Coupled control between pH and level of a process with multititrated concentrations by input/state linearization

This paper presents a control method for handling a coupling effect between the liquid level and pH of the process with multi-titrated concentrations, which an outflow and titrating streams are manipulated inputs. A feedback controller formulated by using input/state (I/S) linearization and optimization technique is used to calculate control actions and estimate process disturbances. A logic of acid/base selection is applied to select suitable titrant feeds. Performance of the proposed method is evaluated and compared with a split-range control through servo and regulatory tests under closed-loop simulation. The results show that the developed controller can force the process to desired setpoints and reject disturbance occurred from pH and flow fluctuation in the influent stream efficiently.