Detectability and Observability Analysis of the Anaerobic Digestion Process

The anaerobic digestion is an important bioprocess for the benefits it produces in energy and ambient. Yet, its monitoring and control are still hampered by the cost and lack of proper sensors. One way to mitigate this problem is the use of observers to estimate the desired variables. Prior to the observer design, an observability analysis can be done in order to determine which variables can be estimated from a given sensor configuration. Being the anaerobic digestion a highly non linear process, the usual observability analysis methods involve very complex calculations. However, analysis methods with less calculation complexity have been proposed in recent works, which also allow considering unknown inputs. Roughly, these methods consist in the dynamical study of the indistinguishable trajectories of the system, if they exist. Particularly, in this work, those methods are applied to the detectability and observability analysis of the anaerobic digestion process considering many sensor configurations. The analysis aims to obtaining a tool to facilitate the selection of sensors, to maximize the information that can be obtained from the process.