Nonlinear Adaptive Control Theory Applied for Chemical Process Control

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Significant improvements in the performance and the reliability of chemical process control systems can be achieved by implementing control strategies the compensate for the interaction between process variables. The objective of this research is to demonstrate that stability and passive operator theory (passivity in this sense refers to the preserving of a property--for example, in all such processes mass is conserved) can be used for motivate and develop nonlinear adaptive controllers for difficult process control problems like polymer and heterogeneous azeotropic distillation systems. The PI plans to investigate and develop an alternative approach to nonlinear process control, an approach that is motivated by physical considerations and exploits a passivity property of thermodynamically closed systems. This property is generic since chemical proceses are modelled by energy and material conservation relationships. Examples of passsive systems include exothermic reactors, heat exchangers, distillation columns and plug flow reactors. A continuous stirred task reactor (CSTR), a plymer reactor and a heterogeneous azeotropic distillation process will be used to illustrate the applicability of the proposed approach. Two topics will be addressed. The first is how to use stability theory to select a feasible combination of measured and manipulated variables. This problem is referred to as the nonlinear structure problem. The second problem to be addressed is the design of adaptive controllers for nonlinear processes that have uncertain and/or completely unknown parameters. This is the transient robustness problem. The result will be used to define feedfoward signals. Due to its simplicity and generality this research may also have a significant impact on the teaching of process control.