Nonlinear system identification of pH process using Hammerstein-Wiener model

This research proposes comparing results from identification of pH process which is a multi-input multi-output (MIMO) system. The experiments have been carried out by feeding wastewater and sodium hydroxide (NaOH) 1.25% by weight to reactor tank. A task of pH adjustment, particularly for a process with a continuous feed, is quite difficult due to inherent nonlinearity and high sensitivity to uncertainty disturbance. Identification in this research has been compared by using the state space model, ARX model, nonlinear ARX model, and Hammerstein-Wiener model. The experimental results show that using a Hammerstein-Weiner model gives a good result. The best fit in this model are 88.35% and 72.70% comparing with pH output and liquid level in pH reactor tank.