Control of a pH neutraliztion process via the Big Bang Big Crunch optimization

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.