Fractional order control of pH neutralization process based on fuzzy inverse model

pH neutralization process is a nonlinear process with time varying characteristics. Usually, the model based control of this process is a difficult task. Regarding to the appropriate modelling of the pH process by a Wiener model, in this paper an inverse model based control scheme is presented in which a fractional order controller is used as a linear controller. To apply this control scheme, firstly the inverse model of the nonlinear static part of the pH process is modelled benefiting from a fuzzy modelling method. Then by using the inverse model of the nonlinear static part, an augmented system is obtained whose behavior is similar to a linear system. Therefore, simple controllers such as PID type controllers can be used to control the augmented plant. In this paper, a fractional order PID (FOPID) controller is applied to the augmented system as a linear controller. The simulations presented in this paper show the efficiency of this type of controller in comparison with the classical PID controller in a similar structure.