8th International Workshop on Modeling and Applied Simulation, MAS 2009, Held at the International Mediterranean and Latin American Modeling Multiconference, I3M 2009, Puerto de la Cruz, Spain, 23 - 25 September 2009, pp.38-43
The control of pH is common in the chemical process and biotechnological industries. The main complexity consists of the nonlinearity reflected in the S-shaped gain curve of the system. However, a model-based controller will inherit all the nonlinearities of pH system. Therefore using the inverse model as a controller in an open loop fashion will produce perfect control if there does not exist any disturbance or parameter variations. In this paper, a new model inversion technique that is based on an evolutionary search algorithm called Big Bang Big Crunch optimization is introduced. Moreover, a hybrid control scheme is proposed where a parallel PI controller, which will be only activated in a model mismatch, is implemented. The beneficial sides of the hybrid control approach based on the proposed model inversion technique are illustrated in a simulation study. This control scheme is applied to control the pH variable in a neutralization process.