Smooth sliding-mode observers for specific growth rate and substrate from biomass measurement

JESÚS PICO; HERNÁN DE BATTISTA; FABRICIO GARELLI

JOURNAL OF PROCESS CONTROL

ELSEVIER SCI LTD

Año: 2009 vol. 19 p. 1314 - 1323

0959-1524

This paper addresses the estimation of specific growth rate and substrate concentration from biomass measurements in fermentation processes. Specifically, sliding-mode observers are proposed, for which finite-time global convergence is demonstrated using Lyapunov stability theory and concepts of variable structure systems. Two observers are developed for specific growth rate estimation, one producing a discontinuous estimation which is used afterwards for substrate estimation, and the other one – based on high-gain observers – that generates a smooth estimation with first-order dynamics and finite-time bounded convergence error. In the case of substrate estimation, an observer that increases the convergence rate to a vicinity of the real substrate concentration while achieving asymptotic convergence despite kinetic model uncertainties in properly excited processes is designed. This observer also exhibits first-order dynamics.