Robust State Estimation in Presence of Parametric Uncertainty by NL-PI observers. An Application to Continuous Microbial Cultures

A state observer with integral action, robust and applicable to uniformly observable systems,is presented in this paper. Asymptotic stability of these observers is demonstrated applying Lyapunov convergence functions. In addition, it is shown that high-gain observers with integral action (NL-PI) provide robust estimation, despite parametric variabilities normally observed in bioreactors. The advantages of the proposed design are compared with a classical high gain observerthrough simulations and real-time cultivations of Saccharomyces cerevisiae.