On-line identification and nonlinear control of an industrial pH process

The control of pH for industrial processes is a highly nonlinear and challe nging problem, especially when the nonlinearity is unknown and time-varying . In this work, a controller is developed and implemented for an industrial pH process with unknown chemical composition. The method used is an applic ation of a general algorithm for pH processes, which is based on a represen tation of the nonlinearity that leads to on-line identification of a small number of parameters. The results show good performance of the pH control a lgorithm under normal operating conditions and satisfactory performance dur ing several unusual hardware or process problems. (C) 2001 Elsevier Science Ltd. All rights reserved.