The aim of this work is to design a super-twisting observer for on-line estimation of the concentration of Volatile Fatty Acids (VFA) in a class of continuous anaerobic digestion (AD) processes. Taking into account the limited availability of on-line sensors for the AD processes, in this contribution is assumed that only the methane outflow rate is available for on-line measurement. The estimation technique is based on a local coordinate transformation that lead the original twodimensional system to an observable normal form. In order to provide robustness properties under perturbation/uncertainty conditions a super-twisting algorithm is proposed. The observer convergence is analyzed by using Lyapunov stability techniques. Numerical simulations illustrate the effectiveness of the estimation scheme for a four-dimensional AD model with uncertainties associated with unmodeled dynamics and disturbances in the inflow composition.
Lara Cisneros, G., & Dochain, D. (2018). On-line estimation of the VFA concentration in anaerobic digestion processes based on a super-twisting observer. IEEE Xplore digital library (IEEE/IET Electronic Library). Published. Proc. CoDIT’ 2018, Thessaloniki, Greece. https://hdl.handle.net/2078.5/171659 (Original work published 2018)