Robust generic model feedback under model uncertainties: Application of a tubular reactor for the treatment of industrial plating wastewater

Abstract

The goal of this work is to describe the design of a feedback controller to regulate the Hexavalent chromium (Cr (VI)) concentration in industrial plating wastewater in a tubular reactor. Cr(VI) is a major pollutant present in industrial wastewaters common to the metal and mineral processing as well as to plating industries. For control purposes, a dynamic model of a plug flow reactor with dispersion is developed in the form of partial differential equations (PDE) via applying classical conservation principles; this model is experimentally corroborated using laboratory data. The proposed controller is based on uncertainty observer to infer unknown terms as diffusive transport and Cr(VI) kinetic rate; also Generic Model Controller (GMC) is coupled with this estimation methodology to provide robustness against model uncertainties. The controller leads to nonlinear PID plus double integral action, where the tuning rules are given in terms of the observer and GMC gains. A theoretical frame is given in order to show the stability properties of the closed-loop system under the proposed controller. Numerical simulation illustrates performance of the methodology proposed; a comparison with observer based I/O linearizing controller and a well tuned PID controller is done, which allows concluding that the observer based Generic Model Controller exhibits better performance.