This paper focuses on the development of a non-linear controller for a neutralization process. Block oriented models, namely the Wiener and Hammerstein model structures, are used for the controller design. A neural network architecture that has the capability to model the steady state behavior of a complex non-linear process is developed. The dynamic behavior is modeled with a linear model. The pH process considered in this study exhibits drastic changes in the gain, even over a small operating range. In this study, the performance of controllers designed using Weiner and Hammerstein models are compared with a PI controller for servo and regulatory changes. The comparison results based on integral square error (ISE) values shows that the Weiner model based controller is suitable for a pH process.

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Abstract:A CSTR is an Continuously Stirred Tank Reactor with the main function of agitation and to achieve constant composition. It has an important role in chemical process plants. A CSTR has an higher degree of nonlinearity when compared with other chemical reactors, this is mainly due to the temperature variations that occur because of uncertainity in feed. Hence, temperature control is a strenuous task. The proposed work focusses on control of temperature in a jacketed chemical reactor, by effectively designing a internal model controller (IMC). The process is a open loop unstable system due to the effect of scale-up on the steady state and other dynamic characteristics. The proposed digital controller is capable of providing system stability, set point tracking and disturbance rejection. The simulation result shows the suitability of using the proposed controllers for control of the unstable CSTR process.