Identification and H-Infinity Control for a pH Neutralization Process

This paper presents the experimental results of the S/KS mixed sensitivity H-Infinity controller implemented in a real pH neutralization plant. For this control system, three variables were considered for control: level, temperature, and pH. To design the H-Infinity controller, linear models for each variable were identified as a first-order plus dead time (FOPDT) transfer function, and a step signal was used to excite each process variable. The system identification process and the design of the H-Infinity controller were implemented using the Matlab toolbox. To begin testing the H-Infinity controller in the real plant, the weight functions were initially defined and then adjusted to ensure robust stability and robust performance for each process variable. The responses of the H-Infinity controller for each variable were compared with those of the PI controller for the same desired reference signals, and the results were satisfactory according to the requirements. In conclusion, we can indicate that the H-Infinity controller is a viable option for use in the industrial processes when the linear model can be obtained.