical fuzzy logic controllers fail to control nonlinear systems, which have strong nonlinearity around a certain operating point. In this case, if it is possible, the block-oriented modeling approach could be adopted to separate the highly nonlinear system into two subsystems as a linear time-invariant subsystem and a memoryless nonlinear subsystem. Thereby, a control operation could be carried out on the linear time-invariant block to control the whole system. Respecting this approach, here, a highly nonlinear system (neutralization process) was modeled by using the ARX–polynomial cascade connection. By this means, an opportunity is obtained that the inverse polynomial is utilized to be able to control the ARX subsystem by a classical fuzzy PI controller. And therefore, the fuzzy PI controller performance in controlling nonlinear processes was enhanced. The success of the new approach was confirmed by the results obtained from the control operation carried out in different pH regions for a chemical neutralization process. And also, the results show that the proposed control strategy is as successful as the multiregion fuzzy PI controller in the highly nonlinear process control.