Estimation of the dilution rate and the states of a microalgae culture using a linear Quasi-Uknown Input Observer

The simultaneous estimation of unmeasured state variables and unknown inputs is particularly relevant in environmental applications, such as biological wastewater treatment or culture of microalgae in open environments. In this paper, a linear Quasi-Unknown Input Observer (QUIO) is designed and applied to state and input reconstruction in a continuous culture of the marine microalga Dunaliella tertiolecta, where the dilution rate is the unknown input and the internal quota and substrate concentration are the unmeasured variables. A linear framework is suitable for this class of bioprocesses operated in continuous mode as a linearization around an operating point is valid and sufficiently robust. The simulation results and offline processing of real data demonstrate the performance of the method.