Control of neutralization processes by robust loopshaping

This paper studies the control of a pH neutralization process by using a ro bust loopshaping approach. The H-infinity loopshaping method is applied to calculate an optimal controller. The problem of choosing the desired shape of the open-loop transfer function needed by this method is addressed by co nsidering the available uncertainty information and applying graphical loop shaping ideas. Thus, this methodology considers not only the robustness pro perties of the shaped plant, but also those of the real plant. The designed controller was tested in real-time on a bench plant. On-line results show that the designed control system allows the plant to operate in a range of pH values, despite variations of the plant parameters, obtaining good perfo rmance at the desired working points. The methodology presented in this pap er can be applied to other chemical processes: It is only necessary to cons ider the possible uncertainty in the nominal model and using available soft ware to design the controller.