An adaptive extension to high gain observer with application to wastewater monitoring

Adaptive version of high gain observers for the strictly triangular systems subjected to constant unknown disturbances is proposed here. Adaptive feature is necessary due to the fact that unknown disturbance enters in a way that cannot be suppressed by the high gain technique. The developed observers are then applied to a culture of microorganism in a bioreactor, namely, to the model of the continuous culture of Spirulina maxima. It is a common practice that just the biomass (or substrate) concentration is directly measured as the output of the process for monitoring and control purposes. This paper shows both by theoretical analysis and numerical simulation that the mentioned high gain adaptive observers offer a realistic option of online software sensors for substrate estimation..