Control of neutralization processes by robust loop shaping

This paper studies the control of a pH neutralization process by using a robust loop shaping approach. The H_∞ loop shaping 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 considering the available uncertainty information and applying graphical loop shaping ideas. Thus, this methodology considers not only the robustness properties of the shaped plant, but also those of the real plant. The designed 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 variations of the plant parameters, obtaining good performance at the desired working points. The methodology presented can be applied to other chemical processes: it is only necessary to consider the possible uncertainty in the nominal model and using available software to design the controller