Adaptive output feedback control of a nonlinear chemical process

Abstract In many cases, by the state transformation including an independent outputs set as a part of new states, a nonlinear chemical process model can be divided into two subsystems; the one is a design model and the other is a disturbance model. Design model is described only in output variables and used for control system synthesis, while disturbance model is described in the original states and its effects on the design model are shown as time varying parameters in the design model. Method for controller synthesis is proposed as a combined form of timevariant input-output linearization method with parameter estimation. Since the parameter estimation method gives the parameter estimates such that the estimated outputs follow the outputs in a specified way, all the uncertainties and disturbances affecting the outputs can be reflected into the estimated parameters, thus making the adaptive linearizing controller robust. The design model in the output variables makes the proposed method suitable for the output feedback control, not requiring the state estimation. The design procedure of choosing the tuning parameters is simple and clear. For the demonstration of its applicability and validity, two control problems taking place in the chemical processes are considered; a regulation of continuous fermenter and a tracking of reference trajectory of a polymerization batch reactor.