Robust software sensor design for the state estimation in a sulfate-reducing bioreactor

The goal of this work is to present a class of state observer in order to infer unavailable concentrations in a sulfate-reducing bioreactor containing an anoxic culture of Desulfovibrio alaskensis 6SR from the measurements of the sulfate concentration. The methodology is applied to the corresponding sulfate-reducing model considering modeling uncertainties. The proposed observer design presents a proportional term plus a sigmoid function structure. The model’s observability was locally analyzed by the observability matrix test, concluding that the sulfate-reducing bioreactor is detectable. A sketch of proof of the observer’s convergence is depicted in order to show the asymptotic convergence characteristics. Numerical experiments provide an overview about the superior performance of the proposed observer methodology compared to a sliding-mode and high order sliding mode observers.