On-Line Identification and Nonlinear Control of pH Processes

The control of pH is widely recognized as a difficult problem. A novel method for representing the nonlinearity of pH processes is developed. A system with several chemical species of unknown concentrations and with pK values in a certain range is viewed as a piecewise continuous distribution instead of a series of impulses. On-line identification of a small number of parameters can then be used to affect the nonlinearity over an arbitrary pH range. The proposed method applies to systems with varying degrees of chemical knowledge. Computer simulations for two systems demonstrate the performance of this method.