Saturated control design for bounded substrate regulation in a continuous anaerobic bioreactor

Diseño de un control saturado para la regulación de sustrato en un bioreactor anaeróbico continuo

A. Morales-Díaz^* and S. Carlos-Hernández

Cinvestav Saltillo, Carretera Saltillo-Monterrey Km. 13.5 Ramos Arizpe Coahuila, 25900, México. *Corresponding author. E-mail: america.morales@cinvestav.edu.mx

Abstract

The aim of the study presented in this paper is the synthesis of a new saturated control, which forces the substrate concentration to reach a pre-specified bounded region without performance degradation in the bioreactor operation. The proposed controller is designed to achieve performance despite input disturbance and kinetic parameters uncertainties; it is based on an exponential bounded function that allows a smooth and fast convergence by setting a tuning parameter in the exponential function. A stability analysis based on the Lyapunov theorem and also some tuning guidelines are presented. Finally, the applicability of the proposed controller is illustrated via numerical simulations in a model representing a CSTR in continuous operation mode.

Keywords: anaerobic bioreactor, saturated control, substrate regulation.

Resumen

En este artículo se presenta el diseño de un nuevo controlador saturado que permite la operación de un reactor anaeróbico dentro de una región previamente especificad, con lo cual se garantiza la estabilidad del proceso y se permite el cumplimiento de los estándares de calidad del agua residual tratada impuesta por las regulaciones ambientales. Dicha región de operación implica límites en la concentración de los sustratos del sistema y así mismo impone límites en la tasa de dilución que corresponde a la entrada de control. La propuesta de control contempla una función exponencial que permite manipular la convergencia del sistema dentro del área de operación de una manera suave y rápida. También se desarrolla un análisis de estabilidad empleando el teorema de Lyapunov y se proporciona una guía para la sintonización de los parámetros del controlador. El desempeño del sistema se muestra mediante simulaciones numéricas, para lo que se utiliza un modelo matemático que representa un reactor continuamente agitado en modo continuo.

Palabras clave: reactor anaeróbico, control saturado, regulación de sustrato.

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