Fuzzy observers for anaerobic WWTP: Development and implementation

In this paper a set of fuzzy observers for anaerobic digestion is proposed to estimate variables difficult to measure in a completely stirred tank reactor. First, a mathematical model for the process is stated and experimentally validated. Then, a methodology based on principal components analysis is developed to select fuzzy variables, which allow the local observers to be adequately activated. The active local observers are interpolated using the Takagi–Sugeno approach, in order to recover the non-linear behaviour; to ensure their adequate performance, the respective stability analysis is included. The whole estimation scheme is validated via simulations and tested in a real process.